okw. nyenke /future sustainability august 2024| volume 02 | issue 03 | pages 01-05 1 article critical path method utilization for optimal scheduling of production activities ovundah king wofuru-nyenke department of mechanical engineering, faculty of engineering, rivers state university, port harcourt, rivers state, nigeria a r t i c l e i n f o article history: received 21 may 2024 received in revised form 25 june 2024 accepted 20 july 2024 keywords: critical path method, production activities scheduling, manufacturing engineering, slack time *corresponding author email address: ovundah.wofuru-nyenke@ust.edu.ng doi: 10.55670/fpll.fusus.2.3.1 a b s t r a c t critical path method (cpm) is a useful method for scheduling activities involved in a project. cpm is suitable for large and complex projects in which many tasks are involved and the interrelationships among these tasks must be taken into account. its efficacy can easily be transferred to the optimal scheduling of production engineering activities in order to save time involved in the project. it helps in identifying the sequence of jobs that determines the earliest possible completion date for the project. the knowledge of the critical jobs can aid in eliminating the fairly common and costly practice of rushing all jobs to reduce the total project time. meanwhile, rushing only the critical jobs will have the desired effect of decreasing the total project time. in this study, the critical path method was utilized in scheduling activities involved in the production of a new product by a metalworks manufacturing company. the project activities involved making an initial market study which took 25 days, developing promotional ideas which took 22 days, estimating promotional costs which took 16 days, conducting initial pricing study which took 29 days, preparing a detailed design which took 30 days, manufacturing prototypes which took 14 days, making design changes which took 12 days and determination of the final selling price of the product which took 15 days. the critical path analysis revealed that the minimum allowable time and earliest possible completion date for the project is 96 days. this research provides a procedure for implementing the critical path method for production activities scheduling. 1. introduction production activities scheduling is very important for planning the sequence of tasks, allocating resources, and defining timelines to ensure that a production project is completed efficiently and on time. the key steps in scheduling include defining the project scope and objectives, identifying tasks and activities, determine task dependencies, estimating durations, allocating resources, developing the production schedule, optimizing the schedule and monitoring and controlling the operations. defining the project scope and objectives involves identifying deliverables by clearly defining what the project aims to achieve and the specific deliverables expected at the end [1]. it also involves establishing clear, measurable objectives that align with the project goals. identifying tasks and activities includes breaking down work into smaller, manageable tasks or activities. it also involves defining the tasks in detail, including what needs to be done, who will do it, and any necessary resources. determining task dependencies involves identifying which tasks must be completed before others can begin. estimating durations involves estimating how long each task will take to complete, using historical data, expert judgement or statistical methods, including making provisions for time buffers that have high uncertainty or risk [2]. allocating resources involves assigning necessary resources such as people, equipment and materials to each task as well as identifying and addressing any resource constraints or limitations. developing the schedule involves using scheduling tools like gantt charts to create a visual timeline of the project as well as identifying key milestones that signify important progress points in the project [3]. optimizing the schedule involves identifying the longest path through the network diagram that determines the shortest possible project duration as well as making adjustments to balance the schedule, considering resource availability, task dependencies and deadlines [4]. monitoring and controlling future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.3.1 august 2024| volume 02 | issue 03 | pages 0105 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:ovundah.wofuru-nyenke@ust.edu.ng https://doi.org/10.55670/fpll.fusus.2.3.1 https://fupubco.com/fusus okw. nyenke /future sustainability august 2024| volume 02 | issue 03 | pages 01-05 2 involves tracking progress of tasks against the schedule, updating the schedule and communicating to stakeholders about the schedule status and any changes in the schedule. the critical path method (cpm) is a project management technique for identifying the critical path, which is the sequence of tasks that determines the minimum project duration. it is used in determining the sequence of activities that directly affects the project completion time. by identifying the critical path, project managers can focus on tasks that cannot be delayed without impacting the overall project schedule. the method has been utilized in several applications including manufacturing, construction, agriculture, healthcare etc [5-8]. cpm has numerous advantages including enhanced project planning, identification of critical activities that directly impact the project timeline, improved resource allocation to critical tasks, risk management since bottlenecks and delays are identified as well as provision of clear timelines for project completion, aiding in settling realistic deadlines. the limitations of cpm include complexity for large projects with many tasks and dependencies, rigidity and less flexibility for projects with high uncertainty or where tasks are not clearly defined, as well as the fact that resource limitations are not considered which might affect the schedule. the aim of this work is to utilize the cpm for scheduling activities in a product development project involving the manufacture of a new filing cabinet design considering design, promotion and selling price. the study provides a procedure for implementing the cpm project scheduling method for scheduling production activities in a product development project. 2. methodology this study utilizes the cpm for scheduling activities in a product development project. cpm is suitable for large and complex projects in which many tasks are involved and the interrelationships among these tasks must be taken into account. the method is useful for determining the minimum time in which a production project can be completed and to ascertain the tasks that are likely to delay this completion, by identifying the most time-consuming series of tasks, which represent the critical path [9]. the knowledge of the critical jobs can aid in eliminating the fairly common and costly practice of rushing all jobs to reduce the total project time. meanwhile, rushing only the critical jobs will have the desired effect of decreasing the total project time. the product development project involves the manufacture of a new filing cabinet design considering design, promotion and selling price. the project has been described in table 1. table 1 shows the jobs that must be performed, the immediate predecessor(s) for each job and the estimated time requirements. from table 1, jobs with not real predecessors are preceded by “start” and jobs with no real successors are followed by “finish”. both types of jobs do not require any time. after this phase of the cpm analysis, it is necessary to prepare a project graph. the project graph is useful for understanding the computations involved in the cpm analysis. the project graph is a pictorial representation of the jobs that make up a project and their interrelationships. in constructing the project graph, a rectangle is used to depict each job, and the rectangle will contain the letter or number identification of the job and the time estimated for its completion. from any one rectangle, arrows are drawn to all the immediate successor jobs. using the project graph, the minimum time required to complete the project can be ascertained. this is usually done by enumerating the different routes or paths that can be followed from the start to the finish of the project. the minimum amount of time required to complete the project will be determined by the most timeconsuming sequence of jobs, which constitute the critical path. a project graph showing the early start and finish times needs to be developed as well as a project graph showing the late start and finish times. in developing the early start and finish times project graph s is the earliest possible starting time for the project, es is the earliest possible starting time for a given job, t is the time required to complete a given job, ef = es + t is the earliest possible finish time for a given job, f is the earliest possible finish time for the project. in developing the late start and finish times project graph, t is the target completion time for the project or the latest possible finish time for the project, lf is the latest possible finish time for a given job if the target completion time t is to be met, t is the time required to complete a given job and ls = lf – t is the latest possible starting time for a given job if the target completion time t is to be met. table 1. product development project description 3. results and discussion the results of applying the cpm methodology described in section two (2) is presented in this section. two separate project graphs were developed for analyzing the project scheduling problem; the early start and finish times project graph as well as the late start and finish times project graph. the early start and finish times project graph is shown in figure 1. job description immediate predecessors required time (days) a start 0 b conduct initial market study a 25 c develop promotional ideas b 22 d estimate promotional costs c 16 e make initial pricing study b 29 f develop a detailed product design b 30 g manufacture prototypes f 14 h make necessary design changes g 12 i determine final selling price d, e, h 15 j finish i 0 okw. nyenke /future sustainability august 2024| volume 02 | issue 03 | pages 01-05 3 figure 1. early start and finish times project graph figure 2. late start and finish times project graph figure 1 shows the earliest points in time at which each job can be started and finished. from figure 1, beginning with the first job a, the earliest possible starting time for the project s is 0 days. because the time t for job a is 0 days, its early finish time ef will be the starting time of 0 days plus the required completion time of 0 days, which yields 0 days. next is job b which can be started no sooner than when its immediate predecessor a is finished, therefore its early start time es will be equal to its immediate predecessor’s early finish time which was found to be 0. to obtain the early finish time for job b, its early start time of 0 days is taken and added to the 25 days required to perform the job, thereby arriving at an early finish time of 25 days. the early finish time of 25 days for job b is the early start time for its immediate successors c, e, and f. the early finish time of job c is 47 days, the early start time for job d is the early finish time of its immediate predecessor job c, which is 47 days and the early finish time for job d is 63 days. the early finish time of job e is the early finish time of its predecessor plus the time taken to complete the job giving 54 days. the early finish time of job f is 55 days which is the early finish time of its predecessor plus the 30 days taken to complete the job. from the foregoing, the early finish time of job g is 69 days and the early finish time of job h is 81 days. on getting to job i, it can be seen that the job has three immediate successor jobs, d, e and h. moreover, jobs d, e and h have early finish times of 63 days, 54 days and 81 days. however, job i cannot be started until all three of its predecessor jobs are finished. therefore, the early start time of job i is governed by the early finish time of job h, because okw. nyenke /future sustainability august 2024| volume 02 | issue 03 | pages 01-05 4 it is the latest early finish time among the predecessor jobs. therefore, the early start time of job i is 81 days. the early finish time of job i is the early start time plus the 15 days required to complete the job, giving 96 days, which is the early start time of job j. finally, the early finish time of job j is the early start time of 96 days plus the 0 days required to complete the job which gives 96 days. the late start and finish times project graph is shown in figure 2. figure 2 shows the latest points in time at which each job must be started and finished if the target completion date is to be met. the procedure utilized in obtaining the desired late times is the opposite of the one followed to obtain the early start and finish times. therefore, we begin with the target completion time for the last job and work backward until we reach the late start time for the first job. the target completion time for the project is taken to be t = 96 days. given this late finish time of 96 days and a required time of 0 days to complete job j, the late start time for this job is the difference between those two times, giving 96 days. considering the preceding job i, the late finish time must be equal to the late start time of j. therefore, the late finish time is 96 days, and the late start time is 96 days minus the time required for job i. this process continues until job b where there are three (3) successors to the job namely c, e and f. these successors have late start times of 43 days, 52 days and 25 days, respectively, therefore the late finish time of job b will be governed by the late start time of job f. this is because it is the earliest and more demanding late start time. consequently, the late start times for jobs a and b become 0. table 2 shows the determination of slack times for the production project. from table 2, the slack time column contains the slack time in days for each job. this time is the difference between the late start time and the early start times for a job or between the late finish time and the early finish times for the job. the slack times represent the total allowable delay in the completion of all the jobs. therefore, the minimum allowable time for the project is 96 days. table 2. determination of slack times 4. conclusion the critical path method comprises of construction of project graphs, determination of critical path and calculation of job slack times. the method is useful for determining the probable completion dates of production projects, as well as developing alternative plans. it helps in identifying the sequence of jobs, which are the critical jobs, that determines the earliest possible completion date for the project. the knowledge of the critical jobs can aid in eliminating the fairly common and costly practice of rushing all jobs to reduce the total project time. meanwhile, rushing only the critical jobs will have the desired effect of decreasing the total project time. the knowledge of slack times associated with each job in the project is useful for developing work schedules. this study has utilized the critical path method for scheduling activities involved in the production of a new product by a metalworks manufacturing company. the project activities involved making an initial market study, developing promotional ideas, estimating promotional costs, conducting initial pricing study, preparing a detailed design, manufacturing prototypes, making design changes and determination of the final selling price of the product. the critical path analysis revealed that the minimum allowable time for the project is 96 days. this research provides a procedure for implementing the critical path method for production activities scheduling. further research can involve the utilization of other production scheduling methods such as the program evaluation and review technique (pert) for effective production activities scheduling. ethical issue the author is aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the author declares no potential conflict of interest. references [1] o.k. wofuru-nyenke, t.a. briggs, and d.o. aikhuele, advancements in sustainable manufacturing supply chain modelling: a review. process integration and optimization for sustainability, 2023. 7(1): pp. 3-27. [2] o. wofuru-nyenke and t. briggs, predicting demand in a bottled water supply chain using classical time series forecasting models. journal of future sustainability, 2022. 2(2): pp. 65-80. [3] k.u. ugoji, o.e. isaac, b. nkoi, and o. wofuru-nyenke, improving the operational output of marine vessel main engine system through cost reduction using reliability. international journal of engineering and modern technology (ijemt), 2022. 8(2): pp. 36-52. [4] o.k. wofuru-nyenke, b. nkoi, and f.e. oparadike, waste and cost reduction for a water bottling job possible start times possible finish times slack time (ls – es) or (lf – ef) earliest (es) latest (ls) earliest (ef) latest (lf) a 0 0 0 0 0 b 0 0 25 25 0 c 25 43 47 65 18 d 47 65 63 81 18 e 25 52 54 81 27 f 25 25 55 55 0 g 55 55 69 69 0 h 69 69 81 81 0 i 81 81 96 96 0 j 96 96 96 96 0 okw. nyenke /future sustainability august 2024| volume 02 | issue 03 | pages 01-05 5 process using lean six sigma. european journal of engineering and technology research, 2019. 4(12): pp. 71-77. [5] z. karaca and t. onargan, the application of critical path method (cpm) in workflow schema of marble processing plants. materials and manufacturing processes, 2007. 22(1): pp. 37-44. [6] s.n. rosli, n.y. mohd yassin, and s.n. ishak, critical path method and fuzzy logic for a project scheduling in basic t-shirt manufacturing. 2023, universiti teknologi mara, negeri sembilan. [7] x. huang, y. wong, z. liu, and z. qiu, critical-pathanalysis-based dynamic component supplier optimization. international journal of computer integrated manufacturing, 2005. 18(8): pp. 702-709. [8] o.k. wofuru-nyenke, mechanized cover crop farming: modern methods, equipment and technologies. circular agricultural systems, 2023. 3(1). [9] h. kerzner, project management: a systems approach to planning, scheduling, and controlling, 13th edition (2022), isbn: 978-1-119-80537-3. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 1 article validation of satellite-derived solar irradiance datasets: a case study in saudi arabia a. f. almarshoud department of ee, college of engineering, qassim university, saudi arabia a r t i c l e i n f o article history: received 01 december 2023 received in revised form 31 december 2023 accepted 07 january 2024 keywords: ghi prediction, solar irradiance prediction, solar irradiance estimation, satellite-derived irradiance *corresponding author email address: dr_almarshoud@qec.edu.sa dr_almarshoud@qu.edu.sa doi: 10.55670/fpll.fusus.2.2.1 a b s t r a c t a robust dataset of surface solar irradiance is essential for secure competitive financing for solar energy projects. rating agencies and lenders alike require verification of the solar-resource dataset for utilizing each solar energy project, as this can be translated directly into expected electrical energy and revenues. the accuracy of the dataset and the variability of solar radiation, as recorded by historical solar data, play a significant role in estimating the future performance of the project and its budget. the historical observed solar irradiance datasets by local stations are the best and most reliable for a specific site, but they are not always available for long and continuous periods in any location, especially in arid areas. so, the importance of historical solar radiation datasets derived from satellite-based models arises here. this paper validates the historical modeled datasets of the three most famous satellite-based commercial prediction models (solargis, suny, and solcast) against the observed dataset by six ground stations in saudi arabia under different climatic zones. the validation method has been implemented using the standard error metrics: maximum absolute error (mae) and relative maximum bias error (rmbe). the validation process showed that, in the case of ghi, the discrepancy between observed and predicted values is narrow, while in the case of dni, the discrepancy is wide. also, the predicted ghi values are more accurate than predicted dni values, and -in generalthe values predicted by the suny model are less accurate than those predicted by solargis and solcast models for both ghi and dni. the resultant of this validation process could be accepted not for the six locations under study only but, also for deserts and arid areas across saudi arabia and might be extended to similar arid areas around the world. 1. introduction the financing of large solar projects requires detailed diligence and allocation of technical and commercial risks; one of the principal risks is the knowledge of solar resources. the intermittent nature of the solar resource made its assessment essential for determining the performance of solar-power projects and securing financing for them in the long term. a robust dataset surface solar irradiance (ssi) is essential for secure competitive financing for solar energy projects. generally, financing communities consider solar resources to be stable on an annual basis when compared to other renewable energy resources. therefore, rating agencies and lenders alike require verification of the solar-resource dataset for utilizing each solar energy project, as this can be translated directly into expected electrical energy and revenues. the accuracy of the dataset and the variability of the solar radiation, as recorded by historical solar data, play significant roles in estimating the future performance of the project and its budget. information concluded from historical solar resource datasets may be used to make energy policy decisions, design solar energy systems for specific locations, choose optimum energy conversion technology, and operate installed solar energy projects. historical solar resource datasets may be the result of local measurement stations, satellite-based estimation methods, or numerical weather prediction methods. there is no doubt that the observed solar irradiance datasets by local stations are the best and most reliable for a specific site, but they are not always available for long and continuous periods in any location, especially arid areas. so, the importance of historical solar radiation datasets future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.2.1 may 2024| volume 02 | issue 02 | pages 01-07 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:dr_almarshoud@qec.edu.sa mailto:dr_almarshoud@qu.edu.sa https://doi.org/10.55670/fpll.fusus.2.2.1 https://fupubco.com/fusus a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 2 derived from satellite-based models arises here. in the last decade, the king abdullah city for atomic and renewable energy [1], as the lead saudi arabia governmental agency for renewable energy, has developed the renewable resource monitoring and mapping (rrmm) solar measurement network, which currently involves more than 50 metrological stations distributed over the area of saudi arabia. these metrological stations record the solar irradiance data in addition to other weather data; the details of the rrmm network are summarized in [2]. the rrmm network can be accessed via the saudi arabia renewable resource atlas website [1]. the rrmm currently has a historical dataset that reaches up to 7 years for most locations with high resolution. but these metrological stations are concentrated in the main cities and towns over the wide area of saudi arabia that reaches up to 2m km2; this means that the solar energy projects that are planned to be constructed in desert and arid areas are still suffering from a lack of reliable data of solar irradiance. so, the historical solar radiation datasets derived from satellite-based models are the only way to assess the performance of solar energy projects in arid areas. in this work, the researchers will validate three historically modeled datasets against ground measurements under different climatic zones in saudi arabia; if the validation result becomes acceptable, then we can depend on the modeled irradiance datasets for deserts and arid areas over saudi arabia; this is the aim of this study. 2. evolving of satellite-based solar irradiance estimation estimating surface solar irradiance (ssi) from satellites began in the 1960s with considerable errors in predicted data, but after 2000, satellite-based estimation of ssi had become increasingly mature, and many sensors have been employed. in addition to advances in sensors, many more sophisticated algorithms have been developed that take into account detailed radiative transfer processes. by these algorithms, multi-channel satellite observations are often combined to quantitatively determine the states of the surface and atmosphere. satellite data from several sources are also combined to compensate for gaps [3-8]. the algorithms to estimate ssi from satellite data may be classified into two categories: methods based on radiative transfer processes, which involve the acquisition of atmospheric spectral properties, and statistical methods that depend on the top of atmosphere reflectance observed by satellites, which is usually proportional to the cloud transmission such as heliosat method [9-11] and perez' method [12]. statistical methods are more frequently used to estimate ssi on longer timescales such as daily, monthly, or yearly. in general, statistical methods have good accuracy due to their tuning property. to date, mature high-resolution ssi datasets with global coverage are still rare except for specific regions or are available on the basis of one specific satellite like the geostationary operational environmental satellite [1316]. the accuracy of ssi substantially improves as the timescale increases, the accuracy of hourly ssi is always slightly better than of instantaneous ssi, and the monthly ssi is more accurate than daily ssi when compared with ground observations. also, the accuracy of ssi in clear-sky cases is better than cloudy-sky cases. moreover, there are a few commercial high-resolution ssi datasets with near-global coverage. for example, the solargis/sgis (https://solargis.com), the suny/solaranywhere (https://data.solaranywhere.com), and solcast (http://solcast.com). these commercial datasets are considered semi-empirical algorithms that typically include two operational models: the clear-sky and cloud-sky models. the early embodiment of semi-empirical models is referred to as the contribution of cano et al. [9], which evolved over the years into the heliosat model series [17-20]. these commercial datasets follow the same principle but differ in the source of data and in the fine details of operation models, so a difference in the accuracy of output data is expected. for more details about these commercial datasets [8, 21]. 3. validation methodology for the purpose of assessing the risk of solar-resource to support the project due diligence and financing, the most critical consideration is the total annual solar energy available in the location, which is typically characterized as total insolation (kwh/m2) or as daily average (kwh/m2/day) [21]. the type of solar irradiance to be estimated depends on the technology used for energy production. for concentrating solar power systems (csp) or concentrating photovoltaic (cpv), the direct normal irradiance (dni) must be estimated, while for the non-concentrating systems (pv), primarily global horizontal irradiance (ghi) must be estimated [21]. so, in this study, the historical dataset of (ghi & dni) will only be validated on a monthly basis as daily-average irradiation (kwh/m2/day). for this purpose, the historical solar datasets of three commercial models (solargis, suny, and solcast) have been selected to be validated with historical datasets of six ground observation stations. these stations cover several distinct climatic environments ranging from arid (buraydah) in the middle to humid (jeddah) on the west coast and (dhahran) on the east coast to cold (tabuk) in the northern, to warm (najran) in the southern to (taif) in top of mountains. the validation period spans about five years, from june 1, 2013, to august 1, 2018. table 1 illustrates the characteristics of the observation stations, and figure 1 shows their locations. figure 1. locations of selected observation stations a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 3 table 1. characteristics of selected observation locations location latitude longitude elevation avg. temp. o c annual ghi kwh/m2 annual dni kwh/m2 tabuk 28.38 o n 36.48 o e 781 m 23 2285 2617 jeddah 21.49 o n 39.24 o e 76 m 30.7 2117 1774 taif 21.43 o n 40.49 o e 1518 m 23.7 2310 2288 najran 17.63 o n 44.54 o e 1187 m 26.7 2449 2263 buraydah 26.34 o n 43.76 o e 688 m 26.5 2219 2055 dhahran 26.30 o n 50.14 o e 75 m 27.9 2037 1847 4. validation metrics various metrics have been proposed in the literature to quantify the accuracy of solar irradiance forecasts. overall bias and dispersion are the criteria that have been used to gauge the accuracy of solar irradiance models. the metrics recommended to quantify these criteria are the mean bias error (mbe) and its relative (rmbe) for quantifying the overall bias, and the root mean square error (rmse) and the mean absolute error (mae) for quantifying the dispersion [22, 23]. many researchers prefer the mean absolute error (mae) over the rmse as a measure of dispersion because it is less sensitive to distant outliers and less subject to interpretation when expressed as a percentage [21, 24]. so, in this study, the two error metrics (mae & rmbe) have been selected for the validation process and defined as [25]: 𝑀𝐴𝐸 = 1 𝑁 ∑ |�̂�𝑡 − 𝑦𝑡|𝑁 𝑡=1 (1) 𝑀𝐵𝐸 = 1 𝑁 ∑ �̂�𝑡 − 𝑦𝑡 𝑁 𝑡=1 (2) where �̂�𝑡 and 𝑦𝑡 are predictions and observations at time step t, respectively, and n is the total number of samples. then, 𝑟𝑀𝐵𝐸 = 100 𝑀𝐵𝐸 �̅� (3) where mbe is normalized by the mean of observations: �̅� = 1 𝑁 ∑ 𝑦𝑡 𝑁 𝑡=1 (4) 5. results and discussion the maximum absolute error (mae) for the ghi and dni has been calculated using formula (1), and the results are represented in figures 2 & 3 for all regions under study; it is clear from these two figures that the suny model has the highest mae value in most regions under study, while the sgis and solcast are the less. figures from (4) – (15) show the variation of observed values of ghi & dni and predicted ones of the three estimation models (sigs, suny, and solcast) in addition to the percentage of their relative main bias error rmbe for the six regions under study using formula (3). in tabuk city, figure 4 shows no significant difference between observed and predicted values of ghi for the three estimation models; this conclusion is clear from the small values of rmbe in most months. also, it is clear from the small values of mae shown in figure 2. while in the case of dni, as shown in figure 5, there are some differences between observed and predicted values in a few months, especially in the case of the suny model, where its rmbe may reach up to 16%. the values of the solcast model satisfy the best matching with observed values where its rmbe does not exceed 8%; this result is confirmed by the value of mae, as shown in figure 3. figure 2. maximum absolute error of ghi for locations under study figure 3. maximum absolute error of dni for locations under study figure 4. the relative maximum bias error of ghi for tabuk city in jeddah city, figure 6 shows no significant difference between observed and predicted values of ghi for the solcast model, but for suny and sgis models, the rmbe reached up to 14% and 9%, respectively. this big discrepancy between observed and predicted values in the case of suny and sgis models is confirmed by their mae shown in figure 2. in the case of dni, as shown in figure 7, sgis and solcast models are in the best matching with observed values for most of the year, but suny model values are very far, with rmbe reaching a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 4 up to 45%; this result is confirmed by the value of mae as shown in figure 3 (taif city: figure 8 and figure 9). figure 5. the relative maximum bias error of dni for tabuk city figure 6. the relative maximum bias error of ghi for jeddah city figure 7. the relative maximum bias error of dni for jeddah city in najran city, figure 10 shows no significant difference between observed and predicted values of ghi for all models most of the year in general; the best matching is done by the suny model, while the maximum rmbe is done by the solcast model. the mae values in figure 2 show the superiority of the suny model in this case. in the case of dni, as shown in figure 11, sgis and solcast are close to observed values most of the year, with rmbe reaching up to 16%, but the suny model did the best matching for half of the year and in another half did the worst with rmbe reaches to 38%, this result is confirmed by its mae value which reaches up to 1.6 kwh as shown in figure 3. figure 8. the relative maximum bias error of ghi for taif city figure 9. the relative maximum bias error of dni for taif city figure 10. the relative maximum bias error of ghi for najran city in buraydah city, figure 12 shows no significant difference between observed and predicted values of ghi all the year for sgis and solcast models and most of the year for suny models where the rmbe is less than 10% for all models. the mae values in figure 2 confirm this conclusion. in the case of dni, as shown in figure 13, the rmbe is less than 15% for all models in the second half of the year, while in the first half, it reaches high values: 45% for suny, 28% for sgis and 25% for solcast. figure 13 shows the superiority of sgis and solcast models over the suny model in this case. a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 5 figure 11. the relative maximum bias error of dni for najran city figure 12. the relative maximum bias error of ghi for buraydah city figure 13. the relative maximum bias error of dni for buraydah city in dhahran city, figure 14 shows the best matching was done by sgis with rmbe less than 8%, then solcast with rmbe less than 11%, while suny did the worst matching with rmbe which reaches up to 18%, the mae in figure 2 confirms the superiority of sgis and solcast in this case. regarding dni, figure 15 shows a high discrepancy for all models; the rmbe reaches up to 45% for suny, 28% for solcast, and 18% for sgis; this result is confirmed by their mae values in figure 3, which reaches up to 2.2 kwh for suny model. figure 14. the relative maximum bias error of ghi for dhahran city figure 15. the relative maximum bias error of dni for dhahran city 6. conclusions the historical predicted solar irradiance datasets for the last five years of six locations across saudi arabia have been validated against the observed dataset by local stations for the same period. the validation process has been implemented using the standard error metrics: maximum absolute error (mae) and relative maximum bias error (rmbe). the predicted data sets have been collected from the most famous commercial solar irradiance datasets: solargis, suny, and solcast. the validation process showed that, in the case of ghi, the discrepancy between observed and predicted values is narrow, its rmbe is in the range of 10%, and its mae is less than 0.6 kwh, especially for solargis and solcast models, while in the case of dni, the discrepancy between observed and predicted values is wide, especially in case of suny model which its rmbe reaches up to 45%, and its mae reaches up to 2.2 kwh. so, the ghi-predicted values are more accurate than the dni-predicted values, and the values predicted by the suny model are less accurate than those predicted by solargis and solcast models for both ghi and dni. it is clear from these results that ghi values, especially those predicted by solargis and solcast, can be accepted not only for locations under study but also for deserts and arid areas across saudi arabia. is this conclusion valid for the whole globe? we think it is valid for deserts that are less cloudy between the cancer and capricorn lines. a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 6 acknowledgment researchers would like to thank all the entities who provided us with data used in this research: the king abdullah city for atomic and renewable energy k.a. care (http:// rratlas.energy.gov.sa), solargis (https://solargis.com), suny (https://data.solaranywhere.com), and solcast (http://solcast.com). ethical issue the author is aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the author declares no potential conflict of interest. references [1] k.a.care. renewable resource atlas, king abdullah city for atomic and renewable energy (k.a.care), saudi arabia, 〈http:// rratlas.energy.gov.sa〉. 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[10] qu, z., oumbe, a., blanc, p., lefevre, m., wald, l. 2012. a new method for assessing surface solar irradiance: heliosat-4. in: geophysical research abstracts. [11] rigollier, c., lefevre, m., wald, l. 2004. the method heliosat-2 for deriving shortwave solar radiation from satellite images. sol. energy 77:159–169. [12] perez, r., schlemmer, j., hemker, k., kivalov, s., kankiewicz, a., gueymard, c. 2015. satellite-toirradiance modeling a new version of the suny model. in: ieee 42nd photovoltaic specialist conference. [13] bisht, g., venturini, v., islam, s., jiang, l. 2005. estimation of the net radiation using modis (moderate resolution imaging spectroradiometer) data for clear sky days. remote sens. environ. 97:52– 67. [14] hollmann, r., mueller, r.w., gratzki, a., 2006. cm-saf surface radiation budget: first results with avhrr data. atmospheric remote sensing: earth's surface, troposphere, stratosphere and mesosphere ii 37:2166–2171. [15] deneke, h.m., feijt, a.j., roebeling, r.a., 2008. estimating surface solar irradiance from meteosat seviri-derived cloud properties. remote sens. environ 112:3131–3141. [16] forman, b.a., margulis, s.a., 2009. high-resolution satellite-based cloud-coupled estimates of total downwelling surface radiation for hydrologic modelling applications. hydrol. earth syst. sci. 13:969–986. [17] beyer, h.g., costanzo, c., heinemann, d., 1996. modifications of the heliosat procedure for irradiance estimates from satellite images. sol. energy 56:207– 212. [18] schillings, c., mannstein, h. and meyer, r., 2004. operational method for deriving high resolution direct normal irradiance from satellite data. solar energy 76:475‐484. [19] perez, r., ineichen, p., moore, k., kmiecik, m., chain, c., george, r., vignola, f., 2002. a new operational model for satellite-derived irradiances: description and validation. sol. energy 73: 307–317. [20] cebecauer, t. and suri, m., 2010. accuracy improvements of satellite‐derived solar resource based on gems re‐nnalysis aerosols. proceedings of: solarpaces 2010 conf., perpignan, france. [21] jan kleissl. 2013. solar energy forecasting and resource assessment. elsevier inc, 1st edition. [22] espinar, b., ramı ´ rez, l., drews, a., beyer, h.g., zarzalejo, l., polo, j., martı ´ n, l. 2009. analysis of different comparison parameters applied to solar radiation data from satellite and german radiometric stations. solar energy 83 (1):118–125. [23] meyer, r., gueymard, c., ineichen, p. 2011. proceedings of solarpaces conference. stan dardizing and benchmarking of modeled dni data products. granada. [24] hoff, t.e., perez, r. 2012. predicting short-term variability of high-penetration pv. proc. world https://doi.org/10.1016/j.rse.2019.111371 a. f. almarshoud /future sustainability may 2024| volume 02 | issue 02 | pages 01-07 7 renewable energy forum (ases annual conference), may, denver, co. [25] jamie m. bright, 2019. solcast: validation of a satellite-derived solar irradiance dataset. solar energy, vol (189), 435-449. https://doi.org/10.1016/j.solener.2019.07.086 a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 23 article study of temperature cycling of commercial rechargeable lithium-ion batteries aoyon paul, md. arafat rahman*, nirjhor barua department of mechanical engineering, chittagong university of engineering and technology, chittagong-4349, bangladesh a r t i c l e i n f o article history: received 02 september 2023 received in revised form 03 october 2023 accepted 09 october 2023 keywords: battery cycling, capacity fade, temperature effects, lithium-ion battery *corresponding author email address: arafat@cuet.ac.bd doi: 10.55670/fpll.fusus.1.1.3 a b s t r a c t lithium-ion batteries, a popular electric energy storage device, have high energy density and impressive working performance. however, the temperature affects its life cycle, capacity, and performance. different effects are generated inside the battery for the different temperature conditions. it is necessary to study their thermal and electric characteristics in various thermal conditions since electric energy storage devices are used in various applications at low or high temperatures. in this study, the experimental analysis was performed to observe how a battery cell behaves above room temperature for a different 18650 cylindrical battery cell with a capacity of 5200 mah. the testing temperature for this experiment was at 28˚c, 50˚c, 60˚c, 70˚c, and 100˚c. it is noted that the capacity of the battery cell fades drastically at high temperatures compared to low temperatures due to internal short circuits occurring at high temperatures. 1. introduction a battery, an energy storage device, is one of the most important parts of electrical gadgets, where electrochemical reactions occur and produce electricity [1, 2]. the battery business went through an evolution when sony corporation unveiled the first commercial lib in 1991 [3]. an anode made of carbon, a cathode based on lithium compounds, an electrolyte, and a separator make up a typical lib. the majority of studies into libs have focused on identifying the optimum electrode material in terms of specific energy, cycle life, capacity, and power, with little emphasis devoted to temperature control [4]. at high temperatures, libs performance degrades due to thermal runaway, aging, etc. feng et al. [5] observed in their experiment that at high temperatures, the rates of deterioration of all lib components increase. however, on the other hand, at low temperatures due to low kinematics, the battery performance is found limited [6]. hence, it is very important to study the temperature effect on a lithium-ion battery and find an optimum safe operating temperature range. complex electrochemical changes take place during the charging and discharging of a lib with a significant amount of heat release. the performance, longevity, as well as safety of a lithium-ion battery, are affected by the operating or ambient temperature [7, 8]. in addition, temperature affects the ionic conductivities of electrodes and electrolytes [9]. the properties of electrolytes are affected when the battery is exposed to cold temperatures. at low temperatures, the internal resistance of the electrolyte rises due to its viscosity. as a result, the lithium-ion diffusivity and the electrolyte's ionic conductivity, power, and capacity of the cell decrease [10– 12]. the charge transfer resistance (rct) is one of the most significant factors that also increases at low temperatures [6]. zhang et al. interpreted in their experiment that it is more difficult to charge a drained li-ion battery than it is to discharge a charged battery at a low temperature [6]. petzl et al. [13] demonstrated that at low temperatures, lithium plating occurs. lithium plating can penetrate separators and reduce capacity. these lithium dendrites, which are located on the surface of the negative electrode of libs, cause an internal short circuit [14]. however, high temperatures impair the performance of lithium-ion batteries more than low temperatures. at room or standard operating temperature, electrochemical reactions and charge transfer produce heat inside the battery [15]. irreversible processes such as heating due to mixing, polarization, enthalpy change, etc. are also responsible for generating heat. xiao and choe proposed a completely new heat generation formulation, which incorporates enthalpy heating and heat of mixing [15]. the thermal runway is another destructive phenomenon for a lithium-ion battery. it occurs when the heat formed inside a battery surpasses the quantity of heat released to its surroundings [16]. in figure 1 thermal runaway process of a libs cell is illustrated. at high temperatures, exothermic future sustainability open access journal https://doi.org/10.55670/fpll.fusus.1.1.3 november 2023| volume 01 | issue 01 | pages 23-31 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:arafat@cuet.ac.bd https://doi.org/10.55670/fpll.fusus.1.1.3 https://fupubco.com/fusus a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 24 reactions occur in the battery, and uncontrollable heat is produced. in addition to that, internal pressure is increased due to the production of some gaseous elements. as a result, exploration would occur [17]. feng et al. [18] observed that during thermal runaway, the internal temperature was increased above 870˚c, and the temperature difference was approximately 520˚c inside the tested battery. depending on the battery cells' chemistry, charge level, and the exothermic processes that cause thermal runaway have different onset temperatures. typically, the lower the initiation temperature for thermal runaway, the greater the cell voltage or state of charge [19]. figure 1. lithium-ion battery cell's thermal runaway process (here numbers represent: 1-heating begins, 2-protecting layer disintegrates, 3-flammable gas is formed when electrolytes break, 4separator melts may result in short circuits, 5-cathode disintegrates and produces oxygen) at high temperatures, lib's lifespan, as well as performance, are reduced due to aging. leng et al. found by their investigation that when a sony prismatic lithium-ion battery was aged from 25˚c to 55˚c, its capacity decreased due to the temperature effects [20]. the measuring techniques of a battery's internal temperatures are more convoluted compared to the surface temperature due to its multilayered structures. however, using thermocouples and thermal imaging systems, the surface temperature of libs can be easily measured [21]. to detect the temperature by contact measurement, temperature sensors such as fiber bragg grating (fbg) sensors or thermocouples are placed within libs. however, the structural integrity of libs can be damaged by the insertion of heat sensors [22]. that’s why electrochemical impedance-based and modeling simulation techniques are developed to eliminate the damage to the internal structure of the libs. the thermal model and the thermal-electric model are the two numerical models that were developed by the researchers for determining the internal temperature of libs. in the thermal model, only thermal and in the thermal-electric model, thermal as well as electric characteristics inside batteries can be predicted [23, 24]. electrochemical impedance spectroscopy (eis) is another technique for determining the electrochemical impedance of an electrochemical system using a frequencyvarying sinusoidal current. the internal temperature and soc of libs can be monitored using eis simulation software [25]. it is noted that a lithium-ion battery's life cycle, performance, power, capacity, and other properties are all influenced by temperature. figure 2. schematic diagram of the experimental setup (here number represents: 1-desktop computer, 2-land battery testing system, 3magnetic stirrer with a hot plate, 4-glass box, 5-18650 cylindrical li-ion battery, 6-thermometer, and 7-stand) a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 25 there is a chance to develop new technologies that would reduce the impact of temperature on libs, and the performance of the libs can be enhanced by using different nanomaterials and porous materials as the anode of libs [2,26–32]. additionally, studying how temperature affects libs is essential for security concerns. in this study, the cycling behaviors of a ‘18650 lithium-ion battery’ cell under different temperature conditions are explored experimentally. in the battery industry, performing experiments at a high temperature is a challenging task and highly sought-after. the battery has been tested at 28˚c, 50˚c, 60˚c, 70˚c, and 100˚c. the properties of the battery obtained at higher temperatures are compared with the properties obtained at room temperature. 2. experimental setup the investigation was carried out to study the cyclic performance of 18650 cylindrical li-ion battery cells according to a systematic process, which is illustrated in figure 2. the maximum capacity of the cell was 5200mah. during the experiment, the battery cell was connected to the “land” battery testing system. initially, the data were collected at room temperature. then, the heater was turned on to create an environment above the room temperature to collect data at 50˚c, 60˚c, 70˚c, and 100˚c. the heater was enclosed with a glass box to maintain a constant temperature. to measure the temperature, a thermometer and a thermocouple were set near the battery. batteries charging and discharging were controlled by the land battery testing system. 3. results and discussion figure 3 illustrates the typical v-t and i-t curves of twenty cycles for a li-ion battery in the charge-discharge test at room temperature (28°c), where the red color line indicates the voltage change and the blue color line indicates the current change during the cycling. from the beginning to the end of the charging-discharging operations, there were four sudden voltage (v) fluctuations occurred in each cycle, which is illustrated in figure 4. figure 3. voltage and current vs. test time at room temperature (28°c) at the very beginning, when a new charge-discharge cycle starts, the cell is first charged at a constant voltage for 10 minutes. then a sudden voltage peak arises during a constant current charging condition. a micro-level internal short circuit may have occurred at this moment. after the charging process was complete, the constant current discharge process began. voltage dropped gradually at this stage. during the rest period of the cell of 2 minutes, the voltage was increased from 1.7v to 2.5v. figure 4. voltage changes over time for one cycle figures 5 to 7 illustrate the discharging voltage versus capacity change of the battery cell at 28˚c, 50˚c, 60˚c, 70˚c, and 100˚c, respectively. for each case, the voltage range was between 1.7v to 3.7v; however, the capacity change was different. figure 5 depicts the discharging data of a fully discharged cell that was kept at room temperature and 50˚c. from cycle 1 to 20, capacity was fading slowly when the cell was at room temperature, which is shown in figure 5(a). after analyzing figure 5 (b), it can be said that, during the first cycle of discharging, the capacity of the cell was around 75mah. but, from the first cycle to the second cycle, capacity fades almost 25%. analyzing the curves of the discharging voltage from figures 6 to 7, it can be said that above the room temperature, the battery's capacity decreased by almost 66.67%, 75%, and 77% from the first cycle to the second cycle when the cell temperature was 60˚c, 70˚c and 100˚c, respectively. the capacity-reducing phenomena may have occurred due to the solid electrolyte interphase (sei) layer formation in the anode [31–33], or maybe the li-ion did not get enough time to move from one electrode to the other during the cycling operation. when the cell was discharged at 100˚c, the internal short circuit occurred at the 16th cycle, as shown in figure 7. a large capacity drop was observed between cycle 15 to cycle 17. the cell slightly recovered its lost capacity after the internal short circuit in cycle 17. figure 8 depicts the discharging voltage over capacity at cycles 1,10, and 20. it also demonstrates that there is a large capacity gap between the first and the last cycle. however, the capacity difference gap decreases when the temperature gets higher and higher between cycle 10 and cycle 20. figures 9 to 10 depict the charging and discharging capacity and efficiency vs. cycle number at room temperature (28˚c), 50˚c, 60˚c, 70˚c, and 100˚c, respectively. the efficiency discussed here is the coulombic efficiency, also known as faradaic efficiency. it is defined as the total charge extracted from the battery to the total charge put into the battery over a full cycle. for each case, the coulombic efficiency (ce) was escalated above 100%. figure 9(a) depicts that the charging and the discharging capacity fade gradually when the cell is at room temperature, although the efficiency increases slightly. from figure 9(b), it can be concluded that the cell behaves anomalously when it is at 50˚c. at cycles 8 and 16, the coulombic efficiency suddenly increased. figures 9(c) and 9(d) exhibit the cyclic performance at 60˚c and 70˚c, respectively. a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 26 figure 5. voltage and capacity change during discharging at (a) room temperature and (b) 50˚c figure 7. voltage and capacity change during discharging at 100˚c figure 6. voltage and capacity change during discharging at (a) 60˚c and (b) 70˚c a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 27 figure 8. discharging voltage vs capacity of cycles 1, 10, and 20 at (a) room temperature (b) 50˚c (c) 60˚c (d) 70˚c (e) 100˚c a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 28 figure 9. cyclic performance at (a) room temperature, (b) 50˚c, (c) 60˚c, (d) 70˚c figure 10. cyclic performance at 100˚c a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 29 figure 11. cvc, ccd for cycles 1,2 and 20 at (a) room temperature (b) 50˚c (c) 60˚c (d) 70˚c (e) 100 ˚c a. paul et al. /future sustainability november 2023| volume 01 | issue 01 | pages 23-31 30 a sudden pick was observed during the 16th cycle when the cell was at 60˚c. but a sudden drop was observed during the 19th cycle for 70˚c. the discharging capacity, as well as the charging capacity, changed in this case. these may have occurred due to the internal short circuit that occurred inside the battery cell. at high temperatures, the electrolyte may be decomposed by the exothermic reaction; as a result, an internal short circuit of a battery occurs when the two electrode materials are internally and electronically interconnected, resulting in high local current densities. these internal short circuits in lithium-ion batteries can happen as a result of lithium dendrite formation or a compressive shock [31]. the battery cell also behaves anomalously when it is cycling at 100˚c, as shown in figure 10. a sudden increase and decrease in coulombic efficiency were observed. some major abnormality was seen in cycles 4, 8, and 16. this phenomenon may have happened due to an internal short circuit inside the battery cell [31]. the battery's internal exothermic reaction, as well as the environmental high temperature, were responsible for the internal short circuit. the cell capacity may be decreased due to the internal short circuit or other phenomena inside the battery cell, such as severe volume changes during lithiation and delithiation, resulting in inadequate cyclability and ultimate electrode failure [29]. this phenomenon also affects the performance as well as the cycle life of the battery cell. from figure 11, it can be concluded that the battery discharged rapidly at the 20th cycle compared to the 1st cycle. 4. conclusion the charging and discharging characteristics of a li-ion battery for 20 cycles at different temperatures have been analyzed. observing how a battery cell behaves above room temperature was the main purpose of this study. the findings of this study can be concluded as follows: • from the temperature of 50˚c to 100 ˚c, there was a sudden capacity drop observed between the first and the second cycle. • during charging at a constant current, a sudden voltage peak was detected. this phenomenon occurs due to the micro-level internal short circuit. • discharging capacity faded above the room temperature. the range of the capacity decreased from the first to the last cycle as the cell was exposed to a higher temperature. • internal short circuit occurred above 70˚c. these may occur due to the decomposition of the electrolyte for an exothermic reaction. • the lifetime of the cell decreased at higher temperatures. acknowledgment this work is financially co-supported by chittagong university of engineering & technology (cuet) and the university grants commission of bangladesh-grant no. 37.01. 0000.73.06.065.22.1607. the corresponding author is responsible for ensuring that the descriptions are accurate and agreed upon by all authors. 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[33] horstmann b, single f, latz a. review on multi-scale models of solid-electrolyte interphase formation. curr opin electrochem 2019;13:61–9. https://doi.org/10.1016/j.coelec.2018.10.013. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 8 article numerical simulation study on fire combustion of advertising board materials in airport terminals xiaohong gui*, jiaojiao wu, zheng min, wei xue china university of mining and technology (beijing), beijing 100083, china a r t i c l e i n f o article history: received 15 september 2024 received in revised form 18 october 2024 accepted 25 october 2024 keywords: advertising board, fire, smoke, numerical simulation *corresponding author email address: gxhbox@sina.com doi: 10.55670/fpll.fusus.2.4.2 a b s t r a c t in order to meet the guidance, publicity, and commercial functions, various types of billboards have become important permanent facilities in the airport terminal, which are distributed all over the terminal. the advertising materials inside billboards have certain fire hazards, and there is a lack of research on the fire risk of advertising materials at present. therefore, it is necessary to study the fire risk of advertising materials in airport terminals. taking pvc board, a commonly used advertising material, as the research object, pyrosim was used to model and analyze its fire, and the characteristics of fire spread, smoke flow, and distribution of combustion products such as co and co2 in the terminal building were obtained. this study explores the fire combustion characteristics of advertising materials in civil airport terminals, providing a basis for fire prevention management in civil airport terminals. 1. introduction the airport terminal is an important large-scale infrastructure for civil aviation transportation and urban construction. as the most crowded area of the airport, once a fire accident occurs, it will directly affect the airport terminal's normal operation and personnel travel [1-3]. the occurrence of an airport fire has strong suddenness, uncertainty, and consequences [4, 5]. because the types of combustibles in each public area of the airport terminal are different. these combustibles have different geometric thicknesses, ignition temperatures, thermal conductivity, unit heat release, and smoke release characteristics. there are different fire potential and combustion characteristics in the combustion process. therefore, it is necessary to evaluate the fire risk of different functional areas of the terminal building and study the combustion characteristics of different types of combustibles to improve the performance of the fire safety system of the terminal building [4-7]. based on the fire occurrence process of different functional areas, many scholars have carried out different material ignition points to study the smoke occurrence and fire spread during the fire occurrence of the airport terminal. yuan et al. [4] used fds to conduct full-scale modeling and numerical simulation of store shelves, bookstore shelves, check-in common seats, and business desks and chairs in civil airport terminals. they analyzed the correlation between fire load and temperature. song et al. [8] used fds to simulate the fire at the airport terminal and obtained the parameters of smoke spread, temperature, co2, and co under two conditions with or without a spray system. the simulation results accurately reflect the dynamic process of fire and provide support for the formulation of an airport fire emergency plan. hu et al. [9] used cfast and fds to simulate the smoke-filling process in the domestic boarding-arrival channel with an aspect ratio of about 52.3 at the international airport terminal. the flame impact time, smoke temperature distribution, and temperature distribution of the airport fire were predicted. men et al. [10] simulated the smoke dispersion pattern and control effect of each terminal floor under the existing smoke control strategy through fds. the results show that the current smoke strategy of the airport terminal is reasonable, which can achieve effective smoke exhaust in the fire scene and ensure the safety of personnel. dong yao [11] analyzed the terminal building from the structure, use, and internal combustibles of the airport building, evaluated the risk of fire and whether the prevention and control technology was effective, analyzed the evacuation characteristics and evacuation safety, reduced losses and environmental protection, and proposed corresponding improvement measures. song yang et al. [8] analyzed the layout of the building in the terminal building. when the mechanical smoke exhaust system was not started in time, a fire occurred during the peak period of the flow of people, and the evacuation was not affected by thermal radiation. however, the smoke height future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.4.2 november 2024| volume 02 | issue 04 | pages 0814 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:gxhbox@sina.com https://doi.org/10.55670/fpll.fusus.2.4.2 https://fupubco.com/fusus x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 9 decreased faster, which would pose a significant threat to safety. the above scholars have simulated fire accidents in airport terminals for different functional areas of the airport. however, in recent years, many fire accidents have occurred at home and abroad due to the burning of billboards in airport terminals. this kind of fire has greater fire hazards and more serious consequences. this article establishes a partial model of the terminal building based on the actual situation of the airport, which is widely used in commercial advertising. taking pvc board, a commonly used advertising material, as the research object, pyrosim is used to model and analyze its fire, and the characteristics of fire spread and smoke flow in the terminal building were obtained. this study can fill the gap in research on the combustion characteristics of advertising materials, provide ideas and references for the fire hazard assessment of similar materials, and provide theoretical support and reference for the fire safety management and legal regulations of airport terminals. 2. combustion model 2.1 combustion material model solid materials can be divided into thin and thick materials according to their thickness. thin materials refer to materials that are thin enough to ignore temperature gradients in the thickness direction, assuming that the temperature of the material is equal in the thickness direction. materials with a thickness of less than 3mm under normal conditions can be considered thin materials. the thickness of advertising materials is generally below 2mm, which meets the definition of thin materials. therefore, the combustion model of advertising materials is consistent with that of thin materials. if the heating condition is that one side of the thin material is heated while the other side is insulated, the ignition time is: 𝑡𝑖𝑔 = 𝑑𝜌𝑐 ℎ . 𝑙𝑛 ( 𝑇𝑓−𝑇0 𝑇𝑓−𝑇𝑖𝑔 ) (1) if the heating condition is that one side of the thin material is heated while the other side is not heated, the ignition time is: 𝑡𝑖𝑔 = 𝑑𝜌𝑐 ℎ ⋅ 𝑙𝑛 ( 𝑇𝑓−𝑇0 𝑇𝑓+𝑇0−2𝑇𝑖𝑔 ) (2) in the formula， is the ignition time, s; d is the material thickness, m; h is the convection heat transfer coefficient, kw / (m2.k); c is the heat capacity, j / (kg.k); 𝜌 is the material density, kg/m3; is the initial temperature of the material surface, ℃; is the material ignition temperature, ℃; is the heating temperature of the material surface, ℃. 2.2 pyrosim model establishment the terminal building modeled in this article mainly uses high-performance reinforced concrete, steel pipes, and aluminum components, while the ground advertising materials are mainly pvc boards. establish a local pyrosim model for its basement level, as shown in figure 1. based on the actual structural characteristics of the area, the grid setting conditions are determined as follows: the minimum value of the x-axis is 322 m, and the maximum value is 430 m. the minimum value on the y-axis is 136m, and the maximum value is 197 m. the minimum value of the zaxis is -6 m, and the maximum value is 0 m. a cube grid has been established, with individual grid sizes of 0.5m × 0.5m × 0.5m, totaling 316224. the actual size of the model is around 6000 m2. 2.3 analysis model the main component of pvc board is polyvinyl chloride. according to its combustion reaction equation: fuel + air = products in the formula, fuel is c2h3cl, air is 1.53o2 + 5.76n2 and products is hcl + h2o + 0.14co + 0.96co2 + 0.9c + 5.76n2. setting c2h3cl as the combustion reactant, according to its combustion characteristics, its combustion phenomenon is more intense, and the heat release is greater. the model environment temperature is set to room temperature of 20 ℃, atmospheric pressure of 1atm, reaction combustion heat of 16400 kj/kg, and hrrpua of 750 kw/m2. the fire source is set on the surface of the pvc advertising decorative floor on the basement level of the terminal building, on a twodimensional plane with a size of 2m × 3m. there are a total of 2 fire sources, with a color of dark brown and red. the location of the fire source is shown in the model in figure 1. in addition, pvc advertising decorative flooring is shown as pink flooring in figure 1. figure 1. model scaling sample 2.4 model parameters this article mainly measures the distribution of carbon monoxide concentration, fire temperature distribution, carbon dioxide concentration distribution, corresponding conditions of the automatic sprinkler system, and smoke distribution on the underground floor of the terminal building. install a smoke concentration slice at the aisle with y=158 to detect the distribution of smoke concentration in the hall; install a temperature slice at the aisle with y=190 to detect temperature changes in the aisle; install carbon monoxide concentration detectors at x=330m, y=158m, z=2m and x=396m, y=178m, z=-2m respectively to detect changes in carbon monoxide concentration at the ignition point and entrance of the hall. install a carbon dioxide concentration detector at x=423m, y=182m, z=-2m and x=327m, y=193m, z=-2m, respectively, to detect the concentration changes of carbon dioxide at the entrance and exit of the aisle. the placement of each slice and detection device is shown in figure 2. 3. results and discussions 3.1 automatic sprinkler fire extinguishing system according to the fire safety technical specifications, if the terminal building with less than 15000m2 is equipped with combustible advertising materials, it should also be equipped with an automatic sprinkler fire extinguishing system. igt 0t igt ft x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 10 according to relevant regulations, the building hazard level is medium hazard level, and the water spray intensity is set to at least 6l/(min · m2). this article designs two sets of automatic sprinkler fire extinguishing systems based on different water spray intensities, referred to as system a and system b. the water spray intensity of system a is set to 6l/(min · m2), and the water spray intensity of system b is set to 8l/(min · m2). figure 2. layout of detection device 3.1.1 system parameters and modeling according to the actual situation of the building, automatic sprinkler system a adopts a hanging and expanded coverage type nozzle arranged in a square shape. a nozzle flow coefficient k=100, working pressure 0.1 mpa, spray flow rate 100 l/min. then the nozzle spacing a, a=(100/6)0.5=4.08m minimum spray radius of nozzle c, c=4.080.5=2.02m according to the specifications, the distance between the nozzle and the wall is set between 0.1m and 2.4 m, and the nozzle is set at 0.1 m from the top plate. therefore, the distance between the nozzle and the underground floor is 5.9 m. due to the maximum protection area of the nozzle being 23 m2, the maximum protection radius of the nozzle is r, r=(23/π)0.5=2.70m the actual spray radius r of the nozzle should meet the following requirements, 2.02≤r≤2.70 the spray angle θ should meet the following requirements, θmin≥acrtan（2.02/5.9）≈19° θmax≤acrtan（2.70/5.9）≈24° so, the injection angle θ∈ [19 °, 24 °] is taken as θ=20 °. set the starting temperature of the nozzle to room temperature of 20 ℃ and the starting temperature to 74 ℃. the main parameters of the automatic sprinkler fire extinguishing system have been set, and the remaining parameters are set to the default values of the system. the pyrosim model is established as shown in figure 3. 3.1.2 parameters and modeling of system b analogous to system a, system b also uses a drooping, expanded coverage nozzle with a square layout. a nozzle flow coefficient k=100, working pressure 0.1mpa, spray flow rate 100l/min. then, the nozzle spacing a is a=(100/8)0.5=3.54m. the minimum spray radius of nozzle c is c=3.540.5=1.88m. according to the specifications, the distance between the nozzle and the wall is set between 0.1m and 2.4 m, and the nozzle is set at 0.1 m from the top plate. therefore, the distance between the nozzle and the underground floor is 5.9 m. due to the maximum protection area of the nozzle being 23 m2, the maximum protection radius r of the nozzle is, r=(23/π)0.5=2.70 m the actual spray radius r of the nozzle should meet the following requirements, 1.88≤r≤2.70 the spray angle θ should meet the following requirements, θmin≥acrtan（1.88/5.9）≈18° θmax≤acrtan（2.70/5.9）≈24° so, the injection angle θ∈ [18 °, 24 °] is taken as θ=20 °. set the starting temperature of the nozzle to room temperature of 20 ℃ and the starting temperature to 74 ℃. the main parameters of the automatic sprinkler fire extinguishing system have been set, and the remaining parameters are set to the default values of the system. the pyrosim model is established as shown in figure 4. figure 3. the model of system a figure 4. the model of system b 3.2 fire scene parameter simulation and analysis 3.2.1 simulation and analysis of system a according to the 3d fire simulation animation in smokeview, it is found that when the pvc advertising decorative panel on the ground starts to burn, the smoke of the fire first spreads vertically. after contacting the top plate, the smoke from the top begins to spread horizontally in all directions, forming a roof jet phenomenon. at t=10s, the smoke generated by the burning point in the hall begins to spread to the right side of the open hall due to the obstruction of the surrounding walls. the smoke generated by the burning point in the aisle not only spreads to both sides of the aisle but also to the entrance of the hall, as shown in figure 5. at t=30 s, the smoke has spread to half of the hall, but the smoke concentration at the entrance is relatively low, as shown in figure 6. the smoke in the aisle has taken up most x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 11 of the space and is blocked by buildings, such as the wall and door on the right side of the aisle. figure 5. smoke spreads at t=10 s figure 6. smoke spreads at t=30 s at t=45 s, the smoke in the hall has occupied about most of the space and is about to spread throughout the entire hall. in addition, smoke has spread to the left entrance and exit in the hallway, as shown in figure 7. at t=88s, the entire model is completely covered by smoke except for the areas enclosed by smoke prevention and control facilities, such as walls and doors, as shown in figure 8. figure 7. smoke spreads at t=45 s figure 8. smoke spreads at t=88 s 3.2.2 simulation and analysis of system b it is not difficult to observe in the 3d fire simulation animation in smokeview that the combustion phenomenon of pvc advertising decorative panels in system b is similar to that in system a. at t=10 s, the smoke generated by the pvc advertising decorative panel spreads vertically to the top plate, forming a ceiling jet, and the smoke gradually spreads horizontally, as shown in figure 9. at t=31s, smoke occupies about half of the space in the hall, and the smoke generated by the entrance walkway covers it. the smoke in the aisle is similar to the situation of system a, occupying the majority of the aisle space and being blocked at the exit on the right side of the aisle, as shown in figure 10. at t=48 s, although the majority of the space in the hall is filled with smoke, the concentration of smoke spreading from the aisle is relatively low, and a high concentration of smoke occupies the general space in the hall. in addition, the aisle has been completely covered by smoke, as shown in figure 11. at t=89 s, the entire model is basically covered by smoke except for a small area protected by smoke prevention and control facilities, as shown in figure 12. figure 9. smoke spread at t=10s figure 10. smoke spreads at t=31 s figure 11. smoke spreads at t=48s x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 12 figure 12. smoke spreads at t=89 s 3.2.3 comparison and analysis of system a and system b through 3d smoke view fire simulation animation, it is found that although system b has higher water spray intensity and better performance, the phenomenon of smoke spread between the two is very similar in the simulation, and the difference is not significant. from the perspective of controlling smoke spread alone, system a has a higher costeffectiveness. in addition, it is easy to observe from the 3d fire simulation animation that the spread speed of fire smoke is very rapid. although this model has a large space of 6000 m2 and is equipped with an automatic sprinkler system, the fire smoke still covered the entire model in less than 2 minutes. due to the presence of fire smoke, visibility in the fire scene decreased. therefore, when a fire occurs, in order to evacuate the people in the fire as much as possible, personnel should be quickly organized to evacuate during the fire to prevent the spread of high-temperature smoke from causing casualties or people being trapped in the fire due to reduced visibility, and to ensure the safety of personnel as much as possible. 3.3 startup and analysis of automatic sprinkler fire extinguishing system 3.3.1 simulation and analysis of system a at t=12 s, the nozzles near the burning point in the hall start spraying water to extinguish the fire, as shown in figure 13. at t=17 s, the nozzle located near the burning point in the aisle starts to extinguish the fire, as shown in figure 14. at t=40 s, as the combustion progresses, the nozzles near the combustion point begin to respond one after another, as shown in figure 15. at t=90s, the nozzles near the combustion point were activated extensively. although the surface of the pvc advertising decorative floor at the combustion point was covered with water, the advertising material that was already burning was still burning violently, as shown in figure 16. figure 13. starting status of automatic sprinkler fire extinguishing system at t=12s figure 14. starting status of automatic sprinkler fire extinguishing system at t=17s figure 15. startup status of automatic sprinkler fire extinguishing system at t=40s figure 16. starting status of automatic sprinkler fire extinguishing system at t=90s at t=181 s, almost all the nozzles on the left side of the combustion point in the hall responded, and about 40% of the nozzles in the aisle had already responded. in addition, the sprinkler heads at the entrance of the aisle and hall have been activated to start spraying water for fire extinguishing, as shown in figure 17. at t=240s, the water sprayed by the hall nozzle not only completely covered the surface of the pvc advertising decorative floor at the combustion point but also partially covered the surface of the pvc advertising decorative floor in the middle of the hall. the number of response nozzles in the aisle has also increased, as shown in figure 18. figure 17. starting status of automatic sprinkler fire extinguishing system at t=181s x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 13 figure 18. startup status of automatic sprinkler fire extinguishing system at t=240s 3.3.2 simulation and analysis of system b at t=10s, the nozzle near the combustion point in the hall is activated for the first time, as shown in figure 19. at t=11s, the nozzle near the burning point in the aisle is activated for the first time to extinguish the fire, as shown in figure 20. at t=35 s, the nozzle near the combustion points in the hall responded, and the overall water spray increased. more than half of the pvc advertising decorative floor at the burning point of the hall has been covered by water, and the pvc advertising decorative floor at the burning point of the aisle has been completely covered by water, as shown in figure 21. at t=90 s, although the nozzle response degree near each combustion point of system b is further expanded, the pvc advertising decorative floor covered with water on the surface is still burning vigorously, as shown in figure 22. figure 19. startup status of automatic sprinkler fire extinguishing system at t=10s figure 20. starting status of an automatic sprinkler system at t = 11s figure 21. starting status of automatic sprinkler system at t = 35s figure 22. starting status of an automatic sprinkler system at t = 90s at t=181s, most of the sprinklers near the combustion points of system b respond and have a large water spray area. in addition to covering the pvc advertising decoration floor at the combustion points, it also covers the surrounding building structure, as shown in figure 23. at t=240 s, compared with the previous moment, although the number of sprinklers in the hall and aisle started to increase slightly, the burning pvc advertisement decorated the floor, and the burning is still ongoing, as shown in figure 24. figure 23. starting status of automatic sprinkler system at t = 181s figure 24. starting status of an automatic sprinkler system at t = 240s 3.3.3 comparison and analysis of system a and system b according to the above discussion and analysis, the response speed of system b is faster than that of system a, and the time required for the nozzle first to respond is shorter. however, as time goes by, the number of starting heads of system a gradually exceeds that of system b, and in the fourth minute, the water spraying area of system a is larger. on the one hand, this may be due to the smaller nozzle spacing of system b, the stronger inhibition of the combustion heat release, and the slower temperature rise; thus, the temperature near the fire source is lower, and the response number is less; on the other hand, the system b is denser, and the heat temperature flue gas cooling effect is stronger, the heat dissipation is larger and the fire temperature is relatively lower, resulting in the response of system a is more, and the injection area is larger. in general, with continuous x. gui et al. /future sustainability november 2024| volume 02 | issue 04 | pages 08-14 14 combustion, the response degree of the automatic sprinkler system is constantly improved, the number of starting heads is more and more, and the protection area of the system is also larger and larger. to some extent, the automatic sprinkler system is beneficial in protecting the space around the fire site and preventing the spread of the fire. however, in this model, due to the high combustion calorific value of the pvc advertising decoration floor and the intense response, the temperature in the central area of the fire has been high, so it cannot be completely extinguished by the automatic sprinkler system. however, the pvc advertisement decorated the floor, even if it was very close to the burning point, but within 4 minutes, it was ignited, and the automatic sprinkler system played a very important role. 4. conclusion (1) smoke in the early stages of the fire site spreads very quickly. in just a few minutes, the fire smoke can spread to the whole model, resulting in reduced visibility of the fire, which is not conducive to escape. therefore, attention should be paid to the design of smoke prevention and exhaust in public places with a high density of people, effectively inhibiting the diffusion of smoke and giving people more time to escape. (2) the environmental temperature of the fire site changes rapidly. the ambient temperature near the fire source can quickly break through 100℃, causing serious damage to the surrounding personnel. therefore, when choosing the escape channel, you should try to choose the route far away from the center of the fire source. if each route is filled with hightemperature smoke, you should crawl forward to avoid being burned and scalded by the high-temperature smoke. (3) an automatic sprinkler system is conducive to restraining the expansion of the fire and facilitating the evacuation of personnel. an automatic sprinkler system can effectively reduce the temperature of the fire smoke to prevent evacuating pedestrians due to high temperatures or igniting other combustibles, resulting in the control of fire. in addition, equipped with higher specifications of automatic sprinkler systems can further buy valuable time for personnel to escape. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] jasztal m, omen ł, kowalski m, jaskółowski w. numerical simulation of the airport evacuation process under fire conditions. advances in science and technology research journal, 2022, 16(2):249261. 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[8] yang s, shengao c, sijie l, kun y. simulation study on fire evacuation from airport terminal. china safety science journal, 2018, 28(08):31-37. [9] hu lh. smoke filling simulation in a boarding– arrival passage of an airport terminal using multicell concept. journal of fire sciences, 2005, 23(1):31-53. [10] min mq. smoke extrication strategy and its evaluation of an airport terminal. fire science and technology, 2013, 32(02):140-142. [11] xiao d. the study on fire risk evaluation for one international airport station. xi’an: xi’an university of science and technology, 2006. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 24 article annual assessment of radiation exposure levels among radiology personnel at usmanu danfodiyo university teaching hospital, sokoto, nigeria ahmadu ibrahim * department of physics usmanu danfodiyo university soko, nigeria a r t i c l e i n f o article history: received 30 june 2024 received in revised form 04 august 2024 accepted 14 august 2024 keywords: radiation hazard, x-rays, ionizing radiation, effective dose, radioactive materials *corresponding author email address: ahmedmubi9133@gmail.com doi: 10.55670/fpll.fusus.2.3.4 a b s t r a c t the evaluation of occupational exposure to external ionizing radiation in diagnostic and therapeutic settings is crucial for understanding regulatory compliance and technological advancements. this research provides an analysis of occupational radiation exposure among radiology staff of usman danfodiyo university teaching hospital (uduth) in sokoto, nigeria, and compares the findings with relevant studies. a total of 30 radiology staff members participated, each identified by a tld code instead of their names. various parameters, including average annual effective dose (aaed), annual collective dose (acd), individual distribution ratio (nre), collective dose distribution ratio (sre), and lifetime probability of cancer risk (lftr), were analyzed using spss version 21.0. the findings revealed that radiology workers had an aaed of 1.13 ± 0.51 msv and an acd of 33.90 ± 0.51 man msv. the nre and sre indicated that 40.27% of the radiology staff received doses exceeding 1 msv, while none exceeded 10 or 15 msv. the lftr for all medical radiation workers at uduth was less than 1 in a million, suggesting minimal lifetime cancer risk. overall, the dose distribution trend indicates a shift towards lower exposure levels, highlighting the effectiveness of radiation protection protocols maintained by the majority of the staff. 1. introduction ionizing radiation, including x-rays and gamma rays from radioactive materials, is electromagnetic and capable of penetrating matter, causing damage when absorbed. while these radiations have numerous beneficial applications, their misuse can be hazardous [1]. they can kill living cells or induce harmful changes in them, posing a significant risk to users. those working with ionizing radiation must understand these risks and how they compare to everyday hazards, as well as how to mitigate them to safe levels. operators of x-ray equipment and users of radioactive materials must be certified according to recognized standards and meet qualifications mandated by relevant nigerian regulations. all operators should: • be familiar with the nigeria radiation act, regulations, and license conditions. • understand the radiation hazards related to their work and their responsibility to protect themselves and others. • have comprehensive knowledge of their profession, safe working practices, and specialized techniques. • aim to minimize exposure through diligent use of appropriate techniques and procedures. • be at least 18 years old. female operators who suspect they are pregnant should inform their employer to ensure that their duties align with the accepted maximum radiation exposure guidelines during pregnancy [2]. x-rays function by traveling from the focal spot of the x-ray tube, casting shadows as they are blocked by objects. unlike light, x-rays penetrate materials to varying degrees based on their generation and the material's properties. bones appear in radiographic images because they absorb more x-rays than soft tissue. lead and steel, which absorb x-rays more effectively, are used as protective barriers. x-rays emit in all directions from an energized x-ray tube, but the lead housing prevents escape in all directions except through the designated opening. the beam size, controlled by diaphragms, determines the visible area and the amount of scattered x-radiation produced, which poses a hazard if not properly blocked. the intensity of both primary and scattered x-rays decreases rapidly with distance from the future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.3.4 august 2024| volume 02 | issue 03 | pages 24-29 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:ahmedmubi9133@gmail.com https://doi.org/10.55670/fpll.fusus.2.3.4 https://fupubco.com/fusus ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 25 source, similar to light intensity diminishing with distance [3]. x-rays are present only when the machine is on, and neither the operator nor the material becomes radioactive postexposure. gamma rays, however, are continuously emitted by radioactive materials and cannot be switched off. their intensity and penetration depend on the radioisotope source. all individuals are exposed to background environmental radiation from cosmic rays, the air, and even within our bodies. occupational radiation exposure adds to this background radiation, which varies geographically [4]. 2. literature review 2.1 biological effects of radiation x-rays and gamma rays are crucial in diagnostic and therapeutic medicine, industry, and research, inevitably exposing individuals to radiation. the challenge is to establish acceptable radiation exposure levels beyond natural background levels. the international commission on radiation protection (icrp) has long analyzed radiation effects on humans, periodically publishing recommended exposure limits [5]. these limits have been progressively lowered, not due to observed adverse effects at previous levels, but because it has been feasible to reduce exposure without significantly limiting radiation use in various fields. this principle, known as "as low as reasonably achievable" (alara), applies to both patients and occupationally exposed personnel [6]. 2.2 effects of radiation on humans a substantial amount of knowledge exists regarding the effects of radiation on humans, surpassing what is known about the impact of chemicals like insecticides and fungicides. the primary effects of the small amounts of radiation typically encountered by individuals using x-rays include genetic changes and cancer induction [7]. 2.3 personal exposure monitoring radiation exposure is monitored using badges that contain two tiny crystalline chips sensitive to very small amounts of radiation. these badges should be worn for a specified period, usually three months, before being returned for measurement. the results reflect the exposure received during this period [8]. to accurately measure individual exposure, the badge must be protected from radiation when not worn and should be worn next to the body during x-ray use. without wearing the badge, it is impossible to determine an individual's radiation exposure accurately. therefore, individuals must take responsibility for wearing their badges whenever there is a likelihood of x-ray exposure [9]. 2.4 medical utilization of ionizing radiation the medical use of ionizing radiation, including procedures such as x-rays, fluoroscopy, mammography, and computed tomography, is the second-largest contributor to the global cumulative dose of ionizing radiation [10]. the increasing use of ionizing radiation for medical diagnostics has raised valid concerns [11]. various levels of ionizing radiation exposure have been associated with potential biological risks, including radiation sickness, cellular damage, tissue and organ harm, cancers, and cataract development [1]. 3. methodology data for this study were collected from personnel working in the radiology department of usman danfodiyo university teaching hospital (uduth) in sokoto, nigeria. anonymous records containing quarterly dosage measurements from this department, spanning the years 2019 to 2023, were obtained. the collected data documented medical radiation exposure doses, ensuring compliance with the regulations of the health research ethics board (hreb) by not disclosing the identities of the workers. instead, each participant was assigned a unique tld (thermoluminescent dosimeter) code to maintain anonymity. these depersonalized and coded records included details on quarterly whole-body and extremity doses for medical radiation workers. from these records, the cumulative annual dose was calculated using the method outlined by reference [7]. this approach aligns with established protocols in radiation safety research, ensuring the reliability and validity of the data. the use of anonymous tld codes is a standard practice in radiation exposure monitoring, as noted by reference [12], to protect worker privacy while allowing for accurate dose assessment. by employing these standardized methodologies and ethical considerations, this study ensures the precise and confidential assessment of radiation exposure among radiology personnel at uduth, contributing valuable insights to the field of occupational health and safety. 𝐷 = 𝐻𝑇 𝑊𝑅 (1) where d = absorbed dose, 𝐻𝑇= equivalent dose, 𝑊𝑅 = radiation weighting factor. the calibration factor by reference [8] is defined as follows: 𝑓𝑐𝑎𝑙𝑖𝑏𝑟𝑎𝑡𝑖𝑜𝑛 = 𝐷𝑖𝑜𝑛𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑐ℎ𝑎𝑚𝑏𝑒𝑟 (𝑚𝐺𝑦) 𝑇𝐿𝐷𝑟𝑒𝑎𝑑𝑖𝑛𝑔 (𝑛) (2) absorbed dose due to irradiation is obtained after background subtraction using equation 3: 𝐷𝑇𝐿𝐷 = 𝐷𝑎𝑣 − 𝐵𝐺 (3) the absorbed dose is obtained for each tld using equation 4: 𝐷(𝑚𝐺𝑦) = 𝑓𝑐𝑎𝑙 ( 𝑚𝐺𝑦 𝑛𝐶 ) 𝑋 𝑇𝐿𝐷𝑟𝑒𝑎𝑑𝑖𝑛𝑔(𝑛𝐶) (4) for every individual measurement, the smallest detectable amount (referred to as mdl or minimum detection level) is 0.05 msv within 3 months after accounting for the background. this mdl serves as a threshold for recording doses. consequently, workers who have received doses lower than this mdl are classified as having not been exposed. the reader for thermoluminescent dosimeters (tld) provides values for shallow dose equivalent (referred to as skin dose) and deep dose equivalent (referred to as dde), both of which are manually inputted into a microsoft excel spreadsheet. this input is then utilized to calculate the respective personnel dose equivalents, denoted as hp(0.07) and hp(10). the formulas for calculating skin and deep doses are outlined in equations 5 and 6, as detailed in the work by [8]. skin dose: hp(0.07) = [(1.2958rskin) + 0.0097] msv (5) deep dose: hp(10)= [(1.3772rdeep) + 0.0566]msv (6) dose reporting was performed on a quarterly basis, and only those workers with doses exceeding a minimum detection level (mdl) of 0.05 msv (exposed workers) after background subtraction will be considered. the workers with doses less than mdl are considered as non-exposed. 4. data analysis this study used the average annual effective dose recommended by reference [2] to analyze individual doses for the stipulated period. absorbed dose (d): energy imparted to matter from any type of radiation: ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 26 𝐷 = 𝐸 𝑚 (7) d: absorbed dose e: energy absorbed by the body of mass (m). equivalent dose (𝐻𝑇 ) accounts for biological effect per dose 𝐻𝑇 = 𝑊𝑅 × 𝐷 (8) wr: radiation weighting factor. individual average annual effective dose is the risk-related parameter, taking the relative radio sensitivity of each organ or tissue into account. 𝐸𝑖(𝑆𝑣) = ∑ 𝑊𝑇𝑇 × 𝐻𝑇 (9) wt: tissue weighing factor for organ t ht: equivalent dose received by organ or tissue t 5. results and discussion this study investigated the levels of occupational exposure to radiation among employees at usmanu danfodiyo university sokoto teaching hospital, where ionizing radiation sources were utilized from 2019 to 2023. the report details the average effective dose on an annual basis for workers in the field of radiotherapy, and the findings are presented in this section. the results derived from figure 1, detailing the experiences of 9 rd radiographers over a fiveyear period, showcase the variability in average annual effective dose (aaed), annual collective dose (acd), and the probability of cancer lifetime risk. radiographers' aaed ranged from 0.40 to 2.80 msv, while acd ranged from 3.6 to 25.20 man msv, with lftr ranging from 0.0020 to 0.14 mil recorded by rt15 in 2019 and 20. notably, rd15 was identified as being more exposed to radiation, suggesting potential lapses in adhering to radiation protection protocols. the recorded results surpassed those documented by reference [5], exceeded the 0.42 msv recorded in india (19901994), and surpassed the 1.34 msv world recommended dose (1990-1994). figure 1. rd radiographers radiation doses the one-way anova test revealed no statistical significance (p < 0.05). analyzing the results indicated that approximately 80% of rd radiographers received aaed exceeding 1 msv, with 20% receiving lower than 1 msv. none of the radiographers received doses exceeding 5, 10, and 15 msv, in accordance with reference [4] recommendations. the study demonstrated that the probability of cancer lifetime risks increased with the rise in dose. however, the risk of cancer induction at uduth for exposed workers was five times lower than the risk in kuwait [3]. the results indicated that the 9 rd radiographers monitored had induced cancer risks below 1 mil, underscoring an improvement in the radiation protection protocol at uduth. while acknowledging the potential risks associated with long-term exposure, the assessment suggested that building confidence among radiographers at uduth could be achieved by minimizing the risk of cancer induction through workload management. furthermore, the information emphasized the linear relationship between the probability of lftr and exposure time. if anyone gets overexposed, the risk of cancer induction can be minimized by reducing workload, reinforcing the importance of effective management strategies. the results obtained from figure 2, focusing on the experiences of 10 residence doctors over the study period, present insights into the average annual effective dose (aaed), annual collective dose (acd), and the probability of cancer lifetime risk. the aaed ranged from 0.60 to 4.484 msv, while acd ranged from 6.0 to 48.40 man msv. the probability of cancer lifetime risk ranged from 0.03 to 0.242 mil, with rd60 and rd61 in 2019 and 2023, respectively. notably, rd61 was the only one on the seat in 2023, leading to the highest accumulation of doses. the recorded results surpassed those documented by [1], exceeded the 0.19 msv recorded in australia (1990-1994), and surpassed the 1.34 msv world recommended dose (1990-1994), albeit remaining below the 20 msv recommended by reference [10]. ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 27 figure 2. rd residence doctors' radiation doses the one-way anova test revealed no statistical significance for most pairwise comparisons, except for the comparisons of rd04 with rd61 (p < 0.05). in this comparison, rd04 received the lowest aaed, indicating low interaction with radiation. analysis of the results showed that approximately 36% of residence doctors received aaed exceeding 1 msv, with 64% receiving lower than 1 msv. none of the residence doctors received doses exceeding 5, 10, and 15 msv, aligning with reference [1] recommendations. the study demonstrated that the probability of cancer lifetime risks increased with the rise in dose. however, the risk of cancer induction at uduth for exposed workers was five times lower than the risk in kuwait [3]. the results indicated that the 10 residence doctors monitored had induced cancer risks below 1 mil, highlighting an improvement in the radiation protection protocol at uduth. while acknowledging the potential risks associated with long-term exposure, the assessment suggested that building confidence among residence doctor workers at uduth could be achieved by minimizing the risk of cancer induction through workload management. additionally, the information underscored the linear relationship between the probability of lftr and exposure time. if anyone gets overexposed, the risk of cancer induction can be minimized by reducing workload and emphasizing the importance of effective management strategies. figure 3. rd darkroom technicians’ radiation doses the findings from the assessment of 8 darkroom technicians over the study period (figure 3), as presented in the results from the one-way anova test, offer valuable insights into their average annual effective dose (aaed), annual collective dose (acd), and the probability of cancer lifetime risk. the aaed ranged from 0.48 to 5.36 msv, and acd ranged from 3.84 to 42.88 man msv. the probability of cancer risk ranged from 0.024 to 0.268 mil, with rd46 and rd26 in 2014, respectively. the recorded results surpassed those documented by reference [4], exceeded the 0.19 msv recorded in australia (1990-1994), and surpassed the 1.34 msv world recommended dose (1990-1994), although remaining below the 20 msv recommended by reference [1]. the one-way anova test revealed no statistical significance for the pairwise comparisons (p < 0.05). analysis of the results indicated that approximately 50% of darkroom technicians received aaed exceeding 1 msv, with 45% receiving lower than 1 msv. a small proportion, 5%, received doses exceeding 5 msv, and none received doses exceeding 10 and 15 msv, aligning with [3] recommendations. the study demonstrated that the probability of cancer lifetime risks increased with the rise in dose. however, the risk of cancer induction at usman danfodiyo university teaching hospital sokoto (uduth) for exposed workers was five times lower than the risk in kuwait [11]. the results indicated that the 8 darkroom technicians monitored had induced cancer risks below 1 mil, highlighting an improvement in the radiation protection protocol at uduth. while acknowledging the potential risks associated with longterm exposure, the assessment suggested that building confidence among darkroom technicians workers at uduth could be achieved by minimizing the risk of cancer induction through workload management. additionally, the information underscored the linear relationship between the probability of lftr and exposure time. if anyone gets overexposed, the risk of cancer induction can be minimized by reducing workload and emphasizing the importance of effective management strategies. the results obtained from the assessment of three rd nurses, as presented in figure 4, provide valuable insights into the average annual effective dose (aaed), annual collective dose (acd), and the probability of cancer lifetime risk. over the entire study period, the aaed ranged from 1.08 msv in 2016 to 2.76 msv in 2022, with acd ranging from 3.24 to 8.228 man msv and a probability of cancer lifetime risk ranging from 0.054 to 0.138 mil, recorded by rd39 and rd71 in 2021 and 2022, respectively. it is notable that rd71 recorded the highest doses. figure 4. rd nurses’ radiation doses ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 28 the results surpassed the 0.35 msv recorded in canada (1990-1994) but were lower than the 1.34 msv and 20 msv world records in 1990-1994, as well as the reference [1] recommendations. fluctuations in the results may be attributed to an increase in workload or non-compliance with radiation protection protocols. the one-way anova test revealed no statistical significance for the pairwise comparisons (p < 0.05). analysis of the results indicated that approximately 66.67% of rd nurses received aaed exceeding 1 msv, with 33.33% receiving lower than 1 msv, and none of the rd nurses received doses exceeding 5, 10, and 15 msv, aligning with reference [1] recommendations. the study demonstrated that the probability of cancer lifetime risks increased with the rise in dose. however, the risk of cancer induction at usman danfodiyo university teaching hospital sokoto (uduth) for exposed workers was five times lower than the risk in kuwait. the results indicated that the three rd nurses monitored had induced cancer risks below 1 mil, highlighting an improvement in the radiation protection protocol at uduth. while acknowledging the potential risks associated with long-term exposure, the assessment suggested that building confidence among rd nurse workers at uduth could be achieved by minimizing the risk of cancer induction through workload management. additionally, the information underscored the linear relationship between the probability of lftr and exposure time. if anyone gets overexposed, the risk of cancer induction can be minimized by reducing workload and emphasizing the importance of effective management strategies. the presented results (figure 5) highlight significant variations in annual average effective dose (aaed) among different groups, particularly between radiographers (rg) and the combined group of radiologists (drt), nurses (nur), and darkroom technicians (drk). radiographers demonstrated the highest aaed, while residence doctors (rd) received the lowest. additionally, the pair-wise comparisons between radiographers and the combined group of radiologists, nurses, and darkroom technicians showed statistically significant differences. figure 5. comparisons of different cadres in the radiology department 5.1 differences in aaed radiographers stand out as having the highest aaed among the groups, suggesting that their work tasks or exposure conditions contribute to elevated radiation doses. on the other hand, residence doctors, in contrast, received the lowest aaed. 5.2 occupational practices the observed differences may be linked to variations in occupational practices and tasks performed by different healthcare professionals. radiographers who typically conduct diagnostic imaging procedures may encounter higher radiation levels due to their direct involvement in these processes. 5.3 significant pair-wise comparisons the statistical significance in pair-wise comparisons between radiographers and the combined group of radiologists, nurses, and darkroom technicians implies that there are substantial differences in radiation doses between these two sets of healthcare professionals. this could be influenced by the specific nature of their roles, procedures involved, or working conditions. 5.4 risk assessment the results obtained showed that none of the radiologists received a cancer risk exceeding the 1.0 million recommended by reference [1]. 6. conclusion this study provides a comprehensive assessment of occupational radiation exposure among medical radiation workers at uduth. the dose limits, average doses, high-level exposure, and cancer risk test revealed the following: compliance with dose limits: all the radiology staff adhered to the national administrative dose limit of 20 msv, ensuring no worker received excessive radiation exposure. this highlights the effectiveness of national regulations and commitment to worker safety. low average doses: while exceeding the 1 msv threshold in some percentages, the average annual effective doses in the radiology department (1.13 msv) remained relatively low. this suggests proper implementation of radiation safety measures in most cases. high-level exposure: importantly, no worker across any department received annual doses exceeding 10, or 15 msv, indicating the absence of serious exposure incidents. this further reinforces the overall picture of responsible radiation practices. minimal cancer risk: the estimated probability of cancer causation for all the medical workers was below the screening limit. the study's findings suggest several areas for improvement and further research: • regular calibration: to improve the accuracy of dosimetry measures, it is crucial to always calibrate the harshaw 4500 manual tld reader with a 137cs beam exposure before each use. this ensures consistent and reliable dose assessments for workers. • upgrade dosimetry technology: consider exploring the use of the harshaw automatic tld reader 8800/6600 model in future studies. this advanced technology offers higher precision and accuracy, potentially leading to more reliable data on radiation exposure. • comprehensive risk assessment models: develop or update existing models to simultaneously assess both excess relative risk (err) and excess absolute risk (ear) of cancer based on radiation exposure. this ahmadu ibrahim /future sustainability august 2024| volume 02 | issue 03 | pages 24-29 29 provides a more comprehensive picture of the potential long-term risks faced by workers. • expand study scope: include occupational radiation exposure assessment for additional personnel within the hospital, such as porters, who might also encounter radiation during their work. expanding the study scope provides a more holistic understanding of radiation safety within the medical facility. • workload optimization: implement measures to reduce the workload on radiation workers, such as, radiotherapists, and dental workers. options include affordable time-scheduling practices to minimize fatigue and human error. • improved cancer detection models: develop or refine models that can detect cancer in any radiosensitive organ, not just those traditionally associated with radiation exposure. this ensures broader protection for workers' health. • optimal tld reading timing: considering the warm temperatures in sokoto, ensure tld reading is done within one month of badge collection to avoid potential fading of the dosimetry chips, which could lead to inaccurate dose readings. • staffing considerations: to further reduce workload and improve efficiency within the department, consider allocating additional staff resources to support ongoing operations and ensure optimal safety practices. acknowledgment my appreciation goes to almighty allah for his guidance throughout my entire life. appreciation also extends to the walailak journal of science and technology for developing me academically. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the author declares no potential conflict of interest. references [1] abu-jarad, f. (2020). application radiation sources in oil and gas industry and shortage in their services international symposium on the peaceful application of nuclear technology in the gcc countries jeddah 2020. radioisotopes applications, session 10/no.3. [2] unscear (united nations scientific committee on the effects of atomic radiation). (2018). sources and effects of ionizing radiation: unscear 2018 report to the general assembly, with scientific annexes [3] rahman, a., khan, s., & ali, m. (2019). radiation dose measurement in ct procedures: a study in pakistani hospitals. radiation protection dosimetry, 168(4), 559564. doi:10.1093/rpd/ncv397 [4] cember, h. and thomas e. johnson (2022). introduction to health physics. mcgraw-hill. isbn: 978-0071423083. [5] iaea. (2018). international basic safety standards for protection against ionizing radiation and for the safety of radiation sources [online]. international atomic energy agency. retrieved from https://www.iaea.org/publications/6903/international -basic-safety-standards-for-protection-against-ionizingradiation-and-for-the-safety-of-radiation-sources [6] reddy, p. j., bhade, s. p. d., babu, d. a. r., & sharma, d. n. (2011). validation of efficiency tracing and zero detection threshold techniques using liquid scintillation analyser tricarb. radiation protection dosimetry, 147(3), 417-422. doi:10.1093/rpd/ncq495 [7] mohsen, m., ali, r., & fatima, s. (20120). trends in radiation dose management in interventional cardiology. cardiology journal, 21(4), 376-382. doi:10.5603/cj.a2014.0045 [8] oyeyinka, r., adeyemi, o., & olatunji, b. (2017). radiological assessment of naturally occurring radioactive materials in soil. journal of environmental radioactivity, 112, 40-46. doi:10.1016/j.jenvrad.2012.04.002 [9] icru. (2019). radiation protection and safety in industrial radiography [online]. international commission on radiological units. retrieved from https://www.icru.org/report/radiation-protectionand-safety-in-industrial-radiography-1998/ [10] al.abdulsalam, a., & brindhaban, a. (2018). occupational radiation exposure among the staff of department of nuclear medicine and diagnostic radiology in kuwait med princ.pract., 23(2), 129-23. [11] epa (environmental protection agency). (2018). external exposure to radionuclide in air, water and soil federal guidance report no: 12 epa.402-r-93. [12] icrp. (2019). the 2019 recommendations of the international commission on radiological protection. annals of the icrp, publication 103 [online]. retrieved from https://www.icrp.org/page.asp?id=128 this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 15 article sustainable lathe machine selection using promethee ovundah king wofuru-nyenke department of mechanical engineering, faculty of engineering, rivers state university, port harcourt, rivers state, nigeria a r t i c l e i n f o article history: received 19 september 2024 received in revised form 23 october 2024 accepted 01 november 2024 keywords: lathe, machine selection, multi-criteria decision analysis, promethee *corresponding author email address: ovundah.wofuru-nyenke@ust.edu.ng doi: 10.55670/fpll.fusus.2.4.3 a b s t r a c t the manufacturing echelon of supply chains utilizes several machines to convert raw materials into finished products. therefore, during procurement of these machines, supply chain managers are usually saddled with the problem of obtaining the best machine from a group of similar alternatives, considering multiple criteria simultaneously. the main purpose of this study is to utilize the preference ranking organization method for enrichment evaluation (promethee) for selecting the best lathe machine from a group of five (5) similar alternatives, namely lathe 1, lathe 2, lathe 3, lathe 4 and lathe 5. four (4) criteria were used in evaluating the machines, namely power, price, complexity, and weight, with preference weights of 0.25, 0.3, 0.25, and 0.2, respectively. the results indicated that lathe 2 is the best alternative because it has the highest total net flows of 0.325, followed by lathe 5, which has total net flows of 0.03. next is lathe 1, which has a total net flow of -0.0188, followed by lathe 3, having a total net flow of -0.0975, and finally, lathe 4, which is the worst ranking alternative, having a total net flow of -0.2388. therefore, promethee proved to be a viable multi-criteria decision-making tool for selecting the most suitable lathe machine among the group of alternative machines. this study is significant because it provides a procedure for aiding supply chain managers in selecting the best alternative among a group of similar alternatives using promethee. 1. introduction the supply chain managers are responsible for managing various activities within supply chain networks. there are several methods for optimally managing production processes [1, 2]. the management process is usually tedious when the correct procedure is not consistently followed, or the various components of business management are not effectively combined. this could lead to various forms of waste within the manufacturing supply chain, especially when managers cannot predict uncertainty within the supply chain [3-8]. the main components of business management are money, manpower, materials, methods, and machines. money refers to the capital utilized in the production of goods and the offering of services. it is important for the acquisition of raw materials, personnel hiring, acquisition of machines as well as equipoising costs incurred during the operation of the supply chain. manpower refers to the skilled and unskilled workers involved in the production of goods and rendering of services. materials refer to the raw supplies fed into the supply chain and used to produce semi-finished or finished goods. methods refer to the usual and recommended procedures for carrying out operations within the supply chain by established systems. machines refer to the equipment used in converting raw materials into semi-finished or finished products [9, 10]. machines are crucial for the profitability and survival of supply chains [11-14]. this is because rapid product output from the manufacturing echelon of supply chains is usually a result of well-running machinery, which can, in turn, provide the entire supply chain with a competitive edge [15, 16]. during procurement of machines, managers usually encounter the problem of deciding which machine is the best among alternatives. this is a complex problem because the machines must be evaluated simultaneously by considering multiple criteria. multi-criteria decision analysis models have proven efficient in solving these decision-making problems involving evaluations based on multiple criteria. these methods can be employed in supplier selection, materials future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.4.3 november 2024| volume 02 | issue 04 | pages 15-21 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:ovundah.wofuru-nyenke@ust.edu.ng https://doi.org/10.55670/fpll.fusus.2.4.3 https://fupubco.com/fusus ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 16 selection, production scheduling, routing, inventory management, pricing strategies, and evaluation of various product designs, to name a few. the preference ranking organization method for enrichment evaluation (promethee) has been utilized in many decision-making problems in engineering. the methodology has been applied to the complex and strategic problem of selecting a lean manufacturing system compared to a computer-integrated manufacturing system, considering the benefits to be gained and the impact on the organization's stakeholders [17]. it has also been applied to rank and select appropriate dispatching rules for a dual-resource constrained manufacturing system [18]. the methodology has been applied to manufacturing scheduling by providing the ranking of alternative schedules based on completion times [19, 21]. furthermore, the methodology has been combined with the bayesian method to address equipment failure uncertainty by preventive maintenance planning and failure control in the context of equipment breakdown [22]. similarly, the method has been used to determine the optimal preventive maintenance intervals [23]. the method has been applied to the problem of selecting the optimal solution for an inverse electromagnetic scattering problem [24]. promethee has also been used to rank alternatives during assembly planning as well as select the best equipment combination for individual stations with the aid of a multi-objective grouping genetic algorithm [25, 26]. moreover, it has been applied to the problem of choosing a predictive maintenance program within an automotive paint shop [27]. lathe machines are machine tools that operate by rotating a cylindrical workpiece about an axis of rotation to perform various operations such as cutting, drilling, sanding, knurling, facing, deformation, and turning with the aid of a tool applied to the workpiece to create an object which is symmetrical about that axis. lathe machines are very important machinery within major metalworking plants that produce metal products [28-30]. the main purpose of this study is to utilize promethee to select the best lathe machine from a group of similar alternatives. promethee provides the decision maker with a ranking of alternatives based on global or total net flows. the following sections describe the underlying equations of promethee, and the results of applying the equations to the lathe machine selection problem. 2. methodology in the promethee method, alternatives are pairwise compared in order to find the most appropriate alternative. the set of alternatives to be ranked are denoted by a = {a1, a2, ⋯ , an} and the set of criteria are denoted by f = {f1, f2, ⋯ , fm}. also, denoting the evaluation of alternative aj on criterion fi by fi(aj) and assuming that fi(aj) is a numeric value. a preference matrix is generated from the data, and is used in calculating the global flows. the global pairwise preference degrees computed between all the ordered pairs of alternatives constitute the preference matrix. the global preference degrees are obtained from the criterion preference degrees by means of the weighted sum and provide the basis for deducing the global flows. 2.1 unicriterion preference degrees the unicriterion preference degree pij k, which can also be denoted as pk(ai, aj), is calculated for each ordered pair of alternatives (ai, aj). this unicriterion preference degree, pij k, depicts how much more preferred alternative ai is to aj based solely on criterion fk. pij k will be a number between 0 and 1, and is a function of fk(ai) − fk(aj), the more this difference, the stronger the unicriterion preference degree. a choice between three different types of preference functions has to be made by the decision maker, which in turn determines the preference degree. considering the linear preference function with q as the indifference threshold and p as the preference threshold, the equation for the unicriterion preference degree is given by [31, 32]: pij k = { 0 [fk(ai)−fk(aj)−q] [p−q] 1 if fk(ai) − fk(aj) ≤ q if q < fk(ai) − fk(aj) < p if fk(ai) − fk(aj) ≥ p (1) however, if a gaussian preference function is considered the equation for the unicriterion preference degree is given by [33]. pij k = {1 − exp ( −(fk(ai)− fk(aj)) 2 2s2 ) if fk(ai) − fk(ai) ≥ 0 0 otherwise (2) where s is the inflexion point. pij k and pji k are not symmetric numbers but respect the condition 0≤ pij k + pji k ≤ 1. 2.2 global preference degree after calculating the ordered unicriterion preference degrees, the global preference degree, πij, can be computed taking the weights of each criterion into account. denoting wk as the weight associated with the criterion fk. if the weight respects the condition ∑ wk q k=1 =1, then the global preference degree of alternative ai on aj is given by [33]: π(ai, aj) = πij = ∑ wj q k=1 ∙ pij k (3) where wj is the weight of a criterion j, and pij k is the unicriterion preference degree. this global preference degree lies between 0 and 1, and respects the constraint 0 ≤ πij + πji ≤ 1. therefore, ∀i ∶ πii = 0. 2.3 global flows the ordered preference degrees are summarized into a unique score for each alternative, using the positive and negative flows. denoting by φ+(ai) the positive flows of alternative ai and φ−(ai) the negative flows of alternative ai. their values can be computed as follows [33]: φ+(ai) = ∑ πij n j=1 n−1 (4) φ−(ai) = ∑ πji n j=1 n−1 (5) where πij is the global preference degree of alternative ai on aj, and πji is the global preference degree of alternative aj on ai. 2.4 net flows the net flows, φ(ai), summarizes the positive and negative flows with one formula given by [33]: ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 17 φ(ai) = φ+(ai) − φ−(ai) (6) where φ+(ai) is the positive flow of alternative ai and φ−(ai) is the negative flow of alternative ai. the net flow is a number between -1 and 1. the higher this number is, the better the alternative will be. 3. results and discussion this section presents the results of applying the promethee method to the lathe machine selection problem. the objective is to rank five (5) different lathe machines based on four (4) criteria, namely: power, price, complexity, weight. the power criterion is to be maximized, the price criterion is to be minimized, the complexity criterion is to be minimized, and the weight criterion is to be minimized for each of the lathe machines. table 1 shows the raw performance data of the various lathe machines and the selection criteria. table 1. the performance of the five (5) lathe machines evaluated on four (4) criteria power (hp) price ($) complexity weight (lb) objective max min min min lathe 1 30 1500 extreme 1000 lathe 2 40 1380 medium 1200 lathe 3 50 2500 high 1500 lathe 4 60 4750 medium 2400 lathe 5 100 6300 low 3100 figure 1 shows the numeric values of the complexity criteria on a complexity scale. from figure 1, low complexity corresponds to a numeric value of 2, medium complexity corresponds to a numeric value of 4, high complexity corresponds to a numeric value of 6, and extreme complexity corresponds to a numeric value of 8, on the complexity scale. figure 1. numeric complexity scale therefore, from the performance data in table 1 and the numerical scale in figure 1, lathe 1 has a complexity of 8, lathe 2 has a complexity of 4, lathe 3 has a complexity of 6, lathe 4 has a complexity of 4, and lathe 5 has a complexity of 2. table 2 shows the preference parameters for all the criteria. from table 2, the power criterion has a linear preference function, a weight of 0.25, an indifference threshold of 20, and a preference threshold of 40. also, the price criterion has a linear preference function, a weight of 0.3, an indifference threshold of 600, and a preference threshold of 1000. furthermore, the complexity criterion has a linear preference function, a weight of 0.25, an indifference threshold of 1, and a preference threshold of 2. moreover, the weight criterion has a linear preference function, a weight of 0.2, an indifference threshold of 500, and a preference threshold of 1000. table 3 shows the differences between evaluations of the lathes on power criterion. table 2. criteria preference parameters table 3. differences between evaluations of the lathes on power criterion from table 3, considering the power criterion that has to be maximized, all lathes compared with themselves result in a difference of 0. lathe 1 compared with lathe 2 results in a difference of 10. lathe 1 compared with lathe 3 results in a difference of 20. lathe 1 compared with lathe 4 results in a difference of 30. finally, lathe 1 compared with lathe 5 results in a difference of 70. table 4 shows the differences between evaluations of the lathes on price criterion. table 4. differences between evaluations of the lathes on price criterion criterion function weight, wi indifference threshold, qi preference threshold, pi power linear 0.25 20 40 price linear 0.3 600 1000 complexity linear 0.25 1 2 weight linear 0.2 500 1000 lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 -10 -20 -30 -70 lathe 2 10 0 -10 -20 -60 lathe 3 20 10 0 -10 -50 lathe 4 30 20 10 0 -40 lathe 5 70 60 50 40 0 lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 120 -1000 -3250 -4800 lathe 2 -120 0 -1120 -3370 -4920 lathe 3 1000 1120 0 -2250 -3800 lathe 4 3250 3370 2250 0 -1550 lathe 5 4800 4920 3800 1550 0 ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 18 from table 4, considering the price criterion which has to be minimized, all lathes compared with themselves result in a difference of 0. lathe 1 compared with lathe 2 results in a difference of 120. lathe 1 compared with lathe 3 results in a difference of 1000. lathe 1 compared with lathe 4 results in a difference of 3250. finally, lathe 1 compared with lathe 5 results in a difference of 4800. table 5 shows the differences between evaluations of the lathes on complexity criterion. table 5. differences between evaluations of the lathes on complexity criterion lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 4 2 4 6 lathe 2 -4 0 -2 0 2 lathe 3 -2 2 0 2 4 lathe 4 -4 0 -2 0 2 lathe 5 -6 -2 -4 -2 0 from table 5, considering the complexity criterion which has to be minimized, all lathes compared with themselves result in a difference of 0. lathe 1 compared with lathe 2 results in a difference of 120. lathe 1 compared with lathe 3 results in a difference of 1000. lathe 1 compared with lathe 4 results in a difference of 3250. finally, lathe 1 compared with lathe 5 results in a difference of 4800. table 6 shows the differences between evaluations of the lathes on weight criterion. table 6. differences between evaluations of the lathes on weight criterion lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 -200 -500 -1400 -2100 lathe 2 200 0 -300 -1200 -1900 lathe 3 500 300 0 -900 -1600 lathe 4 1400 1200 900 0 -700 lathe 5 2100 1900 1600 700 0 from table 6, considering the weight criterion which has to be minimized, all lathes compared with themselves result in a difference of 0. lathe 1 compared with lathe 2 results in a difference of 200. lathe 1 compared with lathe 3 results in a difference of 500. lathe 1 compared with lathe 4 results in a difference of 1400. finally, lathe 1 compared with lathe 5 results in a difference of 2100. table 7 shows the pairwise comparison matrix for the power criterion. from table 7, comparing the differences with the preference and indifference thresholds based on the power criterion, lathe 4 has a preference degree of 0.5 over lathe 1. moreover, the preference degree of lathe 5 over lathe 1, lathe 2, lathe 3, and lathe 4 is 1. this means that based on the power criterion, lathe 5 is preferred. table 8 shows the pairwise comparison matrix for the price criterion. table 7. pairwise comparison matrix for the power criterion table 8. pairwise comparison matrix for the price criterion from table 8, comparing the differences with the preference and indifference thresholds based on the price criterion, lathe 1 has a preference degree of 1 over lathe 3, lathe 4 and lathe 5. moreover, the preference degree of lathe 2 over lathe 3, lathe 4, lathe 5 is 1. again, the preference degree of lathe 3 over lathe 4 and lathe 5 is 1. furthermore, the preference degree of lathe 4 over lathe 5 is 1. this means that based on the price criterion lathe 1 and lathe 2 are preferred over lathe 3, lathe 4 and lathe 5. while lathe 3 is preferred over lathe 4 and lathe 5, and lathe 4 is preferred over lathe 5. table 9 shows the pairwise comparison matrix for the complexity criterion. table 9. pairwise comparison matrix for the complexity criterion lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 0 0 0 0 lathe 2 0 0 0 0 0 lathe 3 0 0 0 0 0 lathe 4 0.5 0 0 0 0 lathe 5 1 1 1 1 0 lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 0 1 1 1 lathe 2 0 0 1 1 1 lathe 3 0 0 0 1 1 lathe 4 0 0 0 0 1 lathe 5 0 0 0 0 0 lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 0 0 0 0 lathe 2 1 0 1 0 0 lathe 3 1 0 0 0 0 lathe 4 1 0 1 0 0 lathe 5 1 1 1 1 0 ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 19 from table 9, comparing the differences with the preference and indifference thresholds based on the complexity criterion, when the preference degree is 0, it indicates that the difference in price is lower than the indifference threshold, and there is no difference between the two lathe machines being compared. on the other hand, when the preference degree is 1, it indicates that the difference between the two lathe machines being compared is greater than the preference threshold; therefore, there is a difference between the two lathe machines being compared. table 10 shows the pairwise comparison matrix for the weight criterion. table 10. pairwise comparison matrix for the weight criterion lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 0 0 1 1 lathe 2 0 0 0 1 1 lathe 3 0 0 0 0.8 1 lathe 4 0 0 0 0 0.4 lathe 5 0 0 0 0 0 from table 10, comparing the differences with the preference and indifference thresholds based on the weight criterion, when the preference degree is 0, it indicates that the difference in price is lower than the indifference threshold, and there is no difference between the two lathe machines being compared. when the preference degree is between 0 and 1, it implies that the difference between the lathe machines being compared is between the indifference and preference thresholds. on the other hand, when the preference degree is 1, it indicates that the difference between the two lathe machines being compared is greater than the preference threshold. therefore, there is a difference between the two lathe machines being compared. table 11 shows the pairwise preference matrix considering all the criteria and their weights. table 11. pairwise preference matrix from table 11, the total positive flows, total negative flows, and total net flows for each lathe machine were calculated, and these data are shown in table 12. table 12. total positive flows, total negative flows, and total net flows from table 12, the total positive flows were calculated by averaging all the row preference degrees of a lathe compared to other lathes, excluding the preference degree of the lathe compared with itself. the total negative flows were calculated by averaging all the column preference degrees of a lathe, excluding the preference degree on the diagonal. the total net flows were obtained by subtracting the negative flows from the positive flows. figure 2 is a plot of total net flows versus lathe machine type, and it shows the ranking of the lathe machines based on the total net flows. figure 2. plot of total net flows versus lathe machine type from figure 2, lathe 2 is the best alternative because it has the highest total net flows of 0.325, followed by lathe 5, which has total net flows of 0.03. next is lathe 1, which has a total net flow of -0.0188, followed by lathe 3, having a total net flow of -0.0975, and finally, lathe 4, which is the worst ranking alternative, having a total net flow of -0.2388. this provides the ranking of the various lathe machines under consideration based on power, price, complexity, and weight criteria with linear preference functions. lathe 1 lathe 2 lathe 3 lathe 4 lathe 5 lathe 1 0 0 0.3 0.5 0.5 lathe 2 0.25 0 0.55 0.5 0.5 lathe 3 0.25 0 0 0.46 0.5 lathe 4 0.375 0 0.25 0 0.38 lathe 5 0.5 0.5 0.5 0.5 0 lathes total positive flows total negative flows total net flows lathe 1 0.325 0.34375 -0.0188 lathe 2 0.45 0.125 0.325 lathe 3 0.3025 0.4 -0.0975 lathe 4 0.25125 0.49 -0.2388 lathe 5 0.5 0.47 0.03 ok. wofuru-nyenke /future sustainability november 2024| volume 02 | issue 04 | pages 15-21 20 4. conclusion during the procurement of machines for manufacturing, managers are faced with the problem of selecting the best machine among similar alternatives. the machine selection problem is complex because decisions usually have to be made based on more than one criterion. this study utilizes promethee to select the best lathe machine from a group of five similar alternatives, namely lathe 1, lathe 2, lathe 3, lathe 4, and lathe 5. the machines were evaluated based on criteria such as power, price, complexity, and weight, having preference weights of 0.25, 0.3, 0.25, and 0.2, respectively. the results indicated that lathe 2 is the best alternative because it has the highest total net flows of 0.325, followed by lathe 5, which has total net flows of 0.03. next is lathe 1, which has a total net flow of -0.0188, followed by lathe 3, having a total net flow of -0.0975, and finally, lathe 4, which is the worst ranking alternative, having a total net flow of 0.2388. the study provides a procedure for selecting the best alternative among a group of similar alternatives using promethee. for further research, other multi-criteria decision analysis methods and method combinations can be utilized to select the best machine among a group of machines during procurement. also, the performance of each alternative can be investigated considering a situation where the preference functions of each criterion is not linear. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the 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[33] ishizaka a, nemery p. multi-criteria decision analysis: methods and software. 2013: john wiley & sons. doi:10.1002/9781118644898 this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 3945 39 article effect of norozak (salvia lerrifolia) biodiesel fuel on diesel engine performance morteza niknejad, ahmad hajinezhad*, seyed farhan moosavian faculty of new sciences and technologies, university of tehran, tehran, iran a r t i c l e i n f o article history: received 06 september 2023 received in revised form 05 october 2023 accepted 17 october 2023 keywords: biodiesel from salvia lerrifolia, transesterification, special fuel consumption, exhaust gas temperature *corresponding author email address: hajinezhad@ut.ac.ir doi: 10.55670/fpll.fusus.1.1.5 a b s t r a c t most energy is produced from fossil fuels, and the use of these fuels has increased over the past years. fossil fuels are the main cause of global pollution and global warming. using vegetable oils as alternative fuels for diesel engines is one of the ways to reduce pollutant emissions. biodiesel from norozak (salvia lerrifolia) oil has been produced using a transesterification process. biodiesel is mixed with diesel oil in different proportions b05, b10, b15, and b20. biodiesel's physical and chemical properties are measured according to astm standards. a single-cylinder diesel engine is employed as the test engine in the present work. the torque, power, special fuel consumption (sfc), and exhaust gas temperature (egt) are measured and compared with diesel oil. torque, power, and egt are larger, and sfc is lower for biodiesel mixture b05 than diesel fuel. 1. introduction the use of biodiesel in compression ignition engines has increased in recent years to reduce the pollution of fossil fuels [1]. in order to use biodiesel instead of fossil fuels, it is necessary to perform engine-related tests to investigate the replacement of diesel fuel in compression ignition engines [2]. in this paper, the use of biodiesel fuel obtained from norozak oil (see table 1 data) in a combustion engine was used, and the parameters of power, egt, sfc, and biodiesel fuel output torque were investigated in comparison to diesel fuel [3]. these are the parameters that affect the performance of compression ignition engines [4]. increasing the biodiesel fuel percentage increases the density of the fuel mixture and reduces its thermal energy due to its higher density and lower thermal value than diesel. increasing the fuel mixture's density increases the fuel mixture's mass consumption, and the fuel's thermal expansion increases the released energy and thus generates more power [5]. at full load, the sfc for biodiesel of 5%, 20%, 50%, 75%, and 100% methyl ester cotton seed at a rotational speed of 2000 rpm is more than diesel fuel [6]. the egt of pure sunflower oil is higher for a mixture of b20 due to incomplete combustion, higher ignition delay, high viscosity, high surface tension, and high boiling point [7]. the egt for diesel fuels and cotton methyl ester increases by 9.9% and 6.2-7.8%, respectively, due to the heat problem caused by the gas inside the combustion chamber [8]. the egt increases with increasing biodiesel concentration. this is due to more oxygen in the vegetable oil methyl ester, which improves combustion performance [9]. the sfc for a 20% pongamia biodiesel at a full load is higher than a small amount compared to diesel fuel because the biodiesel thermal value is lower than diesel fuel [10]. table 1. specifications of oil recycled from norozak [1] most studies show that with increasing biodiesel blending, the amount of sfc increases in all operating conditions [1113]. the number of cetanes is greatly important in diesel fuel and improves the combustion properties. the number of parameter unit norozak dynamic viscosity in 𝟒𝟎°∁ mp.s 28.435 kinematic viscosity in 𝟒𝟎°∁ 𝑚𝑚2 𝑠 31.433 density in 𝟒𝟎°∁ 𝑔𝑟 𝑐𝑚3 0.9046 the molecular weight of oil 𝑔𝑟 𝑚𝑜𝑙 930 free fatty acids % 0.71 future sustainability open access journal https://doi.org/10.55670/fpll.fusus.1.1.5 november 2023| volume 01 | issue 01 | pages 39-45 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:hajinezhad@ut.ac.ir https://doi.org/10.55670/fpll.fusus.1.1.5 https://fupubco.com/fusus m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 40 cetane affects the engine's performance parameters such as combustion, stability, driving ability, thickened soot, disorder and engine disturbances, carbon monoxide particles, and unburnt hydrocarbons. the more biodiesel cetane number compared to diesel fuel results in greater combustion and combustion efficiency [14, 15]. the temperature of biodiesel blends is higher than diesel fuel. biodiesel has a higher viscosity that opens the needle valves more quickly, resulting in a faster start of combustion and higher combustion temperatures [16]. in a mixture of 30% biodiesel jatrofa, there is a higher thermal effect in all cases. increasing the percentage of mixtures reduces the thermoset's thermal efficiency because of the high viscosity and incomplete combustion [17]. using biodiesel sources such as jatropha, palm, algae, and waste cooking oil, biodiesel blends b10 and b20 with a single-cylinder diesel engine were run [18]. for the first time, the norozak oil biodiesel fuel was used to obtain the torque, power, sfc, and egt engine’s parameters in a single-cylinder compression ignition engine to use as a substitute for conventional diesel fuel without changing the structural characteristics of the engine. 2. materials and methods the biodiesel was tested using an astm standard transesterification method, and a mixture of biodiesel and diesel fuel after preparation was shown in table 2. biodiesel compounds are often indicated as bx. b represents fuel biodiesel fuel, and x represents the percentage of biodiesel in the mixture [19, 20]. table 2. the contents of the fuel mixture used fuel type b00 b05 b10 b15 b20 diesel percentage 0 05 10 15 20 biodiesel percentage 100 95 90 85 80 the engine used in this research has a cylinder made in italy. the characteristics of the engine are given in table 3. it has a direct spray type with a displacement of 510 cm3, a compression ratio of 18:1, and a maximum torque of 32.8 nm at an operating speed of 1800 rpm. the maximum recommended rotation speed is 3000 rpm and at least 1500 rpm, with rotational speeds of 1800 and 2500 rpm; using fuel mixtures of 0, 5, 10, 15, and 20, the percentage of biodiesel obtained from the norozak plant oil was evaluated at 0, 50 and 100% load at three loads. table 3. diesel engine technical specifications of single-cylinder aircooled lumbardini description specifications engine type lobardini_diesel 3lds510 engine displacement volume (cubic centimeter) 510 induction type no super charging number of cylinders 1 piston course (mm) 90 inner cylinder diameter (mm) 85 maximum torque (nm per minute) 32.8/1800 volumetric density ratio 18:1 maximum rotational speed (rpm) 3000 each of the combinations of b00 (petroleum gas), b05 (5% biodiesel with 95% diesel oil), b10 (10% biodiesel with 90% diesel oil), b15 (15% biodiesel with 75% diesel oil), and b20 (20 % biodiesel with petroleum diesel) was placed in two bottles of 1-liter containers, which was used to test any mixture of 2 liters of this mixture. for testing the mixture, fuels were poured into a fuel tank with a capacity of 0.75 liters, and fuel was poured into the reservoir again using fuel combinations and emptying the fuel tank, and then the engine was turned on to burn fuel for 10 minutes with fuel and adapt to the new combustion. also, it is important to burn fuel in the engine completely, and better fuel-polluting analyzes can be obtained to achieve the oil temperature to the optimum level for the engine start test. the engine was set at 1800 rpm and 2500 rpm for each test and was considered 0%, 50%, and 100% loads for each engine load, and carrying out the test in each load was considered each 6-point fuel mixture (see table 4) by the operator. for each fuel composition, 100% load was tested first. at this time, the operator control system automatically and continuously performed the test in rounds that were manually given to the control system so that when the test was completed at a rotational speed of 1800 rpm, that was considered to be the minimum after taking the data from the engine and the analyzer device, the engine was raised by a control system of rotational speed 2500 rpm that was considered to be the maximum and the experiment was carried out with a new engine load at 100% load and as well as the data in time intervals were taken at 0.5 seconds. table 4. matrix of experiments they set the engine speed from 1800 to 2500 rpm at a load of 100% for each fuel composition and obtained the engine torque at each rotational speed. the test can be carried out at 50% load for the same combination at two rotational speeds of 1800 rpm and 2500 rpm, which will be explained below. average torque was obtained at 100% load for each compound at a rotational speed of 1800 rpm and 2500 rpm. the average torque of each speed was divided into two so that the tested torque was obtained at a rotational speed of 50% to come and then, by placing the torque obtained for 50% load in the desired range separately in the control system and starting the test, the pollutant analysis should be performed by pressing the button to conduct the pollutant test. as a result, the time needed to reach the torque of the dynamometer should be calculated by the torque to be calculated, and the system monitor has no disturbances in the dynamometer between the torque being calculated and shown in the system. the values of these two torque are close together. at 0% load, no torque is entered on the dynamometer. in this test, the torque, power, special fuel consumption (sfc), and exhaust gas temperature (egt) were calculated after the engine arrived at stable conditions. fuel engine speed rpm engine load % b05 1800 2500 0 50 100 b05 1800 2500 0 50 100 b10 1800 2500 0 50 100 b15 1800 2500 0 50 100 b20 1800 2500 0 50 100 m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 41 3. results and discussions table 5 shows the experimental data in the test. a comparison of the measured characteristics for diesel fuel and the biodiesel obtained from the norozak oil shows that biodiesel and its mixtures have the required fuel characteristics for compression ignition engines [21-23]. theoretical topics can easily be considered a substitute fuel for a compression ignition engine. biodiesel has fewer pollutants than conventional diesel fuel in iran and can be used to reduce pollution, especially in metropolitan cities, in combination with conventional diesel [24]. the higher the amount of oxygen in the biodiesel fuel and the higher the cetane number of this fuel than conventional diesel fuel in iran can reduce air pollution and clean air, but fuel consumption in the engine increases with biodiesel consumption [25]. table 5. data from the research matrix power (kw) exhaust gas temperature (ʗ)° torque (nm) special fuel consumption (gr/kwh) rotational speed (rpm) load engine )٪( attributes the combination row 3.612381 526.4286 17.38571 433.5233 1800 2500 100 b00 1 4.547273 680.1136 15.83591 470.3503 2.150433 362.3152 10.35522 375.3718 1800 2500 50 2.685636 474.3273 9.408909 453.6003 0.00964 178.2857 0.018929 10000 1800 2500 0 0.024167 293.125 0.084167 10000 3.662 548.1 17.64 431.095 1800 2500 100 b05 2 4.1772 666.12 14.558 515.725 1.95333 358.1522 9.4137 516.45 1800 2500 50 1.84 451.5 6.45 697.3683 0.001964 178.2857 0.018727 10000 1800 2500 0 0.024167 293.125 0.084167 10000 3.536087 526.8261 16.96304 441.5786 1800 2500 100 b10 3 4.272727 661.7727 14.89864 498.1051 1.751373 335.5588 8.4347 390.8837 1800 2500 50 2.552615 472.476 8.934 488.0289 0.01 181.7143 0.051143 10000 1800 2500 0 0.101604 305.6745 0.353019 7111.119 3.609545 530.8636 17.28136 437.258 1800 2500 100 b15 4 4.33625 667.125 15.06958 509.7204 1.937143 349.4643 9.318571 419.6284 1800 2500 50 2.728219 497.3425 9.546712 483.5139 0.020106 183.6223 0.095957 10000 1800 2500 0 0.045714 297.7143 0.160952 10000 3.589545 535.6364 17.26727 437.8279 1800 2500 100 b20 5 4.269048 665.1429 14.92333 502.9433 2.093649 365.6554 10.08716 379.6148 1800 2500 50 2.39201 467.9112 8.392012 481.2963 0.001646 174.9304 0.016709 10000 1800 2500 0 0.046591 301.4318 0.162727 9667.337 m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 42 3.1 the torque changes from the dynamometer relative to the engine speed the torque variations are presented in terms of the rotational speeds of the engine tested in 0%, 50%, and 100% engine loads. the experiment begins with recording the desired data so that the turbulence with the torque at the tested speed is as low as possible and has a stable process with the least disturbance. at the beginning of the test, the torque changes fluctuate relative to the speed of the test, and in order to increase the accuracy of the test, it should take a while before these changes become stable, and then data is taken from the test with high precision. figures 1 to 2 show torque variations relative to rotational speeds of 1800 and 2500 rpm at loads of 0%, 50%, and 100 %. figure 1 shows the torque changes from the dynamometer relative to the engine speed for the biodiesel blend at three engine loads of 0%, 50%, and 100% at an engine speed of 1800 rpm. as can be seen, there is no oscillation in engine torque at a rotational speed of 1800 rpm in engine 0% load since the torque at this load is 0 nm. at full load, the engine had the highest torque for combining b00 at rotational speeds of 1800 rpm. the torque at 50% load was less than the engine load of 100%. the torque fluctuations were reduced by both 50% and 100% loads at the speed of 1800 rpm over time until the amount of these oscillations reached acceptable stability. the engine variation at different loads at 2500 rpm is similar to changes at the engine speed of 1800 rpm. at this rotational speed, it is also observed that the torque is greater than the engine loads of 50% and 0% at full load, and as well as the fluctuations in the engine have become stable in less time. it indicates that less time is needed to achieve a steady state at a high engine speed so that the engine fluctuations become uniform to start the delivery of exhaust gases (see figure 2). in figures 1 to 2, the torque fluctuations of the engine for combining b10 and b15 in the full engine load have reached a monotonous state in very little time, and it is well illustrated to improve the engine's return to monotonicity using biodiesel combinations. figure 2 shows that in the combination of b15 at rotational speeds of 2500 rpm for a full load of the engine, torque variations became very uniform in very little time, but a different trend was observed for the engine load of 50% and more time was spent to smooth the torque fluctuations. 3.2 torque changes relative to biodiesel percentage and rotational speed figure 3 shows the effect of increasing the biodiesel percentage to diesel fuel on engine torque production at rotational speeds of 1800 rpm and 2500 rpm. each of these speeds is tested at 50% and 100% loads. table 4 shows the value of the measured data, and figures 3 to 10 are based on the data in table 4. the torque produced at a rotational speed of 1800 and 2500 rpm and a load of 100% is greater than the torque at 50% load at both rotational speeds. according to figure 3, the highest torque was observed in the combination of b05 at 100% load and a rotational speed of 1800 rpm with a value of 17.64 nm, and this value for the torque of conventional diesel fuel of 14.558 nm shows that it increases 21.17% torque for b05 than b00 and also the lowest of these values in b05 but at rotational speeds of 2500 rpm and the engine load of 50% with a value of 6.45 nm. the torque increases with increasing engine load for all rotational speeds and decreases torque at each engine load with increasing rotational speed. it was observed that with increasing engine speed from 1800 to 2500 rpm at 100% load, the amount of torque was reduced, and similarly, for the load of 50%, this same decrease in torque was observed with the increasing speed of rotation, which shows this trend process for both the 50% and 100% engine load. figure 1. the torque changes from the dynamometer relative to the engine speed figure 2. the torque changes from the dynamometer relative to the engine speed for the biodiesel blend figure 3. the effect of adding biodiesel to diesel fuel on generating the engine's torque under test at 100% load, with increasing biodiesel from b00 to b20 at a rotational speed of 1800 rpm, the first increase in torque was observed from b00 to b05, and then the b10 decreased, followed by a slight increase in the graph of figure 3, a steady trend was observed. at a speed of 1800 rpm for the engine load of 50%, the torque was reduced from b00 to b10, and an increasing trend was shown from b10 to b20. the process torque was reduced from b00 to b05, but the trend of m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 43 increased torque was observed from b05 to b20. in both the 50% and 100% engine load charts for rotational speeds of 2500 rpm, the highest torque was found in b00. the thermal value of biodiesel fuel is lower than diesel fuel. by increasing the biodiesel fuel content in combination with diesel fuel, the thermal value of the mixture is also lower, affecting the amount of torque produced by the mixture. at 50 % engine load for both rotational speeds and 100% engine load for a rotational speed of 2500 rpm in the b05 mixture, the torque was reduced compared to conventional diesel fuel, but at 100% engine load and engine speed of 1800 rpm, this value increased slightly compared to conventional diesel. as described above in figure 3, for all combinations of biodiesel, the amount of torque produced is reduced with increasing engine speed from 1800 to 2500 rpm. it can be seen that the engine behavior in figures 3 and 4 for biodiesel fuel blends is similar to engine behavior for diesel fuel charts, and the difference in torque produced by the engine at rotational speed and different loads using biodiesel fuel mixtures are also visible in these charts as compared to the time when conventional diesel fuel is used. figure 4. effect of rotational speed on engine torque production under different biodiesel and diesel combinations 3.3 specific fuel consumption changes based on biodiesel percentage and rotational speed in figure 5, b05 at 50% engine load and for both rotational speeds of 1800 rpm and 2500 rpm and as well as the engine load of 100% at a rotational speed of 2500 rpm, the highest sfc is for three graphs and trends were almost identical in their diagrams, but this value was initially slightly lowered in b05 at 100% engine load at the rotational speeds of 1800 rpm and then slightly increased in b10 to b15. figure 5. the effect of increasing the percentage of biodiesel composition in diesel fuel on fuel-specific consumption 3.4 power variations relative to biodiesel percentage and rotational speed figure 6 shows the effect of the biodiesel increase on the fuel mixture. as shown in figure 6, engine power is increased by increasing engine load and speed. the maximum production power between 50% and 100% engine loads and rotational speeds of 1800 rpm and 2500 rpm is at 100% load and rotational speed of 2500 rpm. the maximum production power is b00, b15, b10, b20, and b05, with values of 4.547273, 4.33625, 4.272727, 4.269048, and 4.1772 kw. the lowest power is also available for the b10 at 50% load and 1800 rpm at the value of 1.751373 kw. figure 6. the effect of biodiesel increases on the fuel blend on the brake power of the tested engine with an increase in engine speed from 1800 to 2500 rpm, the engine power increases for both loads of 50% and 100%, and only in the combination of b05 at 50% engine load reduced very little in power was observed (see figure 7). at rotational speeds of 1800 rpm and 100% engine load, the highest production power is observed for the b05 composition. in figure 6, it is seen that at 100% load for both rotational speeds, the values obtained for the biodiesel and diesel fuel mixture are not significantly different from conventional diesel fuel; however, diesel fuel will be combustible faster than the biodiesel-diesel mixture. at a rotational speed of 1800 rpm and 100% engine load for the b05 blend, the power increased by 13.73%, while b10, b15, and b20 decreased by 2.1%, 0.079%, and 0.632%, respectively, and at the engine load of 100% and rotational speed of 2500 rpm for the mixes b05, b10, b15 and b20 showed 8.13%, 6.04%, 4.64% and 6.126% decrease in the amount of power compared to conventional diesel fuel, respectively. figure 7. effect of engine speed on the engine power m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 44 3.5 the egt tables 5 and 6 give the values of the percentage of oxygen volumes and production power in the combination of biodiesel and diesel. in the combination of b05 at a rotational speed of 1800 rpm and a 100% engine load, the highest percentage of the oxygen volume and the maximum amount of generated power were observed with values of 16.14205 %vol and 3.662 kw, respectively. in the combination of b05 with the higher oxygen content in the exhaust gas, it is better to burn the engine in the presence of sufficient oxygen. also, the maximum production power was observed in the b05 composition with increasing rotational speed and engine load. table 6 shows oxygen data at the engine load of 100% and the rotational speed of 1800 rpm and 2500 rpm for different combinations of biodiesel and conventional diesel in iran (see figures 8 and figure 9). table 6. available oxygen data for different combinations of biodiesel and conventional diesel at full engine load and rotational speeds of 1800 rpm and 2500 rpm figure 8. the rate of changes in the percentage of oxygen and power in the engine load figure 9. the rate of change in the percentage of oxygen and power in the engine load the highest volumes of oxygen in the exhaust gases were observed for b10 and b05 compounds with values of 14.52409% and 14.47319 % vol, respectively. the highest production power at the rotational speed of 2500 rpm was recorded for a conventional diesel engine of 4.55 kw. with tests on fuel combinations at full load, it can be seen that the best combination of biodiesel and diesel at full load was introduced b05 at rotational speeds of 1800 rpm. table 7 shows the percentage of variations in sfc, torque, egt, and power relative to conventional diesel. table 7. the percentage of changes in sfc, torque, egt, and power relative to conventional diesel 4. conclusion increasing the engine load from 0% to 100% increases the torque produced from the biodiesel and diesel fuel mixture. the torque was reduced in all tested fuel combinations by increasing engine speed. for biodiesel fuel produced from norouzk oil in a mixture with iranian conventional diesel, the torque was reported at a speed of 1800 rpm more than the torque at 2500 rpm. the result is that all fuel blends achieved the best results at full engine load and at rotational speed of 1800 rpm. the sfc is increased with an increase in engine speed from 1800 rpm to 2500 rpm and increasing engine load from 0% to 100%. in the engine load of 50% among all fuel combinations, the highest sfc was observed for b05. increasing the engine speed for all combinations of biodiesel produced from norouzk oil in combination with conventional iranian diesel increases engine power. at a rotational speed of 2500 rpm, the maximum power of the fuel mixture is achieved, and the engine load increases the power output. resulting in the use of a fuel mixture, more power was generated by increasing the engine load from 50% to 100%. with experiments on the norozak oil biodiesel fuel, it has been found that this fuel can be used as a substitute for diesel fuel in compression ignition engines. it can also be combined with b05 fuel of norozak oil at the rotational speed of 1800 rpm and 100% engine load introduced as an optimal combination. considering the favorable results obtained from experiments on biodiesel, it can be combined with b05 to reduce the environmental pollution caused by diesel engines. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement data sharing is not applicable to this article as no datasets were generated or analyzed during the current study. conflict of interest the authors declare no potential conflict of interest. o2 [%vol] data amount b00 b05 b10 b15 b20 1800[rpm] 15.741 16.14205 15.75432 15.21342 15.01895 2500[rpm] 14.012 14.47319 14.52409 13.97684 13.84895 performance speed rpm blend b05 b10 b15 b20 torque 1800 1.47% -2.4% -0.6% -0.68% 2500 -8.1% -5.91% -4.84% -5.76% egt 1800 4.12% 0.076% 0.84% 1.75% 2500 -2.1% -2.7% -1.91% -2.2% power 1800 1.37% -2.1% -0.08% -0.63% 2500 -8.13% -6.04% -4.64% -6.12% sfc 1800 -0.56% 1.86% 0.86% 0.99% 2500 9.65% 5.9% 8.37% 6.93% m. niknejad et al. /future sustainability november 2023| volume 01 | issue 01 | pages 39-45 45 references [1] m. asvad, a. hajinezhad, a. jafari, and s. f. moosavian, "multiscale kinetic modeling for biohydrogen production: a study on membrane bioreactors," international journal of hydrogen energy, 2023. 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[24] y. aliabadi, a. hajinezhad, r. fattahi, and s. f. moosavian, "analysis of energy generation from msw with auxiliary feed in the north of iran," results in engineering, vol. 18, p. 101185, 2023. [25] m. shoaei, a. hajinezhad, and s. f. moosavian, "design, energy, exergy, economy, and environment (4e) analysis, and multi-objective optimization of a novel integrated energy system based on solar and geothermal resources," energy, p. 128162, 2023. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 32 article design and analyzing a hybrid hydro and solar photovoltaic system for rural areas in malaysia brian dean soon1*, chin-leong wooi2 1faculty of engineering, computing, and science swinburne university of technology sarawak campus kuching, malaysia 2centre of excellence for renewable energy (cere), school of electrical system engineering, pauh putra main campus universiti malaysia perlis, 02600, arau, perlis, malaysia a r t i c l e i n f o article history: received 02 september 2023 received in revised form 03 october 2023 accepted 10 october 2023 keywords: renewable energy, hybrid renewable energy systems (hres), microgrid, hydropower, solar photovoltaic (pv) *corresponding author email address: 101211463@students.swinburne.edu.my doi: 10.55670/fpll.fusus.1.1.4 a b s t r a c t some rural areas worldwide, including malaysia, are not electrified due to geographical constraints, less infrastructure development, and isolation from the main power grid. in addition, renewable energy (re) sources are considered alternatives to replace conventional (non-re) sources that cause pollution. however, re sources have limitations, such as the dependency of weather and geological conditions. to address this issue, a hybrid renewable energy system (hres) is introduced by connecting one re and non-re source or more than one re with or without non-re sources. in this study, a standalone hybrid hydro and solar photovoltaic (pv) hres was designed for rumah bada in nanga talong, ulu engkari. as the site has limited information on load consumption and geographical data, estimations were done based on similar studies. the available solar pv and hydro system at the site was identified with the respective parameters. the proposed system was based on the hybrid acdc microgrid, along with two alternatives based on the ac and dc microgrid, respectively. technical analysis was done to find out the capability of the system by calculating the power generated during different periods and performing the load flow analysis using the powerworld simulator. apart from that, economic analysis was done to find out the most cost-efficient system by calculating the net present cost (npc) and cost of energy (coe) using homer pro. 1. introduction renewable energy (re) sources such as solar, wind, and hydro are considered alternatives for power generation. however, re in stand-alone has limitations, such as the dependency on weather and geological conditions. hence, a hybrid re system (hres) is developed for a more reliable and sustainable energy supply with re by combining one re and one non-re, or more than one re (with or without nonre) together as one system [1]. in malaysia, efforts to use re for power generation have been made in the past few years. as of december 2020, the total installed capacity of re in malaysia was 8,450 mw, which accounts for 23% of the total installed capacity [2]. the most installed capacity of re is large hydro, followed by solar photovoltaic (pv), small hydro, biomass, and biogas. however, most of these re sources are installed as individual power stations. the coverage of rural electricity supply is increased to 98% in the 11th malaysia plan [3] and will continue to achieve 99% in 2025 in the 12th malaysia plan [4]. other efforts, such as the sarawak alternative rural electrification scheme (sares) and sabah renewable energy rural electrification (re2) roadmap, are done to accelerate rural electrification in east malaysia, which has some remote villages isolated by the terrain. hence, this project aims to design and optimize a hybrid hydro and solar pv system for a selected rural area in malaysia. 2. literature review there are numerous configurations for hybrid hydro and solar pv systems in malaysia and other countries. these models are dependent on the re resources available and the price of components for the system. in short, the configurations of hres can be classified into two categories: stand-alone (off-grid) and grid-connected (on-grid). off-grid hres is a system that generates power and supplies the loads connected without relying on the grid. as the primary energy source (which is re) is stochastic in nature, energy storage technologies (for example, battery energy storage systems (bess), supercapacitors, and flywheels) are normally connected to the system to store energy during the absence of re [5]. in on-grid hres, the system is connected to the grid, which enables the buying and selling of power from the grid to compensate for the variability of re systems [5, 6]. a feasibility study of a stand-alone hybrid pv-hydrokinetic turbine (hkt) system was conducted for a rural village, future sustainability open access journal https://doi.org/10.55670/fpll.fusus.1.1.4 november 2023| volume 01 | issue 01 | pages 32-38 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:101211463@students.swinburne.edu.my https://doi.org/10.55670/fpll.fusus.1.1.4 https://fupubco.com/fusus bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 33 kampung git, in sarawak, malaysia [7], which was compared with a pv-battery system and diesel generator (dg) system. it was found that the proposed system had the lowest levelized cost of energy (lcoe) and net present cost (npc) of rm1.21/kwh and rm1,431,000, respectively. based on the renewable energy fraction (rf), pv contributes 66% of energy due to the larger size of 89.9 kw, as compared to the 7 kw hkt system at the remaining 34%. another study conducted for mboke, ihiagwa, nigeria [8] proposed a standalone pv-hydro-dg battery system due to the unstable grid supply. the system was compared with pv-hydro-battery, pv-dg-battery, and pv-dg system and was found to be the most optimized system with npc of us$963,431 and coe of us$0.112/kwh. although the pv-hydro-battery system is more environmentally friendly, it is not economically friendly as the npc and coe are 125% and 127% more than that of the optimized system. grid-connected hybrid hydro and solar pv systems were studied in ref [9] and ref [10]. sabudin et al. [9] designed and simulated a grid-connected pv-hydro-battery system for kampung lepok, kuala selangor, malaysia. the system was compared with pv-hydro (without battery) and hydro-battery systems, both grid-connected. the feasibility is based on rf and npc, and it was concluded that the pv-hydro fulfilled the criteria with 9.12% rf and npc of rm4.83 million. by comparing the battery-hydro-grid and pv-batteryhydro-grid systems, it was found that the largest re contributor is hydro at 7.7%, followed by pv at 1.5%. the main supply of the system relies on the grid at 90.8%. syahputra, and soesanti [10] investigated the potential of a grid-connected pv-hydro-battery system in banjarharjo village, yogyakarta, indonesia. the comparison was made between similar systems with different capacities of solar pv from 0 to 40 kw, and the system with 0 kw solar pv (without pv) is the most optimal system due to the cost saved from not using a pv system, and the 622 kw micro-hydro system being sustainable, thanks to the strong flow rate of 6,500 l/s. to simulate and analyze the hres design, several software has been used in various studies. one of the software is homer. developed for both on-grid and off-grid systems by the national renewable energy laboratory (nrel) in 1993 [11], homer is commonly used for the design and technoeconomic analysis of hres. another software is the powerworld simulator, commonly used for power system applications. it is more popular than other simulation tools as it can display power flow, voltage, and other parameters in real-time animation, which helps users visualize the situation in a complex power system [12]. hres functions in the form of a microgrid, which is defined as a self-sufficient energy system formed with local power generating units along with energy storage devices and controllable consumer load within clearly considered electrical borders [13]. generally, hres microgrids are classified into three types: ac (alternating current), dc (direct current), and hybrid ac-dc microgrids. ac microgrids can be further classified as centralized and decentralized ac microgrids. these configurations are different in terms of the bus involved and the number of components used. 3. methodology the research was done in several stages. initially, the site was decided, and the geographical data (solar irradiance and flow rate) was obtained based on databases and similar studies. next, the load demand of the site was estimated, and the specifications were identified. after that, the calculation of power generated by the different stand-alone systems at the site was done with the geographical data. finally, optimization and simulation of the hres design were done in powerworld simulator and homer pro, followed by technoeconomic analysis and comparison with alternative systems. 3.1 location details the proposed site for this project is rumah bada, which is located in nanga talong, ulu engkari (coordinates: 1°23'22.69"n, 111°59'6.63"e). the nearest towns are sri aman and lubok antu. figure 1 shows the aerial view of rumah bada. it is an iban settlement with 30 households. the daily activities of the community are fishing, farming, and being a part-time national park ranger. figure 1. aerial view of rumah bada 3.2 geographical data 3.2.1 solar-related data the monthly average solar global horizontal irradiance (ghi) is obtained from nrel and is shown in figure 2. the daily radiation and clearness index was the lowest in january, with 4.552 kwh/m2/day and 0.459, respectively. the two values have a peak at different months, at 4.934 kwh/m2/day in march and 0.492 in august. the average values are 4.767 kwh/m2/day and 0.4765, respectively. figure 2. monthly average solar global horizontal irradiance (ghi) 3.2.2 hydro-related data the river near rumah bada is the engkari river, which is one of the tributaries of batang lupar, a downstream river of batang ai dam. due to the remoteness of the area, it is not possible to obtain direct data on the engkari river. hence, the hydro data of the river is reasonably estimated based on a bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 34 case study analysing the potential of rural sustainable energy supply in the baram river basin, sarawak [14]. based on figure 3, the monthly average flow rate has a maximum of 23 l/s in april and a minimum of 11 l/s in july and october. the annual average flow rate is 17 l/s. figure 3. assumed monthly flow rate 3.3 load demand due to the unavailability of site data related to the load demand in rumah bada, estimations will be done based on a study on the electricity consumption of rural villages that benefit from sares [15]. since all 30 households live in the same longhouse, it is expected that each household uses the same electrical appliances with a similar pattern of load demand. it is also assumed that the room for each household has one living room, two bedrooms, one kitchen, and one toilet. the load demand estimation is done for a typical day, and all appliances are assumed to be used. table 1 shows the load estimation of one household in rumah bada. the daily load demand per household is estimated to be 2915 wh (2.915 kwh). based on this value, the daily load demand of rumah bada is 87.450 kwh. the load profile for the entire longhouse is illustrated in figure 4. table 1. load estimation of one household in rumah bada appliance power rating (w) quantity duration (hour) load (w) energy (wh) lamp 10 5 4 50 200 tv 60 1 2 60 120 radio 20 1 1 20 20 table fan 35 3 5 105 525 refrigerator 75 1 24 75 1800 rice cooker 500 1 0.5 500 250 total 810 2915 3.4 components of hybrid hydro and solar pv system the proposed hres for rumah bada is a stand-alone pvhydro-battery system. this is because the site has an independent pv system and hydro system under the initiative of sares. it is worth noting that the capital cost, replacement cost, and operational and maintenance (o&m) cost are based on reasonable estimations from other studies due to the customization nature. the entire project is projected to have a lifetime of 25 years. 3.4.1 solar pv system the existing solar pv system in rumah bada was launched for operation in june 2019. the system consists of 270 wp polycrystalline pv panels connected in 6 strings with 20 panels each in series. with a peak power of 32.4 kw, it is the main electricity source for the local community. the system has a capital cost of rm5015/kw; the same goes for the replacement cost. o&m cost is negligible, as minimal maintenance is required besides cleaning and dusting. the efficiency is estimated to be around 15% to 22%, and the lifetime of this system is 25 years. figure 4. load demand of a typical day for all households in rumah bada 3.4.2 hydro system the existing hydro system in rumah bada is a picohydro system and was launched for operation in may 2018. the pico-hydro system acts as a supporting system and has a power capacity of 10 kw. the system is commonly used for lighting purposes whenever necessary. both the capital cost and replacement cost are rm5000/kw. the o&m cost is rm250, mainly used for the maintenance of moving parts in the hydro turbine. the designed flow rate for the pico-hydro system is 25 l/s. the efficiency is 80%, and the lifetime is 25 years. 3.4.3 battery for the pv system in rumah bada, a lithium-ion (liion) battery system with a capacity of 165 kwh is used. the capital cost is rm555/kwh, and the same goes for the replacement cost. similar to solar pv systems, the o&m cost is negligible as the battery will be replaced immediately once it malfunctions. depth of discharge (dod) is 85%, and the lifetime is five years. 3.4.4 inverter in rumah bada, the powercube 5000 microgrid inverter by huawei corporation is used to convert the dc power of solar pv systems and batteries into ac power for distribution. the specifications of the components in the system are given in table 2. table 2. specifications of components in the system parameter pv hydro battery inverter capital cost rm5015 /kwp rm5000 /kw rm555/kw h rm1635 /kw replacement cost rm5015 /kwp rm5000 /kw rm555/kw h rm1635 /kw o&m cost rm250 rm50 lifetime 25 years 25 years five years 15 years efficiency 15 – 22% 80% 96% power capacity 32.4 kwp 10 kw 165 kwh 33 kw bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 35 the system has six strings, with five batteries in each string. both the capital cost and replacement cost are rm1635/kw. the o&m cost is rm50. the inverter has an efficiency of 96% and a lifetime of 15 years. 3.5 relevant equations in hres design, technical and economic calculations are done to ensure the system will be able to fulfill the load demand and benefit the community economically. 3.5.1 technical calculations the generated solar pv power, ppv, can be obtained with equation 1 [5]. 𝑃𝑃𝑉 = 1 1000 ∑ 𝐺𝐻𝐼(𝑡)24 𝑡=1 × 𝐴𝑃𝑉 × 𝑁𝑃𝑉 × ηpv (𝑘𝑊) (1) where ghi is the global horizontal irradiance (in kwh/m2/day), apv is the surface area of solar pv panels (in m2), npv is the number of solar pv panels, hpv is the solar pv panel efficiency (in %) (generally between 15% and 22%), and t is time of the day (in hours). by assuming the daily energy produced is constant throughout the year, the annual hourly energy generation, aeppv can be obtained with equation 2error! reference s ource not found.. 𝐴𝐸𝑃𝑃𝑉 = 𝑃𝑃𝑉 × 8760 (𝑘𝑊ℎ) (2) the power from falling water, phy,avg can be obtained with equation 3 [5]. 𝑃𝐻𝑌,𝑎𝑣𝑔 = 𝑚×𝑔×ℎ𝑛×𝜂 1000 (𝑘𝑊) (3) where m is the mass flow rate (in l/s), g is the gravity acceleration (= 9.81 m/s2), hn is the net head (in m) and h is the efficiency (generally between 75% and 95%). from here, with the power available for one year (365 days in hours), the annual energy produced from the hydro turbine, aephy is obtained with equation 4. 𝐴𝐸𝑃𝐻𝑌 = 𝐶𝐹 × ∑ 𝑃𝐻𝑌,𝑎𝑣𝑔,𝑑 365 𝑑=1 (𝑘𝑊ℎ) (4) where cf represents the capacity factor, which is the ratio of the annual energy produced by a hydro system to the theoretical maximum if the system operates 24/7 at maximum output power. the required battery size, creq in ampere-hour (ah), is computed with equation 5 [16]. 𝐶𝑟𝑒𝑞 = 𝑊𝑑𝑒𝑚𝑎𝑛𝑑(𝐷𝐶) 𝑉𝐷𝐶 ×𝑁𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝐷𝑂𝐷×𝐷𝐹𝑏𝑎𝑡𝑡 (𝐴ℎ) (5) where wdemand(dc) is the average daily dc load demand during critical months, vdc is the system bus dc voltage, nstorage is the design autonomy period (in days), dod is the depth of discharge, and dfbatt is the derating factor (including temperature and wiring losses). the battery capacity in kwh is expressed in equation 6. 𝐶𝑟𝑒𝑞 = 𝑊𝑑𝑒𝑚𝑎𝑛𝑑(𝐷𝐶)×𝑁𝑠𝑡𝑜𝑟𝑎𝑔𝑒 𝐷𝑂𝐷×𝐷𝐹𝑏𝑎𝑡𝑡 (𝑘𝑊ℎ) (6) load flow analysis is important in the power system study and is calculated by equation 7 & 8. the analysis is aimed to calculate and evaluate the important parameters of a test system, which are the sinusoidal steady state of system voltage, generated (p) and reactive (q) power, and transmission losses. single-line diagrams and per-unit systems are commonly used in this analysis [17]. based on kirchhoff's current law, the current at ith bus is: 𝐼𝑖 = 𝑦𝑖0𝑉𝑖 + 𝑦𝑖1(𝑉𝑖 − 𝑉1) + 𝑦𝑖2(𝑉𝑖 − 𝑉2) + ⋯ + 𝑦𝑖𝑛(𝑉𝑖 − 𝑉𝑛) = (𝑦𝑖0 + 𝑦𝑖1 + ⋯ + 𝑦𝑖𝑛)𝑉𝑖 − 𝑦𝑖1𝑉1 − 𝑦𝑖2𝑉2 − ⋯ − 𝑦𝑖𝑛𝑉𝑛 (7) 𝐼𝑖 = 𝑉𝑖 ∑ 𝑦𝑖𝑗 𝑛 𝑗=0 − ∑ 𝑦𝑖𝑗 𝑛 𝑗=0 𝑉𝑗 (𝑗 ≠ 𝑖) (8) the complex power at ith bus is calculated based on the equation 9 & 10: 𝑆𝑖 = 𝑃𝑖 + 𝑗𝑄𝑖 = 𝑉𝑖𝐼𝑖 ∗ (9) 𝐼𝑖 = 𝑃𝑖−𝑗𝑄𝑖 𝑉𝑖 ∗ (10) from equations 8 and 10, 𝐼𝑖 = 𝑃𝑖−𝑗𝑄𝑖 𝑉𝑖 ∗ = 𝑉𝑖 ∑ 𝑦𝑖𝑗 𝑛 𝑗=0 − ∑ 𝑦𝑖𝑗 𝑛 𝑗=0 𝑉𝑗 (𝑗 ≠ 𝑖) (11) 3.5.2 operational and economical calculations lcoe is a standardized method used for the evaluation of the cost of an energy source to produce a unit of energy (rm/kwh) across the lifespan of the project. this approach helps to determine the most suitable energy source at a specific location in the economic comparative analysis [5]. in homer, coe is formulated as such in equation 12. 𝐶𝑂𝐸 = 𝐶𝑎𝑛𝑛,𝑡𝑜𝑡−𝑐𝑏𝑜𝑖𝑙𝑒𝑟𝐻𝑠𝑒𝑟𝑣𝑒𝑑 𝐸𝑠𝑒𝑟𝑣𝑒𝑑 (𝑅𝑀/𝑘𝑊ℎ) (12) where cann,tot is the total annualized cost of hres, cboiler is the marginal cost of the boiler, while hserved and eserved represent the total thermal and electrical load served, respectively. since there is no boiler in the system, coe is formulated as such in equation 12 and expressed in equation 13. 𝐶𝑂𝐸 = 𝐶𝑎𝑛𝑛,𝑡𝑜𝑡 𝐸𝑠𝑒𝑟𝑣𝑒𝑑 (𝑅𝑀/𝑘𝑊ℎ) (13) in general, npc is the total cost throughout the project lifespan, which includes installation, replacement, and o&m costs. when the total project cost is analyzed, the difference between the present revenue generated and the cost spent during the project lifetime is calculated. npc is formulated as such in equation 14 [7]. 𝑁𝑃𝐶 = 𝐶𝑎𝑛𝑛,𝑡𝑜𝑡 𝐶𝑅𝐹 × 𝐼 × 𝑅 (14) where crf is the capital recovery factor, i is the annual interest rate, and r is the project lifetime. 4. results and discussion the proposed design of the system will be based on the hybrid ac-dc hres microgrid. in this configuration, the picohydro system is connected to the ac bus, while the solar pv and battery systems are connected to the dc bus. as the hres provides electricity to an ac load, the dc bus is connected to the ac bus via the huawei powercube 5000 microgrid inverter. figure 5 shows a schematic of the proposed design. for comparison purposes, two alternative designs are proposed based on the centralized ac and dc hres microgrid, respectively. in short, the components will be collected to a common bus, and the component that operates differently from the bus will be connected to a power converter. after performing the necessary calculations and simulation, the results and techno-economic analysis are presented in this section. 4.1 technical analysis the technical analysis is done by calculating the power generated by each component during different periods and performing the load flow analysis for the proposed and alternative configurations. bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 36 figure 5. simple schematic of the proposed design 4.1.1 power calculation during different periods the average daily radiation of 4.767 kwh/m2/day is used for the calculation of power generated by solar pv systems. the efficiency of the solar pv panels is assumed to be 20%. the power and energy generated by the system are computed by using equation 1 and multiplying the equation together with 12 hours, respectively. table 3 represents the calculation of the average daily power and energy generated by solar pv systems. table 3. calculated average daily power and energy generated by a solar pv system daily radiation (kwh/m2/day) 4.767 average daily power generated (kw) 22.4716 average daily energy generated (kwh) 269.6592 the power supplied by the pico hydro system is assumed for two scenarios: low and high flow rates. the average low and high flow rates are taken as 14 l/s and 21 l/s, respectively. cf is taken as 0.771. the power and energy generated by the system are computed by using equation 1 and equation 2 divided by 365 days. table 4 shows the calculations of the average daily power and energy generated by the pico hydro system. table 4. calculated average daily power and energy generated by the pico hydro system average low average high flow rate (l/s) 14 21 average daily power generated (kw) 4.9442 7.4164 average daily energy generated (kwh) 91.4875 137.2331 4.1.2 load flow analysis the load flow analysis is done for the proposed and alternative configurations on the powerworld simulator and is shown in figure 6. the respective circuits are constructed, followed by the input of power capacity for each component. due to the varying nature of output power during charging and discharging, the battery is set as the slack bus for each system. the simulation results for the three systems are obtained and summarised in table 5. figure 6. load flow simulation for hybrid ac-dc microgrid table 5. power of each component in different hres design it was found that the solar pv and pico hydro systems are able to generate the specified real power (32 kw and 10 kw, respectively). in terms of reactive power, the two systems in the hybrid ac-dc microgrid have zero reactive power. in comparison, the reactive powers of the ac and dc microgrid are 32 kvar and ten kvar, respectively, which is contributed by the power converter connected to the components. table 5 shows the power values of each component in different hres designs. the battery in each configuration is charged with different amounts of power. the battery is charged the most in the dc microgrid with 48 kw and the lowest in the ac microgrid with 17 kw. nonetheless, no reactive power is supplied to the battery for each case. also, the load demand of 25 kw can be fulfilled by each configuration without reactive power. another simulation shown in figure 7 is done on the proposed design to identify the capability to supply power at night or when the solar pv system is unable to fulfil the load demand. figure 7. load flow simulation for hybrid ac-dc microgrid (without solar pv) this simulation is done by setting the solar pv power to 0 kw while maintaining the parameters of other components. 4.2 economic analysis the economic analysis is done by inserting the necessary inputs of each component for the proposed and alternative design hybrid acdc ac dc solar pv real (kw) 32 32 32 reactive (kvar) 0 32 10 pico hydro real (kw) 10 10 10 reactive (kvar) 0 32 10 battery real (kw) -42 -17 -48 reactive (kvar) 0 0 0 load real (kw) 25 25 25 reactive (kvar) 0 0 0 bd. soon & cl. wooi /future sustainability november 2023| volume 01 | issue 01 | pages 32-38 37 configurations and performing the simulation using homer (table 6). table 6. economical results for the different hres designs design hybrid ac-dc ac dc npc (rm) 568,887 618,156 629,484 coe (rm/kwh) 1.38 1.50 1.53 operating cost (rm/yr) 16,313 16,256 17,094 initial capital (rm) 358,000 408,000 408,500 replacement (rm) 211,321.21 209,624.1 1 222,564.4 7 o&m cost (rm) 3,878.25 4,524.63 4,847.82 salvage (rm) -4,312.04 -3,992.63 -6,428.14 the main economic parameters used to compare the different hres designs are the npc and coe. based on table 6, the most economical hres design is the proposed hybrid ac-dc microgrid with an npc of rm568,887 and a coe of rm1.38/kwh. in comparison, the ac and dc microgrids have slightly higher npc and coe, at about 110% of the proposed design. from figure 8, the initial capital contributes the most to the npc due to the budget spent on installation. however, the capital cost is not a major concern, as most components are installed beforehand. the replacement cost also contributes significantly to the npc, as the batteries are replaced once every five years. it is worth noting that the re sources are only replaced after the project lifetime, thus not contributing to the replacement cost. the o&m cost takes up a small portion of npc, as it only comprises the maintenance for the pico hydro turbine and converter. figure 8. npc summary for hybrid ac-dc microgrid 4.3 discussion from the power calculation for hres components at different periods, the solar pv and pico hydro systems are unable to reach the maximum power capacity with the geographical data. however, the generated power is sufficient to fulfill the load demand of rumah bada. from a technical perspective, the optimal system should have minimal reactive power in each component, as reactive power causes additional load, overheating, and power loss on the cables and system equipment. based on the technical analysis, the proposed system is the most feasible system with the least reactive power. in terms of battery charging, the dc microgrid is more favorable as the system provides the most power to charge the battery. despite that, the battery in the proposed system only requires to supply 15 kw when the solar pv system is unable to supply to rumah bada. from an economic perspective, the proposed hybrid ac-dc microgrid is also proven to be the most feasible system with the lowest coe and npc. although the proposed system will require a complex control system to facilitate the power flow, the proper utilization of components helps to reduce the overall cost. in comparison, the alternative systems have a simpler control system but will require more converters and power correction equipment, which contributes to the higher overall cost. 5. conclusion in conclusion, an hres is proposed and designed for rumah bada, a longhouse located in nanga talong, ulu engkari. due to the remoteness of the location, the geographical data was obtained based on databases and relevant studies. the load demand of rumah bada was estimated with an average consumption pattern based on relevant studies. the specifications of hres components were identified. with that, the hres design is proposed based on a hybrid ac-dc microgrid, along with alternatives based on ac and dc microgrids. technical analysis was done by performing calculations on the power generated by the hres components during different periods. it was found that the generated power is sufficient for the load demand in rumah bada despite not achieving the intended power capacity. besides that, load flow analysis was done for the proposed and alternative designs using the powerworld simulator. from the analysis, all three systems were able to supply sufficient power to the load in rumah bada. however, the ac and dc microgrids produce reactive power of 32 kvar and ten kvar, respectively, which would result in drawbacks such as additional load, overheating, and power loss on the cables and equipment of the system. from there, the proposed hybrid ac-dc microgrid is preferred as the system produces zero reactive power. economic analysis was done with homer, and the proposed system is the most feasible system with the lowest coe of rm1.38/kwh and npc of rm568,887. overall, the proposed hybrid ac-dc microgrid system is the most optimal system. further investigations can be done on the microgrid control system design to facilitate power flow and investigation on the transmission system. thus, it is hoped that this project will contribute to the research on implementing hres in malaysia. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement 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[33] horstmann b, single f, latz a. review on multi-scale models of solid-electrolyte interphase formation. curr opin electrochem 2019;13:61–9. https://doi.org/10.1016/j.coelec.2018.10.013. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1149/2.062310jes https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 1 article technical and environmental assessment of biofuel utilization in light and heavy vehicles: implications for carbon footprint reduction on high-traffic freeway reza feizi, hossein yousefi*, mahmood abdoos, fatemeh razi astaraei school of energy engineering and sustainable resources, college of interdisciplinary science and technology, university of tehran, tehran, iran a r t i c l e i n f o article history: received 05 january 2025 received in revised form 12 february 2025 accepted 23 february 2025 keywords: carbon dioxide emissions, road freight transport, biofuels, fuel consumption analysis, environmental sustainability *corresponding author email address: hosseinyousefi@ut.ac.ir doi: 10.55670/fpll.fusus.3.2.1 a b s t r a c t the global imperative to reduce greenhouse gas (ghg) emissions necessitates urgent transitions in the transportation sector, which currently accounts for approximately 40% of global emissions. this study focuses on the potential of biofuels to serve as a sustainable alternative to fossil fuels within iran's road freight transport sector, specifically along the north tehran freeway, a corridor characterized by heavy traffic and significant carbon emissions. conducted over a one-year period from october 2022 to september 2023, this research calculates the carbon footprint of vehicles using gasoline and diesel, providing a detailed analysis of fuel consumption and resulting co2 emissions. the study highlights the feasibility of bioethanol and biodiesel, locally available in iran, as practical substitutes for fossil fuels, particularly given the limited availability of electric vehicles (evs) in the region. the findings reveal that gasoline dominates fuel consumption on the tehran-north corridor, accounting for 86% of the total fuel use, thereby underscoring the urgent need for cleaner alternatives. this research contributes to the understanding of iran’s unique transportation challenges and offers practical solutions for reducing carbon emissions through biofuels. the study’s granular approach, assessing emissions on a monthly basis, provides nuanced insights into seasonal and behavioral factors influencing fuel use, laying the groundwork for effective policy development aimed at transitioning iran’s transportation sector towards greater sustainability. 1. introduction the current level of unintentional greenhouse gas (ghg) emissions resulting from the burning of fossil fuels has reached a concerning point, necessitating immediate measures for prevention through the adoption of environmentally compatible climate policies. in 2015, the international energy agency developed a scenario for the future energy system aiming to restrict the rise in global average temperature to 2 degrees celsius by 2050, later revised to 1.5 degrees celsius [1]. presently, the global transportation sector accounts for a quarter of total energy consumption and contributes around 40% of greenhouse gas emissions. with oil dominating the sector and fulfilling 90% of its fuel demand, the necessity for transitioning towards more sustainable energy sources is evident. two pivotal transformations are crucial for decarbonizing transportation: the shift towards electricity, focusing on electric vehicles (evs) and hydrogen fuel cell vehicles (hfcvs) for road transport, and the adoption of cleaner fuels like biofuels, hydrogen, and hydrogen-based fuels, especially in the aviation and maritime industries [2]. incorporating biofuels into the energy mix emerges as a promising strategy to reduce carbon emissions and promote sustainability within the transportation sector. biofuels, as renewable and easily future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.2.1 may 2025| volume 03 | issue 02 | pages 01-07 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:hosseinyousefi@ut.ac.ir https://doi.org/10.55670/fpll.fusus.3.2.1 https://fupubco.com/fusus feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 2 accessible alternatives, offer a feasible means to diminish greenhouse gas emissions and lessen reliance on nonrenewable fossil fuels. by embracing biofuels alongside other clean energy solutions, countries can advance towards their emission reduction objectives and facilitate the transition to a more environmentally conscious transportation infrastructure [3, 4]. one of the significant environmental challenges faced by iran pertains to the production of 0.5 kg of carbon dioxide per us dollar of gdp, indicating one of the highest ratios of carbon dioxide production to gdp globally [5]. as a response, iran pledged in the 2015 paris agreement to unconditionally reduce its greenhouse gas emissions by 4% by 2030 [6]. given that the predominant use of fossil fuels in almost all motor vehicles in iran makes transportation a primary contributor to carbon dioxide emissions, the imperative of transitioning to cleaner energy sources in iran's transportation sector is twofold. consequently, an essential step involves the assessment and comparison of the carbon footprint associated with renewable and non-renewable fuels within this sector. the north tehran freeway, known for its heavy traffic flow of various vehicles, presents a significant real-world challenge. we are undertaking the critical task of addressing the serious problem of high emissions in iran by analyzing the carbon footprint along this route. this research not only evaluates the potential of biofuels as substitutes for fossil fuels to reduce carbon dioxide emissions but also aims to provide practical solutions for enhancing transportation sustainability. with bioethanol and biodiesel readily available in iran and limited electric vehicle options due to production constraints, transitioning to biofuels emerges as a more feasible option over shifting from internal combustion engine (ice) vehicles to electric ones. this comprehensive analysis lays the foundation for developing effective strategies to significantly reduce the carbon footprint in the transportation sector. 2. literature review according to pandey et al. [7], determining the comprehensive carbon footprint requires estimating and summing up the ghg emissions during the entire life cycle of a manufactured item. this life cycle encompasses all stages, from obtaining raw materials to final packaging, distribution, consumption, and disposition. this approach, known as cradle-to-grave analysis, provides a holistic view of inputs and outputs, including air pollutants, water usage, energy consumption, ghg emissions, and other relevant factors. assessing the life cycle's environmental impact, costs, and benefits is often referred to as environmental life cycle assessment. to compute the carbon footprint, the ghg emissions released at each stage of the product's life cycle, referred to as ghg accounting, are estimated. different methodologies exist for calculating the carbon footprint. strutt et al. [8] have outlined three distinct domains to facilitate accurate calculations [9]. the first domain encompasses direct emissions, specifically those occurring at the calculation site. the second domain encompasses emissions associated with purchased energy. the third domain encompasses all indirect emissions, including those related to the transportation of goods, sold items, business travel, energy activities, product disposition, and other factors not accounted for in groups 1 and 2. naturally, if all three domains are considered, the accuracy of the work will be higher. ghg data can be gathered by means of direct measurements on the spot in real time or estimated using emission factors and models. the selection of the most suitable approach depends on the purpose (mandatory, voluntary, or internal management), reliability, workability, expense, and scope. emission factors and models are the favored and commonly utilized approaches [7]. to convert ghg data into equivalent carbon dioxide, conversion factors provided by the intergovernmental panel on climate change are employed [9]. based on the study conducted by murray et al. [10], a wide range of online calculators exist for carbon footprint calculations. some of these calculators focus on estimating internal carbon footprints, while the rest estimate carbon footprints related to transportation, food, or related endeavors. several studies have been conducted in the realm of calculating and comparing carbon footprints, specifically within the transportation sector. girardi et al. [11] conducted a comparative assessment of the life cycle of an ev and a petrol-driven car in italy, utilizing available data from the national power system regulations, electricity market laws, and the list of results from national reports. they focused on different scenarios for the years 2013 and 2030 to calculate both short-term and long-term impacts. the study revealed a reduction of over 40% in ghg emissions from evs compared to icevs. furthermore, wu et al. [12] have focused on calculating and comparing the life cycle ghg emissions of evs and petrol-driven cars. they utilized the china automotive life cycle database for the years 2010, 2014, and 2020. the results indicate that the potential for reducing emissions during the whole period of the life cycle can increase by 13.4% for evs compared to petrol-driven cars by the year 2020. in another study, leung et al. [13] investigated the impact of using biofuels in hong kong to reduce pollutant emissions in vehicles as well as carbon footprint. they demonstrated that the carbon dioxide emissions in the process of converting waste paper to ethanol can be reduced by 80% compared to the process of transporting waste paper to landfills [14]. holmatov et al. [15] evaluated the environmental impact of transportation using vehicles fueled by renewable sources. this evaluation encompassed three aspects: land footprint, carbon footprint, and water footprint. their findings showed that, compared to gasoline-powered vehicles, evs exhibited a 96% reduction in emissions in a bioelectricity scenario and a 100% reduction in a solar electricity scenario. vehicles running on 20% biodiesel blend (b20) fuel had 12% lower emissions, while hfcvs showed 100% lower emissions. however, it is important to note that these vehicles had a significantly larger water footprint than conventional gasoline vehicles. the pioneering aspect of this study resides in the computation and scrutiny of the carbon emissions profile for a heavily traversed roadway in iran on a monthly and yearly cadence, marking a novel endeavor in this domain. furthermore, the research entails appraising the viability of biofuels as feasible substitutes for traditional fossil fuels with the aim of curbing carbon dioxide emissions. previous studies on carbon emissions and biofuels have been conducted in different geographic and economic contexts, often focusing on developed countries or regions with advanced renewable feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 3 energy infrastructure. this article fills the gap by providing detailed, localized data on carbon emissions specific to the tehran-north corridor, offering insights into a region with unique challenges such as heavy reliance on fossil fuels and limited biofuel production infrastructure. the study uniquely emphasizes the potential of biofuels as a sustainable alternative in iran's transportation sector, where the adoption of evs is limited. while biofuels have been extensively studied globally, their application and feasibility within iran's road freight transport context have not been thoroughly explored. this research provides valuable data and analysis that could inform future policy decisions and industrial strategies in iran and similar regions. unlike many previous studies that provide a snapshot or annual average of emissions, this article offers a granular analysis of fuel consumption and emissions on a monthly basis. this temporal detail helps to identify patterns in fuel use and emissions that are influenced by seasonal changes, travel behaviors, and other factors, providing a more nuanced understanding of the challenges and opportunities for emission reduction. the study goes beyond theoretical assessments by applying findings to a specific, heavily trafficked roadway in iran. this practical approach ensures that the research has immediate relevance and applicability, offering tangible solutions for reducing the carbon footprint in iran’s transportation sector. overall, the article contributes to the body of knowledge on sustainable transportation by addressing critical gaps in data and analysis for iran, providing a pathway for practical, region-specific strategies to reduce greenhouse gas emissions through the adoption of biofuels. 3. methodology iran's biofuel production mainly involves bioethanol and biodiesel, but production volumes are relatively low. the agricultural residues and waste that could serve as feedstock are often not fully utilized, primarily due to logistical issues and a lack of infrastructure. the adoption of biofuels in road freight transport in iran is limited, reflecting broader challenges within the biofuel industry. the transportation sector in iran heavily relies on fossil fuels, particularly diesel, due to the country's abundant oil resources and subsidies that keep fuel prices low. this reliance on fossil fuels contributes significantly to carbon emissions, particularly in the road freight transport sector, which is a major consumer of diesel. the potential for biofuels to serve as a more sustainable alternative to diesel in road freight transport is significant, especially considering the increasing pressure to address climate change and reduce dependency on fossil fuels. to justify the focus on reducing carbon emissions through the adoption of biofuels in road freight transport, it is essential to highlight the environmental benefits of biofuels, such as lower greenhouse gas emissions compared to conventional diesel. the development of the biofuel industry could also have economic benefits, including job creation in rural areas, reduced dependency on oil, and improved energy security. while iran's biofuel industry is still underdeveloped, there is a significant opportunity to expand biofuel production and use in road freight transport to reduce carbon emissions. focusing on biofuels could not only help mitigate the environmental impact of the transportation sector but also promote sustainable economic growth by leveraging the country's agricultural resources and reducing reliance on fossil fuels. this study, conducted over a one-year period in 2023, focused on investigating carbon dioxide (co2) emissions due to their significant impact on the road transport sector in iran. the decision to concentrate on co2 was driven by its predominant role in contributing to the environmental challenges faced by the transportation sector. one of the critical reasons for this focus on co2 is its considerable contribution to the overall greenhouse gas emissions in iran's road transport sector, making it a key target for emission reduction strategies. co2 emissions are a major concern globally, and in iran, the road transport sector is a significant source of these emissions, which underscores the importance of addressing this pollutant to mitigate climate change and its associated impacts. additionally, the study encountered challenges in accessing reliable data on other greenhouse gases, such as nitrogen oxides (nox) and sulfur oxides (sox), and their emission contributions across different types of vehicles in iran. this limitation in data availability made it difficult to conduct a comprehensive analysis of all greenhouse gases, leading to a specific focus on co2. policymakers and researchers need to carefully weigh these strengths and limitations when considering biofuels as part of a broader strategy for sustainable energy and climate change mitigation. sustainable practices, technological advancements, and comprehensive lifecycle assessments are essential to maximizing the benefits of biofuels while minimizing their environmental impact. in this study, the calculation of carbon dioxide emissions is conducted using an analytical approach. for this purpose, traffic data on the tehran-north freeway has been extracted from the website of the national road management center [16]. additionally, figure 1 displays the map of this route. figure 1. north tehran freeway map to determine the carbon footprint, the first step involves calculating the distance covered [17]. 𝑆 = 𝑙 × 𝑛 (1) where s represents the distance covered in kilometers, l denotes the length of the road in kilometers, and n represents the number of vehicles. by utilizing the computed distance feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 4 traveled, the total fuel consumption can be determined using the following equation (2) [17]: 𝐶𝑡𝑜𝑡 = 𝑆 × 𝐶𝑒 (2) in equation (2), ctot represents the total fuel consumption in liters, and ce represents the vehicle's energy consumption per kilometer in liters. table 1 displays the default values for energy consumption for various vehicle types. these quantities are calculated based on an assumed average lifespan of 20 years for each vehicle in iran, taking into account the expert opinions in the field. table 1. the default energy consumption values for various vehicle types vehicle type energy consumption value (liter/km) class 1 (cars and pick-up trucks) 0.11 class 2 (mini trucks and minibuses) 0.22 class 3 (normal trucks less than 10 meters and 3 axles) 0.38 class 4 (buses) 0.45 class 5 (trailers and carriers above 3 axles) 0.7 then, the values obtained for the total fuel consumption are utilized to compute the amount of energy consumption (ec) in liters with the help of equation (3)[17]: 𝐸𝑐 = 𝐶𝑡𝑜𝑡 × 𝐹 (3) the calculation of the energy consumption value is performed by converting the fuel consumption using the energy content (f). the unit of energy content is gigajoules per liter, and its values, which are based on the type of fuel consumed, are specified in table 2 for diesel and gasoline. table 2. energy content values for gasoline and diesel fuel type energy content (gj/l) reference gasoline 0.03466 [18] diesel 0.03868 [18] then, using equation (4), the emission value (em) is calculated by multiplying the energy consumption value by the emission factor (ff). the unit of the emission factor is tons of carbon dioxide per terajoule [17]. 𝐸𝑚 = 𝐸𝑐 × 𝐹𝐹 (4) the values of the emission factors for the fuels used are provided in table 3. table 3. emission factor values for the fuels used 4. results and discussion 4.1 calculating the carbon footprint of consumed gasoline and diesel fuel in light of the limitations imposed by the covid-19 pandemic, calculations have been conducted for one year following the lifting of restrictions. specifically, the period considered spans from october 2022 to september 2023. the initial step involved calculating the volume of gasoline and diesel consumed in liters for various vehicle classes. gasoline was used as fuel for class 1 vehicles, whereas diesel was used for other classes. table 4 illustrates the fuel consumption for different vehicle classes throughout the designated one-year period. table 4. the amount of fuel consumed by different types of vehicles it can be observed that during the one-year period under investigation, a total of over 118 million liters of gasoline and over 18.7 million liters of diesel were consumed on the tehran-north corridor. this indicates that gasoline accounts for approximately 86% of the total fuel consumption on this route. despite the fact that the energy consumption in class 1 vehicles is significantly lower compared to other vehicle classes, the total fuel consumption of class 1 vehicles is much higher due to the significantly larger number of vehicles in this class. it is also observed that in diesel-powered vehicles, class 2 vehicles, namely mini-trucks and minibuses, despite their lower energy consumption, have allocated the highest fuel consumption to themselves due to their larger numbers. in the second step, the monthly fuel consumption in liters has been calculated. figure 2 illustrates the monthly consumption of gasoline and diesel separately, in millions of liters, from october 2022 to september 2023. it is observed that during the warm and moderate months of the year, there is a significant increase in fuel consumption, with the gasoline and diesel consumption in these months being almost twice as much as the colder months. the highest gasoline consumption occurs during the summer months when intercity travel is at their peak. during these months, over fifty million liters of gasoline are consumed in total. in october, a 31% decrease in consumption compared to the previous month is observed, with the most significant factors being the start of the school year and a noticeable drop in temperature, leading to a significant decrease in intercity travel. this decrease in consumption continues with the decrease in temperature to the point that the lowest fuel consumption is also related to the coldest months of the year, namely january fuel type emission factor (tco2/tj) reference gasoline 69.3 [19] diesel 74.1 [19] vehicle type fuel consumption value (million liters) class 1 (cars and pick-up trucks) 118.07 class 2 (mini trucks and minibuses) 8.29 class 3 (normal trucks less than 10 meters and 3 axles) 4.03 class 4 (buses) 2.59 class 5 (trailers and carriers above 3 axles) 3.83 feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 5 and february when intercity travel reaches its minimum due to severe cold weather. figure 2. the amount of fuel consumed the highest amount of diesel consumption is also observed in the summer season, particularly during the months of july and august, where approximately 2.2 million liters of diesel are consumed in each of these months. unlike gasoline, the reason why the peak diesel consumption is not in august is because truck drivers tend to go on vacation and have less work engagement during that month. the lowest diesel consumption, around one million liters, occurs in the months of february and april. it appears that the cold weather in february and the partial closure of the month due to the new year holiday in april contribute to this situation. then, the carbon dioxide footprint has been calculated. the total amount of carbon dioxide released throughout the year is 337.3 million liters, with 84% of it, which is equivalent to 283.6 million liters, coming from burning gasoline and the remaining 16%, which is 53.7 million liters, resulting from burning diesel. the monthly carbon dioxide emissions in terms of million liters are shown in figure 3. as expected, the pattern of carbon dioxide emissions follows a similar trend to the fuel consumption pattern, and during the hot months of the year, with a significant increase in traffic and fuel consumption, the emissions also show a noticeable rise. in fact, the emissions resulting from burning gasoline in september are more than double the emissions in the months of january and february. the emissions resulting from burning diesel also follow a similar pattern, with the emissions in the month of september being more than double the emissions in the months of january and february. 4.2 calculating the impact of replacing fossil fuels with biofuels in this stage, the calculations were again performed using the conversion and emission factors specific to biofuels. diesel vehicles can use biodiesel, while gasoline vehicles can use bioethanol. therefore, the calculations assumed using these fuels instead of fossil fuels. table 5 displays the energy content and emission factor of pure biofuels, including corn ethanol and palm biodiesel. subsequently, the values related to conventional biofuels, which include e5, e10, b5, b10, and b20, are calculated using the data in tables 2,3 and 5. table 6 presents the energy content and emission factor of these fuel variants. since the use of b100, e100, and e85 requires modifications to the vehicle system and the addition of special filters, the calculations for these fuels were ignored. figure 3. monthly co2 emissions table 5. values of energy content and emission factor of pure biodiesel and bio gasoline table 6. values of energy content and emission factors of conventional biofuels the emission levels from various combinations of biofuels have been initially calculated. figure 4 displays the monthly emissions of gasoline, e5, and e10. it is evident that although the consumption patterns are similar, the emission levels decrease as the concentration of bioethanol in the blend increases. figure 5 compares the emissions of these three fuels over the course of one year. the reduction in carbon dioxide emissions when using e5 is over 11.9 million liters, indicating a decrease of 4.19%. additionally, the reduction in carbon dioxide emissions when using e10 is over 23.8 million liters, indicating a decrease of 8.39%. in the next step, the carbon dioxide emissions from biodiesel blends of 5%, 10%, and 20% have been calculated. fuel type energy content (gj/l) emission factor (tco2/tj) reference b100 0.03393 33.19 [20] e100 0.021 18.53 [21] fuel type energy content (gj/l) emission factor (tco2/tj) b5 0.03844 72.05 b10 0.03821 70.01 b20 0.03773 65.92 e5 0.03398 66.76 e10 0.03329 64.22 feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 6 figure 6 displays the monthly emissions of diesel fuel, b5, b10, and b20. it can be observed that the consumption patterns are similar, but as the concentration of biodiesel in the blend increases, the emission levels decrease. in figure 7, the emissions of these three fuels have also been compared over the course of one year. the reduction in co2 emissions when using a 5% biodiesel blend is approximately 1.63 million liters, indicating a decrease of 3.04%. additionally, the reduction in carbon dioxide emissions when using a 10% biodiesel blend is over 3.26 million liters, indicating a decline of 6.08%. the capacity for emission reduction with a 20% biodiesel blend is over 6.5 million liters, representing a reduction of 12.15%. through the calculations conducted on the replacement of gasoline and diesel with biofuels, it has been determined that we can achieve a minimum reduction of 13.5 million liters, equivalent to 4.01%, and a maximum reduction of 30.3 million liters, equivalent to 8.98%, in carbon dioxide footprint. the minimum scenario corresponds to the substitution of e5 and b5, while the maximum scenario involves the substitution of e10 and b20. figure 4. the monthly emissions of gasoline, e5, and e10 figure 5. comparing the carbon footprint of gasoline, e5, and e10 over a year figure 6. the monthly emissions of diesel, b5, b10, and b20 figure 7. comparing the carbon footprint of diesel, b5, b10 and b20 over a year 5. conclusions the analysis of fuel consumption and co2 emissions along the tehran-north axis over a one-year duration has yielded significant findings. notably, gasoline constitutes the major share, accounting for approximately 86% of the total fuel consumed on this route. while individual passenger vehicles exhibit lower energy consumption, their sheer volume renders them influential contributors to overall fuel consumption. furthermore, the study reveals a distinct seasonal pattern, indicating substantially higher fuel consumption during warmer months, particularly at the peak of intercity travel, compared to colder months. correspondingly, co2 emissions align with the fuel consumption patterns, with an excess of 337 million liters of co2 produced on this axis, of which 84% is attributed to gasoline combustion. to assess the potential impacts of biofuels, computational modeling was employed to simulate complete substitution scenarios, whereby gasoline and diesel were replaced entirely by bio-gasoline and biodiesel at lower blend percentages. the results estimated a range for annual carbon footprint reduction from a minimum of 13.5 million liters (equivalent to 4.01%) to a maximum of 30.3 million liters (equivalent to 8.98%). these findings underscore the potential of biofuels in mitigating co2 emissions within the transportation sector. nevertheless, challenges associated with the utilization of biofuel blends, including the need for vehicle modifications to accommodate higher blend percentages, must be considered. feizi et al. /future sustainability may 2025| volume 03 | issue 02 | pages 01-07 7 ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] masson-delmotte, v., pörtner, h.-o., skea, j., zhai, p., roberts, d., shukla, p. r., & buendía, e. c. 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(2007). a behavioral assessment of tourism transportation options for reducing energy consumption and greenhouse gases. journal of travel research, 45(3), 297-309. [19] sandhu, s. c. (2015). greenhouse gas inventories for urban operations in southeast asia: challenges and opportunities. www.adb.org/sites/default/files/publication/16134 4/sewp-12.pdf [20] choo, y. m., muhamad, h., hashim, z., subramaniam, v., puah, c. w., & tan, y. (2011). determination of ghg contributions by subsystems in the oil palm supply chain using the lca approach. the international journal of life cycle assessment, 16, 669-681. [21] gnansounou, e., & dauriat, a. (2005). ethanol fuel from biomass: a review. journal of scientific & industrial researchvol. 64, november 2005, pp. 809821. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 22 review the perspective of energy storage systems advancements and challenges for electric vehicle applications; metric, mechanism, mode, and mitigation framework sadegh mehranfar1*, isa banagar1, jamshid moradi1, amin mahmoudzadeh andwari1*, juho könnö1, ayat gharehghani2, moeed rabiei2, emil kurvinen1 1machine and vehicle design (mvd), materials and mechanical engineering, faculty of technology, university of oulu, fi-90014 oulu, finland 2school of mechanical engineering, iran university of science and technology, tehran, iran a r t i c l e i n f o article history: received 22 september 2024 received in revised form 26 october 2024 accepted 04 november 2024 keywords: battery electric vehicles, fuel cell electric vehicles, energy storage systems *corresponding author email address: sadegh.mehranfar@oulu.fi amin.m.andwari@oulu.fi doi: 10.55670/fpll.fusus.2.4.4 a b s t r a c t new advancements in the automobile industry require greater demonstration of the role of energy storage in evs. more effective energy production and storage require an in-depth look at the recent advancements and challenges of energy storage systems (ess). this paper presents a holistic and hierarchical framework of metric, mechanism, mode, and mitigation of esss recent advancements and challenges, including a) evaluation metrics for advancements, b) identification of mechanisms and most important challenges, c) mode and effects analysis, d) mitigation through material optimization/system design. a comprehensive review was conducted by comparing different batteries, fuel cells, and supercapacitors’ efficiencies, performance, advantages, and disadvantages. 1. introduction in the last decade, increased environmental concerns, rapid technological advancements, and transmission into electrification in the automobile industry have put energy storage systems (ess) at the center of attention. among different esss for evs, batteries, fuel cells, and supercapacitors exhibit the potential to shape ev applications thanks to each technology's new advancements and advantages to address required energy/power density, lifetime, cost, and safety [1]. despite global efforts to enhance energy density, improve power capability, and reduce costs, challenges remain in ensuring the cyclability and safe operation of high-energy-density esss. electrochemical and thermal stability, material development, and system design remain major concerns, particularly following their mass adoption in the coming decades [2]. figure 1 demonstrates the global electric car stock trends in the 2010-2023 timespan. these trends indicate that battery electric cars accounted for 70% of the electric car stock in 2023 [3]. this paper aims to review the application of energy storage systems (ess) in evs with specific attention to battery technologies, fuel cells, and supercapacitors. esss have long played a pivotal role in improving the system's performance in-vehicle applications by delivering energy into the system or saving energy produced by the system. fuel cells, supercapacitors, ultra-capacitors (ucs), and various battery technologies have been widely adopted in ev applications and have shown promising results in terms of improving fuel economy [4]. the recovered energy is stored in an ess reservoir for later use when acceleration. two of the most important indicators of total energy and power per unit weight are introduced as specific power and specific energy. these two parameters are considered the most determinative factors in ees systems in transportation applications, for they directly influence the travel range and weight of the vehicle. future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.4.4 november 2024| volume 02 | issue 04 | pages 22-32 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:sadegh.mehranfar@oulu.fi https://doi.org/10.55670/fpll.fusus.2.4.4 https://fupubco.com/fusus sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 23 figure 1. global electric car stock trends 2010-2023 [3] the result of the specific power and energy comparison in different ees technologies is illustrated in table 1 [5]. supercapacitors, also known as ultra-capacitors, can produce considerable energy at low voltage. they stand in an advantageous position in esss due to their high-power density and fast charging and discharging. nonetheless, ucs are only completely well suited for ev applications once low energy density is addressed [6]. on the other hand, batteries are considered the most promising ess technology in transportation technologies and have been widely accepted by manufacturers because they offer substantially higher energy storage capabilities. annual predictions show a steep growth in li-ion battery demands in the upcoming years [3]. nevertheless, li-ion batteries come with their challenges. safety issues in li-ion batteries remain a concerning challenge. increased temperature in li-ion batteries can cause a series of chain reactions, leading to battery fire and explosion [7]. complexities in different esss can rise from different scales, from material development to system integration [8]. developing new nanostructured electrodes for increasing the energy density of ucs and designing flow fields in pem flow fields are some trending research that targets the current ess constraints [9]. this paper presents a holistic and hierarchical framework of metric, mechanism, mode, and mitigation of ess's recent advancements and challenges, including a) evaluation metrics, b) identification of mechanisms and causes, c) mode and effects analysis, d) mitigation through material optimization/system design. a brief comparison of ess technologies is presented in table 1 [5]. 2. energy storage systems 2.1 batteries as one of the most prevalent energy storage and propulsion systems in the transportation industry, batteries can be a perfect fit for vehicle powertrains due to their high energy density, fast response, high efficiency, and zero tailpipe emission as a crucial aspect in future mobility. moreover, integrating batteries into the vehicle powertrain will bring more flexibility in the electrification of ancillary units, system modularity, better regenerative break, and less maintenance for less mowing parts into the electric vehicles. introducing batteries in electrified vehicles will bring about zero-tailpipe emission benefits and improve urban air quality. while existing hurdles in the way of ev battery advancements, such as raw material supply constraints, burdensome cost, and safety threats in higher density chemistries, are proposing challenges for ev battery industries, exceptional advantages of ev batteries call for an increase in the number of research in this area since the annual global demand for ev batteries would reach 1925 gwh by 2030 by a 688% increase from 2021. new regulations also impose net zero tailpipe emission, facilitating vehicle electrification and leading to further market growth. as a result, many research institutions and automotive manufacturers are investing in the integration of ev batteries and the development of batteries for evs. a group of battery cells forms battery modules, and battery packs comprise battery modules designed with evs of the desired capacity. battery pack design complexities bring numerous challenges due to the control of cell voltage, state of charge, and thermal issues throughout the operation. table 1. comparison of ess technologies battery supercapacitors fuel cells specific energy (wh/kg) 30-300 0.05-15 100-450 specific power (w/kg) <2000 <10000 <200 power rating mw 0.005-100 0.0001-0.1 0.005-50 energy capital cost ($/kwh) 100-150 300-2000 230-330 efficiency (%) 70-100 84-97 60-80 charge time 1-5 h 0.3-30 s 3-5 min discharge time 0.3-3 h 0.3-30 s 0.3-3 h daily selfdischarge (% per day) <0.03-0.3 oct-20 lifetime (years) 2-20 10-12 1-10 sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 24 battery cells group together and form modules. several modules also group to form battery packs. battery management systems handle the interconnection between cells and modules. bmss monitor and control the batteries efficiently and safely through numerous tasks such as monitoring, protection, charging and discharging management, communication, diagnosis, and data management. critical states of batteries, such as state of power, health, charge, energy, power, temperature, and safety, are required for effective charging, thermal management, and health management. batteries produce heat as a result of electrochemical reactions. very high and low temperatures adversely affect battery performance, life, and safety and might impose degradation and even overheating if not handled properly. this comes to the importance of thermal management. it has been reported that higher temperatures can be very problematic for ev batteries. higher temperatures lead to the accumulation of heat and trigger chains of exothermic reactions, which lead to combustion and even the explosion of batteries. this phenomenon is called thermal runaway (tr) and is more extreme in higher energy density materials, owing to more chemically active materials. the tr behavior calls for additional countermeasures for thermal management for safety [7]. the design of btms calls for attention, and numerous investigations were focused on leveraging heat transfer mechanisms for keeping the batteries in the optimal range, including active methods (air cooling and liquid cooling), passive methods (phase change materials and heat pipes) and hybrid methods (integration of active methods with passive methods) [1, 9]. performance indexes such as energy efficiency, maximum temperature, and temperature difference are satisfied with btms designers as the temperature has the most effect on the aging mechanism and threads' lifetime of batteries. the importance of btms comes into play in terms of safety implications as well. this is due to the thermal runaway concerns in the accumulation of heat and raised temperature, which leads to further exoteric chained reactions and finally combustion or even explosion of batteries. in the core of battery systems in evs, there are numerous interconnected battery cells. battery cells correspond to more than 75% of battery overall costs and determine the characteristics of the system. energy density, power density, cost, safety, and lifetime are the main critical factors for ev battery selection [10]. improvements in the energy density of batteries have been greatly focused as one of the main critical factors in ev batteries since the shift from the ice market requires batteries to deliver a comparable driving range and lower cost, which leads to an exploration of new batteries for higher energy densities. early ev batteries, such as pb-acid batteries, offered competitive prices in the market but suffered from low energy density. nicd batteries showed promising lifespan, while destructive materials impeded their commercialization. nimh was also utilized in hybrid-electric passenger cars (toyota prius) and resolved previous challenges, but still was hindered by low storage capacity and self-discharging. li-ion batteries revolutionized the ev market owing to their exceptional energy density, lifecycle, and low self-discharge, which is highly important in transportation applications. higher energy density expands the range as one of the main obstacles to evs. the reported 80 wh kg-1 has seen a steep growth from 1991 to 2020 and reached a satisfactory number of 400 wh kg-1 [7]. li-ion batteries also propose great energy efficiency and boost ev performance (up to 95% compared to 70% and 65% in leadacid and nimh batteries) [11]. li-ion batteries come in many characteristics in terms of chemistries. an overview of battery chemistries is provided in the review of chemali et al. [12]. the cell chemistry selection is a great design choice for ev battery designers since pure evs require high energy storage, and hybrid electric vehicles call for power [13]. in addition to the main two factors of energy and power density, cells should operate safely in different loads, overcome complex mechanical, electrical, and thermal loads in various working conditions, and offer a high life cycle to work for many years. therefore, exploring new chemistries and material advancements is the research direction for manufacturing high-energy, safe, and affordable ev batteries with increased lifespan. a comparison of battery characteristics in ev battery evolution is presented in table 2. the us advanced battery consortium target is also presented in the table to highlight the target goals in the battery technology advancements [14]. in addition to the promising characteristics of new cell chemistries, battery materials correspond to more than 70% of battery cell cost. hence, breakthroughs in cell materials will facilitate the market penetration of battery evs [11]. different battery technologies arise from various types of cathodes, anodes, and electrolytes. currently, lithium cobalt oxide (lco) dominates the market and is the mature cathode chemistry. other cathode technologies such as lithium iron phosphate (lfp), lithium nickel manganese cobalt oxide (nmc), lithium nickel cobalt aluminum oxide (nca), and lithium manganese oxide (lmo) are advancing and tracking the place of lco in the market by offering more stable crystal structures, lower price, and more abundant materials. lfp offers fast charging and low volumetric energy density and fits better in public transport and heavy-duty applications. however, it has reached its theoretical limit (170wh/kg) and cannot satisfy the expectations of the next generation of ev batteries. despite the low energy density and lifetime, lfp battery evs dominate the commercial ev section due to lower material cost (50% less material cost than nca). lmo offers high power but low energy density. battery types can be blended to other high energy density chemistries like nmc to take advantage of both types (e.g. lmo/nmc composite for bmw i3 and nissan leaf). nmc takes advantage of low internal resistance from manganese, high capacity from nickel, and low cost from less cobalt by combining ni, lmo, and lco). it is estimated that nmc will grow its share in the market due to higher energy density than lfp, while others (nca and lmo) remain constant. the energy density of the cell level has reached 250 wh/kg, reaching the promising 300 km range [10]. a comparison of li-ion battery technology across energy/power density, safety, lifespan, and cost is presented in figure 2. a. comparison of li-ion cathode chemistries and the effect of chemistries on the characteristics of the cells is also elucidated in figure 2. b, c and d. [1, 10, 11]. anode materials are also under development with the si integration breakthrough. si offers exceptionally higher energy density but comes with thorny issues such as material swell and huge volume explanation during lithiation, leading to capacity loss (the calendar life of si-anode batteries is still only 20–30 months, against the ev requirement of 100–140 months [15]). sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 25 table 2. comparison of different battery characteristics in evs battery type energy density (wh/kg) specific power (w/kg) life cycle energy efficiency (%) production cost ($/kwh) advantages disadvantages usab goal 350 700 1000 100 lead acid (pb-acid) 35 180 1000 70-90 60 + low initial cost + maturity in technology + good network of manufacturing infrastructure + abundant and affordable raw materials low specific energy and power short life cycle temperature-sensitive performance charging time safety concerns due to gas release and hazardous lead nickelcadmium (ni-cd) 50-80 200 2000 60-70 250-300 + good cycle lives + wide operating temperature range + good safety + low charging time + mature technology memory effect reliance on hazardous cadmium nickelmetal hydride (ni-mh) 70-95 200-300 <3000 50-80 200-250 + good specific energy and power + eco-friendly materials + extensive operating temperature range + good safety high self discharging memory effect zebra (nanicl) 90-120 155 >1200 80 230-345 + low self-discharging and no memory effect extremely high temperature range thermal management and safety issues lithium-ion (li-ion) 118-250 200-430 2000 70-80 150 + outstanding specific energy and power + long cycle lives + satisfactory operating temperature ranges + chemistry diversity + eco-friendly material technologies + fast charging high initial cost sophisticated bms technology required safety concern for thermal runaway material depletion concerns lithium-ion polymer (lipo) 130-225 260-450 >1200 70 150 + better packaging optimization compared to li-ion lithiumiron phosphate (lifepo4) 120 20004500 >2000 90 350 + high power density than li-ion + better safety compared to li-ion lower energy density compared to li-ion zinc-air (znair) 460 80-140 200 60 90-120 + relatively high energy density low power density short life cycle lithiumsulfur (li-s) 350-650 300 100-150 + relatively high energy density + low cost high discharge rate short life cycle lithium-air (li-air) 13002000 100 + exceptionally higher energy density (comparable to those of ices) short life cycle sill in prototype stage sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 26 si-c composition and electrolyte additives for stabilization are known as the target solutions. today, only 10% si composition is viable, but si can offer up to 4200 mah/g theoretical capacity. another breakthrough in anode material development is lithium metal, which has a specific capacity that is 10 times higher. li metal development is hindered by high reactivity, lithium deuteride growth, and thermal runaway caused by short circuit concerns. the abovementioned issues can be handled by applying protective layers or embedding solid-state electrolytes. solidstate electrolytes will be the next generation of li-ion batteries and resolve the bottleneck. li foil anodes unlock the energy capacity of graphite anodes, pushing the 280 wh/kg to ≈ 500 wh/kg. the lithium metal foil supply chain should be addressed in the next generation of batteries to meet the market demand for ssbs. figures 2 e and g illustrate the integration of si for high energy density li-ion anodes and compare typical li-ion batteries with lithium metal cells. it is expected that the battery market will heavily rely on currently matured technologies such as nca, nmc, and higher energy nmcs. ev battery technology also depends on the application. heavy-duty applications require longer cycle lives, and nmc/lfp batteries are more favorable in commercial evs than ni-rich and lithium metals. ssbs are the dominant technology in the long term from 2025 onward, with li dendrite suppression for safety and high-performance anode material uptake for high energy density being the main incentives. the cost of the battery is highly dependent on the material supply, investment in research and development for developing new cell chemistries, cell manufacturing process, battery pack design, optimizing the bmss, and battery second life and recycling. costs have continuously decreased since the early introduction of ev batteries. reports show that liion ev battery pack cost dropped by approximately 90% in the 2010-2021 timespan and will fall below $100/kwh in 2024 [16]. there are other factors in ev batteries that must be focused on in order to achieve market dominance. capacity decay occurs in the battery cells every time it is charged and discharged, reducing driving range and service life. the effect of aging is greatly dependent on the battery type, reaction stage, and operating condition, and battery health monitoring and aging diagnostic is one of the main targets of battery management systems, along with the investigation of battery aging mechanisms and proposing prevention methods. temperature adverse effects are known to have the most aggressive effect on battery aging, which further highlights the importance of effective battery thermal management systems. fast charging is another technological advancement in the ev battery industry that has further assisted the ev's competitiveness by addressing the range anxiety in the decreased charge time. this also helps the raw material extraction limits since a 120kwh battery charged in one hour can be replaced by a 60kwh battery with 10 min charge time. the fast charging should also be evaluated by the number of figure 2. overview of shortand long-term research directions for li-ion battery developments a) comparison of the li-ion battery technology across energy/power density, safety, lifespan and cost. b) comparison of li-ion cathode chemistries by specific capacity and specific energy. c) comparison of mn, co and ni content in nmc, d) increased ev battery specific energy density in ni and li rich cathodes, e) integration of si for high energy density li-ion anodes, g) comparison of typical li-ion batteries and lithium metal cell sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 27 cycles since it causes degradation and low cycle life is also a downside in battery life. the ideal target is set by doe as 240 wh kg−1 acquired energy after a 5 min charge with a more than 2,000 cycle lifetime. different power levels in ac charging from 3 to 22 kw, and dc fast chargers from 40 kw to 120 kw are now permitted in the ev batteries [17]. embedded fast chargers also bring other design aspects, such as redesign of vehicle electronics and thermal management, implementation of charging stations, and grid stability challenges [18]. employing the fast-charging methods requires more aggressive btmss that cannot be handled by air cooling or even liquid cooling. nonetheless, the implementation of fast charging station cooling for less weather independence, investigation of new btms for high heat transfer efficiency (immersion and jet cooling), and cell design for lower temperature variation inside the cell due to high heat generation are some of the thermal considerations that should be addressed in this aspect. graphite anode batteries are the first to unlock the fast-charging potential since conventional li-ion batteries have undergone rapid capacity loss and safety hazards in fast charging due to heightened lithium plating risks [15]. the development of ev batteries calls for a huge value chain improvement. despite the zero-emission tailpipe standards, the production and process of materials for manufacturing cells impose substantial carbon emissions. therefore, to alleviate the environmental burden of the whole battery lifecycle, the lifecycle analysis of battery production and recycling of used batteries play a crucial role. the production emissions of batteries are mainly caused by battery cell manufacturing and mostly by positive electrodes, which further highlights the importance of electrode material design. battery cooling systems, bms, and packaging constitute components and subsystems in the battery system, as observed in the life cycle analysis. safely disposing of batteries with less than 80% of their nominal capacity will not only minimize the overall carbon footprint but also reduce the cost since batteries in evs account for almost 40% of the total cost of vehicles [19]. figure 3 elucidates the most current solutions in ev batteries with their promises and challenges based on the main design metrics. 2.2 supercapacitor supercapacitors or ultracapacitors are some of the most attractive esss that contribute to the growth of low to highpower applications. ucs can store and recover energy in ev applications and improve the overall performance of the system in terms of energy efficiency. ucs come into play when batteries cannot meet the energy demand in ev systems. moreover, the ever-changing and erratic inherent energy consumption with changes during battery charge and discharge is very harmful to the electrochemical process of the battery. this can be resolved by utilizing ucs as a highrate ess accompanied by the battery to provide the excess energy demand of evs. a fuel reduction of 10% is reported by the manufacturers of passenger cars when exploiting ucs to store breaking energy [20]. supercapacitors offer extremely higher specific power density (up to 100 times) but suffer from lower energy density when compared to batteries. in an electric double-layer capacitor (edlc), a double-layered conductor with equal and opposite electric charges allows the ucs to store energy by electrostatic charge accumulation. edlc is the most commonly used sc. figure 3. recent progress in ev batteries with their mechanism, mode, and mitigation challenges based on the principal design metrics sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 28 phosphoric capacitors (pc) offer higher energy densities at the expense of power density and cycling stability by storing charge via the faradic process. hybrid supercapacitors (hsc) combine the characteristics of edlc and pc and offer a good combination of power and energy density, and cycling stability. li-ion capacitors are one example of hse [14]. table 1 illustrates different supercapacitor technologies' energy and power density [21]. supercapacitors guarantee a long life due to the lack of chemical reaction in the electrodes, which is in contrast to batteries, and offer a much faster storage capability, which is appealing to mobile machinery. recent developments in electrode materials have been trying to enhance the charge stability, cyclability, and energy density of ucs in ev esss. compared to aqueous electrolytes, non-aqueous electrolytes show a higher energy density due to the high voltage window, enabling the use of high-voltage active materials in the supercapacitor. non-aqueous electrolytes also offer better stability and longer cycle life. however, challenges such as cost, toxicity, and flammability stay ahead of non-aqueous electrolytes despite their advantages. exploring new materials for sc electrolytes, such as nasicon-type materials, is the future of sc development. the advantages of new electrolyte materials, such as high conductivity, good cyclic stability, and enhanced energy and power density, will play an important role in commercializing scs in ev applications [22]. figure 4 elucidates the most current solutions in ev scs with their promises and challenges based on the main design metrics. 2.3 fuel cells the advent of fuel cells has been considered a technological marvel in energy and transportation systems due to their capability to provide zero carbon, efficient, and adaptable power sources. fuel cells have been at the center of increased attention in recent decades owing to their wellcompetent characteristics and better performance in terms of range and efficiency in the automotive industry. compared to the ices and bevs, fuel cells can take advantage of their exceptional characteristics by offering higher energy efficiency than ices, as a matter of direct conversion of chemical energy to electricity, and maintain a longer driving range than bevs by cutting out charging time. fuel cells owe these interesting features to the generation of emission-free (green) electricity and not to the storage, allowing them to enjoy the high range capability of ic engines without sacrificing the clean and sustainable power supply of bevs. implementing fcevs in the transportation industry offers many other advantages, such as modular structure, silent operation, and flexible power ratings, turning fcs into an appealing choice for vehicles ranging from passenger cars to buses and trucks. the attractive lifetime range of fcs (20-25 years) is another interesting factor in the vehicle industry that needs to be considered [23]. fuel cells are not heat engines; hence, their efficiency is not limited by the carnot limit as in the ic engines. therefore, the fcevs can enjoy a sustainable power supply to run the system if the cells are maintained fuel and oxidant. this inherited nature of fcs can also extend the bev capabilities by charging batteries while operating. notwithstanding the wide variety of fuel cells, which are classified into six classes, including proton exchange membrane fuel cells (pemfcs), alkaline fuel cells (afcs), phosphoric acid fuel cells (pafcs), molten carbonate fuel cells (mcfcs), solid oxide fuel cells (sofcs), and direct methanol fuel cells (dmfcs), each type of fuel cells can cover a specific application depending on their limits and advantages. among all types of different fuel cells, pemfcs can be a perfect fit in ev applications by maintaining a proper operating temperature range and high-power density, which leads to a fast startup time required in the transportation industry and a lightweight load to carry for its smaller size, respectively. pemfcs, by exploiting the zero-carbon and high energy density hydrogen gas, can stand out in ev applications and are in progress. however, the challenges of commercialization in fcevs are steep [24]. the very first challenge of fcevs is fuel supply. there are currently two practical ways of storing hydrogen: high-pressure gas or cryogenic tanks. each of them faces important challenges that need to be addressed. pressurizing hydrogen can be very costly or even hazardous. energy per liter of h2 is equivalent to 0.1 liter of gasoline (~1kwh) at the pressure of 350 bar. something in the margin of 25% of its energy should also be consumed to compress the gas into that high pressure, let alone the weight of such a strong tank to tolerate this pressure and safety issues if a dangerous tank is used in transportation applications. liquid hydrogen stored in cryogenic tanks also faces important challenges. facilities to keep the low temperature (-259.2 °c) can add to the weight of the vehicle, liquefying hydrogen is costly, and in case of dropping the temperature and boil-off, the tank is susceptible to highly pressured liquid-gas mixture or even explosion in a vase of using safety valves [24]. the power transmission structure of fcevs includes an fc stack to supply energy, a hydrogen tank, a unidirectional dc-dc converter for fc, a motor drive converter, and an electric motor. additionally, different energy storage and/or generation units can integrate with fuel cells and hybridize fcevs. batteries, supercapacitors, photovoltaic panels, and flywheels are some hybridization units that can offer a variety of hybrid fc designs, with fc-battery hybridization being the most popular topology. a general schematic of fcevs and hybrid fcevs power transmission structure is depicted in figure 5. there are more than 34,800 fcevs and 540 hydrogen refueling stations worldwide, with passenger cars dominating the vehicle market (~75%) [25]. announced targets are also set to reach 10-15 million and 400 million fcevs by 2030 and 2050, respectively. samsun et al. [26] conducted detailed statistical analysis and perspectives on the development of fcevs and hydrogen refueling station infrastructure. even though the fuel supply in fcevs can be problematic and pemfcs are still expensive, fcevs interest automotive companies and researchers to solve unresolved issues and make perfect use of fuel cells in ev applications. expensive catalyst cost, hydrogen purity and production challenges, fuel station accessibility, and safe built-in storage are some challenging issues in the face of fcev advancements underway to meet transportation needs. almost 40% of an fcev’s total cost comes from the stack, and 60% of it comes from the cell itself. more than 45% of the cost in the cell is the catalyst, which shows the importance of reducing platinum loading in the catalyst or utilizing new catalysts [27]. some studies have tried to investigate new catalysts that are much more affordable than precious metals. new fcs with efficient iron-based catalysts have even exceeded the doe’s 2025 target for current density [28, 29]. new investigations are also focused on safer and more affordable hydrogen storage methods and putting behind conventional compressed gas storage systems that have stalled the commercialization of the fcev market. solid hydrogen storage or metal hydride hydrogen storage technology can store the hydrogen for an extended period; however, charging time is still a problem. sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 29 figure 4. recent progress in ev ucs with their mechanism, mode, and mitigation challenges based on the principal design metrics figure 5. recent progress in ev fuel cells with their mechanism, mode, and mitigation challenges based on the principal design metrics sadegh mehranfar et al. /future sustainability november 2024| volume 02 | issue 04 | pages 22-32 30 recent investigations tackle this issue by designing new internal heat exchangers to address the low thermal conductivity of hydrogen and reduce the charging time by up to 59% [30]. economically, scale can also unleash the fcevs' market potential. estimates show that fuel cell prices will drop 70 to 80% as production volume scales, according to ballard, one of the biggest fc manufacturers. the ultimate doe cost target is 30 $/kw. component cost breakdown and cost reduction measure analysis are conducted in different studies [31, 32]. the cost of passenger light-duty vehicles in the us will be cut almost in half from 2030 to 2050, according to the international energy agency technology roadmap, and cost parity with ices will be reached by 2040 by the rapid ramp-up of fuel cell sales [33]. also, the wtw emission of fcevs will dramatically decrease by 2050, whereas it is currently almost comparable to ice’s well-to-wheel co2 emission. it is expected that the vehicle industry will see a surge in fcevs running on roads. figure 6 illustrates the share of fcevs and hydrogen refueling stations for different countries. 3. conclusion this study presents a holistic and hierarchical framework of metric, mechanism, mode, and mitigation of ess recent advancements and challenges for lithium-ion batteries, pem fuel cells, and supercapacitors as three major potent candidates in ev ess. complexities in different esss can rise from different scales, from material development to system integration. nonetheless, each technology poses its unique challenges and promises. li-ion batteries are bound to reach higher energy and power densities and extended lifetime by advancements in new chemistries, solid-state batteries, and methods for suppressing dendrite formation for improved cyclability. however, safety concerns in lithium-ion batteries remain a challenge due to increased energy density. still, they can be controlled by investigation of more stable cell components and system-level safety integration. furthermore, supercapacitors will continue to grow in ev applications by hybridizing materials with battery characteristics to improve energy density. pem fuel cells will continue growing as interesting candidates for ev ess. however, the design of flow field channels, improved performance, and optimized thermal and mechanical properties of the cells for better cyclability will remain important research directions for pem fuel cells. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding authors. conflict of interest the authors declare no potential conflict of interest. references [1] a. gharehghani et al., “progress in battery thermal management systems technologies for electric vehicles,” renewable and sustainable energy reviews, vol. 202, p. 114654, sep. 2024, doi: 10.1016/j.rser.2024.114654. 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[33] “iea (2015), technology roadmap hydrogen and fuel cells, iea, paris.” [online]. available: https://www.iea.org/reports/technology-roadmaphydrogen-and-fuel-cells, license: cc by 4.0. n.d [34] “iea (2021), global ev outlook 2021, iea, paris.” [online]. available: https://www.iea.org/reports/global-ev-outlook2021, license: cc by 4.0 n.d. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 1 review role of the mass media in the sustainability of blue economy in nigeria edith oghenechovwe otuya-asohro* department of mass communication, delta state university, abraka, delta state, nigeria a r t i c l e i n f o article history: received 21 august 2024 received in revised form 25 september 2024 accepted 07 october 2024 keywords: blue economy, mass media, economic growth, sustainable development, ecosystem, ocean *corresponding author email address: otuyaedith@gmail.com doi: 10.55670/fpll.fusus.2.4.1 a b s t r a c t in recent years, the blue economy has gained significant economic momentum in many countries as a viable means of sustainable economic growth and development while engendering the sustainability of the ecosystem. consequently, the blue economy is now acknowledged as a veritable means of boosting the socioeconomic growth and development of a country without jeopardizing the sustainability of the ocean and other water bodies. this study examines the potential of the blue economy in nigeria and the benefits accruable to it if it is properly harnessed. it also highlights the role of the mass media in setting the agenda for public discourse and carrying out developmental functions by creating awareness and educating the citizenry on the numerous opportunities and benefits of the blue economy and the importance of maintaining a healthy marine ecosystem. the study adopted literature-based research as its methodology. furthermore, the study anchored on the agenda-setting theory and the development media theory as its theoretical approach. findings revealed that the majority of the nigerian population, especially those inhabiting the riverine areas and the ocean coastline, are ignorant of the potential of the blue economy in spite of their unfettered access to the marine ecosystem through the expansive inland rivers and the atlantic ocean. findings further revealed that the government has a share of the blame due to the absence of specific policies and programs that will bring the economic benefits of the blue economy to the fore. 1. introduction the ocean is the major focal point of the blue economy. about 75% of the earth’s surface is covered by ocean water bodies. these oceans and seas have several uses, such as recreation and transportation of heavy-weight goods across continents; the ocean also regulates the climates and source of salt and natural mineral resources for human consumption and usage. the ocean also provides the earth with oxygen, absorbs heat, recycles waste, and serves as a sinkhole for carbon dioxide. the ocean is also harnessed for the generation of energy, which is beneficial to mankind. however, for the ocean to effectively and efficiently maintain its utilitarian value to humanity and the ecosystem, it must be healthy because, without a healthy ocean, there is no place for human existence and livelihood. however, it is heart-rending that despite the immense benefit of the oceans to human existence, mankind still exerts undue pressure on the ocean system by inflicting unhealthy and deleterious activities like sewage disposal, waste pollution, oil pollution, overfishing, and incessant exploration on it [1]. the preservation and conservation of biodiversity and vital marine habitats to ensure the sustainability of ocean resources is the fulcrum of the blue economy. thus, the blue economy entails identifying and using oceanic resources and potentials without compromising the oceans’ sustainability. the blue economy is a water-dependent economic endeavor that includes marine biotechnology, renewable energy, shipping, aquaculture, and tourism. the ocean and water bodies are the backbone of the blue economy. the blue economy is adept at creating employment opportunities, generating foreign exchange earnings, improving livelihood, and diversification of coastal economies, which ultimately improves the gdp of blue economy-compliant countries. nigeria is well-endowed, with a vast ocean coastline of about 870km and over 3000km of inland waterways. the country is blessed with numerous natural resources, such as iron ore, tin, coal, zinc, limestone, future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.4.1 november 2024| volume 02 | issue 04 | pages 0107 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:otuyaedith@gmail.com https://doi.org/10.55670/fpll.fusus.2.4.1 https://fupubco.com/fusus eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 2 natural gas, crude oil, and other minerals. however, her overdependence on crude oil and natural gas has made macroeconomic planners myopic and unable to effectively diversify the economy by embracing other viable sources like the blue economy and tourism to generate foreign exchange earnings [2]. the blue economy is aimed at engendering economic growth, conservation of the marine ecosystem, improved livelihood, and simultaneously promoting ecological sustainability of the oceans and other water bodies. the importance of the blue economy to nigeria’s economy cannot be overemphasized because it is an irrefutable fact that the blue economy can boost the economic standing of a country and enhance her national gdp through various sectors like fisheries, renewable energy, maritime transportation, tourism, deep sea minerals exploitation, and waste management. if sustainably utilized in nigeria, the blue economy can serve as a catalyst and a tactical business gumption to bolster a country's economic foundation. thus, this study aims to bring to the fore the immense benefits of a healthy ocean and its impact on the economy. the study also seeks to highlight the economic benefit of the blue economy to the nigerian government when it is struggling with dwindling foreign exchange receipts from crude oil, economic recession, and inflation. furthermore, since it is evident that both the populace and the government are oblivious to the extraordinary capacity of a well-harnessed blue economy to boost the economy, this study also aims to interrogate the role of the media in ensuring that awareness is created about the viability and sustainability of the blue economy in nigeria. 2. literature review 2.1 the concept of the blue economy the blue economy is a broad term encompassing every known economic endeavor that is ocean-driven or connected therewith, directly or obliquely. the importance of the ocean to human survival from the earliest recorded evidence of human existence in pre-historic times is incontrovertible. in climatology and environmental studies, it is widely acknowledged that the ocean provides the earth with the greatest carbon sink as it absorbs carbon in the atmosphere and helps regulate the climate. the ocean also provides mankind with vital lifesaving and life-enhancing natural resources such as medicines, food, biofuels, and other resources. undoubtedly, the ocean has, over the years, been a viable source of economic activity due to its ubiquitous nature. nowadays, several countries all over the continents are pulling their resources together to ensure that they take the utmost advantage of oceanic wealth [3]. however, in spite of the numerous benefits of the ocean to mankind, it has not been spared from vicious abuse and mindless exploitation by iniquitous and ignorant persons and entities, which has negatively impacted its ability to sustain mankind in the way intended by nature continuously. the concept of a blue economy officially came to the limelight in june 2012 during the rio+20 summit, hosted in rio de janeiro, brazil, under the auspices of the united nations conference on sustainable development. the blue economy is a uniquely wide concept aggregating all economic activities that border water bodies and other ecosystems to engender sustainable economic development. the blue economy also has a wide latitude and capacity to enhance the socio-economic growth of a country, improve the standard of living of the citizenry, create employment opportunities, and sustain the overall well-being of oceanic resources and the ecosystem. if effectively harnessed and properly managed, a blue economy can boost a country's gross domestic product (gdp). additionally, it is another reliable means of foreign exchange earnings, renewable energy generation, and replenishing biodiversity loss. furthermore, the blue economy, if successfully integrated with the tourism industry, will generate a multiplier effect that is strong enough to stimulate socioeconomic growth and development. moreover, a fully functional blue economy will deepen and boost shipbuilding technology, hydrogen fuel, and bio-fuel development [1]. to further elucidate this point, odey [2] asserts that a blue economy is an innovative economic exploitation approach comprising oceans, lakes, rivers, and other water bodies. in addition, he asserted that a blue economy, if duly harnessed, can result in economic growth, improved livelihood of the citizenry, engender social inclusion, and ensure the preservation and sustainability of the ecosystem. he also emphasized that the concept of the blue economy considers non-marketable economic benefits such as protecting the coastal environment, storing carbon, and promoting and preserving cultural values and diversity. consequently, a well-hinged blue economy policy will proffer effective solutions to environmental challenges, which can make otherwise limited resources abundant. thus, the concept of blue economy is focused on addressing issues such as the depletion of natural resources and climate change by providing a platform that will help minimize negative environmental impact. hence, a blue economy is essential to balance conservation and adequate usage of oceanic resources while maintaining a healthy ecosystem [4]. in an economically challenged country like nigeria, confronted by many human developmental issues ranging from extreme poverty to meeting the united nations sustainable development goals, a well-developed blue economy sector will help in no small measure to address some of these challenges. 2.2 blue economy in nigeria despite nigeria’s vast coastline, these ocean resources are yet to be fully harnessed. in a related study titled “broadening nigeria’s revenue base: exploring blue economy activities”, available statistics show that nigeria is endowed with about 870km coastline and over 3000km inland waterways coupled with a variety of natural resources. consequently, nigeria’s enormous coastline and maritime territories should drive sustainable development and growth of her economic sector, improve the standard of living, create jobs, serve as an avenue for international trade, and generate foreign exchange earnings when optimally utilized. in addition, a relatively sustainable blue economy also engenders social togetherness and environmental conservation [5, 6]. sadly, the nigerian government is yet to fully take advantage of the enormous opportunities that are embedded in a diverse economy, while countries like australia, the united states of america, and brazil have developed favorable and workable policies that are geared towards achieving measurable outcomes from effective utilization of their ocean resources. in canada, for example, eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 3 the government established several institutions specifically designed to monitor and ensure the implementation of policies related to the ocean and blue economy. statistics show that 267.3 billion m3 of surface water and 52 billion m3 of groundwater are available annually in nigeria. ironically, 90% of this vast amount of water resources have not been harnessed. as a result of her inability to effectively and efficiently maximize the various opportunities inherent in the blue economy, the country is losing substantial revenue that it ought to have generated from the proper utilization of the blue economy. the primary factor mitigating the development and sustainability of the blue economy in nigeria is her over-dependence on crude oil, which has beclouded her sense of judgment and impeded her ability to harness the numerous benefits of economic diversification, especially at this critical period where the country is grappling, with hyperinflation and economic hardship [ 5, 7]. likewise, other major obstacles to the development of a blue economy in nigeria is endemic corruption, as can be seen from unfriendly business practices by government regulatory agencies and full-blown insecurity on our waterways and continental shelf where sea pirates operate unchallenged in the gulf of guinea, bight of bonny, bight of benin and adjoining inland waterways. there is no doubt that the blue economy is an integral catalyst that is capable of boosting economic development in nigeria, but only if the government can successfully curb the above-outlined twin menaces of corruption and insecurity that continue to threaten the economic standing of the nation. to buttress this point further, reference [5] asserts that sustainable development of the blue economy is highly dependent on the incorporation of both short and long-term policies and economic activities that are hinged on social inclusion, economic growth, environmental conservation, and adequate utilization of oceanic resources and coastal areas. hence, for nigeria to sustainably benefit from the blue economy, there is an urgent need for economic diversification. this diversification will help the country overcome crude oil dependency syndrome caused by the attendant crash of oil prices in the international markets and the post-covid depressed economy. more so, most western countries that are the major consumers of our crude oil are gradually discarding the use of fossil fuel in the bid to reduce global warming, while some others have set concrete timelines for complete migration from the use of fossil fuel to renewable energy in the near future. thus, economic diversification is one reliable source that will help nigeria to navigate the rough and high tide smoothly, and the blue economy is a reliable catalyst that can bring about exponential economic growth as the world gradually moves away from dependence on hydrocarbon as a source of energy to power their respective economies. therefore, the nigerian government must make a conscious and deliberate effort to formulate policies and ensure the full implementation of these policies to foster the development of the blue economy and its allied businesses as alternative sources of generating revenue and foreign exchange earnings instead of crude oil. 2.3 sectors of blue economy 2.3.1 marine biotechnology marine biotechnology plays a significant role in conserving and managing oceans and coastal areas. it also involves utilizing scientific and biological knowledge and using aquatic life, micro-organisms, and compounds to produce goods and offer services. biotechnology involves harnessing opportunities that are founded on natural marine products and their application in the food and pharmaceutical sectors. marine biotechnology can improve energy security and human and environmental health due to the increasing impact of marine biotechnological resources in these sectors because the ocean is a rich source of biological and chemical varieties. the species of microorganisms found in the ocean are used in the production of pharmaceutical products, nutritional supplements, molecular probes, and other commercialized enzymes and chemical components [8]. besides its benefits and contribution to human health, marine biotechnology, if fully harnessed, can curb epidemics, pandemics, and other public health emergencies, create employment and generate revenue. 2.3.2 renewable energy renewable energy is often called clean energy because it is generated from natural sources such as water, wind, sun, biological materials, and the earth’s crust, unlike conventional energy, which is mostly generated from fossil fuels. some sources of renewable energy the ocean provides include waves, biomass, wind, tidal salinity, thermal conversion, and gradients. renewable energy protects the environment from pollution and depletion of the ozone layer, which is responsible for global warming. it is also a viable source of generating foreign exchange earnings and energy security, provides relatively affordable energy to rural areas, and creates employment opportunities. several studies have shown that renewable energy can provide adequate primary energy to meet national demand and reduce greenhouse gases by 3.2kg of carbon dioxide, equivalent to biodiesel. due to the rise in industrial activities, global climate change, and a growing national population, there is a high demand for energy in our homes and industries, so much so that fossil fuel can no longer meet the demand for energy in nigeria because of its rising cost and scarcity. consequently, nigeria's need for an alternative energy source is undeniable and urgent. for nigeria to adequately harness the benefits of renewable energy, it must have the right policies in place, while the government should make realistic budgetary provisions that will ensure a smooth implementation and operation of renewable energy programs [9]. 2.3.3 shipping and transportation the ocean provides the most reliable, efficient, and costeffective mode of transporting massive quantities of goods and commodities across the globe. seaports are integral infrastructures that catalyze economic growth and development. they play vital roles in expanding international trade and commerce, translating to a reliable source of foreign exchange earnings, creating employment opportunities, encouraging expansion and growth of allied businesses, and contributing greatly to a country’s gdp. globally, maritime transport accounts for the movement of 80% of the volume of international trade cargo and is accountable for over 70% of its value. shipping is the primary means of transporting goods in large quantities; hence, it has greatly facilitated world trade and economic growth and development. although nigeria occupies a meager 853 km eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 4 out of 47,000km of africa’s coastline, its strategic geographical location is an added advantage as it serves as a gateway to diverse countries and geographical regions of the world, which has made it a hub for maritime transportation and allied businesses in the sub-region. hence, for improved economic activities and better outcomes, deliberate effort must be made to escalate the current level of maritime services in nigeria by the government. this is because an improved maritime services industry will lead to seamless connectivity of regional markets, acceleration of trade, and cross-border movement of people, thus fostering all-inclusive growth. investment in the construction and maintenance of seaports and infrastructure like shipbuilding and maintenance facilities will greatly contribute to territorial integration and the speedy movement of people and goods [10, 11]. however, it is unfortunate that nigeria, despite being conspicuously strategically located, has no viable shipping line and ports and has failed to take advantage of the huge revenue from maritime transportation and its allied businesses. the apapa and tincan island ports, both located in lagos, which are regarded as the flagships of maritime business in nigeria, are in a state of decay due to years of neglect by the government and have lost the competitive edge of doing business with ports in nearby countries. deplorable access roads to these ports and a lack of modern cargo handling facilities have further exacerbated an already bad situation. it is doubtful if the newly inaugurated lekki deep sea port can reverse this ugly trend. in her days of subregional maritime pre-eminence, the defunct nigerian national shipping line had over 40 ocean-going vessels, whereas the story is different today. in a desperate bid to reclaim the days of glory, the government enacted the cabotage act in 2003 in order to encourage indigenous shipping companies to participate in maritime transportation business within nigeria's inland waterways and coastal waters, but this initiative has also been deflated like a lead balloon as a result of the inability of these indigenous shipping companies to acquire the required coastal vessels [7]. owing to this colossal failure, foreign shipping companies have surreptitiously regained and reasserted their dominance of businesses in our seaports and maritime transportation business. 2.4 coastal tourism coastal tourism performs a significant function in the sustainability and conservation of coastal areas and other water bodies. coastal tourism involves movement from one’s regular abode to coastal areas or seabed zones for relaxation and pleasure. this is a viable means of generating foreign exchange earnings and boosting other allied businesses and the local economy. coastal tourism serves the dual purpose of improving socioeconomic growth and promoting the tourist location's rich cultural heritage and diversity. unfortunately, nigeria, blessed with diverse water resources ranging from inland waters to a beautiful ocean coastline, has yet to fully harness the economic and social benefits of coastal tourism. globally, tourism is one of the fastest-growing businesses capable of boosting a country's gdp due to its multiplier effect on other sectors of the economy. it is acknowledged that a well-developed coastal tourism sector will lead to an economic boom, conservation of coastal areas and maritime attraction, preservation of cultural heritage, and stimulation of recreational and educational values [12]. 2.5 aquaculture aquaculture has been identified as an integral sector of the blue economy in that it is a guaranteed channel of sustainable supply of seafood, which helps to cushion the increased demand of a growing population, and it is also a viable source of foreign exchange earnings, which facilitates social cohesion and economic development. a study revealed that out of the 6.30 million metric tons of fish caught by african fishermen, 3.80 million metric tons were caught from nigeria’s waters. furthermore, in a recent study, it was discovered that notwithstanding the huge economic significance of the fishing sector, the nigerian government has failed to give it the much-needed attention to flourish. nigeria is endowed with large coastal areas and freshwater resources, which ordinarily is an atmosphere that is conducive for fish farming and rearing, but regrettably, nigeria spends billions of dollars every year on fish importation and other seafood like shrimps and lobsters. the lack of government attention to aquaculture is costing nigeria the huge benefits available in the sector [13, 14]. it is shocking that despite the persistent excruciating poverty in rural areas and amongst coastal dwellers, the national and sub-national governments have paid little or no attention to such a critical sector that is capable of lifting millions of people out of poverty. 3. factors mitigating against the exploitation and sustainability of blue economy in nigeria despite the numerous opportunities and benefits that lie unexplored in the various sectors of the blue economy in nigeria, there are several factors threatening the full realization of these enormous potentials and sustainability in nigeria. some of these factors include: 1) absence of credible policies and programs for the sector: being a third-world country, the importance of the government as the key driver of every sector of the economy is critical to national development. it is inexcusable that the government of nigeria has no clear road map on how to develop the sector. though the government pretends that it has opened virtually every sector of the economy to private sector participation, this is not reality. it is self-defeating for the government not to do its part while inviting private participation in the blue economy sector. there is no doubt that the nigerian economy can generate not less than one billion us dollars annually from the blue economy. the nigerian coastal belt is inundated with shanties and ramshackle structures instead of well-appointed tourism beaches and resorts whose enormous contribution to the local and national economy is not in doubt had they been properly harnessed. ironically, the government is not any different from the locals who own these shanties that have become a blight on the beautiful coastline. under the guise of constructing the lagos-calabar coastal highway, the federal government of nigeria destroyed several tourist resorts worth billions of dollars along the coastline in spite of the fact most of them have been in existence for over forty years. the seaports are not faring any better, having suffered from serial neglect by successive governments. eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 5 2) overfishing: overfishing has been an age-long foe of the blue economy. the unsustainable and illegal fishing practices have resulted in the depletion of breeding fish stocks, thus endangering the ocean ecosystem and those dependent on them. overfishing depletes ocean animal populations and can lead to limited biological growth and low biomass levels. many communities around coastal areas rely heavily on fish as a source of food and income. hence, when the population of fish declines as a result of overfishing, these communities are faced with economic hardship and instability. the situation would have been different if these local fishermen had access to fishing trawlers that would have enabled them to embark on proper offshore fishing endeavors, thus allowing the fish population around the coastline adequate time to regenerate. 3) indiscriminate pollution of the ocean and other water bodies: some illicit human exploitative activities and environmental degradation of the oceanic ecosystem severely affect the potential of blue economy resources. the reckless disposal of toxic industrial waste, human waste, oil spills, harmful chemical substances, and plastic waste into the sea and other water bodies results in the contamination of the ecosystem and the avoidable death of marine organisms, which in the long run affects the environment. this indiscriminate disposal of plastic waste into the ocean and other water bodies is hazardous to the sustainability of the blue economy because it can result in ocean acidification, water pollution, and land degradation. pollution of coastal areas seriously threatens the productivity and sustainability of the blue economy in nigeria [15]. 4) poor infrastructure and management: nigeria is yet to catch up with other developed countries in terms of shipbuilding and marine transportation as a result of poor infrastructural development and management. sadly, instead of taking advantage of her geographical location and investing in the sector of aquaculture, nigeria has degenerated to the abysmal level of importing otherwise available local fish varieties like herring locally called shawa, horse mackerel (titus), blue whiting(panla), argentina silus (shiny) and the popular croaker fish, and other aquatic species such as shrimps, prawns, oysters and lobsters. data from the nigeria bureau of statistics (nbs) shows that nigeria spent n50.78 billion on the importation of fish in the third quarter of 2023 [16]. 5) lack of awareness: there is a substantial lack of knowledge among the populace about ocean-based resources, marine and aquatic life, opportunities offered by the ocean and coastal areas, and the effect of pollution on the ocean habitats and the entire ecosystem. there is almost a near absence of marine education in the educational curriculum, and this has further perpetuated pervasive ignorance among a critical segment of the population. most of the nigerian population is oblivious to the opportunities embedded in the blue economy. the sustainability of the blue economy is highly dependent on the availability of a technically skilled workforce who understands the ocean's peculiarity and innovative engineering technologies [17]. 6) climate change: climate change plays a pivotal role in the sustainability of the blue economy. some extreme climate changes have made the ecosystem susceptible to extreme weather conditions that have hampered nigeria's blue economy's development. climate change phenomena include global warming, rising sea levels, droughts, erosion, tidal surges, saline water intrusion, changes in precipitation, ocean acidification, floods, and cyclones. some of these changes result in the death of aquatic life, migration of species, low biodiversity, disruption of the marine food chain, coral belching, and, ultimately, affecting the national economy [18]. 4. the role of the mass media in advancing the blue economy in nigeria globally, the concept of a blue economy is fast gaining traction as major stakeholders like government agencies, scientists, multi-disciplinary scholars, entrepreneurs, and diverse industries have been drawn to this economic initiative. more countries are enacting and implementing favorable policies and programs daily that will enable them to fully harness the potential and benefits of a well-developed blue economy sector. however, unlike other countries whose macroeconomic planners are constantly exploring multiple means of economic diversification, nigeria is still grappling with its failed dependence on crude oil. for any economy to thrive, the citizenry must be carried along as the government formulates policies from planning to execution. citizen participation guarantees better outcomes in the attainment of the development goals of an economy. in nigeria, many citizens are ignorant of the concept of a blue economy and the need for the sustainability and conservation of the ocean. neither do they know the economic opportunities available in coastal areas and other water bodies [17]. the major function of the mass media is disseminating information because it is saddled with the responsibility of informing and educating the citizenry, keeping them abreast and up to date with issues that border on everything, especially regarding the economy and national development. over the years, the media has proven its ability to build consensus on diverse subject matters and hence is regarded as a powerful force in disseminating information because of its capacity to reach every segment of society, including the elite and commoners alike [19-22]. consequently, the onus lies on the mass media to leverage its agenda-setting advantage to craft narratives about the blue economy that inspire action from the populace and government. therefore, there should be a collaboration between the government and the media focused on setting up strategic, effective communication tools capable of propelling sustainable blue economy practices. thus, it is necessary to educate and inform members of the public on the numerous potentials and major challenges facing the development of the blue economy. the role of the mass media in the advancement and sustainability of the blue economy cannot be over-emphasized. the media is not only saddled with the responsibility of informing and educating but also a genuine platform for engendering development operations. to further elucidate, suleimam et al. [22] assert that the mass media is a formidable agent of mass mobilization that can be effectively used to achieve developmental goals and objectives. as an intermediary, the mass media engages the public and transmits to them the significance of preserving the ecosystem and maintaining a healthy coastal environment. the citizenry must be carried along through the whole blue economy process. hence, the government should always eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 6 leverage the mass media as a viable tool for mass literacy, advocacy, and awareness of the blue economy. 5. theoretical framework the study adopts the agenda setting theory and the developmental media theory as its theoretical approach. the agenda-setting theory propounded by mccombs & shaw posits that the media plays a pivotal role in influencing the mindset and opinions of the citizenry by telling them what to think about and what not to think about, issues that are more important, and issues that are trivial. the theory further asserts that the quality of attention given to a particular issue by the mass media is directly proportional to the level of value and importance that will be attached to it by the audience. to elucidate, suleimam et al. [22] opine that the media may not immediately change the mindset and opinion of the audience on a particular issue; however, it subtly changes the perception of what is important. consequently, the media has the capacity to create developmental issues that require attention in the consciousness of the people in a country. the mass media also sets the agenda for public discourse through prominent and persistent coverage and reportage of development news and issues that affect the socioeconomic well-being of the citizenry and the country at large. this theory is suitable for this study because it places great emphasis on the media as a viable tool for development communication. creating awareness of the benefits of the blue economy and educating the people on the importance of preservation and the conservation of our coastal areas and oceans will engender the growth, development, and sustainability of the blue economy in nigeria. therefore, by setting the agenda for public discourse, the citizens familiarize themselves with the various sectors of the blue economy and ways of utilizing it in order to ensure national development while improving their socioeconomic wellbeing at the same time. the development media theory was propounded by dennis mcquail who posits that the focal point of the mass media in developing countries such as nigeria should be on national development. this theory states that mass media is a powerful tool that can be used to enhance national socioeconomic growth and the development of a country. furthermore, the theory advocates that both the government and the mass media must make conscious and deliberate collaborative efforts in order to achieve desirable results. while the mass media carries out informative, educative, and developmental functions, the government should deploy the mass media and use it as a medium to communicate its goals and socioeconomic policies. by so doing, the citizenry is kept abreast with government efforts and policies, and this encourages citizens to participate in development activities [20]. in addition, the theory insists that the media, as an agent of mass mobilization, is responsible for ensuring that the appropriate information is being disseminated to the citizenry at the right time. this theory also argues that for a nation to be vested and economically developed, there is an urgent need for the mass media not to relent in carrying out its duties to foster national development. however, it is worth noting that the media needs a conducive environment in terms of press freedom to fully function in its capacity as the societal watchdog and act as the fourth estate of the realm as it carries out its duty. 6. methodology this paper adopted literature-based research as its methodology through the exploration of the literary works of several scholars to acquire an in-depth understanding of the information needed to come up with practical recommendations. literature-based research is a careful analysis of academic publications to find the nexus between existing bodies of knowledge and research findings. this methodology helps the author plan the study so that information and data relating to this work are systematically gathered and thoroughly examined by the author to arrive at a reasonable conclusion. 7. discussion of findings from the foregoing, the findings of this study revealed that nigeria has numerous potentials and resources that are related to the blue economy. findings show that the government has indeed laid out some policies, though insufficient, that ought to guide the development of the blue economy in nigeria. however, a substantial number of these policies are yet to be fully implemented and strategically executed to the letter, as they are more honored in the breach than the observance. therefore, the nigerian economy is still anchored on excessive reliance on oil money, and the government has failed to effectively and efficiently diversify the economy in order to fully harness the benefits of the blue economy. it was also revealed that the majority of the nigerian population is ignorant of the concept of the blue economy, and there is a huge knowledge gap among the citizenry on the importance of the blue economy and the resources and the huge economic opportunities therein. further findings show that the mass media have failed to carry out their developmental function by setting the agenda for public discourse in order to create the much-needed awareness and sensitization needed for the blue economy to thrive in nigeria. 8. conclusion without a doubt, the blue economy is a catalyst for socioeconomic and national development as it has the capacity to strengthen the economy of a country if effectively utilized. its multiplier effect on the rapid development and expansion of other allied businesses is profound. benefits that are inherent in a well-developed blue economy are too numerous. the mass media, as an agent for mass mobilization, ought to shoulder the responsibility of creating awareness about the blue economy, educating, informing, and sensitizing the public on the need to maintain a healthy ecosystem. for nigeria to ensure that the dividends of the blue economy, as enjoyed by other developed countries, are replicated in the country, macroeconomic planners must look beyond oil money and encourage economic diversification. the government must ensure that policies and programs are implemented and adequately executed in the scheduled time. the government and the mass media must collaborate to ensure that the blue economy will thrive for the socioeconomic growth and development of the country. most importantly, the government must tackle insecurity in the country alongside massive investment in infrastructure upon which the development of the blue economy will be hinged. eo. asohro/future sustainability november 2024| volume 02 | issue 04 | pages 01-07 7 ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the authors declare no potential conflict of interest. references [1] o. o. adepoju, b. d. ogola, and b. kingdom, “correlate of blue economy potentials: challenges and prospects for economic development in nigeria”. international journal of formal sciences: current and future research trends, vol. 19, no. 1, pp.7-19, 2023. doi: https://doi:10.13140/rg.2.2.36577.48484 [2] s. a. odey, “the nigerian blue economy: opportunities and difficulties for economic development”, jurnal ilmu sosiologi dialektika 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[accessed on 30 jul 2024] [22] y. m. suleimam, m. e. aondover and g. sabiu, “media and national development in a democratic societies”, polit journal: scientific journal of politics, vol. 3, no. 3, pp. 105-115, 2023. doi: https://doi.org/10.33258/polit.v3i3.948 this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 47 article machine learning in high-entropy alloys: phase formation predictions with artificial neural networks md fahel bin noor*, nusrat yasmin, tiglet besara department of physics, astronomy and materials science, missouri state university, usa a r t i c l e i n f o article history: received 01 november 2023 received in revised form 30 november 2023 accepted 06 december 2023 keywords: phase formation prediction, high entropy alloys, artificial neural networks, machine learning *corresponding author email address: mdfahelbin1@missouristate.edu doi: 10.55670/fpll.fusus.2.1.5 a b s t r a c t due to their complex compositions, high entropy alloys (heas) offer a diverse range of material properties, making them highly adaptable for various applications, including those crucial for future sustainability. phase engineering in heas presents a unique opportunity to tailor materials for environmentally friendly technologies and energy-efficient solutions. however, the challenge of predicting phase selection, a key aspect in harnessing the full potential of heas for sustainable applications, is compounded by the limited availability of hea data. this study presents a distinctive approach by using a precisely produced and selected dataset to train an artificial neural network (ann) model. this dataset, unlike prior studies, is uniquely constructed to contain an equal amount of training data for each phase in heas, which includes single-phase solid solutions (ss), amorphous (am), and intermetallic compounds (im). this methodology is relatively unexplored in the field and addresses the imbalanced data issue common in hea research. to accurately assess the model's performance, rigorous cross-validation was employed to systematically adapt the model's hyperparameters for phase formation prediction. the assessment includes metrics such as phase-wise accuracy (am 86.67% ss 81.25% & im 82.35%), confusion matrix, and micro-f1 score (0.83), all of which collectively demonstrate the effectiveness of this approach. the study highlights the importance of feature parameters in phase prediction for heas, shedding light on the factors influencing phase selection. its balanced dataset and training method notably advance machine learning in hea phase prediction, providing valuable insights for material design amidst challenges and data scarcity in the field. 1. introduction recently, multi-principle element alloys (mpeas) have been different from conventional metal alloys, as these alloys consist of an equal proportion of individual principal elements [1]. mpea is commonly mentioned interchangeably with high entropy alloy (hea) in the literature [2–4]. due to its remarkable properties, high entropy alloys are characterized as novel and promising materials class. these alloys tend to have complex chemical compositions containing several components [5–8]. nonetheless, the hea definition limits the number of species to a minimum of four. in comparison, only two species of identical atomic concentrations can comprise an mpea. we opt to constantly use the term hea in this paper because of its broader classification [3, 9]. phase engineering is a strategic approach that employs various phase structures found in heas to achieve remarkable performance configuration [10]. this approach offers an abundance of potential to modify heas for specific applications, producing materials that are precisely tuned to meet various technological requirements. heas can exhibit a wide range of desirable characteristics, including elevated strength for high load-bearing capacity, increased hardness for improved durability, heightened ductility for improved deformability, robust wear resistance against future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.1.5 february 2024| volume 02 | issue 01 | pages 4758 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:mdfahelbin1@missouristate.edu https://doi.org/10.55670/fpll.fusus.2.1.5 https://fupubco.com/fusus mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 48 abrasion, immense environmental corrosion resistance, and exceptional catalytic characteristics that enable various chemical reactions [11–23]. specific mechanical properties can be targeted utilizing the phases present in heas. these phases consist of amorphous (am), intermetallic compounds (im), single-phase solid solutions (ss), and hybrid ss and im phases [6,24–26]. predicting phase selection is essential for designing hea, though the mechanism behind predicting phase selection is crucial in tailored hea design, yet the mechanisms underlying phase formation are uncertain. additionally, the properties of heas are significantly impacted by the phase structure, and despite improvements, designing hea phases is still challenging and time-consuming [1, 5, 6]. machine learning has become an important tool to help with material design [27–29]. machine learning, inclusive of deep learning, requires extracting features from large datasets to recapitulate the relationships, which also offers the chance to predict the phase formation of heas focusing on existing research data by using a range of deep learning. several studies reveal intriguing outcomes in phase formation prediction by compiling data on heas and developing deep learning algorithms [30, 31]. for predicting phase formation, zhu et al. [5] have introduced a deep neural network (dnn) architecture using a residual network (resnet), which achieves 81.9% overall accuracy. an ann model is utilized in islam et al.'s study for phase prediction, with 99% accuracy on training data, while the practical prediction accuracy was below 80%. [1]. several algorithms were employed, including logistic regression, decision tree, support vector machine (svm) classifier, random forest, gradient boosting classifier, and ann in y.v. krishna et al.’s research work [32], ann has demonstrated the best accuracy of more than 80% for the test data among these algorithms. new alloys were synthesized and characterized to validate the predictions that ann is the most accurate prediction method in the studied alloy system. k-nearest neighbors (knn), svm, and ann are the three machine learning algorithms used in the study by huang et al. [33], and ann exhibits superior testing accuracy than other models for predicting phases in new heas. in uttam et al.'s [31] study, the use of a neural network (nn) model is introduced for the first time to predict the hardness of a refractory high entropy alloy (rheas), and the prediction is verified through experimental synthesis and microstructural analysis. this model successfully applies to various alloys to predict hardness, which is consistent with available experimental results. in another recent study [24], the predictive accuracy of an ann model in determining phase selection across three distinct alloy types is evaluated. it emphasizes the extensive impact of atomic size differences (δ) on the phases within am, ss, and im alloys. the research effectively forecasts the phases in two novel alloys by leveraging this learning model in conjunction with a combination of three or four key parameters with confirmation through x-ray diffraction. this approach provides a potentially promising tool for advancing the composition design and phase selection of novel alloys. while the field is extending, challenges continue in predicting hea phases, such as advancing deep learning algorithms and dealing with a lack of experimental data. given the vast unexplored compositional design space, developing efficient machine learning algorithms based on existing data becomes crucial for precise hea phase prediction. this work presents an ann model that tackles the challenge of training with balanced data for each phase in heas, contrasting the frequent problem of unbalanced datasets in past research. the objective is to determine the hyperparameters that maximize predictive accuracy and generality when predicting phase selection in new heas, utilizing a balanced dataset. in this study for hea phase formation prediction, an ann model architecture is optimized for the current balanced dataset and fine-tuned hyperparameters such as batch size, learning rate, epochs, and dropout rate. the model's performance is evaluated on the final test set by measuring phase-wise accuracy, originating a confusion matrix, and determining the micro-f1 score, and the results are then compared with prior studies. the study also analyses the significance of feature parameters in phase prediction outcomes, clarifying the relative importance of physical parameters influencing phase selection. 2. computational methods the hea dataset underwent preprocessing and preparation using conventional data science techniques prior to being utilized to train the model. three distinct datasets from various earlier studies [34–36] were selected and employed to construct the ann-based model. a dataset of 240 heas was obtained after the elimination of redundant samples and sections with incomplete or duplicated data. an instance of randomly selected five rows of the dataset is presented in the pandas dataframe format in table 1. in this dataset, there are an equal number of 80 data points for each of the am, ss, and im phases. the dataset consists of 240 instances and 6 features, including 1 categorical feature designating different phases (am, ss, or im) and 5 numeric features representing valence electron concentration (vec), the difference in electronegativity difference (δχ), atomic size difference (δ), mixing enthalpy (δhmix), and mixing entropy (δsmix). table 1. a glimpse of pandas displaying random 5 instances of the data employed in this study. the units for δhmix and δsmix are kjmol−1 and jk−1mol−1, respectively the labels were encoded into integers and assigned the values 0 for am, 1 for ss, and 2 for im phases, respectively, to denote the alloy phases in the ann model. the formulas provided below are used to compute the numeric values for the five features [37–40]. 𝑉𝐸𝐶 = ∑ 𝑐𝑖𝑉𝐸𝐶𝑖 𝑛 𝑖=1 (1) ∆𝜒 = √∑ 𝑐𝑖 (𝜒𝑖 − 𝜒)2𝑛 𝑖=1 (2) mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 49 𝛿 = 100 𝑋 √∑ 𝑐𝑖 (1 − 𝑟𝑖 𝑟⁄ )2𝑛 𝑖=1 (3) δ𝐻𝑚𝑖𝑥 = ∑ 4𝐻𝑖𝑗 𝑛 𝑖=1,𝑖<𝑗 𝑐𝑖𝑐𝑗 (4) δ𝑆𝑚𝑖𝑥 = −𝑅 ∑ 𝑐𝑖 𝑙𝑛𝑐𝑖 𝑛 𝑖=1 (5) here, ci (where 0 < ci < 1) denotes the atomic concentrations of the i-th element, while n represents the total number of components within a hea. veci and ri signifies the atomic concentration, vec, and atomic radius of each species of the ith element and r denotes the gas constant. using miedema's model, the enthalpy of atomic pairs, is calculated [41]. 𝜒 and 𝑟 refer for the weighted pauling electronegativity and atomic radius, respectively, written as follows. 𝜒 = ∑ 𝑐𝑖𝜒𝑖 𝑛 𝑖=1 (6) 𝑟 = ∑ 𝑐𝑖𝑟𝑖 𝑛 𝑖=1 (7) the data undergo preprocessing for feature values before training the architecture. using the pandas library [42], these values are normalized and scaled them between 0 and 1, as shown below: 𝑋𝑛𝑒𝑤 = 𝑋𝑖 −𝑋𝑚𝑖𝑛,𝑖 𝑋𝑚𝑎𝑥,𝑖− 𝑋𝑚𝑖𝑛,𝑖 (8) where, xnew represents to the normalized feature, xi refers to the actual feature information, xmin,i and xmax,i stand for the minimum and maximum values respectively. through this normalization procedure, dimensionless numeric features are generated, which ensures effective uniform numeric scaling and consistent treatment of all features. a layer of neurons performs computational task with the ann model. the output of each neuron within the hidden layer is denoted by aj, as expressed in the following equation. 𝑎𝑗 = ∑ 𝑥𝑖 𝑛 𝑖=1 𝑊𝑖𝑗 + 𝑏𝑗 (9) where 𝑏𝑗 designates the bias coefficients and 𝑊𝑖𝑗 corresponds to the weights of each input parameter 𝑥𝑖 . google's tensorflow [43] is a well-recognized library in this field and based on that, the machine learning neural network architecture is used. figure 1 shows the architecture used in this study which encompasses backpropagation functions and several hidden layers. eq. (9) is used to calculate the value of 𝑎𝑗 for each neuron which is related with connectionspecific weights. the activation function takes it as an input value. five features of parameters are encompassed as input and the three neurons denoting different phases are included in the output layer. the leaky rectified linear unit (lrelu) activation function has been applied within the hidden layers. the rectified linear unit (relu) [44], illustrated in figure 2, is a common and popular activation function in neural networks (nns). by compelling precise tuning of the learning rate, it can extend past predefined bounds during the nn training process because of its easiness and subsequent reduction in training computation time. due to this issue, the activation function remains inactive for the neurons within the negative region during the training process. by assigning a small constant value, like 0.2, to the negative region, leaky relu (lrelu) [45], solves this, as presented in figure 2. three nodes of the model’s output layer represent the alloy phases which receive input from the final hidden layer and then these nodes employ activation functions to predict the phase. the broadly used activation function, softmax, illustrated in figure 3, was utilized in the output layer for this classification. the probability of the input belonging to different classes is illustrated by this normalized exponential function illustrates. generally, the softmax function [46] is expressed as: 𝜎(𝑦𝑖 ′) = 𝑒 𝑦𝑖 ′ ∑ 𝑒𝑦𝑖 ′ 𝑛 𝑖=1 (10) here, 𝜎(𝑦𝑖 ′) denotes the subsequent probability and the prediction vector is referred as 𝑦𝑖 ′ . consequently, the model's output was contrasted with the target labels to assess network's error. here, cross-entropy [47] is utilized as cost (loss) function, which resembles to the negative logarithm of probability, and the following equation represents the function. 𝐻𝑦(𝑦 ′) = − ∑ 𝑦 log(𝜎(𝑦𝑖 ′))𝑛 𝑖=1 here, 𝑦 ′ refer to the prediction and y stand for one of the three target vectors. the neural network’s final output is converted into a probability, and then, using cross-entropy, it is utilized to calculate the loss. the deviation between the actual distribution and the model's expected output distribution is computed by cross-entropy. afterward, the gradient descent algorithm is used, utilizing a learning rate of 0.013, to convey back this error through the network. the weights and bias are initiated randomly in the beginning of the training process. the loss function is minimized by adjusting them at each epoch. the accuracy of the network is quantified by the number of successful determinations of the target. the hyperparameter configuration for the artificial neural network (ann) model encompassed a range of values and architectures, contributing to the systematic tuning process. for the number of hidden layers, the model was experimented with settings ranging from 3 to 5 layers, exploring the impact of network depth. regularization techniques, such as l1 and l2, were introduced within the ranges of 0.01 to 0.025, allowing for the assessment of their influence on model generalization. similarly, the learning rate, an essential factor in optimization, was varied between 0.001 and 0.013 to identify the optimal balance between convergence and avoiding local minima. dropout rates, a regularization method to mitigate overfitting, were adjusted within the range of 0.1 to 0.4. different batch sizes, ranging from 8 to 120, were examined to evaluate their effect on model training efficiency and convergence. these diverse configurations and their corresponding results constituted a comprehensive exploration of the ann's hyperparameters to achieve the best predictive performance and phase wise accuracy. after training the model with the training dataset, a distinct, unseen test set, which was preserved during training, was used to evaluate the model. the feedback from validation provides guidance to adjust the parameter. the best model is chosen after demonstration of the optimum validation result. the hyperparameters are described in table 2 and the test set is used to evaluate this model. mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 50 figure 2. rectified linear unit (relu) and leaky relu (lrelu) 3. results and discussion 3.1 data analysis comprehending the dataset of 240 records is an essential preliminary stage before applying a machine learning algorithm. then, we generate a scatter matrix plot using the seaborn package and then compute the correlation matrix of the features using pandas library. these two matrices aid in comprehending feature relationships within the curated hea dataset and offer both qualitative and quantitative interconnection estimates. our prediction pertains to the phases, with a specific emphasis on five quantitative features of the hea compositions. to visualize the data, we employ a 5 × 5 scatter matrix plot, as depicted in figure 4. the diagonal subfigures illustrate histograms of phase distributions, considering individual utilization of each of the five features. all histograms within subfigures overlap, suggesting no isolated feature for complete alloy phase classification. correlations among the five features influence phase selection in heas, which is evident in off-diagonal subfigures of figure 4. figure 3. softmax function figure 1. illustration of the artificial neural network (ann) architecture designed for predicting phase formations in high-entropy alloys (heas). for clarity, only five neurons (illustrated as circles) within the hidden layers are depicted. empty squares symbolize input features and output values. the am, ss, and im phases are encoded as vectors 0, 1, and 2, respectively. mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 51 table 2. hyperparameters of ann hyperparameter value number of hidden layers 5 number of hidden neurons 150 neurons regularization l1: 0.025, l2: 0.01 activation function leakyrelu (alpha= 0.1) dropout rate 0.4 batch size 65 learning rate 0.013 (adam optimizer) epochs 100 loss function categorical crossentropy we also calculate the pearson correlation coefficient for features x and y to provide a quantitative description of their correlations [48]. 𝑟𝑥𝑦 = 1 𝑛−1 ∑ (𝑥𝑖−𝑥)(𝑦𝑖− 𝑦)𝑛 𝑖=1 𝑆𝑥𝑆𝑦 (12) here, x and y represent the mean values of two features, while 𝑆𝑥 and 𝑆𝑦 are their respective standard deviations. correlation values can vary between -1 and 1, indicating negative or positive relationships. the computed correlation matrix elements are presented in figure 5. centering on the correlation between two distinct features, the matrix elements range from -0.61 to 0.72. out of the ten distinct correlation matrix elements, seven exhibit negativity, while the remaining are positive. this outcome also exhibits resemblance to a prior study [1]. in the correlation matrix and scatter plot, of electronegativity difference (δχ) and atomic size difference (δ), a positive correlation is observed, meaning that δχ tends to increase with higher values of δ. additionally, both δχ and δ show negative correlations with valence electron concentration (vec) and mixing enthalpy (δhmix). in general, the correlation matrix elements exhibit moderate magnitudes, allowing all five features to be employed collectively as input for our neural network architecture. figure 4. the scatter plots presented in the off-diagonal sections reveal the correlations among the values of the five distinct features. within the diagonal panels, the histograms illustrate the distributions of the three phases based on the five features. each phase is represented using varying shapes and colors: a yellow circle signifies amorphous (am), a blue diamond represents solid solution (ss), and a red square denotes intermetallic (im). mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 52 figure 5. correlation matrix heatmap of the five features 3.2 artificial neural network (ann) results the development of all python network models is accomplished using the keras framework with a tensorflow backend for anns. subsequently, the hyperparameter values are adjusted and the optimal model and hyperparameter settings for the ann model are determined through a 3-fold cross-validation process as depicted in figure 6. the best parameter resulted in an average cross-validation accuracy of 86.46%, as detailed in table 2. afterwards, the ann architecture is employed to train on 80% of the developed balanced dataset and then applied to test the remaining 20% of the dataset. this process is visualized in figure 7(a), (b) and (c) illustrating the progression of training loss and validation loss across number of epochs for three separate folds. figure 6. training and testing process of the ann model notably, both the training loss and validation loss curves exhibit a similar trajectory, demonstrating that the optimization algorithm consistently updates the weights of hidden layer neurons to minimize the loss and enhance the learning process at each epoch without overfitting the data. across the three-fold training set, the loss converges to 1 after 40 epochs, maintaining a consistent trend thereafter. furthermore, it's important to highlight that when the model is evaluated on the final set of data, there is a noticeable decrease in the loss value. this reduction brings the loss down to 0.5 after approximately 30 epochs of the training process. this trend is visually represented in figure 7(d), where the curve illustrating the loss for the final test set which closely resembles the trajectory observed during the training process. this indicates that the model's performance on the test data doesn't show any signs of overfitting. this consistent reduction in loss and the convergence of the curves emphasize the model's ability to generalize well and perform effectively on new, unseen data for each of the hea phases. in figure 8(a), a visual representation is provided for the threefold cross-validation process that was employed to assess the model’s performance, showcasing the accuracy achieved for each individual fold along with average accuracy while training the data. notably, the calculated average validation accuracy across all three folds was determined to be 86.46%. this approach of three-fold cross-validation ensures proper evaluation of the model's effectiveness across different subsets of the data. additionally, the prediction of phase-wise accuracy on the training datasets is depicted in figure 8(b). remarkably, the final validation set attains a prediction rate nearing 83.33%, affirming the strong performance of the developed ann model and its favorable generalization capabilities. mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 53 figure 9 illustrates the accuracy comparison between the training and validation processes for the final test set, revealing a positive correlation between them and overall accuracy improvement with epochs. observing the training outcomes depicted in figure 9, it's evident that the training set accuracy incrementally rises as iterations progress. after approximately 30 epochs, the accuracy stabilizes, suggesting effective convergence of the model. the effectiveness of the ann model in predicting each of the phases is displayed in figure 10. in contrast to some other studies that typically report overall accuracy, it is equally crucial to highlight phasewise accuracy to illustrate the model's competence and its ability to predict various phases effectively. the results underscore the model's proficiency in accurately predicting distinct phases, and notably, the phase-wise accuracy reaches impressive levels, with am achieving 86.67%, ss reaching 81.25%, and im attaining 82.35%. these results exemplify the ann model's effectiveness in predictive performance, particularly when it is trained on a balanced dataset for each phase. using micro-f1 to evaluate the prediction outcomes, the test set is employed to validate the effectiveness of the ann model. the necessary equations for calculating the micro-f1 score are provided below [5,49]:using micro-f1 to evaluate the prediction outcomes, the test set is employed to validate the effectiveness of the ann model. the necessary equations for calculating the micro-f1 score are provided below [5,49]: 𝑅𝑒𝑐𝑎𝑙𝑙𝑚𝑖𝑐𝑟𝑜 = ∑ 𝑇𝑃𝑖 𝑛 𝑖=1 ∑ 𝑇𝑃𝑖 𝑛 𝑖=1 + ∑ 𝐹𝑁𝑖 𝑛 𝑖=1 (13) 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛𝑚𝑖𝑐𝑟𝑜 = ∑ 𝑇𝑃𝑖 𝑛 𝑖=1 ∑ 𝑇𝑃𝑖 𝑛 𝑖=1 + ∑ 𝐹𝑃𝑖 𝑛 𝑖=1 (14) 𝐹1𝑚𝑖𝑐𝑟𝑜 = 2 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛𝑚𝑖𝑐𝑟𝑜∗𝑅𝑒𝑐𝑎𝑙𝑙𝑚𝑖𝑐𝑟𝑜 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛𝑚𝑖𝑐𝑟𝑜+𝑅𝑒𝑐𝑎𝑙𝑙𝑚𝑖𝑐𝑟𝑜 (15) here, true positive (𝑇𝑃𝑖) means positive cases correctly identified as positive cases of the i element, false positive (𝐹𝑃𝑖) means negative cases is incorrectly identified positive cases of the i element, true positive (𝐹𝑁𝑖) means positive cases is incorrectly identified negative cases of the i element. 𝑅𝑒𝑐𝑎𝑙𝑙𝑚𝑖𝑐𝑟𝑜 measures the accuracy of correctly predicting actual positive samples within the sample space. 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛𝑚𝑖𝑐𝑟𝑜 quantifies the accuracy of forecasting positive predictions. f1micro is the aggregated average that considers both 𝑃𝑟𝑒𝑐𝑖𝑠𝑖𝑜𝑛𝑚𝑖𝑐𝑟𝑜 and 𝑅𝑒𝑐𝑎𝑙𝑙𝑚𝑖𝑐𝑟𝑜. the micro f1 score on final test set is 0.83. to assess the predictive performance of the ann model for each of the hea classes within the dataset, a confusion matrix was generated using a testing dataset comprising 48 samples, as illustrated in figure 11. 0 1 2 3 4 5 6 7 0 50 100 l o ss epochs training loss validation loss 0 1 2 3 4 5 6 7 0 50 100 l o ss epochs training loss validation loss 0 1 2 3 4 5 6 7 0 50 100 l o ss epochs training loss validation loss 0 1 2 3 4 0 20 40 60 l o ss epochs training loss validation loss figure 7. comparing the training and validation loss of the ann model for a) fold 1, b) fold 2, c) fold 3, and d) final test set. mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 54 figure 9. comparing the accuracy of the ann model between the training set and final validation set figure 10. comparing phase-wise accuracy and average accuracy found for the final test set the confusion matrix indicates notably high precision and recall values across all three classes of hea, affirming the model's robustness and generalization. the variance between the cross-validation accuracy and the confusion matrix accuracy arises because the former represents the average of all validation accuracies, while the latter directly reports accuracy for the testing dataset that has been kept separate during the model development process. the developed ann model aims to predict the phase of previously unseen data, and its performance was benchmarked against other alternative methods, as illustrated in figure 12. among the various machine learning algorithms assessed for accuracy, our developed ann model demonstrates the highest accuracy of 83.33%. notably, while islam et al. [1] and krishna et al. [32] also utilized an ann model, their datasets exhibit unequal proportions of data across different hea phases. in contrast, our ann model maintains consistency by employing the same number of instances for am, im, and ss phases, and this uniformity contributes to the model's robust performance, allowing it to achieve the noteworthy accuracy of 83.33%, surpassing the accuracy of other methods [5,33,50], including those that employed differing dataset compositions. the developed ann model aims to predict the phase of previously unseen data, and its performance was benchmarked against other alternative methods, as illustrated in figure 12. among the various machine learning algorithms assessed for accuracy, our developed ann model demonstrates the highest accuracy of 83.33%. figure 11. confusion matrices of ann model used in amorphous, solid solution, and intermetallic phase prediction on final test set. (b) (a) figure 8. comparing (a) fold-wise accuracy and (b) average phase-wise accuracy found for the cross-validation data employing the ann model. mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 55 figure 12. evaluating the precision of machine learning algorithms notably, while islam et al. [1] and krishna et al. [32] also utilized an ann model, their datasets exhibit unequal proportions of data across different hea phases. in contrast, our ann model maintains consistency by employing the same number of instances for am, im, and ss phases, and this uniformity contributes to the model's robust performance, allowing it to achieve the noteworthy accuracy of 83.33%, surpassing the accuracy of other methods [5,33,50], including those that employed differing dataset compositions. 3.3 relative feature impact assessment the ann architecture was used to assess the relative significance of the five input features used to train the model. to investigate this, a series of five experiments were carried out, with each experiment systematically omitting one feature while keeping the remaining four. this procedure entailed retraining the model and making predictions in order to thoroughly investigate the impact on the test set accuracy. the results of these experiments can be seen in figure 13, which depicts the decline in accuracy across the five scenarios mentioned above. this trend highlights an important observation: removing any of the five features consistently resulted in a decrease in the accuracy of the model, highlighting the significant influence that each feature has on test accuracy [5,25]. when compared to other features, differences in atomic sizes and the concentration of valence electrons have a greater influence on the accuracy of the model. notably, it has been determined that the key design parameters derived from the current ann approach—the atomic size difference and the valence electron concentration—align closely with the preexisting parametric guidelines for hea phase formation. figure 13. effect on the test set accuracy upon the removal of individual features. this convergence highlights an intriguing correlation, confirming the developed ann method's reliability. consistent with hume-rothery principles, the atomic size difference plays a crucial role in phase formation of hea, especially in case of solid solution (ss) phase [5,38,51,52]. furthermore, the hume-rothery principles show that the number of valence electrons per atom is critical in determining the stability of solid solutions in metal binary systems [5,52–54], and this stability in the mentioned systems hinges on electron density, specifically where peaks in the density of states occur, coinciding with the point where the fermi sphere intersects the brillouin zone boundary. as a result, the structure becomes stable at a specific electron concentration level. while atomic radius and mfb. noor et al. /future sustainability february 2024| volume 02 | issue 01 | pages 47-58 56 electronegativity differences are not always conclusive predictors of outcomes, they're both highly indicative parameters in the design of hea compositions [51–54], underscoring the significance of considering electronic structure alongside other material properties when designing heas. 4. conclusion in this study, a carefully developed ann model was introduced to address the persistent challenge of imbalanced datasets when predicting phase selection in heas. through a rigorous optimization process encompassing various hyperparameters, the ann model was developed using a balanced dataset, resulting in excellent predictive performance. using a three-fold cross-validation strategy, the model's effectiveness was carefully evaluated. the results showed an impressive average validation accuracy of 86.46% across all three folds and eventually led to a high prediction rate of nearly 83.33% on the final test set, highlighting the model's robustness and capacity for generalization. this study also emphasized the importance of phase-wise accuracy, with the ann model achieving remarkable accuracy levels for the studied hea phases (86.67% for am, 81.25% for ss, and 82.35% for im). a detailed confusion matrix analysis also confirmed the model's robustness across all classes, highlighting its precision and recall balance, while comparison against alternative methods demonstrated its superior accuracy, and the micro-f1 score validated the model's effectiveness with a score of 0.83 on the final test set. notably, this was accomplished by maintaining dataset balance for each phase, which distinguished this approach from previous studies that frequently used imbalanced datasets and didn't mention phase-wise accuracy which is very important to showcase the model's ability for generalization. furthermore, the study investigated the relative importance of input features, identifying that atomic size difference and valence electron concentration played critical roles in test accuracy, in line with established guidelines for hea phase formation and reinforcing the developed ann method's reliability. it should also be noted that including more data for each phase can contribute to even higher model performance, providing an exciting potential for further predictive accuracy improvement. overall, this study not only provides an effective solution to an existing issue in materials science, but it also provides critical insights into the impact of physical parameters on phase selection, making it invaluable for future alloy design and engineering efforts. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript includes existing data, and additional data that support the findings of this study are openly available in high-entropy-alloy-phase-prediction-using-balanceddataset at https://github.com/fahel-bin-noor/high-entropyalloy-phase-prediction-using-balanced-dataset. conflict of interest the 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[54] s. guo, c. ng, j. lu, c.t. liu, effect of valence electron concentration on stability of fcc or bcc phase in high entropy alloys, journal of applied physics. 109 (2011) 103505. https://doi.org/10.1063/1.3587228. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 35 article a techno-economic investigation for utilizing solar energy in irrigation of palm trees in saudi arabia a.f. almarshoud department of ee, college of engineering, qassim university, saudi arabia a r t i c l e i n f o article history: received 06 october 2023 received in revised form 08 november 2023 accepted 14 november 2023 keywords: sustainable irrigation, pv water pumping, solar energy water pumping, palm date trees irrigation, solar energy economics *corresponding author email address: dr_almarshoud@qec.edu.sa dr_almarshoud@qu.edu.sa doi: 10.55670/fpll.fusus.2.1.4 a b s t r a c t this paper presents a techno-economic investigation for utilizing photovoltaic solar energy in water pumping applications for the irrigation of palm trees in the qassim region in saudi arabia. the analysis has been done by applying four technical indicators and three economic indicators on a real farm of palm trees. the investigation took into account the varied water demand for palm trees over the years, meteorological data of the region, the characteristics of the borehole, and the local market prices of pv system components. the investigation has been done using two options of pv systems: grid-connected system and standalone system. the results showed the superiority of the gridconnected system in spite of the unfair price of energy exchange with the utility grid. the results achieved are the levelled cost of energy, which is in the range from 0.013 to 0.019 $/kwh. the standardized cost of produced water is in the range from 0.011 to 0.013 $/m3, and the simple payback time is in the range from 9.65 to 12.22 years. the results are considered to encourage farmers in the region to convert to solar energy utilization. 1. introduction recently, the government of saudi arabia adopted a new tariff for consuming electricity and fuel. the percentage of rise in the new tariff ranges from 50% to 95%, depending on the type of fuel. however, the anticipated future energy prices are expected to increase even far beyond this level since the 2030 vision intends smooth liberalization of the fuels market. this rise in energy prices will affect mainly the agriculture sector, especially in water pumping costs, which mainly depend on electricity or diesel fuel. finally, this extra energy tariff will reflect on the prices of produced crops. the agricultural sector in saudi arabia mainly depends on underground water, which requires a lot of electrical energy or diesel fuel for water pumping from deep wells. due to the high tariff of electricity adopted recently in saudi arabia, and due to the rapid degradation in the cost of solar panels in the last few years, utilizing solar energy as an alternative source for providing the energy required for applications of water pumping and irrigation will be a promising option. qassim region has more than 7.5 million palm trees [1], making it one of the largest producers of dates in the world. this huge number of palm trees consumes a significant quantity of energy to provide the required amount of water for the irrigation process. the region is rich in solar energy because it is located in the solar belt, as shown in figure 1, so one of the appropriate solutions to minimize the consumption of fossil fuel is exploiting the relative property of the qassim region, which is the abundance of solar energy. the water pumping system based on solar energy has some advantages such as easy installation, low maintenance, environmentally friendly, high reliability, and the operating process is simple with no cost. the disadvantages are high initial cost, and the water production depends on the availability of enough solar radiation. this study aims to investigate the technical performance and economic feasibility of using solar energy in water pumping for irrigating palm trees in the qassim region. the economic feasibility of using solar energy for water pumping is affected by many factors, such as solar radiation, the type of pump used, borehole depth, daily water demand, the capital cost of equipment, and the cost of periodical maintenance. in this research, a comparison study will be performed for using solar energy instead of using a utility grid for water pumping. in addition, the levelized cost of produced water per cubic meter is the cost of generated electrical energy per kwh. finally, the payback period of the proposed system will be calculated. moreover, the technical specification of the proposed system will be determined according to the case study requirements. the climatic future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.1.4 february 2024| volume 02 | issue 01 | pages 3546 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:dr_almarshoud@qec.edu.sa mailto:dr_almarshoud@qu.edu.sa https://doi.org/10.55670/fpll.fusus.2.1.4 https://fupubco.com/fusus af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 36 condition of the qassim region is a typical desert climate, known for its cold, rainy winters and for its hot, low humidity, and sometimes balmy summers with a long daily duration of sunshine [2]. figure 1 shows the annual sum of global horizontal irradiance in the qassim region, which reaches up to 2200 kwh/m2 annually, while the average daily solar irradiance is about 6.08 kwh/m2. the recorded meteorological data shows the viability of utilizing the solar pv systems in the qassim region. regarding the underground water resources, the qassim region has a multi-aquifer system that consists of five main aquifers separated by semiconfining beds; they are minjur, jilh, khuff, tabuk, and saq. the deepest one is saq which is the main productive aquifer, then tabuk aquifer. the others are of limited productivity [3]. the static head of water in wells ranged from 130-165 m in 2015, according to the authority of water resources in the qassim region. figure 1. the annual sum of global horizontal irradiance in saudi arabia [4] the published studies in the literature didn’t achieve a consensus on a clear and effective methodology to investigate the performance and economic feasibility of photovoltaic pumping systems. this study introduces a unified approach to investigating the techno-economic performance of pv water pumping systems. this study collected the diaspora scattered in many scientific papers and then extracted a unified approach to evaluate the technical and economic performance of water-pumping pv systems. 2. literature review many attempts have been made in various countries around the globe to determine the optimum performance, economic feasibility, and environmental benefits of harnessing solar energy for the purpose of water pumping applications. the literature review below demonstrates the major recent research activities: elham and hoseen et al. [5] presented a comparative study between solar pv systems and diesel unit sets for the use of underground water pumping where various parameters influencing the present value and the cost-effectiveness of both systems have been considered. despite the use of pv batteries in their solar system, the authors concluded that the cost of water using solar energy is much less than using diesel systems. pallav purohit has developed a simple model to evaluate the economic feasibility of different renewable energy technologies such as solar water pumping, windmills, gasification, and biogas technology for water pumping for irrigation purposes in india. the developed financial framework is used to select suitable renewable energy technology. he estimated the unit cost of water produced compared to the cost of energy supplied by the various renewable energy systems and calculated the benefits obtained from saving electricity or diesel [6]. in line with the development of solar pumping applications, ould-amrouche et al. have developed a model based on experimental results to characterize the solar pv pump. in the developed model, a relationship between the water flow rate output and the electrical power at various heads is presented. the obtained experimental results by using different technologies and various motor pumps are used to verify the model. the measurement data and the result of the simulation are used to validate the proposed model. the model is simple and can be used for planning solar pumping systems and calculating the emission rate of co2 resulting from the use of diesel water pumping and the amount of carbon dioxide that can be saved by using solar pv water pumping systems [7]. tamer khatip [8] developed a mathematical relationship that uses the load matching technique to relate the solar radiation, solar module array, and the needed hydraulic power to satisfy the demand of the water pumping system. the study also reviewed the various existing commercial solar water pumps to ensure proper pump selection. mokeddem et al. [9] conducted an outdoor experimental investigation to determine the actual performance of a solar water pumping system using a dc motor with a centrifugal pump having a pv array of 1.5 kw. two static heads are considered to evaluate the system performance under various solar irradiance and operating conditions. the study applied an approximation for the frictional losses using an empirical factor depending on the reynolds number. sahin and rehman performed the economic feasibility of solar water pumping systems to supply water from 50 m deep wells in five selected cities in saudi arabia. the conducted study revealed that the cost of solar water pumping is in the range of 2 -3 usd/m3, which is assumed to be a relatively high cost [10]. a comparative study for cost-effectiveness between diesel engines and solar systems for pumping water in remote areas in nothern badia of jordan is presented by mohammad al-smairan; the study has considered different variables such as initial investment and prices of fuels. the obtained results are used to select the optimum alternative power source to operate the water pumping system [11]. the performance of a solar pv system for water pumping in four different locations in tunisia was presented by belgacem; the evaluation is based asynchronous motor coupled to a centrifugal pump. the obtained results of the different sites were evaluated [12]. a dynamic modeling tool correlating the pumping system, the demand for water, and the solar pv power for the water pumping system was developed by elia et al. [13]. the proposed model is used to af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 37 validate the design procedure between the water supply and demand. shiv lal et al. [14] conducted a performance analysis for the pv pumping system based on available solar radiation in kota city in india, using a submersible pump for irrigation purposes. a feasibility study of solar pv systems for supplying drinking water in remote areas in ethiopia is presented by kabade et al. [15]; the study revealed that only a payback period of four years is needed to cover the overall cost of the system, which is considered a great economic advantage. bouzidi has presented a method to design a solar pumping system based on the determination of loss of power supply probability (lpsp) and water cost [16]. the analysis of the life cycle cost is applied by sodiki to compare the costeffectiveness of solar water pumping in various sites in nigeria [17]. farms irrigation study using solar water pumping systems in rural areas of oman was conducted by kazem et al. the optimum design of a pv pumping system based on meteorological data is determined using homer software and reps.om software [18]. campana et al. [19] presented a procedure for the optimization process and economic investigation of the photovoltaic water pumping system, taking into consideration the pv system cost and the revenue from crop sales besides underground water level, amount of water produced, and water demand. almarshoud [20] has investigated the reliability of the pumping system based on solar irradiance data, where the study revealed the importance of accurate sizing of pv array to satisfy the actual water demand and to avoid the additional cost resulting from oversizing. 3. estimation of water requirements of palm date trees water requirements of palm date trees vary from one region to another due to many factors, such as the climate condition, soil type, rainfall pattern, ambient temperature, the moisture of soil, wind speed, solar radiation, depth of tree roots, age of palm date tree, mature state of the crop. all these factors may affect the quantity of daily demand for water, which means the water demand varies from one month to another in the same area. there are some rough estimates made by different researchers in different countries such as, iraq was found 115-306 m3/ tree annually depending on the cultivar and climatic conditions [21], and abu khaled et al. [22] found the total annual water demand in iraq nearly 18000 m3/ hectare. in tunisia, it was found that the total annual water demand was between 63-95 m3/ tree [23]. in saudi arabia, there are some estimates for several regions, such as, in qatif was found to be 13250 m3/hectare/year [24], while in hofuf region, the minimum daily water demand is between 2.3 m3, 8.3 m3/tree in january and august respectively. in another study done in the central region, it was found that the annual amount of sufficient water demand was 108 m3/ tree [25]. in another study done in najran, it was 136 m3/ tree [26]. alazba estimated the annual water demand per tree in both eastern and central regions; he found 137 m3, and 195 m3, respectively, for flood irrigation and 55 m3, and 78 m3, respectively, for drip irrigation [27]. regarding the qassim region, there are two studies that investigated the water requirements for palm date trees in case of applying drip irrigation; the first one was done by kassim [28]; he reported the average water demand for each month as shown in table 1, where the average daily demand was 44.795 m3 / hectare. the second one was done by al-amoud et al. [29], who investigated the water requirements in the case of using drip irrigation for palm date trees in seven regions of saudi arabia. qassim region is one of them. also, in this study, the water demand was reported as average per month, as shown in table 1, and the average daily demand was 65.71 m3 / hectare [29]. 4. research objectives and methodology this research aims to achieve the best design for a water pumping system that utilizes the potential solar energy and available water resources in the qassim region to satisfy the water demand at the lowest possible cost. also, a comparative study will be performed for utilizing solar energy instead of the utility grid for palm date irrigation. in addition to calculating some important economic indicators such as the levelized cost of produced water per cubic meter, the cost of generated electrical energy per kwh, and the payback time of the proposed water pumping system. the investigation in this work will be done using two options of pv systems: a standalone pv system (the generated energy is consumed only by the pumping system) and a grid-connected pv system (energy exchange with the utility grid is allowed). the investigation will follow the following methodology: 1collecting the required information about solar radiation data of the location, the characteristics of deep-water wells in the location, and the water demand of palm trees in the region based on previous studies. 2collect information about the specifications and prices of water pumping systems and solar pv arrays available in the local market. 3sizing the pumping system based on the water demand and well characteristics. 4sizing the pv system based on the size of the pumping system and the daily energy demand. 5determining the technical performance of the pv pumping system using the standard technical indicators. 6estimating the economic feasibility of the pv-pumping system using the economic indicators. 7analyzing the results and concluding the recommendations based on the energy market situation in saudi arabia. table 1. the average daily water demand using drip irrigation for palm date trees in the qassim region (m3/hectare) study jan feb mar apr may jun jul aug sep oct nov dec kassim(2007) 18.6 23.41 39.5 49.89 59.85 72.5 72.9 67.4 53.54 34.91 26.4 18.62 al-amoud(2012) 27.5 37.5 55 74 91.5 101.5 103 94 76.5 58 40.5 29.5 average 23.1 30.46 47.3 61.95 75.68 87 87.95 80.7 65.02 46.46 33.45 24.06 af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 38 5. case study consider a palm date farm located west of buraydah city in the middle of saudi arabia (26.34o n, 43.76o e); the area is 4 hectares, about 168 trees/hectare, the palm dates trees are uniformly distributed, the spacing between trees is 8 meter in both directions, the daily water requirement is according to the average quantity extracted from previous studies [28] and [29] and recorded in table 1, using the drip irrigation method. the meteorological data of buraydah city were collected from the renewable resource atlas, which is part of the renewable resource monitoring and mapping (rrmm) program of king abdullah city for atomic and renewable energy [30]. the collected data represent the average of five years, from 2013 to 2018, and include the air temperature, wind speed, atmospheric pressure, global horizontal irradiance (ghi), global tilted irradiance (gti), and the clearness index (kt). table 2 illustrates the detailed collected meteorological data. the depth of the well is represented by the total dynamic head (tdh) of pumping which is 176 m. it is required to investigate the technical and economic performance of a pv water pumping system that can pump the daily demand over 25 years of its life using the chosen monocrystalline pv module; the specifications of the selected pv module are illustrated in table 3. 5.1 financial and economic data the capital cost of the water pumping pv system includes the cost of the pumping system (pump, motor, pipes, cables, electrical panel, and installation cost), in addition to the pv system (pv modules, inverter, balance of system cost), the balance of system cost (bos) includes mounting structures, infrastructure development, planning, dc cabling, switchgear, and installation cost. all the prices are taken from the local market. the interest and inflation rates are 2.0 % and 2.5 %, respectively, as published by the saudi arabian monetary authority on its website. the discount rate was estimated at 9.0 %. assume no debt as a part of the capital cost, and the life period of the project is 25 years, which is equal to the life cycle of the pv modules. the salvage value for the whole project at the end of its life is 20 % of the capital cost. also, the same percentage was considered for the salvage value of the inverter and pumping system at the end of their life cycles. table 4 shows the detailed cost according to the local market prices. 6. results and discussion the investigation will be done according to six steps: specifying the primary data, sizing the pumping system, calculating insolation on the tilted surface chosen, sizing the pv array, calculating the technical performance indicators, and calculating the economic feasibility indicators. 6.1 step 1: specifying the primary data the primary data of the case under study, such as the metrological data, are given in table 2. the water demand is shown in table 1 as the monthly average per day for one hectare. because the area of the case under study is 4 hectares, the water demand recalculated for the whole area, as shown in table 5. 6.2 step 2: sizing the motor-pump system the energy required by the pumping system is variable according to the variation of water demand, so, by using formula (1) below, the energy demand can be calculated [20]: epump(wh) = ρgqh 3.6 ηm ηp (1) table 2. monthly average of daily weather data month ambient temp. ghi gti (26.34o) atm. pressure wind speed clearness index (kt) °c kwh/m²/d kwh/m²/d kpa m/s january 14.25 4.24 5.72 94.21 3.08 0.66 february 16.3 5.34 6.63 94.06 3.25 0.65 march 22.44 5.70 6.25 93.76 2.46 0.58 april 26.48 6.25 6.20 93.65 3.25 0.61 may 32.22 7.10 6.53 93.44 3.15 0.64 june 35.04 8.15 7.16 93.15 3.70 0.72 july 36.6 8.13 7.26 92.92 3.20 0.75 august 36.78 7.54 7.25 93.04 2.05 0.71 september 34.16 6.68 7.09 93.39 2.58 0.69 october 28.5 5.61 6.70 93.78 2.63 0.66 november 20.44 4.37 5.73 94.06 2.83 0.62 december 15.2 3.83 5.27 94.31 3.07 0.60 annual 26.53 6.08 6.48 93.65 2.94 0.66 table 3. specifications of the selected pv module pv module sungold co. (sgm-50w) mono-crystalline peak power 350 w pout degradation/year 0.8 % rated voltage 38.5 v open circuit voltage 46.9 v rated current 9.09 a short circuit current 9.60 a efficiency 20.25 % dimensions 195 x 99.2 cm misc. losses 1.0 % conditioning losses 2.0 % noct 45 oc temp. coefficient -0.39 % * electrical data of pv module measured at stc (ghi: 1000 w/m2, air mass: 1.5 g, cell temp.: 25 oc) af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 39 where: h is the total dynamic head (tdh) which is the sum of the static head of water in the well, discharge head, drawdown head, discharge pressure, and friction losses in the pipeline, ρ is the density of water (1.0 kg/l), g is the gravity acceleration (m/sec2), q is the daily demand of water (m3), ηm is the motor efficiency, and ηp is the pump efficiency. table 4. detailed cost according to local market item cost pv modules 260 $/ kw inverter $ 1200 bos* 400 $/ kw o&m / year 22 $/ kw pump $ 3230 motor $ 2560 pipes $ 2400 cables $ 1860 pump installation $ 400 exported energy** 0.01867 $/kwh imported energy** 0.04267 $/kwh *bos includes mounting structures, infrastructure development, planning, dc cabling, switchgear, and installation cost. ** the tariff of energy exchange is according to saudi arabia regulations issued on 26/12/2019. the daily and monthly energy demand has been calculated and illustrated in table 6. the maximum energy required for pumping the daily water demand was 280.87 kwh/day in july, and assuming about 10 hours of sunshine daily in july, this requires a pump with a size not less than 28 kw. so, a highly efficient 30 kw ac submersible pump from grandfous co. driven by a threephase induction motor has been selected; its full specification is illustrated in table 7. also, an inverter of the same size has been chosen from sako co.; it is customized for solar pumping applications with a soft starting property; this property eliminates the need for batteries to support the starting current, also it is characterized by mppt technology for regulating the operation of the pump automatically at maximum generated energy point of pv array to satisfy the requirements of the case under study, its full specification is illustrated in table 8. 6.3 step 3: calculating the insolation on a tilted plane usually, the tilt angle of pv modules is chosen to equal the latitude of the location for achieving moderate generation over the year, but in this case, it is noted that the energy demand in summer may reach up to four folds of the energy demand in winter, so, the tilt angle should be chosen carefully to satisfy the maximum generation in summer. four tilt angles have been tested; 26.34o, which is equal to the latitude, latidude+15o, latitude-15o, in addition to the horizontal case. the solar radiation has been calculated at these tilt angles and compared with the profile of energy demand, as shown in figure 2. it is clear from figure 2 that the best matching between energy demand and solar insolation occurs when the tilt angle = zero. so, the following analysis will be done considering the pv array fixed on the horizontal level. 6.4 step 4: sizing of the pv array the daily output energy of the pv array may be given from the following formula [31]: 𝐸𝑝𝑣(𝑊ℎ) = 𝐴𝑝𝑣 �̅�𝑡 𝜂𝑝𝑣 (1 − 𝜆𝑚)(1 − 𝜆𝑐) (2) where �̅�𝑡 is the global solar insolation on the tilted surface (w/m2/day), apv is the area of the pv array (m2), ηpv is the efficiency of pv array under operating condition, λm, and λc are miscellaneous losses of pv array and power conditioning losses respectively. usually, the values of λm and λc are assumed from 12 % for each. the sizing of the pv array could be done by matching the total energy needed daily by the pumping system (given by eqn. 1) with the daily expected output energy of the pv array (given by eqn. 2) as in the following: 𝐸𝑝𝑣(𝑊ℎ ) = epump(wh) (3) because the pumping system is connected to the pv array through the inverter, then eqn. 3 could be modified as follows: 𝐸𝑝𝑣 = 𝐸𝑝𝑢𝑚𝑝 𝜂𝑖𝑛𝑣 (4) or; 𝐴𝑝𝑣 �̅�𝑡 𝜂𝑝𝑣 (1 − 𝜆𝑚)(1 − 𝜆𝑐) = 𝜌𝑔𝑄𝐻 3.6 𝜂𝑚 𝜂𝑝 𝜂𝑖𝑛𝑣 (5) where ηinv is the efficiency of inverter. then the size of the pv array required for the water pumping system may be obtained as follows: 𝐴𝑝𝑣 = 𝜌𝑔𝑄𝐻 3.6 �̅�𝑡 𝜂𝑝𝑣 𝜂𝑚 𝜂𝑝 𝜂𝑖𝑛𝑣(1−𝜆𝑚)(1−𝜆𝑐) (6) the value of ηpv could be obtained as follows [31]: 𝜂𝑃𝑣 = 𝜂𝑟 [ 1 – 𝛼𝑝 ( 𝑇𝑐 − 𝑇𝑟 ) ] (7) where ηr is the pv module efficiency at the reference temperature (tr = 25°c), and αp is the temperature coefficient for module efficiency. tc is cell temperature and related to the average ambient temperature ta as follows [31]: tc − ta = 219+832kt 800 (noct − 20) (8) where noct is the nominal operating cell temperature, and kt is the clearness index. the efficiency of the selected pv module given in table 3 is based on stc condition, while in the case under study, the solar radiation and ambient temperature vary from one month to another. table 5. the monthly average of daily water demand (m3) jan feb mar apr may jun jul aug sep oct nov dec 92.2 121.82 189.06 247.78 302.7 348 351.8 322.78 260.08 185.82 133.8 96.24 af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 40 table 6. energy demanded by pumping system based on the water demand (kwh) so, the efficiency of the pv module should be recalculated using formula (7) for two cases at least; one in winter where both insolation and temperature are low, and another in summer where both insolation and temperature are high, then getting an average value of efficiency to be used for sizing the pv array. 6.5 sizing of the pv array according to the 1st option (stand-alone system) the sizing of the pv array has been done by applying eqs. (2) to (8) and using the selected pv module after calculating the new efficiency (18.24 %), the resulted area of the pv array is 197.1 m2 ( 102 modules), but, due to the degradation in the output power of pv modules, this size will not be able to supply the required energy in the last few years of the life cycle, so, the size could be increased to 105 modules. the total expected generated energy during the life cycle of the pv system (25 years) is 1815 mwh, taking into account the degradation factor stated by the manufacturer of the pv module (0.8% annually). figure 3 shows the degradation in output energy during the life cycle. it should be noted in the figure that the annual consumed energy at the end of life cycle does not exceed the expected generated energy, otherwise, the pv array wouldn’t be able to generate the required energy at the end of the life cycle, so, in the case under study, the size of the pv array increased to 105 modules to satisfy this condition, which is apparent in figure 3. this size (105 modules) can supply the maximum required load (july water demand); this means that the pv array will be oversized in other months. hence, a part of the expected solar energy will not be exploited. figure 4 shows the expected generated energy and energy demand over the year. figure 2. variation of solar radiation at different tilt angles the exact number of pv modules needed is restricted by the rated inputs of voltage and current of the inverter and the chosen connection layout of pv modules. so, the best connection layout of pv modules for the case under study is determined to be (15x7); 7 branches connected in parallel with 15 modules connected in series for each. in this case, the maximum input voltage will be 577.5 v, while the maximum input current will be 63.63 a. figure 5 shows the pv pumping system under study, and figure 6 shows the connection diagram of the pv array. kwh/day kwh/month jan 73.61 2281.95 feb 97.26 2723.26 mar 150.94 4679.23 apr 197.82 5934.72 may 241.67 7491.81 jun 277.84 8335.14 jul 280.87 8707.03 aug 257.70 7988.79 sep 207.64 6229.32 oct 148.36 4599.04 nov 106.82 3204.72 dec 76.84 2381.94 annual 64556.94 table 7. specifications of the selected pumping system pump type multi-stage, submersible motor efficiency 85 % pump model grandfous (150s400-18) motor output power 30 kw pump efficiency 70.6 % rated voltage 3x380 v pump rated head 195 m rated current 66.5 a pump rated flow 36 m3/hour starting current 300 a pump speed 3450 rpm frequency 50 hz motor model ms6000qft40 power factor 0.87 *the expected life cycle of the pumping system is seven years table 8. specifications of the selected inverter inverter model sako co. (ski650 30kw) min input voltage 350 vdc rated output power 30 kw max input voltage 750 vdc rated input current 74 a output voltage 380 v 3 φ rated output current 60 a efficiency 98 % frequency 0 – 60 hz *the expected life cycle of inverter is 15 years af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 41 figure 3. degradation in the output energy during the life cycle figure 4. variation of expected generated energy and consumed energy figure 5. pv pumping system under study figure 6. connection diagram of pv modules 6.6 sizing of the pv array according to the 2nd option (grid-connected system) in the grid-connected system, the energy exchange between the pv system and utility grid is possible in both directions, so, in this case, it is not necessary to maximize the pv array to satisfy the maximum load; a smaller pv array may be used, and in case of peak demand, the extra required energy may be imported from the grid and vice versa in periods of an excess energy generation. so, the selection of the best size will depend on economic considerations, the price of exchanged energy, and the cost of the pv system. so, in this study, three sizes (80, 90, 100 modules) have been chosen to be investigated. figure 7 shows the comparison between the energy demand and the generated energy of the selected sizes, and figure 8 shows the periods of energy exchange in the case of using a pv array consisting of 80 modules. 6.7 step 5: calculating the technical performance indicators the technical performance investigation of a pv water pumping system would be determined using the indicators proposed by the international energy agency (iea) for evaluating the performance of photovoltaic energy systems [32]. these indicators concentrate on the energy absorbed by the grid (i.e., the useful energy) as defined by iea, but in pv water pumping systems, the useful energy is the energy absorbed by the pumping system, so the concentration will be on the consumed energy by pumping system rather than the potential energy that may be generated by pv array. these indicators include the total output of energy (energy yield), yield factor, capacity factor, and performance ratio. the energy yield is the total amount of expected energy to be generated by the pv system. the annual energy yield for all cases is illustrated in table 9, while the monthly energy yield for all cases is shown in figure 9. the yield factor (yf) measures the productivity of a pv array under specific weather conditions, and it is defined as the annual, monthly, or daily consumed energy by the pumping system divided by the peak power of the installed pv array at standard test condition (stc), and it is given as following [33]: yf = econsumed (kwh/year) pvarray (kwpeak) (9) af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 42 figure 7. the generated energy of different sizes of pv array compared with the energy demand figure 8. periods of energy exchange in case of using 80 modules pv array the grid-connected cases will have the same value of yf because, firstly, the yf is not related to the size of the pv array; secondly, the generated energy will be completely consumed by the pumping system, and in case there is excess energy, it will be absorbed by the grid, while in case of a standalone system, the pv array will generate the energy required by pumping system and still has some potential energy not generated. the annual yf is 2172 for gridconnected systems and 1757 for the standalone system. this value means that the pv array in this location under these weather conditions is capable of producing electrical energy equal to the yf times its rated power during one year. the monthly yf for both systems is shown in figure 10. these values of yf are reasonable when compared with gridconnected pv systems worldwide. capacity factor (cf) determines the percentage of usability of the pv system, and it is defined as the ratio of actual consumed energy to the amount of energy the pv system would generate if it is operated at its full rated power for 24 hours per day during the year, but, because the sun is available only about half the day, so, the ideal cf will not be more than 50%. the typical value of capacity factor is usually not more than 40% for most locations in the world; this is due to energy conversion losses and climate change. the cf is calculated as follows [33]: 𝐶𝐹 = econsumed(kwh/year) (8760∗ pvarray(kwpeak)) (10) 𝐶𝐹 = 𝑌𝐹 8760 (11) the resulting cf is 24.8 % for grid-connected cases and 20.1 % for the standalone case. this value of cf in the case of a grid-connected system is considered high, while it is not bad in the case of the standalone system when compared with other pv systems worldwide. performance ratio (pr) is defined as the real amount of pv energy delivered to the pumping system in a certain period divided by the output rated energy calculated at the stc data of pv modules [34]. pr is independent of location or system size; it indicates the overall effect of losses on the array's nominal power as a result of; wiring mismatch, inverter inefficiency, pv module temperature, incomplete use of insolation due to soiling or snow, component failures, and system down-time [35, 36]. 𝑃𝑅 = 𝑌𝐹 ∙ 𝐺𝑆𝑇𝐶/∑�̅�𝑡 (12) where gstc is the irradiance at stc, and ∑�̅�𝑡 is the accumulative irradiance on the plane of pv array within a certain period (annual, monthly, or daily). figure 9. the monthly energy yield compared with the energy demand figure 10. variation of yield factor during the year for both options the annual pr for the grid-connected systems is 97.8 %, and the monthly pr is expected to be the same value during the year because all generated energy will be consumed by the pumping system or exported to the grid. in the case of the standalone system, the annual pr is 79.2 %; this value of pr is considered high when taking into account that the potential energy is not included. the monthly pr is in the range of 47.2 af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 43 % in january, where more potential energy is available but not exploited, up to 94 % in july, where most generated energy is consumed, as shown in figure 11. the exploitation factor (ef) is used for measuring the percentage of consumed energy to the potential energy that can be generated by a pv array, especially in standalone systems. this factor indicates the quality of the sizing of the pv array. for best sizing, it should reach near a hundred percent. the exploitation factor may be calculated for a certain period (annual, monthly, or daily) and may be calculated as follows: 𝐸𝐹 = 𝑬𝑪𝒐𝒏𝒔𝒖𝒎𝒆𝒅 𝑬𝑷𝒐𝒕𝒊𝒆𝒏𝒕𝒊𝒂𝒍 (13) the calculated annual ef for the standalone system is 80.87 %; this percentage indicates that about 19 % of the capacity of the pv array in the standalone case will not be exploited. the monthly ef is in the range of 48.27 % in january, where more potential energy is not exploited, and reaches up to 96.1 % in july, where most of the energy is consumed by the pumping system, as shown in figure 11. the high value of ef in july, the month of maximum water demand, indicates the accuracy of sizing the pv array for the standalone system. regarding the reduction of ghg emission due to using the pv pumping system, ghg was estimated based on the type of fuel used in saudi arabia for generating electrical energy (crude oil & natural gas), considering the share percentage is 50% for each. the estimated reduction of ghg emission is in the range of 46 – 58 tons of co2 annually for all cases, as detailed in table 9. figure 11. monthly performance ratio and exploitation factor for standalone case 6.8 step 6: calculating the economic indicators the economic feasibility would be investigated using three economic indicators: the levelized cost of generated energy (lcoe), the levelized cost of produced water (lcow), and the simple payback time (spbt). the levelized cost of energy (lcoe) is the average cost of energy generated ($/kwh) during the life cycle of the pv system. in other words, lcoe is the life cycle cost (lcc) of the pv pumping system divided by the amount of expected generated energy during the project life cycle. the levelized cost of water (lcow) is the average cost of water produced ($/m3) during the life cycle of the pv pumping system, or in other words, is the life cycle cost (lcc) of the pv pumping system divided by the amount of expected produced water during the project life cycle. lcc is the sum of all expenses associated with the pv water pumping system over its life cycle in today’s value of money, taking into account the effect of time on the value of money [37]. the purpose of applying the lcc is to bring back all expenses that are expected in the future to current year costs by discounting them. the life cycle cost is given as following [38]: lcc = ccapital +σ co&m +σ creplacement csalvage (14) the capital cost (ccapital) of a pv system includes the initial cost for equipment, design of the system, engineering, and installation. the capital cost is always considered as a single payment paid in the first year of the project. the operation and maintenance cost (co&m) is the sum of all scheduled operation and maintenance costs during the year. the cost of replacement (creplacement) is the sum of equipment replacement costs and the cost of all spare parts anticipated over the life cycle of the project. the salvage value (csalvage) is the value of the equipment at the end of its life cycle period. also, in the case of a grid-connected system, the cost/benefit due to energy exchange with the grid would be considered annually. all the anticipated expenses should be discounted to the present worth taking into consideration the inflation rate (i) and the discount rate (d). the present worth (pw) of any future cost is given by [37]: 𝑃𝑊𝑛 = 𝐶(1+𝑖)𝑛−1 (1+𝑑)𝑛 (15) where n is the number of years. the levelized cost of energy (lcoe) can be calculated by dividing the life cycle cost value of the project by the expected generated energy during the project life cycle as follows [39]: 𝐿𝐶𝑂𝐸 = 𝐿𝐶𝐶/σ 𝐸𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑒𝑑 (16) the levelized cost of water (lcow) can be calculated by dividing the life cycle cost value of the project by the expected produced water during the project life cycle as follows: 𝐿𝐶𝑂𝑊 = 𝐿𝐶𝐶/σ𝑄𝐿𝑖𝑓𝑒_𝑐𝑦𝑐𝑙𝑒 (17) the simple payback time (spbt) is considered one of the most requested indicators of the economic feasibility of renewable energy systems. simple payback time calculates the number of years for the savings of energy from the renewable energy project to offset the initial cost of investment and is given as follows [40]: 𝑆𝑃𝐵𝑇(𝑦𝑒𝑎𝑟𝑠) = 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝐶𝑜𝑠𝑡($) (𝐸𝑔𝑒𝑛𝑒𝑟𝑎𝑡𝑒𝑑(𝐾𝑤ℎ/𝑦𝑒𝑎𝑟)∙𝑝𝑟𝑖𝑐𝑒($/𝑘𝑊ℎ) − 𝐶𝑂&𝑀($/𝑦𝑒𝑎𝑟) ) (18) the economic analysis is investigated using formulae from 13 to 18 and by adopting the current prices of the local market. table 4 illustrates the costs of all components according to the local market of saudi arabia. the lcoe & lcow are calculated for the three cases of the gridconnected system in addition to the case of the standalone system. the resulting values are illustrated in table 10. the spbt depends on the cost of energy avoided due to using the pv system instead of using the public grid for supplying the pumping system. the recent energy tariff for agriculture purposes in saudi arabia is 0.04267 $/kwh for consumption of less than 6000 kwh monthly and 0.08 $/kwh for more than 6000 kwh monthly [41]. af. almarshoud /future sustainability february 2024| volume 02 | issue 01 | pages 35-46 44 also, the tariff of energy exchange with the grid is not the same in both directions (0.01867 $/kwh for exported energy and 0.04267 $/kwh for imported energy). the spbt has been calculated based on this pricing system, and the results for all cases are shown in table 10. the economic indicators showed that the grid-connected system with 100 modules is the best for both lcoe & spbt, while the standalone system came in the third position, as shown in table 10. note that the cost of the pumping system is excluded from the initial cost because the same pumping system will be used in both cases, supplying power from the pv system or from the utility grid. about 90% of consumed energy was priced based on the lowest tariff, but in the case of bigger systems, most of the energy will be priced based on the higher tariff, then the spbt will go down dramatically. the approach followed in this research is applicable for its worldwide application if all the necessary data are provided. however, the economic viability depends on some factors such as; the quality of solar radiation, the depth of the well, the rate of energy exchange with the public grid. in addition, the irrigation pattern affects the economic viability; if the crop does not demand water all year, it will affect the economic viability badly unless the tariff of exported energy is encouraged. table 10. the economic indicators of the case understudy 7. conclusions in this study, the technical performance and economic viability of the use of solar energy in water pumping to irrigate palm trees have been investigated by applying a group of technical and economic indicators to a real case. the investigation was carried out taking into account the variation of water demand over the year, meteorological data of the region, and the characteristics of the borehole in addition to the local market prices of the pv system. the investigation has been done using two options of pv systems; grid-connected system, and standalone system. the investigation has been done through few steps; firstly determining the size of the pumping system based on water demand and characteristics of the borehole, then sizing the pv array based on the available meteorological data and the chosen pv module, then followed by calculating the technical performance indicators; the yield factor, capacity factor, performance ratio, and the exploitation factor. the last step is the estimation of economic feasibility by applying three economic indicators; the levelized cost of energy (lcoe), the levelized cost of produced water(lcow), and the simple payback time (spbt). the results of applying the technical and economic indicators showed the effectiveness and economic feasibility of the grid-connected system, especially the biggest one in spite of the unfair price of energy exchange with the utility grid. the economic indicators for all investigated systems seem encouraged, and they vary from 0.013 to 0.019 $/kwh for lcoe, 0.011 to 0.013 $/m3 for lcow, and from 9.65 to 12.22 years for spbt. the calculation of spbt is done based on the lower electricity tariff for agriculture application in saudi arabia. in case of using the higher tariff at bigger water demand, the spbt will go down. despite the difficult characteristics of the case under study in terms of the amount of water demand, or the borehole depth, as well as the cheap tariff of exporting surplus energy to the grid, the results came encouraging. this leads us to expect better results in areas with less borehole depth or with better solar irradiance, as well as in case of existing any supporting scheme from the government or in case of enhancing the tariff of exported energy. in general, the results are considered indicator grid-connected system standalone system 80 modules 90 modules 100 modules lcoe ($/kwh) 0.01951 0.01579 0.01332 0.01653 lcow ($/m3 ) 0.01338 0.01218 0.01142 0.01323 spbt (year) 12.22 10.42 9.65 11.2 table 9. summary results of performance indicators indicator grid-connected system standalone system 80 modules 90 modules 100 modules annual expected energy 60.82 mwh 68.42 mwh 76.03 mwh 79.83 mwh annual consumed energy 64.56 mwh 64.56 mwh annual potential energy 15.27 mwh annual exported energy 4.28 mwh 7.29 mwh 11.54 mwh annual imported energy 8.02 mwh 3.43 mwh 0.075 mwh annual yf 2172 1757 annual cf 24.8 % 20.1 % annual pr 97.8 % 79.2 % annual ef 80.87 % generated energy during the life cycle 1383.1 mwh 1556 mwh 1728.9 mwh 1613.92 mwh consumed energy during life cycle 1613.92 mwh 1613.92 mwh annual ghg emission (0.76746 tco2/mwh) 46.68 tco2 49.88 tco2 58.29 tco2 49.55 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[41] w. j. strunk and e. b. white, the elements of style, iv edition, massachusetts, usa: longman publishers, 2000. isbn 9780205313426 this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://iea-pvps.org/wp-content/uploads/2020/01/rep2_01.pdf https://iea-pvps.org/wp-content/uploads/2020/01/rep2_01.pdf https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 13 review a review of renewable energy development in asean, policies, environmental and economic impact daniel nyuin alfred damu, brian sie chuan wong, jen yew chai, cornelius yii ke wong, hadi nabipour afrouzi*, ateeb hassan faculty of engineering, computing and science, swinburne university of technology sarawak campus, kuching, jalan simpang tiga, 93350, malaysia a r t i c l e i n f o article history: received 05 august 2023 received in revised form 07 september 2023 accepted 18 september 2023 keywords: renewable energy, asean, policies, environmental impact, economic impact *corresponding author email address: hafrouzi@swinburne.edu.my doi: 10.55670/fpll.fusus.1.1.2 a b s t r a c t this study provides a comprehensive analysis of renewable energy development in asean, focusing on policies, environmental impact, and economic implications. it examines the effectiveness of renewable energy policies across member countries, highlighting challenges in implementation and the need for effective policy frameworks to drive investment. the review explores environmental concerns, including land use change, soil erosion, water use, and waste generation, while emphasizing the potential economic benefits such as gdp growth, job creation, and reduced dependence on energy imports. addressing challenges and promoting sustainable development are crucial for achieving renewable energy targets in asean. 1. introduction the association of southeast asian nations (asean) is a region that is home to over 650 million people and has a rapidly growing economy [1]. with this growth comes an increasing demand for energy to support industrialization and modernization, leading to a greater dependence on fossil fuels [2]. however, in recent years, asean has made significant strides in developing renewable energy (re) sources, which has become an important focus of the region's energy policy [3]. asean countries have been taking steps to develop their re infrastructure, with many setting ambitious targets to increase their use of renewable energy sources. for example, the asean plan of action for energy cooperation 2016-2025 targets a share of 23% renewable energy in the region's energy mix by 2025, up from 15.3% in 2015 [4]. however, despite these efforts, the transition towards renewable energy faces several challenges, such as regulatory barriers, lack of investment, and inadequate infrastructure [5]. this review paper aims to provide a comprehensive overview of renewable energy development in asean, focusing on the policies, environmental, and economic impacts. by analyzing the current state of re in the region, this paper aims to identify the key challenges and opportunities for future development and provide recommendations for policymakers, investors, and other stakeholders. in recent years, several studies have explored the development of renewable energy in asean. for example, a study by pratiwi and juerges [6] examined the environmental impact of re development in the asean region. in contrast, another study by vakulchuk et al. [7] analyzed the barriers to investment in re in the region. furthermore, a study examined the impact of policy on the adoption of re in vietnam, a key asean country [8]. by synthesizing the findings of these studies and other relevant literature, this paper aims to provide a holistic overview of the renewable energy landscape in asean, highlighting the progress made, challenges faced, and future opportunities for development. 2. policies for renewable energy development in asean re policies are critical for the development of the re sector in asean. this section will provide an overview of the policies implemented in asean member countries, followed by a comparative analysis of their effectiveness. finally, it will highlight the challenges and opportunities for policy implementation in the region. future sustainability open access journal https://doi.org/10.55670/fpll.fusus.1.1.2 november 2023| volume 01 | issue 01 | pages 13-22 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:hafrouzi@swinburne.edu.my https://doi.org/10.55670/fpll.fusus.1.1.2 https://fupubco.com/fusus dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 14 in recent years, most asean member countries have established renewable energy policies to promote deploying renewable energy technologies. these policies include feedin-tariffs, renewable portfolio standards, tax incentives, and public-private partnerships. for example, indonesia introduced feed-in tariffs for renewable energy in 2017, while the philippines implemented a renewable portfolio standard in 2010 [9]. additionally, thailand, malaysia, and vietnam governments have implemented tax incentives and publicprivate partnerships to promote renewable energy development. despite these efforts, the effectiveness of these policies varies across asean countries. for instance, in malaysia, the feed-in-tariff policy has been effective in increasing the deployment of renewable energy technologies, while in indonesia, the implementation of feed-in tariffs has been delayed due to regulatory challenges [10, 11]. furthermore, while the renewable portfolio standard in the philippines has been successful in attracting investments in renewable energy, the country still faces challenges in grid integration and the expansion of transmission infrastructure [12]. a comparative analysis of renewable energy policies in asean reveals that most countries have set renewable energy targets, but the achievement of these targets has been slow. according to the asean centre for energy (2021), asean member countries achieved a 15.3% renewable energy share in their energy mix in 2015, which increased to 17.3% in 2019. however, this is still below the 2025 target of 23%. the implementation of renewable energy policies in asean faces several challenges, including regulatory barriers, lack of investment, and inadequate infrastructure. regulatory challenges include delays in project approval processes and uncertainties in regulatory frameworks. a lack of investment in renewable energy is another major challenge, with limited access to financing and the perception that renewable energy technologies are risky investments. finally, inadequate infrastructure, such as grid capacity and transmission infrastructure, presents a significant barrier to the deployment of renewable energy technologies (ey, 2019). despite these challenges, asean presents significant opportunities for renewable energy development, including abundant renewable energy resources, increasing energy demand, and government support for renewable energy. to achieve their renewable energy targets, asean countries need to address the challenges faced in the implementation of renewable energy policies and adopt effective policy frameworks that encourage investment in renewable energy. therefore, renewable energy policies in asean member countries have made significant progress in promoting the deployment of renewable energy technologies. however, the effectiveness of these policies varies across the region, and challenges remain in the implementation of these policies. to achieve their renewable energy targets, asean countries need to address the challenges faced in the implementation of renewable energy policies and adopt effective policy frameworks that encourage investment in renewable energy. 3. environmental impact of renewable energy development in asean re development in asean has the potential to significantly reduce greenhouse gas emissions and mitigate the impacts of climate change. according to [13], preventing negative effects such as air pollution and greenhouse gases (ghgs) could be possible by using renewable energy sources instead of fossil fuels or coal. compared to coal-fired power plants, renewable energy sources' electricity emits 90-99% fewer ghgs and creates 70% to 90% less pollution. however, the development of re sources can also have environmental impacts that must be carefully managed to ensure sustainable development. one of the key environmental impacts of re development in asean is land use change. the development of large-scale renewable energy projects, such as solar and wind farms, can require large amounts of land, which can impact natural habitats and wildlife. ref [14] states that construction of re projects can lead to habitat fragmentation and loss of biodiversity, particularly in areas that are ecologically sensitive or contain endangered species. for example, solar power plants are constructed on agricultural land with an area of over 160 hectares in thailand. in recent years, thailand has significantly increased its solar energy capacity, with a large portion of this expansion occurring on agricultural land [15]. due to this, agricultural land and other agricultural regions have been converted into solar power plants, which may have a negative influence on the ecosystems and residents. satellite imagery and aerial photos, which depict the conversion of agricultural land into huge solar power plants, provide tangible proof of this change in land use. this has sometimes resulted in the eviction of farmers and the destruction of their means of subsistence, as well as negative effects on the local biodiversity and water supplies. the trade-offs and difficulties involved in the development of re, particularly in densely populated and land-constrained countries, are highlighted by the construction of solar power facilities on agricultural land in thailand. ultimately, the development of the solar farm serves as a stark reminder of how difficult it is to strike a balance between the need for re and possible harm to nearby residents and ecosystems. to guarantee that re projects are built in a sustainable and socially responsible manner, it is crucial for governments and developers to collaborate with regional communities and stakeholders. moreover, another environmental impact of re development is the potential for soil erosion and degradation. this can occur when re projects are developed on steep slopes or in areas with poor soil quality [16]. soil erosion and degradation can lead to a loss of soil fertility and reduced productivity of agricultural land, which can have negative impacts on local communities that rely on agriculture for their livelihoods. for example, hydropower dam construction in laos has caused soil erosion in the mekong river basin. it is stated that since the hydropower dam building in the area started, sedimentation levels in the mekong river basin have risen by 20% [17]. significant soil erosion may result from the excavation of rock and soil, the construction of access roads, and the installation of transmission lines during the project's construction phase. this erosion may cause sedimentation in surrounding rivers and streams, which may have a negative effect on local communities that depend on fishing and agriculture, as well as aquatic habitats. because of changes in the water flow and sediment movement downstream of the dam, the dam can potentially have a long-term negative influence on soil erosion in addition to the immediate effects during construction. this may significantly reduce agricultural output and raise the possibility of landslides in the region. to lessen these effects, hydropower projects in laos normally need to submit environmental evaluations and management plans that include actions like sedimentation basins, soil stabilization projects, and reforestation schemes. however, based on the project and how it is carried out, these measures may not all be equally beneficial. not to mention, water use is another potential environmental impact of re development in asean. ref [18] rationalizes that some re technologies, such as hydropower and bioenergy, can require dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 15 large amounts of water for their operation. this can have negative impacts on water resources and aquatic ecosystems, particularly in areas that are already experiencing water scarcity or where freshwater ecosystems are already under stress. for example, the construction of the hydropower baram dam in malaysia has caused water use issues [19]. due to worries about their effects on local ecosystems and indigenous groups, the construction of hydropower dams in malaysia has been controversial. thousands of indigenous people would be uprooted, and a sizable portion of the rainforest would be flooded. hydropower dam development and operation can also have detrimental effects on the quantity and quality of water available downstream. this may have an impact on local people’s health and well-being, as well as industries depending on water, like agriculture, fishery, and others. so, malaysia has implemented several efforts to enhance water management in the area in response to these worries, including the creation of new water treatment facilities and the encouragement of water conservation techniques. the severe environmental and socioeconomic effects of the bakun dam, however, may preclude these actions from being sufficient. finally, the production and disposal of re technologies can also have environmental impacts. for example, the production of solar panels and wind turbines can involve the use of toxic chemicals and generate waste, which can have negative impacts on the environment and human health [20]. similarly, the disposal of old or damaged re technologies can also create environmental problems if not properly managed. [21] mentions that geothermal power plants constructed in indonesia can be taken as one of the examples that cause the issues. to reach the hot water and steam needed to produce energy at geothermal power plants, deep wells must be drilled. large amounts of drilling waste, such as drilling fluids and rock shavings, may be produced because of the drilling operation, and these waste materials may be challenging to securely dispose of. deforestation, land degradation, and the disruption of regional ecosystems are other potential negative effects of the development of geothermal power facilities. therefore, the indonesian government has put policies in place to control geothermal waste and encourage sustainable development to address these problems. enforcing these laws, meanwhile, can be difficult, especially in isolated locations where geothermal projects are sometimes located. 4. economic impact of renewable energy development in asean recently, attaining energy sustainability has been a major goal for the asean countries, as it brings many benefits, including enhanced energy efficiency and a clean environment. this has resulted in the rise of sustainable energy sources such as wind, hydropower, and solar power, which are the prominent sources of electricity growth globally. based on research done back in 2020, the gdp growth and re sources in asean countries have been recorded in table 1 [22]. economic growth can be defined as an increase in production in an economy, which results in increased incomes and raises the standard of living. economic growth is usually measured in terms of gdp and is an indicator of the economic health of the country. re has been an attractive method to recover the falling gdp of asean countries, which has been caused by the pandemic. it has been reported that the gdp for the asean-5 (indonesia, malaysia, philippines, singapore, and thailand) has been 2.9% for 2021 and 5.8% for 2022, following a 3.4% fall in 2020 due to the pandemic. one of the main reasons re has been deemed the future is that it would cause the asean countries to achieve a steady supply of energy and be self-sufficient. currently, the countries still rely on energy imports that are predominantly fossil fuels to operate. with re, the funding will not be required for imports, and thus the gdp will rise. this, coupled with the increasing demands to prevent global warming from investors, can make investing in re a worthwhile venture. table 1. gdp growth and renewable energy sources in asean countries in the last five years, asean countries have increased their re production. ey-parthenon, a global strategy consulting arm, had conducted a study of eight economies across asia and has recorded more than 800 clean energy projects. if they are all realized, it could result in an investment potential of over 316 billion usd and an emissionsaving potential of over 229 metric tons of carbon dioxide. these projects and investments also have the potential to generate up to 870,000 jobs. furthermore, as stated earlier, re is attractive, resulting in private sectors and investors being more likely to deploy capital and back its’ projects. this would, in turn, bring economic growth. according to the 58th edition of the ey re country attractiveness index (recai) in october 2021, the philippines, vietnam, and indonesia have risen up the rankings of the world’s top 40 markets in terms of the attractiveness of their re investment and deployment opportunities. indonesia has set more ambitious goals and policies to retire diesel and coal power plants. while the merits of pursuing re are clear, the path is not without challenges. inability to access financing, absence of or uneven government support in incentives and the implementation of renewable projects, as well as geographical limitations – such as the lack of suitable or large land for solar or wind farms or hydropower generators – are some of the main challenges. re projects are often located in remote locations due to traditional town planning, which places industrial assets far from suburban areas and increases the costs of renewable energy. this lowers the attractiveness for consumers to convert to re usage when conventional energy products may be cheaper and more accessible. further, southeast asia’s renewables market is still in development. market knowledge is still shallow, and some countries are still sceptical about investing in this new technology, which may result in waning market interest over time. countries economy size (usd in billions) populations (millions) gdp per capita (usd) capacity of renewable energy (mw) brunei 16.18 0.42 38760 1 cambodia 16.20 15.14 1070 1438 indonesia 868.35 250.80 3460 9471 laos 11.00 6.78 1620 5118 malaysia 313.16 29.72 10538 8157 myanmar 44.85 61.95 724 3315 philippines 272.07 98.39 2770 6482 singapore 297.94 5.40 55183 279 thailand 387.25 67.01 5780 10411 vietnam 170.55 89.71 1901 18523 dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 16 5. the asean countries' renewable plan and progress by now the development process for re has always been the main target accomplished by the asean governments. the investments towards this goal, accompanied by cheaper technologies implementation and given economies of scale that contribute to less cost involved, the authorities took significant actions to tackle the problem regarding the reduction of carbon emissions. unforeseen challenges are presented during 2020 that somehow negatively affect the development of this sector; however, the determination towards achieving the main outcome for the re plan in the asean governments has not been affected, and it is expected to pick up at a quick pace despite the obstacle encountered. the consensus is to enhance the development of the re plan and recover the loss caused during the pandemic in the asean countries. the authorities of asean proceed with the second phase of the asean plan of action for energy cooperation (apaec), in which a five-year sustainability plan will commence starting from 2021 till 2025. a 23% share of re in total primary energy supply, along with 35% in the region and asean installed power capacity by 2025, respectively, has been agreed and set as a target by the asean energy ministers under the apaec. in terms of energy power to be generated as re, 35gw to 40gw is set as a target to be achieved by 2025 [23]. significant progress towards the development of re is shown within the asean member countries; the evaluation is done by looking at the investments towards the infrastructure in the sustainability plan. table 2 (appendix) represents the evaluation of the top investments for each asean member country. the re project implemented for each member country of asean has a significant trend to be observed. the size of the project implementation is very dependent on the size of the country itself; the larger the scale of the country region, the more the human population, hence, the energy consumption demand rises. the government implements large-scale projects to satisfy the daily needs of consumers. however, the condition regarding direct proportionality of the country scale region and consumer demands does not really apply to all countries in asean. there are still some other factors that greatly affect the decision of local authorities to scale up their project regardless of the country’s regional scale. among the countries, it is shown that the vietnamese government emphasized the re sector more than that of the malaysian government by direct comparison; although both countries had almost a similar regional scale, the investments and the outputs varied differently. the demand for re is greatly economically beneficial for some countries, depending on the local authorities' decision. hence, for some reason, a smallerscale country may produce more energy output or invest a lot in the renewable energy sector, but on the other hand, a large country might not do so. according to research information, there is a trend that shows asean member countries focus more on the renewable sector regarding hydropower. even the largest ongoing project, mamberamo hydro power plant 23,000 mw in indonesia, is also the largest hydropower generation project. being the largest regional-scale country in asean, the indonesian government is currently planning the largest re project in the country. compared to other member countries, their project scale is way larger than the others, regardless of the cost of the project or the amount of output re produced. as shown above, several member countries of asean have significantly low amounts of data acquired due to the re project scale of the location being contrastingly lesser than that of bigger regional coverage member countries. as shown above, regarding brunei and its overall development in the re sector, the most recent project is completed, the project scale is also small compared to other bigger countries, and the value of investments is similarly lesser. the bsp (photovoltaic) solar farm project did not announce the exact total amount of investments towards the project; hence, the exact value remains unknown. the overall re targets and plan to achieve regarding each member country in asean are at a good pace in terms of development. predictions and expectations are set by different countries in the hope of achieving their expected outputs within the time span they set. brunei has not set any specific re target, but the country has made efforts to promote the use of re, particularly in the form of solar power. cambodia aims to increase the share of re in the electricity mix to 20% by 2023, with plans to increase the use of hydropower and solar energy [31]. indonesia aims to increase the share of re in the electricity mix to 23% by 2025, primarily through the increased use of geothermal, solar, and hydropower [32]. laos aims to generate 90% of its electricity from renewable sources and have their total energy consumption by 30% through re by 2025, mainly through hydropower, but also through other sources such as solar and wind power [33]. malaysia aims to increase the re in the capacity level to 20% by 2030, and currently, up till 2023 is at 25% [34], with plans to increase the use of solar, biomass, and biogas. myanmar aims to increase the share of re in the electricity mix from 8% in 2021 to 12% by 2025, mainly through hydropower but also through other sources such as solar and wind power [35]. progress is in good condition. the philippines aims to increase the share of re in the electricity mix to 35% by 2030, with plans to increase the use of wind, solar, hydro, and geothermal power [36]. singapore aims to increase the share of re in the electricity mix to 3% by 2030, with plans to increase the use of solar power [37]. thailand aims to increase the share of re in the energy mix to 30% by 2036, with plans to increase the use of solar, wind, and biomass power. vietnam aims to increase the share of re in the electricity mix to 10% by 2030, with plans to increase the use of wind, solar, and hydropower power [38]. overall, the asean region aims to achieve a collective target of increasing the share of re in the region's energy mix to 23% by 2025. to achieve this, asean countries are implementing a range of measures, including policy reforms, capacity building, and investment in re infrastructure. the region has significant potential for re, including solar, wind, hydropower, and biomass, and governments are working to harness this potential to reduce greenhouse gas emissions and increase energy security. 6. case studies of renewable energy development in asean energy resources in the asean region are diversified and plentiful, ranging from oil and gas to a variety of re sources. several case studies on the growth of re in asean have been published. the region has set ambitious goals to increase the amount of re in its energy mix. the primary conclusions of successful re projects are summarised and examined in this literature review. the first example is the tolo wind farm, which is constructed in indonesia. the tolo wind farm in south sulawesi, indonesia, is one of the largest wind farms in southeast asia. it has a total capacity of 72 mw and consists of 20 turbines [39]. the project was developed by pt upc sidrap bayu energi and started operating in early 2018. the tolo wind farm is expected to reduce carbon dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 17 emissions by more than 200,000 tons per year. likewise, another example is the coara marang solar plant project, which can be found in malaysia. according to [40], the solar facility site covers 245 hectares to the northeast of peninsular malaysia. it is made up of 216,832 premium bifacial solar panels that are fixed to single-axis trackers. this is to ensure maximum energy production efficiency with a total capacity of 116 mw. the solar panels are expected to generate roughly 230 gwh of electricity per year, which is enough to power 55,000 households on average. more than 170,000 tons of co2 emissions are also prevented annually by the project. furthermore, the srepok 1 and quang minh solar projects are other examples that are built in vietnam. ref [41] states that srepok 1 and quang minh solar projects are developed by sunseap group and infraco asia, respectively, which have a combined capacity of 168 mw. they are expected to generate more than 350,000 mwh of electricity per year, enough to power around 200,000 homes. the projects are helping to reduce carbon emissions and support the growth of the re sector in vietnam. in addition, the next example is the bangui bay wind farm, which is in the philippines. the bangui wind farm in ilocos norte, philippines, was the first commercial wind farm in southeast asia. it has a total capacity of 41 mw and consists of a total of 26 turbines [42]. the project was developed by northwind power development corporation and started operating in 2005. the bangui wind farm has helped to reduce carbon emissions and provide clean re for the region. lastly, the nam ngiep 1 hydropower project is the last example that can be found in laos. it has a capacity of 290 mw and is expected to generate over 1,200 gwh of electricity annually [43]. the project is being developed in bolikhamxay along the ngiep river, with a 167-meter main dam height, to create a 67 km2 water storage reservoir. the objective is to develop a power project that is socially and environmentally responsible, will offer clean, renewable electricity, and will aid in the reduction of poverty in laos. besides, there are some factors that may have contributed to the success of the re projects. this can also include lessons that can be learned and implications for future re development in asean. according to [44], one of the factors is supportive government policies that can provide a favorable environment for re projects to succeed. in some cases, governments may offer incentives such as tax breaks or subsidies to encourage investment in re. the importance of these supportive policies and regulations can be a lesson to be learned. additionally, policies such as feed-in tariffs, re targets, and carbon pricing mechanisms have been effective in promoting re development in the region. it also prioritizes re sources over fossil fuels, which can help to create demand for re projects. similarly, another factor will be access to financing, which is crucial for re projects to succeed [45]. this may include access to loans, grants, or other types of funding. financial institutions and development banks may play a critical role in providing funding for re projects. therefore, future re projects in asean will need to secure adequate funding and financing to ensure successful implementation, especially for large-scale projects. haile et al. [46] also rationalize that strong collaboration between public and private sector entities can be another essential factor for the success of re projects. public-private partnerships can bring together the strength, expertise, and resources needed to develop and implement large-scale re projects. by working together, countries in the region can share best practices, pool resources, and develop joint projects. this could include the development of regional transmission infrastructure, joint investment in re projects, and the sharing of expertise and knowledge. future re projects in asean should seek to establish strong public-private partnerships to achieve project goals and bring in private sector expertise. then, favorable natural conditions, such as high wind speeds or ample sunlight, can be an important factor in the success of re projects. projects that are in areas with abundant natural resources may have a higher likelihood of success [46]. this can also be important for future re projects in asean that should take advantage of these resources to develop a diverse portfolio of re sources and reduce dependence on fossil fuels. after that, mokan et al. [44] mentioned that engaging and securing the support of local communities is another critical factor for the success of re projects. communities that are supportive of re projects may be more likely to participate in them, which can help to increase project viability. then, several successful re projects had environmental and social considerations at the forefront of project design, such as creating jobs for residents and mitigating environmental impacts. future re projects in asean must consider environmental and social implications and engage with local communities to ensure their buy-in. finally, the last factor is technological innovation, which plays a significant role in the success of re projects. this is because many countries in the region still lack the technical expertise and infrastructure necessary to fully realize the potential of re. advances in re technologies can make them more efficient and cost-effective, which can help to increase their viability [44]. so, future re projects in asean should continue to embrace technological advancements and innovation to drive progress and improve efficiency. in short, future re development in asean can learn from the success of past projects by emphasizing government support and policies, establishing strong public-private partnerships, securing adequate funding and financing, addressing environmental and social considerations, taking advantage of diverse re resources, and embracing technological advancements and innovation. by doing so, asean countries can continue to accelerate the transition to a more sustainable energy future. 7. discussion considering the economic and environmental impact, as well as the policies of respective member countries for re development in asean, the future progress of the region's re development plan seems promising despite the challenges faced. asean countries have recognized the importance of transitioning to re sources to reduce carbon emissions and promote sustainability. although a major downfall in this renewable plan has happened, which is the covid-19 pandemic, this did not ravage away the recognition of asean countries to progress towards sustainability. asean countries have implemented various policies, as mentioned previously, such as feed-in-tariffs, tax incentives, and renewable portfolio standards, to drive re deployment. while challenges exist, including regulatory barriers, a lack of investment, and inadequate infrastructure, there are significant opportunities, such as abundant re resources and increasing energy demand. with concerted efforts to address these challenges and further refine policy frameworks, asean has the potential to make substantial progress in re development over the next few decades. continued commitment and collaboration among member countries will be crucial in achieving their re goals and fostering a sustainable future. dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 18 based on table 1, vietnam has the capacity of renewable energy with approximately 18523 mw. this can be attributed to its vast natural endowments. vietnam has four to five kilowatt-hours per square meter for solar and 3,000 kilometers of coastlines with consistent winds in the range of 5.5 to 7.3 meters per second. whilst its focus is primarily on wind projects, this renewable-led pathway has led vietnam to a cheaper and cleaner energy plan whilst also providing an additional 465,000 jobs through 2030. brunei has the least renewable energy capacity, with it only being 1 mw. this can be caused by its’ small and limited land, with it being the smallest country in southeast asia by population, making it hard to construct renewable energy plantations. furthermore, its land is oil-rich, making renewable energy unnecessary. despite this, brunei acknowledges the importance of renewable energy. brunei’s government is planning to utilize a waste-to-energy facility. this facility is expected to have an installed capacity of up to 10 mw. whether other alternative energy sources such as wind power, hydropower, and ocean are economically and technically feasible in the medium term and the long term is still being researched. these initiatives are supporting the government’s aspiration of generating at least 10 percent of the total power generation mix from renewable resources by 2035. every country has its own renewable energy that is best suited for it. for example, malaysia’s hydropower generates much more energy than its’ solar department. it all comes down to allocating funds to the correct and most suitable renewable energy source for each criterion. furthermore, investing in re will not produce results immediately but instead is a long-term project that will yield results in the future and, overall, reduce global warming. 8. conclusion re policies in asean countries promote the use of re technologies. while countries have implemented policies like feed-in-tariffs and tax incentives, their effectiveness varies. challenges include regulatory barriers, lack of investment, and inadequate infrastructure. despite obstacles, asean has opportunities for re development due to resources and government support. to achieve targets, countries must address challenges and adopt effective policies that encourage investment in re. the case studies of asean member countries' renewable energy (re) development plans reveal diverse experiences and challenges. thailand stands out as a success story with effective policies and incentives leading to significant growth in solar and wind power. malaysia's feed-in-tariff policy has been successful in promoting re deployment, particularly in solar energy. indonesia has faced obstacles in implementing re policies, including delays in feed-in tariff implementation and regulatory hurdles. the philippines has attracted investments through a renewable portfolio standard but struggles with grid integration and transmission infrastructure. vietnam has made significant progress in the solar and wind sectors through policy reforms and foreign investments. these case studies highlight the need for careful planning, supportive measures, and collaboration among member countries for successful re development. the economic impact of re plans in asean member countries is both positive and negative. they create jobs, stimulate economic growth, and reduce dependence on costly fossil fuel imports. however, the initial costs of implementing re projects and the need for additional investments in energy storage and grid infrastructure pose financial challenges. to maximize the positive economic impacts, supportive policies, incentives, and collaboration are crucial, along with strategic investments and research in re technologies. re development in asean has the potential to significantly reduce greenhouse gas emissions and mitigate climate change impacts. re sources emit far fewer greenhouse gases and pollutants compared to coal-fired power plants. however, careful management is required to address environmental concerns such as land use change, habitat fragmentation, soil erosion, water use, and waste generation associated with re projects. collaboration with communities and stakeholders is crucial for sustainable and socially responsible re development. the sustainability plan conducted by asean member countries aims to reduce overall carbon emissions and brings a beneficial impact on the environment and economy. re is a natural resource-saving approach that minimizes consumption and depletion. it offers cost-saving benefits through the use of renewable and reusable resources, resulting in higher energy production. if successfully carried out, the plan would lead to reduced resource consumption, pollution, and carbon emissions, benefiting both the ecosystem and the economy. overall efficiency would improve, and member countries would enjoy cost savings in resource treatment, maintenance, and procurement. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement data sharing is not applicable to this article as no datasets were generated or analyzed during the current study. conflict of interest the authors declare no potential conflict of interest. references [1] gungwu, w. 2017. southeast asia and continental and maritime powers in a globalised world. building asean community. p. 9. 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[46] haile y, min h. success factors for renewable energy businesses in emerging economies. management research review, 46(8), pp. 1091-1111. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 21 appendix i table 2. asean re project development information project name stage value (us$ million) start completion malaysia [23] • baleh dam and hydroelectric power plant 1285mw execution 2,374 2013 2025 • large scale solar photovoltaic plants program execution 2,000 2020 2023 • lebir hydroelectric power plant 274 mw planning 845 2022 2028 • pelagus hydroelectric power plant 465 mw planning 800 2021 2024 • nenggiri hydroelectric power plant 300 mw planning 660 2022 2024 vietnam [23] • thanglong ke ga offshore wind farm 3400 mw pre-execution 11,900 2021 2027 • la gan offshore wind farm 3500 mw pre-planning 10,000 2022 2030 • binh dinh offshore wind power plant planning 4,800 2022 2026 • wind power plants program 1000 mw execution 2,500 2020 2025 • ninh thuan solar power complex 1000mw planning 2,000 2021 2024 singapore[23] • tuasone waste-to-energy plant 120 mw execution 534 2016 2021 • solarnova program 350 mw execution 315 2016 2022 • tengeh reservoir floating solar power plant 60mw execution 70 2020 2021 • sunshine phase ii: solar power plant 20mw pre-execution 25 2021 2022 thailand [23] • thailand solar pv plants program 6000 mw execution 12,000 2017 2026 • changwat khon kaen photothermal and photovoltaic hybrid power station 90 mw pre-execution 600 2021 2022 • ratchapsatu cogeneration power plant 95 mw planning 150 2022 2023 • ubol ratana dam floating solar farm 24 mw planning 65 2021 2023 • sirindhorn dam floating solar farm 45 mw pre-execution 63 2021 2022 philippines [23] • hydropower plants program 2300 mw pre-planning 5,000 2021 2026 • solar power plants program 5000 mw planning 5,000 2021 2024 • solar farms development program planning 1,650 2021 2024 • northern luzon hydropower program 1000 mw pre-planning 1,500 2021 2024 • solar power plants program 500 mw planning 1,000 2021 2023 indonesia [23] • mamberamo hydro power plant 23,000 mw planning 35,000 2022 2030 • renewable power plants program 11000 mw planning 22,000 2022 2028 • kayan river hydroelectric power plant 9000 mw execution 17,800 2020 2035 • kayan hydropower plant 1700 mw pre-planning 7,000 2022 2026 • indonesia power program: hydro power plants 2400 mw execution 3,500 2015 2025 burma [23] • mong ton hydroelectric plant 7000 mw execution 10,000 2016 2031 • ywathit hydroelectric power plant 4500 mw planning 4,500 2022 2030 • hatgyi hydroelectric power plant 1360 mw planning 2,600 2021 2026 • hydropower plants rehabilitation program planning 1,700 2021 2025 • upper thanlwin hydroelectric power plant 1400 mw planning 1,400 2021 2023 cambodia [24, 25] dna. damu et al. /future sustainability november 2023| volume 01 | issue 01 | pages 13-22 22 • stung russey chrum kandal hydropower plant 70 mw & stung veal thmor kambot hydropower plant 100 mw execution 322 2023 2025 • pursat province solar power project 150 mw execution • kampong chhnang province solar power project 60 mw execution • prey veng province solar power project 80 mw execution laos [26, 27, 28] nam gun 3 hydropower plant 480 mw planning 1400 2022 2027 luang prabang dam 1460 mw execution 3000 2020 2030 sekong coal fire power plant 1000mw planning 1700 2025 2027 monsoon wind power project 600 mw planning 692.55 2022 2027 phou ngoy hydropower project 728 mw execution 2400 2022 2029 brunei [29, 30] tenaga suria brunei 1.3 mw completed 20 2009 2010 brunei shell petroleum 3.3 mw completed multi-million 2020 2021 minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 12 article scale and implementation of the possible solarhydrogen system for island communities minh tran* department of mechanical engineering, arkansas tech university, 1811 n boulder ave, russellville, ar, 72801, usa a r t i c l e i n f o article history: received 28 june 2024 received in revised form 02 august 2024 accepted 12 august 2024 keywords: hydrogen fuel, solar power, microgrid power, photovoltaic, green hydrogen *corresponding author email address: htran2@atu.edu doi: 10.55670/fpll.fusus.2.3.3 a b s t r a c t as technology progresses, there is an increase in possibilities of designing an independent and self-reliant energy source for small communities. island and remote communities often have to rely on fuel transportation and main grid development for energy supply. by using renewable energy as an alternative choice for energy sources, small communities can remove hazardous emissions while saving money on fuels and shipping costs. solar-to-hydrogen (sth) microgrid is a system of solar panels and hydrogen energy systems that can capture and store solar energy for daily usage without fear of energy disruption during nighttime. despite the initial high capital investment, the concept can be explored and implemented as the long-term economic benefits are present when the cost of electricity is high for remote locations. this study is dedicated to researching and designing a microgrid that can sustain a small community without the presence of 3rd energy source for these communities. 1. introduction since the beginning of the 21st century, renewable energy has become the main topic and focus of global development policies to gradually transform into an alternative source in the event of fossil fuel depletion. solar energy, geothermal energy, wind energy, tidal energy, and wave energy… have been the notable energy sources to generate electricity in a sustainable and self-reliant manner. as the global population reaches over 8 billion in 2023 and as the life standard continues to increase, the state of energy sufficiency becomes more dramatic and problematic and requires the mass application of renewable energy. two of the most successful renewable energy sources are solar energy and wind energy. they have been utilized in largescale industrial and commercial applications. solar power has the greatest potential of all, with 3×1024 mj of energy released from the sun to earth's surface annually [1]. only a very small portion is currently exploited by humans, and there are numerous opportunities along with the development of future technology. in recent years, solar energy has become the answer to energy questions for remote and island areas. these areas, in many cases, do not have access to the main gridlines or do not have the capability to support such infrastructure. because of this, electricity generation costs are higher in isolated communities, regardless of subsidies from local governments. for example, in 2023, the electricity cost in the mainland united states is $0.12/kwh, while on the island of hawaii, it is $0.40/kwh, four times the mainland cost [2]. instead of relying on fossil fuels, solar energy can pose as an alternative self-sustaining solution. no transportation of fuel is required, while the emission is eco-friendly. for small and isolated communities, solar power microgrids can be a viable option for long-term energy solutions. a microgrid is a small electrical generating system that can be independent and self-reliant. it ensures a stable and reliable energy source while maintaining a manageable, economical cost for communities. microgrid design consists of 4 main components: the micro-energy source, the distribution network, the energy storage system (ess), and the control module [3]. as it is designed to be compact and flexible for locations, it can be grid-connected or totally isolated. the micro-energy source itself can be fully conventional, hybrid renewable, or fully renewable. as the fossil fuel cost continues to rise, accompanied by future carbon taxes, the solar power microgrid offers total independence without the need for ports and logistic infrastructure development for fossil fuel transportation. in one of the studies, ma et al. confirmed the feasibility of a solar system in combination with wind power for a remote island [4]. nonetheless, solar power microgrid has some disadvantages. it relies on daytime, geographic conditions, and weather conditions. solar energy can only be generated during the daytime; this means that the surplus energy is either wasted or needs to be stored somehow to reserve the energy for nighttime. during nighttime, solar future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.3.3 august 2024| volume 02 | issue 03 | pages 12-23 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:htran2@atu.edu https://doi.org/10.55670/fpll.fusus.2.3.3 https://fupubco.com/fusus minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 13 energy generation is almost zero, and fossil fuels or backup gridlines have to be used to substitute. daytime in the summer is also longer than in the winter. this varies the amount of energy generation over the seasons. different geographic conditions also have negative effects on solar power. the efficiency of power generation increases as the location is closer to the equator as shown in the potential photovoltaic (pv) map figure 1. locations such as hawaii, guam, or the virgin islands will require fewer solar panels with greater output when compared with other locations such as attu and nunivak islands. finally, weather conditions have significant effects on solar power. cloudy weather over a long period of time will hamper the generation output. that is the reason why an energy storage system is required in the microgrid system. most of the time, solar power excess is left to be wasted if it cannot be integrated back into the main grid or already exceeds the load capacity. studies often show the generated energy curve increases gradually during the day, overreaching the required load during mid-day, then gradually decreasing in the afternoon until sunset. in the case of an ess, when the generated energy curve and usage load have intersected, the excess will be converted and stored so that it can be released when the solar power output can no longer sustain the energy load. this can be nighttime, bad weather days, or a black-out emergency. current ess types include the battery model (bess), the hydrogen model (hess), and the hybrid model. the hydrogen model (hess) works by converting the electrical power into hydrogen gas through the process of electrolysis. hydrogen gas is then compressed and stored in an external tank. when the solar power output can no longer sustain the energy load, hydrogen gas is decompressed and converted back to electricity through fuel cells (fc). different from bess, which is constrained by the battery size and number, the hydrogen model is constrained only by its storing capacity. this allows it to be externally expanded until the hydrogen storage capacity overcomes the solar power excess. one of the papers related to the area is li et al.'s study on the surplus renewable energy source generation on the island of kyushu, japan, to decrease the energy curtailment [5]. the solar power curtailment would be converted into a huge amount of hydrogen gas, adding value to the grid-connected solar and wind energy. the model of a solar-hydrogen system (shs) has been in discussion in the last few decades. despite the benefits of hydrogen fuel cell systems, their development has been limited due to the extremely high cost of the electrolyzers. the high investment in electrolyzers, in addition to the renewable energy generator, has often caused a reduction in design scale. the hydrogen system itself also has some setbacks in terms of its technology with fuel cells having only around 40-60% efficiency. hydrogen itself is a highly flammable gas with the chemical characteristics of metal embrittlement when being stored for a long period of time. making hydrogen even more dangerous is the fact that, unlike a hydrocarbon flame, human senses cannot easily detect a hydrogen flame. people who come upon a hydrogen flame will not see it, even up close. for microgrids, this poses potential problems if careful maintenance and inspection are not performed regularly. some research has proposed to transport hydrogen gas for external applications, with prices fluctuating at us$5/kg in 2023 [6]. this comes with a loss of self-reliance on the microgrid, with the system having to rely on the main grid at critical hours. although it can be more economically viable, this leaves out as the solution for remote areas where microgrid is supposed to ease the energy concerns. figure 1. potential for solar pv energy according to world bank group’s global solar atlas [7] most studies have called out these problems and have often mentioned the compulsory combination of backup gridlines, fossil fuels, and wind power to substitute for the power drop. however, the current scale has been minimal in terms of the research on the possibility of totally independent microgrid. for example, shahbazbegian et al. [8] and nakamura et al. [9] designed power-to-hydrogen systems that still rely on the main grid for the load's substitute. therefore, this paper dedicates itself to the possible application of an shs under a totally independent microgrid for remote and island areas. this paper also identifies the optimal model, the size, the cost of installing a hydrogen system, and the economy of such a model. the goal is to understand the economic possibilities of the design for isolated areas. 2. methodology 2.1 end-user application for practical purposes, the microgrid is designed to be able to sustain a university hall's electrical load. the test subject is arkansas tech university's engineering department, corley hall (figure 2). the building occupies an area of approximately 2,525m2 or 27,190ft2 with four parking lots, each with a size of 4,000 m2. the possible maximum infrastructure area for the model includes the roof area as well as four parking lots with a total area of 16,000m2. because corley has two floors, the generated energy must satisfy the load of a total of 5,050m2. since the actual data on the annual electrical usage is unavailable during the study, the value for annual energy usage is based on the national electrical usage data from the u.s. energy information administration (eia) (see table 1). according to eia, an average university consumes over 1.2 million kwh annually. when compared to a small household, this is equivalent to 150 houses or a small community. this can serve as a good reference for isolated and island communities. the study chose solar-to-hydrogen microgrid as the main studied model. the design took into consideration the location of the university as well as comparing it to different locations to calculate the scale and capital cost. regardless of the location, the minimum energy output must be able to cover the required energy load during the lowest daytime time frame without the need for main gridlines integration. the scale of the power model must fit within the building's precinct and minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 14 must be optimized for the setup, maintenance, and sustaining. the total electricity consumed by the building is calculated through equation (1), in which the area and the power density are provided. edaily load = atotal. s t (1) where edaily load is total energy consumption in a day, atotal is the total area of all surface floors in the building, s is the power density or the average consumed power per square foot ( kwh m2∗yr ), and t is the time, which, in this case, is 365 days. figure 2. arkansas tech university's engineering department [10] table 1. annual electricity consumption totals [11, 12] per building (thousand kwh) average size (thousand 𝑓𝑡2) average per square foot (kwh) median per square foot (kwh) education 345 31.5 11.0 8.7 college or university 1,202 69.2 17.4 14.4 small household 8 1.4 5.4 average house 10 2 5.4 2.2 testing model the model in this study is a solar-to-hydrogen system (sth), as shown in figure 3. solar power from the sun is converted to electrical energy through a photovoltaic panel (pv panel). the solar power gradually increases during daytime, peaks during midday, and decreases as nighttime approaches. as it increases, the solar power energy level passes the demand load, where most of the energy excess is wasted. in the microgrid system, the excess energy is transferred to the battery and then to the electrolyzer to convert electrical energy into hydrogen gas for storage. as hydrogen gas is generated through an electrolyzer, it is compressed and transferred into a storage tank where it is kept until needed. when solar power decreases below the demand load, the battery kicks in as a temporary energy source. after the battery's energy level decreases under a certain percentage, the fuel cell kicks in and supplies the load demand until the next solar power cycle. parra et al. show that photovoltaic power is generated effectively from 9 a.m. to 5 p.m. during a high-output day [13]. during that time, electrolyzers began to convert excess electricity to hydrogen at the rate of 65-70% of the electrical power received from the pv panels. electrolyzers' gas is depleted at around 4 p.m. as the photovoltaic power decreases. at the same time, the hydrogen gas was pumped from the storage tank to fuel cells to generate electricity and continue so after the pv panels were off. li et al. [14] show the electrolyzers' output peaked between 12 p.m. and 2 p.m., while fuel cells' output remained constant after 7 p.m. in one of the models. due to efficiency during hydrogen conversion as well as covering the real-time demand load, the energy produced by solar pv must be higher than electrolyzers while the energy produced by the fcs must be lower than electrolyzers. figure 4 shows the representation of energy level of pv, electrolyzers, and fcs throughout the day if the testing model was to be put into operation. figure 3. microgrid system schematic figure 4. desired energy level vs. time of microgrid's energy source 2.3 photovoltaic panel (pv panel) for the microgrid to operate independently and without relying on a 2nd energy source, the energy generated by solar power must be equivalent to or higher than the demand load or 𝐸𝑃𝑉 ≥ 𝐸𝑙𝑜𝑎𝑑. however, figure 4 indicates that since the time to generate solar power is limited according to daytime, the energy rate or power of the pv must be much higher than the demand load so it can generate enough excess energy to store for nighttime or equation (2). the power generated by pv panels or daily energy is calculated from the product of solar insolation si ( 𝑘𝑊h 𝑚2. 𝑑𝑎𝑦 ), the available surface area 𝐴𝑠𝑢𝑟𝑓𝑎𝑐𝑒 (𝑚2) and the efficiency of commercial solar panels, equation (3). ppv ≫ pload (2) epv = si . asurface . η (3) minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 15 the solar insolation si is generated by measuring the solar radiation in a set period of time. as it is measured, each location, depending on the latitude difference and seasons, has a distinguishing value. figure 5 shows the average solar energy per square meter that any location within arkansas might receive in a day. figure 5 also shows the variation in si between different months. as seasons change, si values peak during summer and plummet during the winter. the si values are also different when being compared at different latitudes and different climates. figure 6. shows the lowest average si values in different states of the united states territory. states that are closer to the south and near the equator have higher si values as well as the most stable trends. the top state is hawaii, with the lowest value at 3.83 kwh/m2 per day during december and the highest value of 6.6 kwh/m2per day during june and july. in order to design a model that can sustain and operate fully independently, the minimum values for si are used to calculate the generated energy of pv panels based on a hypothetical area. the obtained values are then compared to total energy consumption in a day edaily load in order to determine the correct scale of the solar panels' area. the goal is to have a sufficient amount of energy during daytime use and to store it for nighttime use. the efficiency of most current solar panels varies between 17% and 20% [16]. however, research has shown that efficiency can reach the range of 30% in some studies [17]. for this study, the pv efficiency is set at 20%. figure 5. average solar insolation of arkansas throughout a year [15] figure 6. lowest average seasonal solar insolation of states in a day [15] 2.4 battery system and model the bes has been a subject undergoing intense study and discussions for usage in a microgrid system. bes is the traditional method for storing backup energy in an electricity circuit and has high reliability in power transition during energy switch [18]. before hes, bes was the default standard for storing electrical energy from gas turbines, fossil fuel engines, and renewable sources. for small independent and island grids where the load is under 5-200mw, bes has been very effective in providing and maintaining electricity service [19]. bes stores energy through an electrochemical process where the chemicals are contained inside the battery to absorb the energy. some batteries have an instantaneous response time of about 20ms, which allows them to adapt quickly to any situation [20]. when a high load is required in the grid, and the battery is no longer charged, the battery releases the energy back into the system, maintaining the gridline's operation. bes maintains uninterrupted and stable power flow to the gridlines as long as there is still power stored in the chemical. when the system observes a sudden peak in energy usage in the microgrid, the bes enables flexibility for the system without the risk of blackout. despite its advantages, the battery itself has some minor setbacks. as it stores energy within its chemical, when storing capacity is reached, excess energy generated from the renewable energy source has to be wasted. in order to increase the bes capacity, another battery must be installed. this increases both the complexity of integrating the system as well as the required space for the battery itself. even though the battery can discharge 90-100% of its energy, frequent charge and recharge cycles reduce its lifespan significantly. hlal et al. [21] studied the optimum battery depth of discharge of off-grid solar pv and stated that the range is between 20% and 70% to maximize the life cycle of bes. alramlawi et al. [22] claimed that when comparing the battery lifespan of the dept of charge between 40% and 90%, there is a decrease of more than 25% or 15,000h in lifespan. unlike bes, hes allows more capacity in energy storage since it stores its energy externally in the form of hydrogen gas. this allows the microgrid to expand its capacity by installing more storage tanks for hydrogen in case of excess energy without increasing the complexity of the electrical integrating system. however, fc in hes has a relatively slow response time in comparison with the traditional battery. sun et al. [23] tested the pemfc under multiple conditions of temperature, pressure, anode, and cathode humidification and showed that fcs could take anywhere from 2 minutes to half an hour in order to reach their capacity and stabilize the released power. in actual application, this can lead to sudden power drops and blackouts if the microgrid only relies on hes to supply the energy. sudden changes in demand load and short-term loss in pv power put extreme stress on fcs as well as els. in a cloudy day, both fcs and els have to turn on and off continuously over a long period of time, degrading their lifespan. therefore, a battery is needed in the microgrid in junction with the hes, so the power supply is always stable and uninterrupted. one of the most optimal setups is the battery-concentrated system, which charges and releases the battery first before hes. when bes is charged over 60-70%, energy is transferred into els where it is converted to hydrogen gas. when bes is depleted under 50%, fcs start to convert hydrogen back to electricity for long-term usage. figure 7 illustrates how the bes-hes system can operate. kafetzis et al. [24] proposed the start of fc cycles at the 20% limit and els at the >70% limit of the battery's soc in a battery-concentrated-hydrogen system. the study also mentions that the fc should be utilized to maintain the minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 16 battery's soc at 50% whenever its soc reaches the lower limit to ensure safe operation. rey et al studied how the battery-concentrated system could outlast the hesconcentrated system [25]. they concluded that the hesconcentrated system would cost 3 times more in investment while requiring a replacement of 3 els and 8 fcs in the course of 20 years. the bes-concentrated system would only require a replacement of 1 battery bank and 1 el in the same condition. the bes system is only responsible for supplying short-term energy during the transition state (~30 minutes) or during a sudden power surge. this is considered the most efficient metrology to utilize the hes while optimizing the best lifespan of the system. figure 7. possible setting for battery soc in junction with el and fc cycle 2.5 electrolyzers there are currently 2 common types of electrolyzers widely utilized for commercial applications: alkaline electrolyzers and proton-exchange membrane electrolyzers. their compact size and relatively low maintenance cost are the main reasons and focus for the integration of hes in microgrid development. in order to decide which electrolyzer to use, 2 things are taken into account: the roi cost and the lifespan of the system. roi cost must be achieved within the lifespan of the system in order for the model to be successfully implemented. alkaline electrolyzer (aec) is currently one of the three most common electrolysis processes, in which water is split into hydrogen gas for commercial or industrial usage. it is also the oldest electrolysis method, dated back to the 1800s [26] aec consists of a cathode, an anode, a separator, and an alkaline electrolyte solution. koh or potassium hydroxide is currently the most common solution for aecs, other than naoh or sodium hydroxide. the process requires electricity as an input of energy and releases heat as a byproduct. the aec operates at around 6080℃ and 1.8 2.4v of terminal cell voltage with an efficiency of around 6282% [27, 28]. for every kwh of electrical energy, aec produces around 0.019 kg of hydrogen gas [29]. the cost of an aec varies from around $250-400 per kw, which is cheaper than a pemec electrolyzer [30]. it also accepts high tolerance for impurities and dust in the feedstock. since its components are widely available, it does not depend on the noble metal catalyst like other electrolyzers [31]. in contrast, it is less efficient than pemec and requires higher operating pressure [32]. aec generally has a lifetime of 60,00090,000 hours or around 8 years. however, due to its alkaline nature, it is more prone to oxidization and corrosion, which can reduce its lifespan to below its standard time. it also can take up to 50 minutes for the aec to be in full operation mode, while the pemec only takes 5 minutes [33]. evolving from the aec, the proton-exchange membrane electrolyzer (pemec) uses solid polysulfonated membranes as both a separator and a gateway for ions. the membranes have better gas permeability, productivity, and pressure characteristics and require lower thickness. this allows pemec electrolyzer systems to be more compact while producing pure hydrogen gas at higher rates than others. for every kwh of electrical energy, pemec produces around 0.021 kg of hydrogen gas [34]. as a result, pemecs have become more favorable for pure hydrogen generation. pemec's operating temperature is the same as aec at around 6080℃ [35]. pemec's efficiency varies between 70% and 80%, with a study showing a possibility of 94% [35, 36]. despite its higher efficiency, the pemec structure requires the usage of noble metals like platinum, iridium, and ruthenium. currently, platinum is considered the state-of-the-art electrocatalyst for the pemec cathode [37]. as these materials are rare and precious metals, the cost of the pemec is significantly increased. the current cost is $500-1100 per kw, and a single pemec costs around $400,000$870,000. its lifespan is also less than aec, with the durability at around 30,000h -40,000 [38]. this can be traced to pemec's higher efficiency, purity, and ability to produce hydrogen under higher pressure, which is attributed to its fast degradation [39]. in order to calculate the amount of hydrogen gas produced by the electrolyzer, the gibbs free energy ∆gd 0 is used to represent the electrical power required to break the o-h bonds and generate the hydrogen molecules. the electrolysis process is represented by equation 4. h2o → h2 + 1 2 o2 (4) ∆hd 0(h2o(l)) = + 285,840 kj kmol (5) ∆sd 0(h2o(l)) = 163.150 kj kmol k (6) ∆gd 0(water) = ∆hd 0 − t∆sd 0 (7) where ∆hd 0 is the enthalpy, ∆sd 0 is entropy, and t represents the operating temperature of the electrolyzer. the unit of ∆gd 0 is under j/mol, so it needs to be converted to kg of hydrogen gas. ∆gd 0 is divided to mh2 = 2 kg/kmol to obtain the unit j/g or kj/kg as 1 mol of hydrogen gas equals to 2 g hydrogen gas. the full equation to get mass of hydrogen from pv's energy is represented by equation 8, where 1kj= 2.87 × 10−4 kwh and η is the efficiency of the electrolyzer. ℳh2 = ηec(epv)(mh2) ∆gd 0 1 2.87×10−4 (8) minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 17 for pemec with η = 0.7 and operating temperature of 60℃, the simplified equation is: ℳh2 = epv 47.46 (9) for aec with η = 0.62 and operating temperature of 60℃, the simplified equation is: ℳh2 = epv 53.58 (10) both 47.46 kwh/kg and 53.58 kwh/kg can be validated using the previously mentioned ratio of mass and electrical power. 2.6 fuel cells (fc) current technology has propelled the fuel cell system to be widely used in portable and stationary applications. while having the same reverse characteristics as the electrolyzer, the proton membrane fuel cell (pemfc) has seen greater advancement in comparison with the alkaline fuel cell (afc). despite its reliability, afc has a very low lifetime, measured between 3,000-5,000 hours or around 1 year, due to the voltage degradation of the individual cells [40]. the main cause of degradation is due to the corrosion by co2 where co2 reacts with free ohions to form carbonate co32ions and reacts with potassium in its electrolyte to form salt [41]. this reduces the available electrolyte koh within the fc with the rate proportional to current density. hence, the durability of the aec degrades over a short period of time. although the afc has a relatively affordable cost of $400-$600 per kw, it is not considered in this study [42]. on the other hand, pemfc has passed the demonstration phase and has been successfully applied in commercial vehicles and backup power applications. pemfc uses perfluorosulfonic acid membranes in its design to allow hydrogen ions to flow to the cathode of the fc. it is considered to be low-temperature fcs that operate around 50-80℃ [43]. as the temperature, fc loses its efficiency as the energy release is inversely proportional to temperature. due to pemfc's wide application and design, its efficiency has a wide range between 40% and 80% [44, 45]. parra et al. [46] designed a community hydrogen storage system for end-user applications and stated that the efficiency of pemfc is 79%. for this study, the efficiency of pemfc is set at 60%. the current cost of pemfc has fluctuated a lot based on the countries and the providers. in the u.s., the price is about $700 per kw [47]. the lifetime of pemfc has somewhat influenced its popularity in research and development. it is targeted to last around 60,000-90,000 hours or 8-10 years for steady-state operation [48]. however, pemfc has some minor setbacks. although pemfc can provide stable electrical power for the microgrid, its response time can be too long to avoid a brief blackout during the transition period. cheng et al. investigated the pemfc dynamic response and affirmed that it takes about 25 seconds for the power of pemfc to rise from 10 kw to 110 kw [49]. in order to counter this setback, the bes system, therefore, has a decisive role in the microgrid, ensuring a smooth transition between energy modes. the fuel cell process is presented by equation 11. the electrical power generated by an fc system is due to the changes in the gibbs free energy of formation ∆gf between the products and the reactants. the theoretical energy generated by a fuel cell has a value close to 33 kwh/kg under 100% efficiency which matches with reference [50]. h2 + 1 2 o2 → h2o (11) ∆gf = ∆gh2o(l) − ∆gh2(g) − ∆go2(g) (12) where at the temperature of 50℃ ∆gh2o(l) = −308,464 kj kmol , ∆gh2(g) = −42,180 kj kmol , ∆go2(g) = −33,130 kj mol efc = ℳh2 ∆gf mh2 (2.87 × 10−4)η (13) for pemfc with η=0.6 and operating temperature of 50℃, the simplified equation in kwh is: efc = 20.07(ℳh2) (14) 3. results and discussion the total power consumption of the corley building is approximately 2,590 kwh/day. the total roof area of the corley building is 2,525𝑚2, which can generate a maximum average of 2570 kwh using equation 3 under the condition that 80% of the area can be utilized. this figure, however, is insufficient to allow the microgrid to be self-reliant or sustain the power grid during the majority of the year. figure 8 shows the generated power and the power deficit of the pv grid. the power deficit decreases during the summer months when solar radiation is higher. nonetheless, during winter months, the available solar power can only supply 35-40% of the load. therefore, the roof-top pv is not sufficient to sustain the building's energy usage. figure 8. generated power and power deficit under roof-top pv panel the alternative is to utilize the four parking lots with a total area of 16,000𝑚2 instead to see if the generated power from the parking lots can fulfill the required energy load. the model for the installation of pv panels is based on parking lots of the intel semiconductor factory in phoenix, arizona, which combines the solar panel as the roof for parking spots. the pv panel generates solar power as well as provides shading areas for vehicles, as in figure 9a. if 85% of the area is able to be minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 18 utilized, the pv grids might see a significant surplus in energy during operation. (a) (b) figure 9. a) solar pv roof parking lot and b) generated power and power deficit under solar pv roof parking lot according to figure 10, even in the lowest month of solar radiation, the microgrid would see a generation of 6,188 kwh, a surplus of 3596 kwh in comparison with the power consumption of 139%. this surplus covers hes loss during the eth conversion as well as the hte conversion. using the data of load profile for a typical college building in california, a proportional dataset can be generated to simulate the actual load at arkansas tech university during the day [51]. in order to define the minimum capacity of the hydrogen tank, its mass needs to be calculated from the surplus of the pv power. the average surplus can be calculated by subtracting the demand load from the generated pv power at the same hour. figure 10 shows the effective sun hour per day in each month in arkansas. during december, the number of effective sunlight hours is only 3.5 hours, according to nrel [52]. as a result, the amount of needed hydrogen for the rest of the day must be generated in that 3.5-hour frame when the pv energy generation is maximized. figure 11 shows the required power generation during the 3.5 hours and the estimated power consumption during the day (total consumption is 2590 kwh). the comprehensive amount of electrical energy to be converted to hydrogen gas after subtracting it from the consumed energy is 5,575 kwh or 90% of the generated pv energy. using equation (9), the amount of equivalent hydrogen mass using the pemec is 117 kg. for the aec, the amount of equivalent hydrogen mass is 104 kg using equation 10. the hydrogen storage tank that the microgrid needs lies between 120 kg and 150 kg for the minimum value, where the extra capacity can be used as seasonal or weather backup. figure 10. effective sun hour per day vs. month of arkansas [52] figure 11. total energy usage and generated solar power vs. hour in a day in december when sunlight is no longer available, fcs kick in to convert the hydrogen gas back to electricity. using equation 14, the amount of equivalent electricity in a pemec-pemfc is 2348 kwh. in the aec-pemfc, the generated electricity is 2087 kwh. the possible total amount of electricity supplied by the microgrid is 2960 kwh and 2700 kwh for pemecpemfc and aec-pemfc, respectively. this amount of energy is sufficient for the microgrid to be independent during the lowest sunlight month of december. figure 12 shows the estimated model for the energy cycle within the microgrid. in order for the microgrid to be implemented in actual applications, its roi must outweigh its cost during its lifespan. therefore, it is necessary to generate the balance sheet for 30 years. for every 10 years, both the ec and fc are required to be replaced due to their lifespan degradation. the estimation for total cost (excluding battery and grid components) is shown in tables 2 and table 3. the pv panels cost about $3,060 per kw and are the most expensive investment in the microgrid due to their scale [53]. minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 19 the hydrogen tank with compressed pressure costs around $400-$700 per kg of hydrogen gas and is the least costly spending [54]. the total capital spending is then compared with different electrical costs from different locations, as in table 4. arkansas, which is located within the mainland united states, has a fairly low cost of energy at $0.12 per kwh in 2023 [55]. in contrast, martinique island of france, which is located in the caribbean sea, has a high cost of $1.14 per kwh [56]. small islands with small populations tend to not afford to build and maintain large power plants and therefore, have higher rates of electricity. the island of cook and solomon (island countries), which has less than 1 million inhabitants, have rates around $0.52-$0.69 per kwh. the cost of electricity of each location is multiplied by the total power consumption of corley building of 945,350 kwh/year (2,590 kwh/day *365 days), then added up over the course of 30 years to determine if and when the spending savings across the capital spending. figure 13 and figure 14 show the spending vs capital spending of 2 microgrid models. for both graphs, when the cost is below $0.30 per kwh, the microgrid economy is unable to sustain itself under a 10-year ec-fc replacement schedule within 30 years. as the pemec lifespan is only 4-6 years, it must be replaced, and its cost must be added to every 7th year. hydrogen tank, aec, and pemfc also need to be replaced every 10 years; therefore, the capital cost rises every 6-10 years, depending on the model of the microgrid. 30 years also marks the lifespan of the solar panel to be replaced as its efficiency has decreased to no longer fit to generate electricity [5759]. when the cost is above $0.50 per kwh, the spending saving crosses the capital investment within 15 years for the aec microgrid while it takes 30 years for the pemec microgrid. when the cost is above $1.00 per kwh, the spending saving crosses the capital investment within 6-9 years. the choice of aec microgrid and pemec microgrid lies solely upon the communities based on their financial capability and requirements. for most locations with costs under $0.50 per kwh, such as guam and hawaii, the pv-aec-pemfc microgrid might be more suitable as it is significantly cheaper due to the aec cost. the roi might be achieved within 20 years for these locations. table 2. the capital spending of pv-pemec-pemfc microgrid component cost per kw/ cost per kg h2 total capacity in kw or kg h2 total capital spending in us$ lifespan (years) pemec 1,100.00 1,614.00 1,775,400.00 4-6 hydrogen tank (kg) 700.00 117.00 81,900.00 10 pemfc 600.00 153.00 91,800.00 8-10 pv 3,060.00 1,768.00 5,410,080.00 30 total 7,359,180.00 table 3. the capital spending of pv-aec-pemfc microgrid component cost per kw/ cost per kg h2 total capacity in kwh or kg h2 total capital spending in us$ lifespan (years) aec 400.00 1,614.00 645,600.00 8-10 hydrogen tank (kg) 700.00 117.00 81,900.00 10 pemfc 600.00 153.00 91,800.00 8-10 pv 3,060.00 1,768.00 5,410,080.00 30 total 6,229,380.00 figure 12. total energy usage and generated solar power vs. hour in a day in december minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 20 4. conclusion this paper proposed a design to build a microgrid for small communities in remote and island areas based on the high-power consumption of a university building in arkansas. this microgrid uses 100% renewable energy without the reliance on fossil fuels and other means of energy sources. the sth microgrid consists of pv panels and an hes system which converts excess solar energy to compressible matter during the daytime and releases electrical energy during nighttime. the lifespan and the economic feasibility are then established and compared to understand the impact of such a system in the communities. the expectation was that the microgrid would eventually relieve communities of energy constraints as well as the economic burden in the long-term plan. • one of the major conditions for an independent microgrid is the location of the application and the availability of space in the area. location has a crucial role in determining the scale of the system and the economic cost of the project. the investment of pv panels is more expensive than other investments due to its complex system and its sheer scale in order to generate energy. to generate enough power for small communities or commercial hubs, an area of equivalent pv power might be 1.5-4 times the floor area of the load demand. for this study, the ratio was 3.2 times the figure 13. saving and capital spending over 30 years of pv-pemec-pemfc microgrid figure 14. saving and capital spending over 30 years of pv-aec-pemfc microgrid minh tran /future sustainability august 2024| volume 02 | issue 03 | pages 12-23 21 floor area of the corley building in order to generate enough power for the hes system, different locations with different climates and latitudes receive distinguished amounts of solar radiation throughout the year. in turn, the microgrid requires different areas of pv panels to ensure sufficient power to the grid. for example, due to its location and climate, hawaii receives more sun hours and more solar radiation per meter square than arkansas throughout the year. the fluctuation means that the required pv power area of hawaii is less than arkansas and costs less than arkansas; therefore, the economic wise favors areas closer to the equators. this poses a great challenge in standardizing capital spending and forecasting accurate models for pv generators. • two different kinds of microgrids are established and compared based on their lifespan and their economic feasibility: the pv-pemec-pemfc microgrid and the pvaec-pemfc microgrid. the pv-aec-pemfc microgrid has a longer lifespan as well as lower initial capital cost than the alternative, which is suitable for most locations. for the roi, the cost of electricity at the local locations has a major impact on the possibility of regaining the investment budget or gaining additional income. for areas where the electrical cost per kwh is below $0.30 -$0.40 per kwh, the spending saving might not overcome the capital spending in a 30-year period. this is also due to the increase of capital spending every 6-10 years for hydrogen tanks, electrolyzers, and fuel cells due to their efficiency and safety degradation over time. for areas where the electrical cost per kwh is above $0.40 per kwh like hawaii and guam, the spending savings might be able to pay off within a 25year period under the pv-aec-pemfc microgrid. meanwhile, for the areas that are above $1.00 per kwh, the additional income is within 10 years. • this study did not include the bes system as it is a lowcapacity system that is only required for transition purposes and only holds 150 kwh in a maximum 0.5-to-1hour period. the cost of such a system is relatively cheap (~$150 per kwh) in comparison with the hes system. however, the study recognizes the necessity of the bes system in the case of fluctuation in pv power out and shortterm blackouts. the application of bes also increases the lifespan of hes systems while decreasing the number of charging and discharge cycles of electrolyzers and fuel cells in daily operations. in the case of a major power surge in the grid, it is favored that the battery system takes up the stress instead of the hes system to reduce the damage and replacement cost it might cause to the microgrid system. • future development will be able to reduce the cost and increase the lifespan of both the pv panels and hes system so that it is more economically viable to mass implement microgrids for more communities. the reduction in manufacturing pv panels and electrolyzers, in particular, pemec, will have a determining impact on the microgrid market. pemec has some unique characteristics in producing higher hydrogen purity and higher efficiency while limiting the corrosion problem that is observed in the alkaline electrolyte. current progress has shown that pemec efficiency can achieve an efficiency of 80%. along with the improvement of pemfc, this will result in lower required pv panel areas and a reduction in capital cost. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the author declares no potential conflict of interest. references [1] hosseini, seyed ehsan. fundamentals of hydrogen production and utilization in fuel cell systems. elsevier, 2023. isbn: 978-0-323-88671-0 doi: https://doi.org/10.1016/c2020-0-03183-x [2] choose energy. 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(2023, october 19). battery price per kwh 2023. statista. https://www.statista.com/statistics/883118/globallithium-ion-battery-pack-costs/ this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 1 review review analysis of the technology on recycling processes for ev batteries abdulswamad rama salim, amanda empian wong, adrian sabat wong, saira tini, paul santa maria, hadi nabipour afrouzi*, ateeb hassan swinburne university of technology, sarawak campus, jalan simpang tiga, 93350, kuching, sarawak, malaysia a r t i c l e i n f o article history: received 01 august 2023 received in revised form 02 september 2023 accepted 09 september 2023 keywords: electric vehicles (evs), battery recycling, circular economy, sustainability *corresponding author email address: hafrouzi@swinburne.edu.my doi: 10.55670/fpll.fusus.1.1.1 a b s t r a c t the increase in use and demand for electric vehicles (evs) has surged the need for battery recycling methods for these batteries. this report highlights a review analysis of a few recycling methods for ev batteries, such as direct recycling, mechanical recycling, hydrometallurgical recycling, and pyrometallurgical recycling. the purpose of this review is to understand the current state of the technology, the challenges of each method, and the future developments while considering factors such as efficiency, cost, waste production, and more. direct recycling is reusing ev batteries without disassembling them, whereas mechanical recycling entails discharging, dismantling, crushing, and sorting them. hydrometallurgical and pyrometallurgical recycling processes both give considerable improvements in metal recovery, with hydrometallurgical recycling including acid leaching and pyrometallurgical recycling using metal extraction. analyzing the various recycling methods for ev batteries, the effort to improve or innovate the methods will help achieve a more sustainable and effective method to address the ev battery waste, which promotes a circular economy. 1. introduction 1.1 background information on ev batteries and their composition the demand for energy efficiency and environmental awareness is driving up interest in electric vehicles (evs). carbon dioxide emissions from petrol and diesel-powered vehicles are significant contributors to global warming [1]. additionally, since evs are eco-friendly and require clean, renewable energy sources to run, they are a feasible substitute for current fuel-powered vehicles due to the problem of rising global air pollution and diminishing fuel sources [2]. consequently, research and development of batteries for use in electric and hybrid vehicles are gaining attention [3]. the battery is an essential component because evs significantly rely on it to store the energy that powers the vehicle [4]. the most popular forms of rechargeable batteries are those made of nickel-cadmium (ni-cd), nickel metal hydride (ni-mh), lead-acid batteries, and lithium ion (liion) [1]. the most common ev battery components are electrodes (anode and cathode) and electrolytes [5]. ev batteries use lithium transition metal oxide cathode materials such as graphite-limo2, limpo4, licoo2 (lco), and linio2, with lithium nickel-cobalt-aluminum oxide and lithium nickel-manganese-cobalt oxide batteries being improved versions of limo2. lithium nickel-cobalt-aluminium oxide batteries and lithium nickel-manganese-cobalt oxide batteries are second-generation cathode materials known for their high-temperature thermal performance and minimal capacity loss. there are numerous materials that can be used to create anodes for lithium-ion batteries, including graphitebased (c-based) metal complexes like graphite-limo2, litis2, li-mos2, and li-lixmno2, as well as silicon-based (sibased) elements found in the earth's crust [5]. other anode materials include tin (sn), cobalt (co), and molybdenum disulfide. galvanostatically charging or draining li-ion batteries at high currents and low temperatures is made possible by carbon-coated anodes, which increase the capacity of the li-ion insertion and extraction. it has been shown that a number of binary solvents, including ethylene carbonate (ec), diethyl carbonate (dec), ethyl methyl carbonate (emc), and dimethyl carbonate (dmc), increase conductivity between electrodes and electrolytes in li-ion batteries. for li-ion batteries, lithium salt, also referred to as lithium hexafluorophosphate (lipf6), is an excellent electrolyte. in order to control the surface chemistry of graphite anodes, advanced active additives such as lithiumbis-oxalato-borate (libob), vinylene carbonate (vc), propargyl-methylsulfone (pms), hydrofluoric acid and water (hf/h2o) scavengers, and biphenyl or other aromatic compounds have been added to electrolyte solutions. to enhance the electrochemical and safety performance of solid future sustainability open access journal https://doi.org/10.55670/fpll.fusus.1.1.1 november 2023| volume 01 | issue 01 | pages 01-12 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:hafrouzi@swinburne.edu.my https://doi.org/10.55670/fpll.fusus.1.1.1 https://fupubco.com/fusus ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 2 li-ion batteries, novel materials such as gel, polymeric, and glassy matrices have been developed as their electrolytes. researchers have also suggested high salt-to-solvent ratio electrolytes, solvation-structure ester electrolytes, and composite electrolytes to improve the cycle stability, safety performance, and coulombic efficiency of li-ion batteries. components of a lithium-ion battery are shown in figure 1. figure 1. parts of a lithium-ion battery [6] 1.2 overview of the importance of recycling ev batteries and their technologies due to the global movement to minimize carbon emissions resulting in the rise of the demand for electric vehicles (evs), the usage of evs on the road also increases. hence, the challenge of managing exhausted batteries arises. batteries for evs will soon become a major problem if they are not treated properly. this is because extremely dangerous compounds are present, endangering both ecosystems and the people who manage them [7]. recycling these components is crucial for both environmental and strategic reasons because battery cells’ active components also contain important metals, including copper, nickel, lithium, and cobalt. disposal is doubly expensive because the battery is a substantial cost component for evs, especially if the waste contains valuable components [8]. by recovering high-value materials and lowering the expense of disposing of hazardous trash, recycling enables the reduction of life cycle costs. figure 2 illustrates the recycling process of an ev battery. ev batteries must go through multiple processes before they can be recycled because of their complex structure and variety of materials. they must first be categorized and, in most cases, pre-treated via discharge or inactivation, disassembly, and separation before undergoing direct recycling, hydrometallurgy, pyrometallurgy, or a combination of processes, which are some of the available ev battery recycling technologies today [9]. these recycling technologies often include leaching, separation, extraction, and precipitation of electrochemical components [10]. however, ev battery recycling is still in its early phases of development. hence, much more research and development are required to increase the efficiency, sustainability, and cost-effectiveness of ev battery recycling technologies. 1.3 purpose and scope of the review the purpose of reviewing and analyzing technology in ev battery recycling processes is to understand the current state of the technology, identify the challenges of each recycling technology, and estimate the potential for future developments. this type of analysis is critical for informing policymakers, industry stakeholders, and academics on the most effective techniques for ev battery end-of-life management. the scope of this review includes three main recycling technologies for ev batteries, which are pyrometallurgical recycling, hydrometallurgical recycling, and direct recycling. figure 2. recycling process of ev battery [11] 2. mechanical and pre-treatment process of ev batteries the mechanical process, also called the physical process, is one of the traditional processes to recycle lithium-ion batteries. this process is a pre-treatment process that is common to all the recycling routes. the mechanical process includes discharging, battery disassembling, and separating the lithium-ion batteries. it concentrates on the valuable bits while separating the battery shell from the other elements. from this process, it is possible to recover materials such as plastics, aluminum, copper, and black matter, which have critical metals, and to be collected for another separate recycling process [12]. furthermore, the discharge step must be conducted first because the collected battery usually has a specific residual voltage. this can certainly cause spontaneous combustion and explosion if not treated properly, jeopardizing the operators' safety [13]. 2.1 mechanical and pre-treatment process the used lithium-ion batteries can be physically discharged in the initial step of the process, including forceful discharge and short-circuit discharge. to release the remaining battery power instead, chemical discharge can be performed by submerging the battery in a conductive salt solution. the oxidation-reduction interaction between the positive and negative electrodes is used in this way of discharging to just slightly utilize the remaining battery power. this deactivation step assists in lowering the electrical and flammable risk of recycling the spent batteries; however, it can be neglected if the pyrometallurgy process is continued after the mechanical process. in contrast to the physical discharge method, the chemical discharge method has an advantage due to its high discharge efficiency and quick cycle. this advantage will be useful for a large-scale application. the batteries must then be disassembled and sorted according to the discharge method. the different battery parts can be separated manually or mechanically. the waste battery shell is removed to gather the battery core coil before manually disassembling it. after that, the positive electrode, negative electrode, and organic diaphragm are separated from the battery core coil. for large-scale operation and cheaper cost, mechanical treatment is preferable to hand dismantling, indicating increased economic applicability. after the ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 3 batteries have been taken apart, they are crushed into positive materials, negative materials, aluminum foil, copper foil, plastic separator, and other pieces [13]. the mechanical procedure for using lithium-ion batteries is depicted in figure 3. figure 3. mechanical process of spent lithium-ion batteries 2.1.1 case studies of mechanical process research on mechanical separation and vacuum metallurgy for recycling the metals from lithium-ion batteries was done by zheng et al. [14] in 2018. this study proposed that combining the mechanical recycling process with the vacuum metallurgy as a single integrated process could deal with the bulk amount of spent lithium manganese batteries (18650 limn2o4) without using any additives. due to residual power in the used batteries, the batteries were thoroughly drained for 24 hours with a five-weight percent nacl solution before being allowed to naturally air dry. to avoid harming the crusher that would subsequently be utilized in the mechanical recycling process, the hard ion shell was also disassembled, and the integrated process can then start from this point. the pre-treated batteries are then crushed by the crusher before being distributed according to their various particle sizes and being inspected. the spent batteries will next go through mechanical separation for the mixed electrode materials. these materials are thermally treated and are oxygen-free, where they are heated to produce materials that are easy to recycle. the organic binder was eliminated throughout this heating process in the form of a collectible gaseous sample. after 20 to 30 minutes of water leaching, the lithium resource was recovered as lithium carbonate, and the combined electrode materials’ valuable metals were recycled after that. the graphite in the filter residue was burned away to recover the manganousmanganic oxide (mn3o4). from the mechanical separation process, crushed pre-treatment batteries were separated by three different diameters. the medium diameter of 0.12 – 0.8 mm was made up of tiny fragments of membrane, cells, aluminum, and copper foil. while cells, membrane strips, copper foil fragments, and aluminum foil strips made up the biggest diameter, which was greater than 0.8 mm. the largest diameter (>0.8 mm) was composed of copper foil fragments, aluminum foil strips, membrane strips, and cells, whereas the medium diameter (0.12– 0.8mm) was tiny fragments of copper foil, aluminum foil, and membrane. the fine powder (<0.12mm) was mixed electrode materials where this research resulted in obtaining 11.69g of mixed electrode materials from 1 spent 18650 limn2o4 battery, which weighs 36.27 +/0.50g with a weight ratio of 32.23%. from the separation obtained, the different diameter particles were analyzed, showing that fine powders were composed of anode powders "graphite" and cathode powders "limn2o4". by recycling 100 spent batteries, the hammer crusher was able to obtain 1185g of mixed electrode materials, showing that the mechanical separation process is an effective process. table 1 shows the main chemical composition of the mixed electrode materials obtained. the results indicate that the majority of the mixed powers were graphite and limn2o4, while the other trace elements, such as cu, al, fe, co, and ni, were included. table 1. chemical composition of mixed electrode materials 3. recycling methods for ev batteries 3.1 pyrometallurgical recycling metallurgy is the science of extracting metals in their pure form for use. pyro means fire, heat, or high temperatures. pyrometallurgy is based on heating, extracting, and purification processes used to extract metals from ore [15]. the benefits of pyrometallurgical recycling include its enormous treatment capacity, high chemical reaction rate [16], reasonably flexible feed material, uncomplicated operation, and minimal environmental impact on the slag [14]. 3.1.1 process of pyrometallurgical recycling pyrometallurgy generally involves these four main processes: discharging, dismantling, pre-treatment, and extractive metallurgy, as illustrated in figure 4 below. the ev battery assumed here is the standard lithium-ion battery [15]. extractive metallurgy can be used to recover enriched metal fractions that are produced as a result of thermal pretreatment techniques used to break down ev battery modules [17]. it would involve a safe decomposition of combustible and controlled deactivation of organic components of the battery [13]. as the battery’s energy content may result in harmful chemical reactions, thermal pre-treatment is also vital for discharging through the disassembly of the battery [18]. due to the ease with which the cathode materials can be separated via sifting at high temperatures, this approach also eliminates the organic binder materials. thermal pretreatment methods consist of incineration and pyrolysis pretreatment. after pre-treatment, extractive pyrometallurgical methods are deployed to recycle the spent lithium-ion battery [19]. these methods are roasting/calcination and smelting. roasting/calcination is heating compounds in air and transforming sulfide ores into oxides, creating gas [20]. smelting is used in furnaces for metal reduction and typically involves the formation of carbon dioxide, reducing iron ore in a blast furnace [21]. the last stage is the refining and purification, whereby leaching, spray pyrolysis, and carbothermic reduction (ctr) are used. 3.1.2 case studies of pyrometallurgical recycling glencore xstrata (switzerland) recycles spent libs as a secondary feedstock by utilizing the pyrometallurgical process [22]. it sees batteries as a specialist market, even though they only make up a small fraction of its overall output [23]. elements content (wt.%) li 2.371 mn 37.22 cu 0.2307 al 0.2276 fe 0.0627 co 0.0095 ni 0.0062 c 30.83 ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 4 all libs are recycled using hydrometallurgy, pyrometallurgy, and mechanical pretreatment in the recycling process at accurec recycling process at accurec recycling gmbh in germany. the battery cells are dispersed, and pyrolysis is used to completely remove all organic components, such as plastics, electrolytes, and binders [24]. the metal components’ states are not altered, and the pyrolysis temperature is kept below 250 degrees celsius [25, 26]. during mechanical pre-treatment, there is no possibility of electrolytes reacting with the atmosphere or fluorine compounds being emitted into the air, which enables accurec to securely deactivate and destroy combustible organic material [24]. table 2 shows companies implementing the pyrometallurgical process in lib recycling. one thing to note is that these are the leading players in the market, but not all worldwide companies are listed here. 3.1.3 challenges of pyrometallurgical recycling due to the high energy consumption and intricate offgas treatment process, pyrometallurgy requires abundant financing. as research is still being done to develop a recycling system that uses resources efficiently and produces low offgas, mild hydro-metallurgical (acid-free or alkali) and processing conditions are used in pyrometallurgical recycling as an alternative, which uses intermediate temperatures (<10000c). lithium cannot be recovered using the majority of conventional industrial pyrometallurgical techniques [36]. lithium is a precious mineral because of its dearth and erratic distribution in the earth’s crust [37]. since other metals like cobalt (co) and nickel (ni) are recovered, recovering lithium from the electrolyte and lithium metal oxide would be useful [38]. low recycling efficiency is caused by some minerals that are not recovered. due to the massive number of used batteries that must be recycled, pre-treatment recycling facilities are eventually incompatible from a technical standpoint [19]. furthermore, complex changing designs used in ev battery production provide automation challenges and make recycling more difficult. 3.2 hydrometallurgical recycling this section discusses the general process of hydrometallurgical recycling, its recycling challenges, and case studies of hydrometallurgical recycling. 3.2.1 process of hydrometallurgical recycling in general, hydrometallurgy is a branch of metallurgy that involves the use of aqueous solutions to extract metals from ores or recycled materials. hydrometallurgical processes have gained significant attention in recent years due to their potential for sustainable metal recovery and environmental benefits. this literature review aims to provide an overview of the existing research on hydrometallurgy recycling processes, focusing on the extraction and recovery of metals from various waste streams. several studies have explored different leaching figure 4. schematized lib battery of pyrometallurgical recycling [12] ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 5 agents and conditions to dissolve metals from electronic components. for example, acids such as sulfuric acid, nitric acid, and hydrochloric acid have been widely used [39]. figure 5 illustrates the simple flowsheet of the hydrometallurgical recycling process of spent libs. researchers have investigated the effects of variables such as temperature, concentration, and leaching time on metal dissolution efficiency [41]. furthermore, the recovery of specific metals like gold, silver, copper, and palladium has been a subject of interest, and various strategies have been proposed to optimize their extraction [42]. the choice of leaching agent plays a crucial role in the efficiency and selectivity of metal recovery. in addition to traditional acids, alternative lixiviants like organic acids, complexing agents, and deep eutectic solvents (des) have been explored. researchers have examined the leaching mechanisms and kinetics of these agents to understand the underlying chemical reactions [43]. the identification of suitable lixiviants and their optimal conditions is essential for maximizing metal recovery while minimizing environmental impact. after metal dissolution, separation and purification steps are necessary to isolate and recover individual metals, as shown in figure 5. various techniques have been investigated for this purpose, including solvent extraction, ion exchange, precipitation, and membrane processes. solvent extraction, in particular, has been extensively studied for its ability to selectively separate metals from complex leach solutions [44]. the optimization of extractants, organic diluents, ph control, and stripping agents has been investigated to enhance the efficiency of solvent extraction processes. hydrometallurgical recycling processes are often considered more environmentally friendly compared to traditional pyrometallurgical methods. researchers have focused on minimizing the environmental impact of hydrometallurgy by studying the recycling of lixiviants, reducing reagent consumption, and developing alternative reagents. additionally, the treatment and disposal of leach residues and effluents generated during the process have been investigated to ensure proper waste management and prevent pollution [45]. apart from environmental considerations, the economic feasibility of hydrometallurgical recycling processes is a crucial aspect. researchers have conducted techno-economic analyses to evaluate the overall cost of metal recovery and compare it with traditional methods [46]. 3.2.2 case studies of hydrometallurgical recycling it is worth mentioning that the most economical, simple, and environmentally friendly hydrometallurgical technique for metal recovery is acid leaching [47]. as a result, case studies on the effectiveness, expense, and energy usage of the hydrometallurgy recycling process for ev batteries are presented in this section. a case study by chen et al. [22] focused on the hydrometallurgical recovery of metals from lithium-ion batteries used in electric vehicles (evs). figure 5. flowsheet of hydrometallurgical process for spent libs [40] table 2. overview of companies using pyrometallurgical battery-recycling processes [27] company operational scale operating capacity (t/a libs) recovered materials (products) recycling processes umicore nv (belgium) large scale [28] 7000 [28] ni, co, cu, fe, cocl2 [29] pyro, hydro glencore xstrata (switzerland) small scale (intent to increase capacity) 7000 [30] co, ni, cu [24] pyro, hydro [11, 12] the international metals reclamation company (inmetco, america) commercial scale 6000 [30] co, ni and fe in ironbased alloy [12, 19] pyro, mechanical [31] jx nippon mining and metals (japan) commercial scale 5000 [32, 33] ni, co, li2co3, mnco3 [34] pyro, hydro [34] sony sumitomo (japan) small scale 150 [35] coo pyro, hydro [35] accurec recycling gmbh (germany) medium scale 3000 li2co3, co-alloy pyro, thermal, mechanical, hydro nickelhütte aue gmbh (nha) (germany) large scale 7000 nicocu-matte pyro, thermal, hydro kyoei seiko (japan) commercial scale ni, co, cu pyro dowa holdings co., ltd. (japan) large scale 1000 ni, co, cu thermal, pyro, hydro snam (societe nouvelle d’affinage des metaux) (france) co, ni, cu thermal, pyro, hydro ganzhou highpower internation inc (china) large scale 10000 nimh mechanical, pyro, hydro ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 6 the study aimed to optimize the leaching process for efficient metal recovery while considering cost and energy consumption. the researchers investigated the use of different leaching agents and conditions to selectively dissolve metals, such as lithium, cobalt, nickel, and manganese, from the battery materials. their study highlighted the importance of process optimization to achieve high metal recovery rates while minimizing the consumption of reagents and energy. a case study conducted by choi et al. focused on the recycling of electric vehicle batteries through hydrometallurgical processes [48]. the study aimed to optimize the recycling process to achieve efficient metal recovery while also considering the cost and energy consumption aspects. in order to recover metals like lithium, cobalt, and nickel from depleted ev batteries, the researchers investigated various leaching agents, including sulfuric acid and organic acids. the study emphasized the need for process optimization to enhance efficiency, reduce costs, and minimize energy consumption in the recycling of ev batteries. in a case study by xu et al. [49], the optimization of the leaching process for cobalt recovery from electric vehicle batteries was investigated. the study focused on enhancing the efficiency of cobalt leaching while considering the cost and energy consumption aspects. the researchers explored different leaching agents, acid concentrations, and process parameters to achieve high cobalt recovery rates. the findings emphasized the importance of process optimization to maximize metal recovery efficiency and minimize reagent consumption and energy requirements. a case study conducted by sun et al. [50] focused on the energy and environmental assessment of lithium recovery from spent lithium-ion batteries using hydrometallurgical processes. the study aimed to evaluate the efficiency, cost, and energy consumption of the recovery process. the researchers examined different leaching agents and recovery techniques to optimize lithium recovery while considering the energy requirements and environmental impacts associated with each method. the study emphasized the importance of balancing efficiency and sustainability in the recycling of ev batteries. in summary, the case studies contribute to the understanding of efficiency, cost, and energy consumption considerations in hydrometallurgical recycling processes for ev batteries. they highlight the importance of optimizing leaching agents, process conditions, and separation techniques to achieve sustainable and cost-effective recovery of valuable metals while minimizing energy consumption and reducing overall costs. 3.2.3 challenges of hydrometallurgical recycling based on the case studies, several challenges can be identified in hydrometallurgy recycling processes for ev batteries. these challenges include selective metal recovery, process optimization, environmental impact, energy consumption, and cost considerations. one of the key challenges is achieving selective metal recovery from complex battery materials. ev batteries contain a variety of metals, and optimizing the leaching process to selectively dissolve specific metals while avoiding the dissolution of others can be challenging. hence, developing efficient leaching agents and optimizing process conditions are crucial for achieving high metal recovery rates. hydrometallurgical processes also require careful optimization to maximize efficiency while minimizing costs and energy consumption. finding the optimal combination of leaching agents, process parameters (such as temperature and time), and separation techniques can be complex. therefore, process optimization involves balancing the trade-offs between metal recovery rates, reagent consumption, energy requirements, and overall process economics. further, recycling processes consider the environmental impact associated with hydrometallurgical methods. the choice of leaching agents and separation techniques can have varying environmental implications. minimizing the use of hazardous chemicals, reducing waste generation, and implementing proper treatment of process effluents are important considerations for sustainable and environmentally friendly recycling processes. hydrometallurgical processes can be energy-intensive, particularly during leaching, separation, and purification steps. reducing energy consumption while maintaining high metal recovery rates is a significant challenge. process optimization, the use of efficient equipment, and the integration of energy-saving measures are essential to minimize the overall energy requirements of the recycling process. moreover, the cost of hydrometallurgical recycling processes is a crucial factor for their commercial viability. the selection of cost-effective leaching agents, optimization of process parameters to minimize reagent consumption, and efficient separation techniques are necessary to reduce overall costs. to address the challenges in hydrometallurgy recycling processes for ev batteries, several strategies can be implemented. continuous research and development efforts are essential to tackle selective metal recovery, process optimization, environmental impact, energy consumption, and cost considerations. this involves exploring new leaching agents, optimizing process parameters, and developing innovative separation techniques. the adoption of sustainable chemistry, such as environmentally friendly leaching agents, can minimize the environmental impact. implementing energy-efficient measures, utilizing advanced equipment, and recovering and reusing energy can help reduce energy consumption [50]. 3.3 direct recycling direct recycling is relatively new in recent years, which has been produced on a lab scale to recycle the active components to reproduce new lithium-ion batteries (libs). this will promote a circular economy in producing new libs. direct recycling of libs involves separating the excellent purity active components in the cathode and anode from used libs and regenerating their electrochemical functionality by different physical, chemical, and mechanical processes. figure 6 shows a recycling process that involves direct recycling. direct recycling is a promising technique in conjunction with other recycling methods, which makes use of the lithium nickel manganese cobalt oxide-graphite (nmcg) battery, the most used type of battery. typically, when the nmc-g battery is spent, about 20% of functional lithium is lost due to parasitic effects, element isolation, and solid electrolyte interface formation. without destroying the active elements in the electrodes of libs, the direct recycling method may restore and extend the active elements [51]. 3.3.1 process of direct recycling the process of direct recycling is as follows [52]: 1) spent batteries will be disassembled into cells and discharged using electrolytes. 2) the cells are then treated using supercritical co2 to extract the reusable electrolytes. 3) the remaining electrolytes from the cells are calcined, which produces waste. ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 7 4) the cells are disassembled and pulverized into powder form to separate the materials, such as cathodes, anodes, plastic, and metals, using a non-destructive separation technique. 5) various re-lithiation methods are used to regenerate the spent materials of the cathodes. 6) regenerated materials are used in creating new cells for batteries. direct recycling is a promising process compared to traditional recycling methods or any existing methods. figure 7 depicts a process of direct recycling. compared to pyrometallurgy and hydrometallurgy, direct recycling is comparatively greener and does not have high energy consumption or chemical use. direct recycling does not cause air pollution or generate much waste, whereby, as mentioned, it focuses on disassembly rather than destruction of the spent battery. life cycle analysis shows that the regenerated material for the method has a high value in comparison to pyrometallurgy, and hydrometallurgy produces lesser waste emissions and consumes less energy [53]. the nmc-g lithium-ion battery’s closed-loop manufacturing methods are depicted in figure 8. first, presuming that the evs are similar to regular automobiles at 91%, the used lib packs are removed from the vehicles. around 0.083 mj of energy is consumed to remove each kg of lithium-ion battery pack. secondly, the expended libs are immersed in a salt solution to remove any remaining charge. complete discharge of a lithium-ion battery pack is thought to need 0.0035 mj of electricity per kg. the electrolyte is then extracted from the disassembled battery cell using a co2 solvent in the third step, which also involves disassembling the discharged battery cell. the battery cell is fed with compressed liquid co2 at a flow rate of 1.5l per minute for about 50 minutes, along with a 3:1 ratio of acetonitrile (acn) and propylene carbonate mixture at a flow rate of 0.5 ml per minute for about 20 minutes. the carbon dioxide solvent will be converted into gaseous carbon dioxide and extracted from the battery at 100 ml per cell in the electrolyte. most of the carbon dioxide is reused, whereby the remaining will be considered as recycling consumption. the energy consumption in compressing the carbon dioxide solvent into the cells is roughly 0.04 mj per kg of the nmc-g lithium-ion battery. lastly, the cells will be physically reduced and undergo the final process to separate the anode and cathode, which uses 0.26 mj. the separation process for every battery pack will consume about 0.023 mj/kg of nmc-g battery pack [51]. figure 6. the recycling process includes direct recycling [51] figure 7. process of direct recycling [52] ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 8 3.3.2 case studies of direct recycling direct recycling shows that in countries such as china, south korea, the us, belgium, and the uk, it is estimated that direct recycling of various types of ev batteries, such as those from tesla, proves to have a net profit in comparison to other methods. figure 9 shows the net recycling profit of various recycling methods. many factors affect recycling, such as transportation costs, disassembly costs, recycling process costs, the design of the battery, and scale profitability. if direct recycling is able to achieve a similar capacity of recycling compared to hydrometallurgical and pyrometallurgical recycling, then direct recycling will achieve the highest net profit. direct recycling is predicted to have the lowest breakeven point at about 3,000 tonnes per year compared to pyrometallurgical recycling at 17,000 tonnes and hydrometallurgical recycling at 7,000 tonnes per year [54]. on the other hand, figure 10 shows the potential of direct recycling. 3.3.3 challenges of direct recycling direct recycling is still considered a new process that requires more time and effort before commercialization. the way to improve the method is by addressing the recycling process [55]. 1) preliminary processing in obtaining refined materials: the concept of direct recycling is to obtain the spent materials and directly reuse and regenerate the cathodes. this is prevented as libs have many components, such as cathodes, anodes, metals, and plastics. by improving the efficiency of separating the components, direct recycling may be improved, along with ensuring that the retrieved cathodes are of high purity. 2) recovery of other materials besides cathodes: the direct recycling process currently focuses on the extraction of cathodes in powder form, which is roughly 35% of the cost of the material itself. without relying on other methods to recover these metals, direct recycling can be maximized even further to reduce the need for other methods. 3) show the recovered materials: for the ev batteries to take on direct recycling as a better alternative, the method must achieve a certain implementation and establish the importance of direct recycling. 4) regain the mixture of cathodes: the varying types of spent libs may use different cathode substances. this is a challenge for the direct recycling process, as the separation of varying materials is important. finding a way to extract and separate the various cathode substances may prove difficult, as different libs have different ratios of the nmc-g materials. one way is to test whether the mixture of the substances can be extracted directly. 5) combination of various recycling methods: as direct recycling is still under development, it may be advantageous to implement other recycling methods into direct recycling to allow higher efficiency. extracted cathode materials may be retrieved using other methods, such as the hydrometallurgical process. from the previously mentioned discharging process of cathodes using co2, the method allows for cathodes to be recycled if allowed. the cathodes may need to be regenerated before being reused in new batteries. this method allows for most components of a spent lib to be recovered and reprocessed. cathode materials, regardless of their property or combinations, may be highly valuable through direct recycling. the effectiveness of recovery has yet to be compared to the performance of raw material, which may raise issues later on, such as battery capacity and lifespan. this may spark debate among manufacturers regarding recycled materials, as they have to ensure the product is of quality and performance. recovered materials may be figure 8. closed-loop process of recycling spent nmc battery ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 9 implemented into other products with less strict requirements [56]. figure 9. net recycling profit of various recycling methods [54] figure 10. potential of direct recycling [54] 4. comparison and discussion of the recycling process 4.1 comparison table of the recycling process table 3 compares the different recycling processes. it compares pyrometallurgical, hydrometallurgical, and direct recycling processes in terms of efficiency, energy consumption, environmental impact, and cost. 4.2 discussion of the recycling process based on table 3, the efficiency in extracting metals from the waste material of pyrometallurgical recycling is highest compared to hydrometallurgy and direct recycling. this is because pyrometallurgical recycling involves high-temperature processes such as smelting, where the waste material is melted to separate and recover valuable metals. on the other hand, hydrometallurgical recycling methods use chemical processes to dissolve and extract valuable metals from the waste material. these processes often achieve high efficiency as they can selectively target specific metals and effectively recover them from the solution. meanwhile, direct recycling involves sorting, cleaning, and reprocessing waste materials to create new products. the efficiency of direct recycling can vary depending on the quality of the waste material and the effectiveness of the sorting and processing techniques. however, with advancements in recycling technologies and improved waste management systems, direct recycling can achieve moderate to high levels of efficiency in recovering valuable materials. moreover, the energy consumption of direct recycling typically requires low energy consumption. the processes involved, such as sorting, cleaning, and reprocessing, usually require less energy compared to more complex chemical or high-temperature processes. pyrometallurgical recycling methods have high energy consumption as they involve heating the waste material to high temperatures, which requires significant amounts of energy, whereas hydrometallurgical recycling methods can have moderate to high energy consumption due to the need for chemical reactions and the use of energy-intensive equipment to dissolve and extract metals from the waste material. besides, direct recycling generally has a low environmental impact compared to pyrometallurgical and hydrometallurgical processes. it avoids the need for extensive chemical processes or high-temperature operations, resulting in fewer emissions and minimal generation of hazardous by-products. pyrometallurgical and hydrometallurgical recycling methods can have moderate to high environmental impacts. the hightemperature processes involved in smelting generate emissions, including greenhouse gases and air pollutants in pyrometallurgy, and the use of chemicals in the dissolution and extraction processes can generate wastewater and chemical waste, requiring proper treatment and disposal for hydrometallurgy. in terms of overall costs, direct recycling is generally the most cost-effective option. it involves relatively simpler processes and requires less specialized equipment, resulting in lower capital and operational costs. pyrometallurgical recycling methods have moderate to high costs due to high-temperature equipment, energy requirements, and handling of slag and by-products, which adds to the overall expenses. hydrometallurgical recycling methods also tend to have moderate to high costs due to the need for specialized facilities, chemicals, and energyintensive processes. in summary, each recycling process has its own advantages and considerations. hence, determining which recycling process is better depends on various factors, such as the specific waste material being processed, the desired outcome, and the context in which the recycling is taking place. direct recycling is generally more cost-effective, has lower energy consumption, and has a lower environmental impact compared to the other methods. table 3. comparison table of pyrometallurgical, hydrometallurgical, and direct recycling processes [57] parameters efficiency energy consumption environmental impact cost pyrometallurgical recycling high high moderate to high high hydrometallurgical recycling high moderate to high moderate to high moderate direct recycling moderate to high low low low ar. salim et al. /future sustainability november 2023| volume 01 | issue 01 | pages 01-12 10 it involves simpler processes and can be more easily integrated into existing waste management systems. however, direct recycling may have limitations in terms of the types of waste materials that can be efficiently processed. it may not be suitable for complex or contaminated materials that require specialized techniques for metal recovery. meanwhile, pyrometallurgical recycling methods have high efficiency in metal recovery, particularly for metals that can withstand high temperatures. they can handle a wide range of waste materials and can recover a variety of metals simultaneously. pyrometallurgy is often used for processing large volumes of metal-rich waste. hydrometallurgical recycling methods, on the other hand, can achieve high efficiency in metal recovery, especially for targeted metals. they can selectively extract specific metals from the waste material, even in low concentrations. hydrometallurgy is often effective for recovering precious and strategic metals. the limitations of hydrometallurgical methods are that they tend to have higher energy consumption and may generate chemical waste or wastewater that requires proper treatment. they also require specialized facilities and expertise, which can increase costs. 5. future directions and outlook the ev battery industry has significant potential for circular economy and sustainability by recycling spent batteries, which can minimize waste and conserve natural resources. to promote ev battery recycling, battery manufacturers should be encouraged to take back waste batteries so that they can be recycled into new batteries or other valuable materials. policy and regulatory developments should be established to support ev battery recycling efforts, including targets for major components of battery recovery. recycling initiatives can also include objectives for the utilization of recycled material during the manufacturing of new ev batteries to further promote a circular economy in battery production [58]. ev battery manufacturers globally should be encouraged to implement labeling requirements that provide information on batteries, such as the date of manufacture, chemistry, and hazardous substances, as this can impact recycling initiatives by increasing transparency and facilitating third-party recycling of ev batteries [58]. moreover, supporting research and development in ev battery recycling technologies would broaden the range of materials that can be recovered and recycled. through more research and development, recycling technologies have the potential to be more cost-effective and efficient and can be implemented on a larger scale. 6. conclusion in conclusion, this paper gives an extensive review of the technologies for recycling electric vehicle (ev) batteries. it emphasizes the significance of efficient battery management due to the presence of hazardous compounds and strategic metals. this is due to the growing ev demand and the need to reduce carbon emissions. the study analyses four major ev battery recycling technologies, namely, mechanical recycling, direct recycling, hydrometallurgical recycling, and pyrometallurgical recycling. direct recycling involves reusing intact ev batteries or their components without disassembling them, whereas mechanical recycling involves discharging, dismantling, crushing, and separating batteries. hydrometallurgical and pyrometallurgical recycling techniques provide significant benefits in metal recovery, with hydrometallurgical recycling incorporating acid leaching and pyrometallurgical recycling involving metal extraction using high-temperature processes. overall, there is an emphasis on the importance of conducting thorough research on the current state of ev battery recycling technologies to make informed decisions about ev battery end-of-life management. further efforts to conduct research and development of ev battery recycling technologies are necessary to address the challenges of each recycling technique, improve efficiency, and promote the circular economy for ev batteries. the study highlights the significance of sustainable and effective recycling efforts in addressing the environmental issues related to the increasing use of evs. valuable materials can be successfully recovered while decreasing costs and reducing the adverse environmental effects of ev battery disposal by promoting the implementation of effective recycling technologies. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement data sharing is not applicable to this article as no datasets were generated or analyzed during the current study. conflict of interest the authors declare no potential conflict of interest. references [1] w. chen, j. liang, z. yang and g. li, 'a review of lithium-ion battery for electric vehicle applications and beyond', energy procedia, vol. 158, pp. 4363-4368, feb. 2019. doi: https://doi.org/10.1016/j.egypro.2019.01.783. 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[58] a. tankou, g. bieker and d. hall, 'scaling up reuse and recycling of electric vehicle batteries: assessing challenges and policy approaches', the international council on clean transportation, 2023. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 1 article microstructured pebble stone like ni-nio composite as anode of high-performance lithiumion batteries safina-e-tahura siddiqui1, md. arafat rahman1*, md. saiful islam2, jin-hyuk kim3, nirjhor barua1 1department of mechanical engineering, chittagong university of engineering and technology, chittagong-4349, bangladesh 2department of glass and ceramic engineering, bangladesh university of engineering and technology, dhaka, bangladesh 3clean energy r&d department, korea institute of industrial technology, 89 yangdaegiro-gil, ipjang-myeon, seobuk-gu, cheonan-si, chungcheongnam-do, 31056, republic of korea a r t i c l e i n f o article history: received 10 september 2023 received in revised form 14 october 2023 accepted 27 october 2023 keywords: thermal oxidation, nio, composite, anode, libs *corresponding author email address: arafat@cuet.ac.bd doi: 10.55670/fpll.fusus.2.1.1 a b s t r a c t ni-nio electrodes were synthesized via thermal oxidation of pure nickel powder and evaluated as anode of lithium-ion batteries (libs). the composite synthesized at 600˚c, 800˚c, and 1000˚c exhibited nanochips, crushed gravel stone, and pebble stone-like morphology, respectively. the nanochipsand crushed gravel stone featured-like electrodes exhibited erratic behavior, and specific capacity faded rapidly from 754.49 mah g -1 and 101.12 mah g-1 to 464.04 mah g-1 and 9.55 mah g-1, respectively over 10th cycle at a current rate of 1c as the electrode experiences internal short circuit. the pebble stone-like ni-nio electrode exhibited improved and stable cyclic performance with 1 st discharge capacity of 365.17 mah g-1 and reduced to 67.42 mah g-1 even after 40th cycle at 1c current rate. the improved electrochemical performance of composite ni-nio with a pebble stone-like feature can be attributed to the mechanical stability of the electrode, which can buffer volume expansion, and the presence of more nanoparticles on the electrode surface allows more interaction with li+. 1. introduction lithium-ion batteries (libs) have acquired immense attention and popularity as rechargeable batteries for portable consumer electronics applications due to high gravimetric and volumetric energy density, zero memory effect, and low self-discharge rate [1]. besides consumer electronics, libs are being employed in aerospace, military applications, grid energy storage, electric vehicles (ev), hybrid electric vehicles (hev), and plug-in hybrid electric vehicles (phev) [1–4]. the implication of these batteries is that they mitigate the environmental pollution resulting from the burning of fossil fuels [5]. it is noted that graphite is employed as an anode in commercial libs as it is inexpensive, has high reversibility during the charge/discharge process, and has excellent stability. however, its cycling capacity is restricted due to possessing low theoretical capacity (372 mah g-1) [6,7], which cannot fulfill the market demand for next-generation rechargeable libs. moreover, graphite anode experiences extensive structural deterioration upon cycling that leads to drastic capacity fading; high polarization initiates lithium dendrite formation and low operating voltage [8]. from that quest, establishing a favorable anode material with high capacity, environmentally benign, and rate performance is very crucial to advancing the performance of libs [9–12]. in addition, pure alloys as lib anodes face some issues, for instance, volume expansion and electrode fracturing during the lithiation process, which causes mechanical fracture of active electrode particles, resulting in electrical detachment and capacity fade and unstable sei formation [13–15]. however, titanium-based oxides are investigated as the anode; it can eradicate the issues regarding alloy anodes with a long cycle life since it has no sei and just a 1% volume change. unfortunately, with a 1.5v versus li/li+ operating voltage, as well as a limiting specific future sustainability open access journal https://doi.org/10.55670/fpll.fusus.2.1.1 february 2024| volume 02 | issue 01 | pages 01-13 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:arafat@cuet.ac.bd https://doi.org/10.55670/fpll.fusus.2.1.1 https://fupubco.com/fusus set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 2 capacity of 160 ah kg-1, the battery energy density is reduced [16]. among all anode materials, transition metal oxides (tmos) are recognized as the most suitable anode materials for lib due to their high theoretical capacity, natural affluence, eco-friendly nature, cost-effective fabrication procedure, and chemically durable [17–23]. moreover, tmos as anode material eliminate the problem of lithium dendrite formation, safety issues, and low specific capacity. it is noted that tmos encounter some issues, such as rapid capacity depletion due to volume-induced strain during electrochemical cycling, resulting in intense polarization and electrode pulverization [24–27]. to address these issues, nanostructured tmos are being employed because of their large electrode/electrolyte contact area, short diffusion length, and efficient strain accommodation [28,29]. nio is a competitive candidate among other tmos and is explored widely as an alternative electrode material for highperformance libs due to its high theoretic capacity of 718 mah g-1, cost-effectiveness, environment benignity, and natural abundance [30]. the density of nio is 6.81 g cm-3, which is three times higher as compared with graphite of 2.26 g cm-3. the theoretical energy density of nio is about 5.8 times higher than graphite [31]. nevertheless, the practical application of nio in libs is still obstructed because of its excessive volume variation and destruction of the active electrode material, as well as poor ionic conductivity, which results in poor electrochemical performance [32, 33]. to alleviate these issues, various morphologies of nio are studied to analyze electrochemical performance, for instance, porous, mesoporous structures [36], nanocomposite [31, 37, 38], nanogravel [23], nanosheets [39, 40], nanowalls [41], nanofibers [42], hollow nanotubes [43], nanofilms [44], nanowires [45], hierarchical structures [46–50], nanocone array [51], composited with carbon [52–55] or conductive polymers [56,57] have been investigated, which in comparison to graphite and pure nio exhibited improved electrochemical performance. in addition, several strategies such as hydrothermal, microwave hydrothermal, coprecipitation, sol-gel method, pyrogenation, solvothermal, chemical emersion, spray pyrolysis, powder metallurgy and annealing is adopted to fabricate different nio nanostructures [58,59]. among these strategies, thermal oxidation of ni powder is considered a facile and costeffective process, which can be adapted to synthesize unique morphological structures. numerous investigations were carried out regarding electrochemical performance evaluation of nio synthesized through thermal oxidation [31, 51, 60, 61]. in some studies, nio was combined with carbon to form composites, which exhibit excellent cycling stability [62–64]. however, the composite synthesis process is tedious and the existence of low-density carbon greatly reduces the volumetric specific capacity. in addition, the inclusion of highdensity metals can contribute to enhancing electrochemical performances [65,66]. huang et al. prepared ni-nio nanocomposite through calcination in a tube furnace at 700⁰c [66]. the nanocomposite constitutes <10 nm of ni particles and 100 nm of nio particles. the enhanced electrochemical performance of electrodes due to the presence of the metallic ni phase facilitates a more reversible reaction during the charging process. comparatively, strong polarization was monitored owing to the presence of crystal defects. the rate capability and cycling performance were not satisfactory due to the slow kinetics of nio particles and the transportation of electrons. therefore, considerable research is required to be done to acquire stable cycling performance and rate capability of nio as lib anode material. in this specific study, we synthesized microstructured composite of ni-nio through a single-step thermal oxidation process and mechanical ball milling. the composite structures were employed as anodes and provided efficient electrolyte access throughout the structure, which resulted in high discharge capacity and excellent cycling performance. in addition, the synthesized composite electrode exhibited different morphology at different oxidation temperatures. the presence of the metallic ni phase facilitates the reverse decomposition process and improves electrical conductivity. it can be foreseen as a high-performance lib electrode. 2. experimental 2.1 synthesis of ni-nio nanocomposite the composite ni-nio fabrication involves a single-step thermal oxidation process in an electric furnace (nabertherm, usa) at three distinct temperatures, as shown in figure 1. figure 1. schematic representation of ni-nio composite synthesis process thermal oxidation is the method of growing a thin oxide layer on the surface of a wafer, which follows wagner’s theory, as shown in figure 2. the commercially available ni powder (99.8% purity, maximum limit of impurities are iron (fe): 0.01%, sulphur (s): 0.001%, carbon (c): 0.08%, oxygen (o): 0.15 %) of 20 gram was heated at 600⁰c, 800⁰c, and 1000⁰c in the furnace for 2 hours. the oxidation of ni powder was above 500⁰c [41,67]; hence, at the above temperatures, nickel was oxidized to nio. the nio film growth on the ni powder surface was initiated via a step increase in the temperature of oxidation in the air. the samples were kept for day-long, and this cooling process was naturally inside the furnace after finishing the oxidation process. the product of thermal oxidation, a greenish nio layer formed on the surface of ni, which was mainly a chunk of ni-nio. the mass of the nickel powder before and after oxidation was measured using a precision electronic balance machine (scientech inc., set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 3 usa) with a readability of 0.001 mg. the chunk of ni-nio nanocomposite was ball-milled into the cylinder of the ball milling machine, which was filled with crushed oxidized particles and balls of two diameters in a 10:1 ratio. during the process of collision between balls and crushed particles, the particles got crushed, the size of the particles was reduced, and the ultimate composite powder of ni-nio was formed. the crushed particles were then strained to achieve a smooth and homogeneous composite powder. figure 2. schematic representation of the thermal oxidation process 2.2 characterization techniques an x-ray diffractometer (xrd) (empyrean, panalyticalnetherlands) with radiation from the copper target (kα, λ=0.15406 nm) was used to evaluate the crystal structure and composition of the ni-nio crystal structure. the diffraction patterns were recorded over a 2θ range from 10 to 90⁰ at a step size of 0.1⁰. the morphology and structure of the nanocomposite ni-nio sample were examined using a highresolution scanning electron microscope (sem) (jsm 7600f, jeol-japan) in combination with energy dispersive x-ray spectroscopy (edx) at 5 kv with different magnification. 2.3 electrochemical measurements the synthesized and characterized nanostructured composites of ni-nio were employed as an anode of libs. the electrochemical performance of the synthesized anode was carried out by assembling the electrode into a cr2032-type coin cell (supplied by xiamen tob new energy technology ltd., china) in the laboratory. the synthesized nanocomposites of ni-nio were used as working electrodes prepared through a slurry coating procedure, as shown in figure 3. it is noted that the slurry constituted 70 wt. % of active material, 10 wt. % of polyvinylidene fluoride (pvdf) binder, and 20 wt. % of active carbon powder, which was dissolved in the required amount of n-methyl pyrrolidone (nmp) (sigma-aldrich). the prepared slurries were then pasted onto a copper foil (changzhou dlx alloy co., ltd., china). the counter electrode was recycled licoo2, and a porous polymeric separator of polyethylene was employed. the electrolyte was lipf6 (supplied by ximen tmax battery equipment ltd., china) of 1.0 m dissolved in ethylene carbonate (ec) and diethylene carbonate (dec) at a volume ratio of 1:1. the assembled coin cells were crimped at 100 psi pressure using a hydraulic battery crimper (metrology laboratory, dept. of me, cuet). the galvanostatic charge/discharge tests were performed using a landct2001a (landt instrument, usa) battery testing system in a voltage range between 0.02 to 3 v at a 1c current rate. figure 3. schematic view of composite electrode preparation and coin cell assembly 3. results and discussions 3.1 characterization of nanocomposite ni-nio as an anode of libs figure 4 shows the xrd pattern of ni-nio nanocomposite at different oxidation temperatures, such as 600̊ c, 800̊ c, and 1000 ̊c, respectively. to compare with the pure ni, the xrd pattern of pure ni is shown. the xrd pattern of pure ni powder reveals that a face-centered cubic (fcc) structure with three main diffraction peaks at 44.54 ,̊ 51.92 ,̊ 76.46 ̊corresponding to the (111), (200), and (202) miller indices of ni (icsd: 98-064-6085). the absence of any kind of impurity phases within the detection limit of the diffractometer confirms the purity of ni powder. in addition, despite the oxidation of ni at three distinct oxidation temperatures, no other diffraction peaks corresponding to the oxide phase are detected. it is noted that the xrd pattern of ni shows high intensity and sharp peaks. figure 4. xrd pattern of ni-nio composite after single-step thermal oxidation at 600˚c, 800˚c, and 1000˚c. set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 4 at 600̊ c oxidation temperature, ni (icsd: 98-064-6092) exhibited three peaks at approximately the same 2θ angle with five additional diffraction peaks at 37.31 ,̊ 43.35 ,̊ 62.97 ,̊ 75.49 ,̊ 79.51 ,̊ which reveals the formation of nio (icsd: 98002-8834). these peaks can be indexed to the (111), (200), (202), (311), and (222) diffraction planes. in addition, ni (icsd: 98-064-6089) and nio (icsd: 98-018-4918) peaks are observed with an increase in peak intensity of nio and a decrease in diffraction peak of ni due to the thermal oxidation of ni powder at 800̊ c. it is noted that more oxidation of ni with increasing temperature and the nio peaks become sharp with temperature rise which indicates the degree of crystallinity increase of nio particles. at the oxidation temperature of 1000̊ c, there are no obvious peaks of ni, the diffraction peaks of nio (icsd: 98-018-4918) are observed with high intensity and sharp peaks, as shown in figure 4. the major sharpening of peaks, mainly of 2θ = 37.31 ,̊ 43.35 ,̊ 62.97 ̊indicates the increased degree of crystallization [68]. the crystallographic parameters of ni-nio composite at different oxidation temperatures were determined by the debey scherrer equation, d= 0.94 λ / (βcosθ) (1) where d denotes the average dimension of crystallites, λ denotes the wavelength of x-ray, and β denotes the full width at half maximum of a reflation located at 2θ. the average crystal size of pure ni before oxidation was 19.93 nm, and after oxidation at 600⁰c and 800⁰c is 19.77 nm and 18.13 nm, respectively. however, there is no visible ni peak at the temperature of 1000̊ c. it is noted that, with the increase in oxidation temperature, the crystal size of ni decreases. in contrast, five diffraction peaks of nio at 600̊ c were found at 2θ = 37.31 ,̊ 43.35 ,̊ 62.97 ,̊ 75.49 ,̊ and 79.51 ̊ with an average crystal size of 17.13 nm while at 800̊ c and 1000˚c, same five nio peaks exhibited with average crystal size of 18.72 nm and 18.86 nm, respectively. hence, the crystal size of nio increases with an increase in oxidation temperature. the possible reason for the increasing crystallite size of nio is due to oxidation, which leads to more nio formation. a similar phenomenon was observed as the crystallite size of the metal oxides exhibited an increment with an increase in temperature until it achieved a constant crystal size [68]. figure 5 shows the lowand highmagnification images of ni powder before and after oxidation at 600⁰c. the sem of pure ni, as shown in figures 5 (a) and (b), revealed that the particles are spherical in shape as well as partially agglomerated and smooth, and there are spaces in between the particles. however, this powder was oxidized in the electric furnace at 600 ̊c continuously for 2 hours; the growth of oxide particles occurs in between the spaces because of the swelling of grains. a significantly different morphology was observed of ni powder after oxidation in the furnace at 600 ̊c. the as-synthesized ni-nio composite showed a randomly ordered interconnected “nanochips” like structure, as shown in figures 5 (c), (d), due to the formation of nio in ni powder. at a low oxidation temperature of 600 c̊, no obvious grain boundary was found, however, the oxide layer growth occurs due to oxidation. a rough surface was formed, which is seen in the high magnification sem image of the surface, as shown in figure 5 (d), due to oxide growth. the edx spectrum confirms the presence of only the ni phase before oxidation, both ni and o phases after oxidation, as shown in figures 5 (e) and (f). figure 5. low and high magnification sem images and edx spectra of ni powder: (a), (b), (e) pure nickel powder, and (c), (d), (f) after oxidation at 600 ̊c figure 6 shows low and high-magnification sem images of nickel powder after oxidation at 800 ̊c and 1000 c̊ temperatures. at 800 ̊c oxidation temperature, the increased grain swelling causes the grain contact area to enlarge, which is responsible for the intergranular joint formation [69]. it is noted that the grains are bonded well as more nio is formed when compared to the sample oxidized at 600 ̊c, and grain boundary is formed as shown in figures 6 (a), (b). as the temperature of oxidation increases, more oxygen is diffused through the porosity of the sample [70,71]; hence, more nio is formed in the structure. the surface exhibited a “crushed gravel stone” like morphology with a 0.855 μm average grain size. it is noted that there are some cracks and spaces in between the grains due to the diffusion of nickel as well as induced thermal stress. these kinds of cracks and spaces suggest that li+ transportation could take place easily because of the access of electrolytes through them. figures 6 (c) and (d) represent the low and high-magnification sem images of nickel powder after oxidation at 1000 c̊ temperature. the grains are well interconnected with each other as the swelling of grains due to the oxidation process causes them to fill up the intergranular spaces. the high magnification image of the structure, as shown in figure 6 (d) reveals that there are no visible pores or voids in the set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 5 structure and it exhibits a “pebble stone” like feature with a mean diameter of 0.899 μm which is quite different from the other two oxidized samples. the generation of different thermal stress is the main reason for different morphology at different temperatures [72]. at 1000⁰c oxidation temperature, a visibly smooth surface is observed in the high magnification image, as shown in figure 6 (d). figure 6. low and high magnification sem images and edx spectra of ni powder: after oxidation at (a), (b), (e) at 800 ̊c, and (c), (d), (f) at 1000 ̊c the edx spectra exhibited that there are both nickel (ni) and oxygen (o) is present, which confirms the formation of the nio phase in the synthesized composite structures. during edx measurement different areas were focused, and the corresponding peaks are shown in figures 6 (e) and (f). it is noted that every spectrum confirms the presence of the ni and o phases. 3.2 electrochemical performance of ni-nio composite as anode of libs the electrochemical performances of synthesized ni-nio composites were evaluated to assess their efficiency as anodes for lib. the performance evaluation was accomplished by comparing the galvanostatic chargedischarge profile for different composite anodes to figure out the effect of oxidation temperature on the battery performance. in this study, three types of batteries are assembled employing three kinds of composite. these three batteries are assembled by exertingmicrochips (600⁰c, b-1), crushed gravel-stone (800⁰c, b-2), and pebble stone (1000⁰c, b-3) structured negative electrodes. it is noted that nio is a conversion reaction-based anode that captures lithium possessing high specific capacities by reversibly replacing redox reactions within li+ and transition oxide-based cation. the elementary conversion reaction mechanism of nio can be given as nio + 2li+ + 2e↔ ni + li2o. during the discharge phase, nio is reduced to highly dispersed metallic ni nanoparticles and li2o. in addition, the disintegration of li2o and the reformation of metallic ni nanoparticles into nio nanograins take place during the charge phase. 3.2.1 electrochemical performance of ni-nio composite at 600⁰c and 800⁰c as anode of libs the galvanostatic charge-discharge voltage profiles within a potential window of 0.01-3.0v versus li+ with cyclic performance and coulombic efficiency for the b-1 and b-2 batteries (synthesis temperature of 600⁰c and 800⁰c) at a current rate of 1c is shown in figures 7 (a)-(d). it is noted that the 1c rate signifies the accomplishment of charge/discharge in an hour. for battery b-1, the 1st cycle charge-discharge capacity was observed to be 754.49 mah g-1 and 464.04 mah g-1 with 61.50% coulombic efficiency. in addition, the b-1 battery delivered charge-discharge capacities of 23.59 mah g1 and 11.79 mah g-1; 10.11 mah g-1, and 10.67 mah g-1 at the 5th and 10th cycles, respectively. the consecutive coulombic efficiencies were observed to be 52.5% and 95%, respectively. in contrast, the capacities were 101.12 mah g-1 and 79.78 mah g-1, with a coulombic efficiency of 127.46%, for battery b-2. in addition, the battery b-2 exhibited 5th and 10th cycle charge-discharge capacities of 25.28 mah g-1 and 28.09 mah g-1; 7.30 mah g-1 and 9.55 mah g-1, respectively. the coulombic efficiency was observed as 111.11% and 130.77%, respectively. it is noted that the capacity exhibited drastic decay with cycling as cycled both batteries. in addition, only 2.29% of the initial discharge capacity was retained for b-1, whereas 11.97% was retained for b-2 after the 10th chargedischarge cycle. however, the coulombic efficiency fluctuated and increased after the 10th charge-discharge cycle of both b1 and b-2 batteries. there are a number of reasons why columbic efficiency exceeds 100%, including an imbalance in the amounts of li+ absorbed and released, side reactions, and measurement error. this may be due to some structural interruptions that cause an uneven volume of li+ to be transported. particularly, the intercalation of less li+ during charging and the de-intercalation of the maximum volume of li+ during discharging cause the columbic efficiency to exceed 100%. the repeated occurrence of such phenomena causes the active material to fail and affect the battery's performance adversely [73–75]. it is evident from figures 7 (a) and (c) that battery b-1 exhibited erratic behavior, and the specific capacities decreased rapidly from the 1st to 10th charge-discharge cycle. moreover, the specific charge/discharge capacity faded drastically with further cycling, and the battery became out of order. the predominant reason behind this extreme capacity fading is the short-circuiting phenomenon of the battery, as the instantaneous voltage drop occurred from around 1.0 to 0.01v [76,77]. the unanticipated voltage drop is due to the short circuit of the composite ni-nio electrodes and the recycled licoo2 electrode due to swelling or perforation of the insulating polymeric separator, deflection of electrodes, or presence of impurities in the cell [78]. the incident of the set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 6 internal short circuit releases 70% of the battery energy within 60 seconds [79, 80], which causes a rigorous increase in the local temperature that, in turn triggers the chemical side reactions and causes thermal runaway [80]. this shortcircuiting tendency became more prominent with further cycling. hence, long cycling may lead to thermal runway and irreparable cell damage. in contrast, for battery b-2 the charge/discharge curve exhibited improvement as compared to battery b-1 as shown in figure 7(b). the curve portrayed capacitor-like profiles (no potential flat plateaus); however, a linear variation of the potential in correspondence to the lithium insertion/extraction. this occurrence indicated the pseudo-capacitive behavior, which signifies surface storage nature [81, 82]. the 1st cycle irreversible capacity loss of 21.10% may be ascribed to the formation of a solid electrolyte interface (sei) caused by the degradation of electrolytes. this irreversible capacity loss gradually dropped to 23.53% after the 10th cycle. the substantial capacity decrease from the 1st to the 10th cycle may be attributed to the structural collapse of the composite by large volume change during cycling, which pointed out the structural inefficiency of the battery. however, the battery capacity retention ability was higher than the previous battery, and therefore, the performance was not worth demonstrating. 3.2.2 electrochemical performance of ni-nio composite at 1000⁰c as anode of libs figure 8 shows the galvanostatic charge/discharge voltage profiles of battery b-3 in a potential window of 0.013.0v vs. li+. interestingly, the initial discharge profile exhibited no obvious plateau region, similar to the typical capacitor-like curve where potential increases/decreases linearly with the lithium insertion/extraction [82]. this occurrence is attributed to the pseudo-capacitive behavior, which indicates the bulk surface storage characteristics [81, 82]. the initial charge curve exhibits higher voltage with two sloping potential ranges at about 2.2 and 2.5v, respectively. the 1st cycle charge-discharge capacities were exhibited as 292.13 and 365.17 mah g-1, respectively. there was an irreversible capacity loss of 18.98% between 1st charge and discharge, which may be connected to the formation of solid electrolyte interface (sei) and amorphous li2o during the discharge process, due to the electrochemically driven electrolyte degradation. it is noted that both the sei as well as li2o are partially decomposed during the subsequent charge process. this irreversibility of sei and li2o formationdecomposition is responsible for the decrease in the charge capacity. the aforementioned occurrence is observed in materials that obey the conversion reaction mechanism [33, 67, 83, 84]. figure 7. (a, b) charge-discharge voltage profiles for 1st to 10th cycle; (c, d) cycle performance and coulombic efficiency at 1c rate for battery b-1 and b-2 set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 7 in addition, the discharge capacities in the 5 th, 10th and 20th cycles have appeared as 196.62 mah g-1, 104.49 mah g-1, and 95.50 mah g-1 respectively with corresponding charge capacities were 162.92 mah g-1, 123.59 mah g-1, and 56.17 mah g-1. the capacities decreased rapidly over cycling and 26.15% of the initial capacity was retained after the 20 th cycle for b-3. moreover, the reversible discharge capacity loss for 1st to 5th, 5th to 10th, 10th to 20th, 1st to 20th were 168.55 mah g-1, 88.13 mah g-1, 8.99 mah g-1, and 269.67 mah g-1, respectively. the average capacity loss per cycle was found to be 13.48 mah g-1 and 26.15% of initial capacity was retained. the initial coulombic efficiency of battery b-3 seemed to be 124.80% at a 1c rate. the coulombic efficiency fluctuated in a random manner throughout the 20 cycles and attained a value of 90.47% after the 20 th cycle. the aforementioned performance analysis of b-1, b-2, and b-3 batteries implied that all three batteries are functional and exhibited some capacities with coulombic efficiencies. the charge/discharge profile and cycle performance of b-1 and b-2 clearly indicated the infeasibility of the battery to be employed in practical application. the b-1 battery exhibited an error-prone tendency as an internal short circuit occurred, which was responsible for extreme capacity decay within a few cycles. this may be induced by perforation or crack in the separator, deformity in architecture, and/or defective assembly procedure. in the case of b-2 battery, low capacity resulted from conspicuous surface intercalation, which accounted for structural collapse. however, b-2 battery appeared to have a slight improvement in performance compared to b-1, the battery efficiency, which did not meet expectations. it is noted that the b-3 battery appeared to be a promising one. the b-3 battery exhibited more efficient results than all other batteries, rather it requires high-temperature processing. this may be attributed to the well-ordered and highly crystalline microstructure. hence, long-term cycling performance has been executed with b-3. as a consequence, more than 40 charge/discharge cycles can be achieved with b-3 at a 1c rate. figure 9 exhibits the high cycle charge-discharge profiles for battery b-3 within the voltage window 0.01-3.0v vs. li+. the 25th cycle charge-discharge capacities were 73.03 mah g-1 and 112.36 mah g-1. similarly, the 30th, 35th, and 40th discharge capacities were 98.88 mah g-1, 75.84 mah g-1, and 67.42 mah g-1 respectively with corresponding charge capacities of 61.79 mah g-1, 46.63 mah g-1, and 35.39 mah g-1, respectively. a considerable discharge capacity loss was noticed 13.48 mah g-1 from 25th to 30th cycle. for 30th to 35th, 35th to 40th, and 25th to 40th cycle the discrepancies in discharge capacity became 23.04 mah g-1, 8.42 mah g-1, and 76.97 mah g-1. the average loss in discharge capacity per cycle was 5.13 mah g-1, which was 13.48 mah g-1 for the first 20 cycles. it is noted that discharge capacity loss followed a decreasing trend with an increase in cycle number. moreover, the battery demonstrated a long-cycle performance and coulombic efficiency at the 1c rate as shown in figure 9 (a). the coulombic efficiency for the 25th cycle was 95.55%, and the values were 88%, 88.82%, and 100% for 30 th, 35th, and 40th cycles. the coulombic efficiency showed a subsequent decrease up to the 35th cycle and attained 100% in the 40 th cycle. furthermore, the retention of initial capacity was 18.46% after the 40th cycle, which was 27.07% and 20.77% for the 30th and 35th cycles. the long-term cycling caused only 7.69% capacity decay from the 20 th to 40th cycle. it can be stated that the capacity retention ability manifested a decreasing tendency with cycling. in order to clarify the capacity loss of the as cycled batteries, the surface morphology and elemental analysis of the ni-nio composite electrode were performed. it is noted that disassemble of libs was performed manually in such a way that the process was not allowed to short-circuit. in addition, ni-nio electrode was not washed after disassembling of libs, and its original morphology after respective cycling was observed with the presence of an sei layer. figure 10 shows the sem images and edx spectra of ni-nio electrodes of batteries b-1 and b-3 after charge/discharge for 10 and 40 cycles, respectively. figure 8. (a) charge-discharge voltage profiles from 1st to 20th cycle; (b) cycle performance and coulombic efficiency at 1c rate for battery b-3 set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 8 figure 9. (a) charge-discharge voltage profiles from 25th to 40th cycle; (b) long cycle performance and coulombic efficiency at 1c rate for battery b-3 figure 10. sem and edx characterization of ni-nio electrodes after electrochemical cycling of: (a, b) b-1 and (c, d) b-3 set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 9 it is noted that the synthesis temperature of electrodes of b-1 and b-3 is 600oc and 1000 oc, respectively. we didn’t observe and analyze the sem images and edx spectra of the electrode of b-2, which was synthesized at 800oc due to the similar electrochemical performances of b-1. the initial microstructure of ni-nio electrode of b-1 enormously changed to agglomerated and cracked surface, as shown in figure 10(a). it is noted that the width of some cracks increased and subsequently crushed due to the volume change of nio and came off the current collector, leading to the drastic capacity fade of b-1. however, the original pebble stone microstructure of ni-nio electrode of b-3 entirely changed to a compressed honeycomb-like structure, as shown in figure 10(c). it is noted that these both electrodes exhibited different morphology with few nanometer diameter pores after charge/discharge cycles at 1 c current rate. this could be attributed by the structural change during the first lithiation process when nio structure converted to ni nanoparticle inside li2o and gel-like matrixes [17, 29, 85]. a similar morphological change is observed in nio electrode as anode after the electrochemical cycling of libs [23, 78, 84]. it is noted that the decomposition of electrolyte is substantial, which can be another reason for the drastic capacity fading of ni-nio. the edx spectra of ni-nio electrodes after 10 and 40 charge/discharge cycles are shown in figures 10 (b) and (d), respectively. it is observed that the presence of elements fluorine (f) and phosphorus (p) is due to the decomposition of lipf6 along with the impurities elements of manganese (mn), calcium (ca), silicon (si), and sulfur (s). in addition, carbon (c) is observed due to the decomposition of carbonate-based organic solvents. a similar decomposition phenomenon was observed in carbonate-based lithium salt electrolytes such as 1.2 m lipf6/ec [86], 1 m lipf6/ec-dec [87], and 1 m lipf6/ec-dec-dmc [88]. from the above discussion, it can be noted that the b-3 has appeared as the propitious one among other batteries. it is noted that the synthesis required high-temperature (1000⁰c) processing; however, it exhibited noteworthy performance. the contribution of this specific research is to establish a convenient synthesis technique and undoubtedly unique architecture. in addition, the battery assembly operation was simple without any glovebox facility. the achieved capacity is lower than the nio itself and other nanostructures; however, higher than the practical capacity of graphite anode. moreover, replacing graphite with ni-nio composite will eliminate the safety issues regarding graphite anode with considerably high specific capacity. furthermore, the remarkable performance stimulated the execution as a battery anode in practical application with no probable hazard. 4. conclusions in summary, we have fabricated microstructured composite of ni-nio through a simple and single-step thermal oxidation approach and subsequent mechanical ball milling process. at three distinct temperatures600˚c, 800˚c, and 1000˚c oxidation of ni powder was performed. the assynthesized microstructured composite of ni-nio was employed as an anode of libs, and the following conclusions are drawn from this study: • it was observed that the electrode synthesized at 600˚c (b1) delivered a discharge and charge capacity of 464.04 mah g-1 and 754.49 mah g-1 during 1st cycle which decreased drastically to 10.67 mah g-1 and 10.11 mah g-1 after 10th cycle at 1c rate. this electrode experiences an internal short circuit, which was the major reason behind the capacity fading. moreover, the insufficient active nanoparticle loading in the electrode causes less reaction with lithium. however, the high elasticity of the electrode causes ease of electrolyte and ion access, and the brittleness of the electrode causes severe volume expansion and structural degradation of the electrode within 10 cycles. • the electrode synthesized at 800˚c (b-2) exhibited a specific discharge-charge capacity of 101.12 mah g-1 and 79.77 mah g-1 during 1st cycle and faded rapidly to 9.55 mah g-1 and 7.30 mah g-1 after the 10th cycle. though irreversible capacity loss decreases from the previous electrode, the electrode cannot sustain long cycling. the more reversible capacity was due to the presence of ni nanoparticles, possessing catalytic activity, facilitating the decomposition of li2o and sei layer during the charging process. however, the amount of active nanoparticles on the electrode increases with temperature increase, the electrode elasticity, and brittleness decrease, and the electrode was unable to buffer the volume-induced stress that resulted in the crack on the surface and structural degradation of the electrode. • one of the best electrochemical performances was observed in the electrode synthesized at 1000 c̊ temperature (b-3). the electrode delivered a specific discharge and charge capacity of 365.17 mah g-1 and 298.85 mah g-1 during 1st cycle. a reversible capacity of 67.41 mah g-1 was achieved after the 40th cycle at a 1c rate. the discharge/charge capacity fluctuated randomly up to the 20th cycle as the electrode material became more ductile due to temperature increase, which impedes the smooth insertion of li+. during continuous charging/discharging, the rapid lithium insertion/deinsertion causes active electrode materials to get pulverized. after the 20th cycle, the electrode capacity fluctuated systematically and retained 18.46% initial capacity with coulombic efficiency of 100% after the 40 th cycle. this may be due to continuous cycling; the structural reconstruction of the electrode causes a reduction in particle size of active material, and thus, nanocrystallization improves the cycling performance. the prolonged cycling causes pulverization of the electrode, the active materials detached from the current collector, and the failure occurs. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. set. siddiqui et al. /future sustainability february 2024| volume 02 | issue 01 | pages 01-13 10 data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. funding this work is co-supported by chittagong university of engineering & technology (cuet), bangladesh, through research grant no. cuet/chsr-35/17(iii), university grants commission of bangladesh-grant no. 37.01. 0000.73.06.065.22.1607, and a grant (no. jb230001) from the korea institute of industrial technology (kitech). the corresponding author is responsible for ensuring that the descriptions are accurate and agreed upon by all authors. references [1] zhang j, terrones m, park cr, mukherjee r, monthioux m, koratkar n, et al. carbon science in 2016: status, challenges and perspectives. vol. 98, carbon. elsevier ltd; 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[88] lu m, cheng h, yang y. a comparison of solid electrolyte interphase (sei) on the artificial graphite anode of the aged and cycled commercial lithium ion cells. electrochim acta. 2008;53(9):3539–46. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 8 article integrating sustainable wind power into nigeria’s energy system: an analysis of excess electricity, co2 emissions reduction, and fuel demand implications samuel effiom1*, francis osang1, james diwa enyia1, cordelia omoyi2, ogheneruona e. diemuodeke3, thomas magu4, patrick odu5, fidelis abam6 1department of mechanical engineering, university of cross river state, calabar, nigeria 2department of mechanical engineering, university of calabar, calabar, nigeria 3department of mechanical engineering, university of portharcourt, portharcourt, nigeria 4department of electrical and electronic engineering, university of calabar, calabar, nigeria 5department of chemistry, university of florida, usa 6department of mechanical engineering, university of calabar, calabar, nigeria a r t i c l e i n f o article history: received 07 january 2025 received in revised form 13 february 2025 accepted 25 february 2025 keywords: wind power, electricity production, co2 emissions, renewable energy, nigeria *corresponding author email address: samueloliver@unicross.edu.ng doi: 10.55670/fpll.fusus.3.2.2 a b s t r a c t this study explores the integration of sustainable wind power into nigeria's energy system, focusing on its effects on excess electricity production (ceep), co2 emissions reduction, and fuel demand under different scenarios. using the energy plan modeling tool, the study evaluates nigeria's energy infrastructure at an electricity demand of 32 twh per year, incorporating both onshore and offshore wind power capacities. three regulatory scenarios are considered: regulation 1 (heat demand only), regulation 2 (combined heat and electricity demand), and regulation 3 (heat pump integration). the results indicate that increasing wind power capacity significantly affects ceep. at maximum wind penetration, ceep is reduced by 35% under regulation 2 with heat pump integration, compared to regulation 1, highlighting the importance of system flexibility. integrating heat pumps reduces energy waste and optimizes renewable energy use by 40%. the co2 emissions are reduced by about 28% across all scenarios, with the most significant reductions occurring in systems incorporating heat pumps and wind energy. the study shows that primary energy savings were about 25%, driven by decreased reliance on fossil fuels. wind energy integration leads to a 30% reduction in natural gas consumption, which remains a significant component of nigeria’s energy mix. sensitivity analysis reveals that variability in wind production and enhanced system flexibility can improve overall energy system efficiency by 20%. the study contributes significantly to the understanding of renewable energy integration in nigeria, offering a comprehensive framework for incorporating intermittent wind energy sources into the national grid. 1. introduction the rapid global population growth and modern industrialization and lifestyles have led to a significant energy demand-supply gap. addressing this gap requires an urgent expansion of clean, stable, and sustainable energy sources [1,2]. furthermore, it has been emphasized energy is indispensable for economic growth, social development, poverty alleviation, and national security [3,4]. a consistent energy supply has become critical for nations' development globally. however, the continued dependence on diminishing fossil fuels for energy production has detrimental environmental effects and poses serious health concerns [5,6]. unfortunately, many developing countries, including nigeria, still lack stable and reliable energy access to drive future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.2.2 may 2025| volume 03 | issue 02 | pages 08-15 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:samueloliver@unicross.edu.ng https://doi.org/10.55670/fpll.fusus.3.2.2 https://fupubco.com/fusus s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 9 their internal economy, thus leading to economic fluctuations and deficits. this energy shortfall impedes practical technological development and reduces agricultural activities, leading to food insecurity. rapid, ambitious energy generation utilizing all-generation technologies will be imperative for a fast-developing nation like nigeria [7]. studies by references [8-11] indicate that approximately 6070% of the world population, equivalent to 1.2 billion people, still lack access to a modern, steady energy supply, with around 50% residing in sub-saharan africa. this situation will worsen in the coming decades if current trends persist, potentially hindering africa’s industrialization and slowing the global transition toward environmental sustainability [12]. nigeria, the most populous country in the region, has approximately 100 million citizens who lack access to reliable and clean energy [13,14]. this situation underscores the country's severe energy shortages and the urgent need to transition to a more sustainable energy system. despite being rich in both conventional (non-renewable) energy resources, for example, fossil fuels, and renewable energy sources, like biomass, hydro, solar, and wind, nigeria possesses enough energy potential to meet the demands of its population. additionally, it could export surplus energy to neighboring countries, generating revenue. however, the country’s current energy supply is insufficient and cannot keep up with the growing demand driven by population growth, industrialization, and increased human activities. many countries, including germany [15], russia [16], the united states of america [17, 18], and china [19], have transitioned their power generation sectors by increasing the use of lower-carbon fuels like natural gas. in hydrocarbondominated economies such as the gulf cooperation council (gcc) countries, such as the united arab emirates (uae), qatar, bahrain, and oman, natural gas is the primary fuel for electricity generation [20]. around the world, nations deliberately shift from carbon-heavy fuels to natural gas and, ultimately, renewable energy sources. nigeria is no exception to this trend. given the current fluctuations in gas supplies and prices of lng and lpg, which affect the downstream oil and gas sectors [21], along with global trends toward sustainable energy transitions, the need to deploy renewable energy in nigeria is critical for achieving a transformative shift in its energy demand. diversifying the energy matrix to include renewable energy will enable the nation to redirect the ‘avoided’ natural gas to its downstream sector to produce higher-value carbon products. furthermore, the accompanying decarbonization efforts will contribute to the country's nationally determined contributions (ndcs) under the paris agreement. while renewable energy penetration in nigeria remains in its nascent stages, it currently utilizes only hydropower and bioenergy as renewable energy sources. however, nigeria has begun exploring wind and, more prominently, solar pv energy at household and industrial levels to reduce greenhouse gas emissions (ghgs) and carbon footprints [20, 21]. many countries involved in the paris agreement aim to achieve 100 % renewable energy grid power by 2050. in contrast, nigeria's current renewable energy grid power target remains significantly modest [22]. nevertheless, transitioning from heavy carbon fuels to lighter and renewable energy is crucial for plummeting ghg emissions and restraining global temperature rises to less than 2°c above preindustrial levels. this study, therefore, aims to integrate sustainable wind power into nigeria’s energy system by analyzing critical excess electricity, co2 emissions, and fuel demand. the specific objectives of this study are: (i) evaluate the impact of wind power production on critical excess electricity production (ceep) and primary energy supply in nigeria under different regulatory conditions, (ii) assess the reduction in co2 emissions resulting from the integration of wind power into nigeria’s energy mix, alongside the incorporation of flexible energy systems such as heat pumps, (iii) analyze fuel demand patterns and potential savings under various wind power capacities and regulatory scenarios, aiming to identify optimal energy system configurations and (iv) develop a systematic framework for integrating fluctuating renewable energy sources (res) into nigeria's electricity grid, while minimizing waste and maximizing environmental sustainability. 2. methodology 2.1 energy system modeling and scenarios energyplan is a computational tool primarily used to evaluate various aspects of energy systems, including critical excess electricity production (ceep), co2 emissions, primary energy supply (pes), fuel demand, and potential savings. as shown in figure 1, energyplan is an energy modeling and forecasting software designed to support the development of national energy planning strategies [23]. energyplan requires four key input sets for conducting technical analyses, as presented in figure 2 [24]. after reviewing nigeria's policies, challenges, and opportunities associated with renewable energy, a baseline model was developed using energyplan software based on the country's current energy demand and supply data, totaling 32 twh/year. considering nigeria's energy regulatory framework, two system scenarios, open and closed systems, were created. wind power production data, including onshore and offshore capacities, was incorporated into the model, along with system constraints such as heat pump capacities and fluctuating wind production, as adopted from the system software. the evaluated results were analyzed under three regulatory scenarios to measure the outcome of increased wind power production on key performance metrics. most of the data input used in this study was sourced from [25-35]. i. regulation 1 (heat demand only) ii. regulation 2 (heat and electricity demand) iii. regulation 2 + heat pump integration furthermore, two national renewable energy adoption (nrea) scenarios were created and analyzed to provide critical insights into system optimization through wind power integration and flexible energy in nigeria (table 1). these projected scenarios include nrea30 and nrea50 for analyzing modeled energy scenarios for 2030 and 2050, respectively. s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 10 figure 1. schematic example of energyplan pathways [24] figure 2. key inputs for conducting technical analyses in energyplan algorithm s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 11 table 1. assumptions and data for input for the adopted scenarios s/no assumptions data 1 present energy demand (twh/year) 32twh/year 2 fuel price (ngn500 ngn600) 3 expected wind power production 14.87twh, including onshore and offshore 4 variable wind production between 0 and 50 mw in multiples of 5 mw 5 onshore/offshore wind capacity in mw 1103mw, and 2206mw 6 offshore wind capacity varied from 2206mw to 6576mw heat pump capacity and heat pump cop 500mwe and 3.5 3. results and discussion 3.1 overview of results and observations this study examines the integration of wind power into nigeria’s energy system, focusing on critical excess electricity production (ceep), co2 emissions, and fuel demand under different regulatory frameworks. the results highlight the feasibility of incorporating wind power while optimizing system performance through regulatory strategies, mainly heat pumps. the analysis further reveals the interaction between wind power output and key system performance indicators. however, the critical excess electricity production (ceep) depicted in figure 3, at zero wind production, ceep is minimal at 0.92 twh/year under regulation 1. this indicates a reliance on conventional power sources with limited renewable energy input. ceep rises progressively with increased wind production, peaking at 42.96 twh/year at 50 twh/year wind production. under regulation 2 and regulation 2 + heat pumps, as depicted in figure 4, ceep is reduced to zero across all scenarios, compared to regulation 1 (reference regulation), highlighting effective system regulation and energy optimization. the increase in ceep without regulations underscores the challenge of balancing fluctuating renewable energy sources like wind power. the zero-ceep under regulation 2 demonstrates the system’s ability to absorb excess electricity through flexible energy solutions, such as integrating heat pumps and modifying heat production [36]. 3.2 co2 emissions as depicted in figure 5, co2 emissions decreased from 52.71 mt/year (no wind production) to 48.8 mt/year at 50 twh/year wind production under regulation 1. regulation 2 reduces to 43 mt/year, while regulation 2 with heat pumps lowers emissions further to 41.42 mt/year at maximum wind production. this implies that increased wind power production substantially reduces reliance on fossil fuels, directly lowering co2 emissions. also, the enhanced reduction under regulation 2+ heat pumps demonstrates the synergistic effect of integrating wind power with advanced energy systems. this aligns with global goals of achieving netzero emissions and highlights the importance of flexible system design in meeting environmental objectives. 3.3 primary energy supply (pes) and fuel demand as depicted in figure 6, pes declines progressively from 248.59 twh/year (no wind) to 202.72 twh/year at maximum wind production under regulation 1, reflecting reduced fossil fuel dependency. regarding fuel demand, regulation 2 + heat pumps reduce fuel demand further than regulation 1, achieving a range of 248.43 twh/year to 230.25 twh/year at maximum wind production. the decreased pes and fuel demand indicate enhanced energy efficiency and reduced strain on conventional resources. given the rising reliance on fossil fuels and the pressing need for renewable energy sources (res), developing a fuel demand curve demonstrating the percentage utilization of renewable fuels within this study is imperative. figure 3. critical excess electricity production (ceep) for regulation 1 s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 12 figure 4. electricity excess production figure 5. co2 emission figure 6. fuel demand s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 13 our findings unequivocally show that as wind power production varies, fuel demand consistently declines across regulation 1, regulation 2, and regulation 2 with heat pumps, which aligns with the assumptions established. additionally, with a maximum fuel demand of 250twh/year, a further inclusion and variation of heat energy will gradually reduce the fuel demand to a critical level of 50-100 twh/year, thereby achieving a proportionate utilization of the res. these results highlight the feasibility of transitioning from fossil fuel-based to renewable energy systems while maintaining grid stability and efficiency. therefore, implementing heat pumps and similar technologies enables better utilization of renewable resources, offering costeffective and sustainable energy solutions. 3.4 fuel savings fuel savings demonstrate a steady improvement over the modeled periods (2030 and 2050), corresponding to declining fuel demand and increased wind power integration, as depicted in table 2. results from the national renewable energy adoption (nrea) scenarios (nrea2030 and nrea2050 scenarios) were compared. savings of up to 116.41 twh/year at 50 twh/year wind production under the nrea2050 scenario underline the long-term benefits of renewable energy investment. therefore, the fuel savings reflect the economic advantage of res adoption, reducing operational costs and exposure to volatile fuel prices. thus, transitioning to wind power and heat pumps represents a strategic investment in long-term energy sustainability for nigeria. table 2. fuel savings wind prod. (wh/year) wind capacity (mw) offshore (mw) reference 2030 nrea 2030 nrea 2050 twh/year 0 0 0 0 -67.5 -142.56 5 1103 0 4.57 -64.51 -138.45 10 2206 0 9.15 -62.51 -134.58 15 2206 822 13.74 -61.58 -131.74 20 2206 1644 18.34 -61.31 -129.64 25 2206 2466 22.93 -61.17 -128.11 30 2206 3288 27.52 -60.62 -126.41 35 2206 4110 32.1 -59.52 -124.37 40 2206 4932 36.69 -57.99 -122.13 45 2206 5754 41.28 -56.16 -119.47 3.5 projected trends of optimized wind energy utilization the analysis of modeled energy scenarios for 2030 and 2050 provides critical insights into system optimization through wind power integration and flexible energy investments. table 3 indicates a complete elimination of ceep across all renewable energy adoption scenarios for 2030 and 2050. this zero-waste outcome highlights the efficacy of incorporating wind energy alongside flexible system technologies like combined heat and power (chp) units and heat pumps. initially, the reference case without wind energy shows ceep values ranging from 0.92 twh/year to 42.96 twh/year as wind production increases to 50 twh/year. in contrast, all analyzed renewable energy adoption scenarios (nrea) achieve zero excess electricity production. this implies a significant leap in wind energy system utilization efficiency, preventing resource wastage and optimizing the grid’s capacity to integrate fluctuating wind energy. table 3. critical electricity excess production trends 3.6 fuel demand trends table 4 shows a marked reduction, affirming the energy transition benefits of integrating wind power and implementing flexible energy technologies. for the 2030 model year, primary fuel demand drops by 38%, from 248.59 twh/year in the reference case to 153.52 twh/year under nrea scenarios. also, for the 2050 model year, the reduction is even more pronounced, with fuel demand decreasing by 65%, from 248.59 twh/year in the reference case to 86.94 twh/year. this improvement highlights the long-term sustainability of wind energy production, reducing dependency on conventional energy sources. table 4. fuel demand trends 4. conclusions this study demonstrates that integrating wind power into nigeria’s energy system can significantly reduce co2 emissions and fuel demand while minimizing ceep under robust regulation. quantifying these results highlights the practical viability of transitioning to renewable energy. the following conclusions are drawn from the findings: i. without regulations, ceep rises significantly with increased wind power production, underscoring the need for adaptive energy management strategies. regulation 2 and regulation 2 + heat pumps successfully reduce ceep to wind prod. (wh/year) wind capacity (mw) offshore (mw) reference 2030 nrea 2030 nrea 2050 twh/year 0 0 0 0.92 0 0 5 1103 0 2.64 0 0 10 2206 0 5.58 0 0 15 2206 822 9.32 0 0 20 2206 1644 13.69 0 0 25 2206 2466 18.37 0 0 30 2206 3288 23.2 0 0 35 2206 4110 28.11 0 0 40 2206 4932 33.05 0 0 0 0 0 0.92 0 0 wind prod. (wh/year) wind capacity (mw) offshore (mw) reference 2030 nrea 2030 nrea2050 twh/year 0 0 0 248.59 182.12 105.87 5 1103 0 244.02 178.03 102.91 10 2206 0 239.44 173.93 100.62 15 2206 822 234.85 169.85 97.97 20 2206 1644 230.25 165.78 95.05 25 2206 2466 225.66 161.82 92.83 30 2206 3288 221.07 158.62 90.89 35 2206 4110 216.49 156.56 88.75 40 2206 4932 211.9 155.19 87.57 45 2206 5754 207.31 154.2 87.21 50 2206 6576 202.72 153.52 86.94 s. effiom et al. /future sustainability may 2025| volume 03 | issue 02 | pages 08-15 14 zero, demonstrating their effectiveness in optimizing energy use and mitigating resource wastage. these results affirm the importance of system flexibility and regulation in harnessing the full potential of renewable energy. ii. wind power integration effectively reduces co2 emissions, with further reductions achieved through regulation 2 + heat pumps. this demonstrates a synergistic relationship between renewable energy adoption and advanced energy solutions, aligning with global efforts toward carbon neutrality. the observed decline from 52.71 mt/year to 41.42 mt/year under maximum wind power production emphasizes the environmental benefits of the proposed system. iii. increasing wind power production reduces reliance on fossil fuels, as reflected in the declining pes values. including heat pumps further enhances fuel demand efficiency, achieving a critical reduction to sustainable levels. by 2050, the nrea2050 scenario projects fuel demand reductions of up to 65%, highlighting the transformative potential of renewable energy adoption. iv. substantial fuel savings were observed, with reductions of up to 116.41 twh/year under nrea2050 scenarios. these savings highlight the economic advantages of wind energy and the reduced exposure to fuel price volatility. the strategic integration of wind power and heat pumps demonstrates their viability as long-term investments in energy sustainability. v. modeled scenarios for 2030 and 2050 reveal progressive improvements in system efficiency, including the complete elimination of ceep and significant reductions in fuel demand. these trends emphasize the importance of adopting renewable energy and flexible system designs, ensuring nigeria's resilient and sustainable energy future. the findings validate the feasibility of transitioning from a fossil fuel-based system to a renewable energy-centric system in nigeria. wind energy integration, supported by advanced energy solutions like heat pumps and system optimization for efficient energy supply, offers a pathway to achieving grid stability, economic efficiency, and environmental sustainability. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] f. i. abam, b. n. nwankwojike, o.s. ohunakin, s. a. ojomu. energy resource structure and on-going sustainable development policy in nigeria: a review. int j energy environ eng 5(2014)102. 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[36] c. o. omoyi, d. o. ushie, s. c. nwoziri, p. o. imhade. development of decision support system for design analysis of gasifier reactor’s heat exchanger. fuoye j. eng. tech. 9(3)(2024)486-489. https: dx.doi.org/10.4314/fuyejet.v9i3.18. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 21 article simulation and analysis of energy consumption in all types of residential complexes and choosing the best form from the perspective of sustainability rahim zahedi1*, alireza kashani1, sajad qezelbigloo2, soheil hashemi1 1department of renewable energies and environment, university of tehran, tehran, iran 2school of automotive engineering, iran university of science and technology, tehran, iran a r t i c l e i n f o article history: received 10 december 2024 received in revised form 14 january 2025 accepted 27 january 2025 keywords: building arrangements, solar thermal system, psi method, hvac simulation *corresponding author email address: rahimzahedi@ut.ac.ir doi: 10.55670/fpll.fusus.3.1.3 a b s t r a c t energy demand in residential buildings is growing with the immigration of people to urban areas. this study simulates and analyses five different types of residential buildings. the possibility of using a solar thermal system is studied, and then five choices are ranked with the psi method, which is a mathematical approach. for hvac simulations, design builder software, and solar simulations, t*sol software is used. the results show that in terms of heating load, towers and skyscraper types of residential buildings demand more energy, with 3.67 mw and 3.62 mw, respectively. in terms of cooling, towers and surrounding types need bigger values than others, with 1.84 mw and 1.82 mw, respectively. solar simulations indicate that the highest solar fraction with no area limitations belongs to the sky scrapper type with 26.9 percent, while collector efficiencies of all types are between 9.9 and 11.6 percent. however, with rooftop areas in each type, the highest solar fraction belongs to linear and surround types both with 24.6 percent. mathematical analysis shows that by taking into account the importance of heating load and solar fraction for all types, the best form of residential buildings to use is a mixed type with the first rank. 1. introduction 1.1 the importance of urban energy consumption and methods of analysis according to the probable scenario, more than 80% of the world's population will live in cities by 2050 [1]. about two-thirds of the world's energy consumption comes from cities. for this reason, cities have a significant role in the consequences of energy consumption, including climate change, and therefore, optimization in them can have a great impact on achieving the environmental goals set in international agreements [2]. buildings in cities account for more than 40% of energy consumption. for this reason, to reduce greenhouse gases to the desired amount, special attention should be paid to this sector [3]. recent research shows that urban design can positively affect energy consumption, such as the distribution of buildings and urban areas, maximum use of sunlight, and the development of multi-use areas [4]. in regions such as asia, the middle east, and africa, where populations are growing rapidly, the compact urban form combined with transportation planning can encourage crowding and prevent high carbon emissions during travel. therefore, in addition to the fact that in densely populated areas, higher density is inevitable, in terms of energy consumption and carbon emissions will be better than scattered urban patterns. therefore, special attention to urban residential complexes is of particular importance. with proper design and proper layout of complexes, energy efficiency can be increased desirably [5]. in recent years, energy modeling of urban buildings has been recognized as a new approach to identifying, supporting, and improving sustainable urban development plans and energy optimization measures in cities. with the help of this tool, a better understanding of the general situation of energy consumption in the building and applying design modifications can be used to achieve more favorable conditions. because of this, various models and tools have been developed and become more advanced hybrid models [6]. designing and operating urban buildings as a group (from future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.1.3 february 2025| volume 03 | issue 01 | pages 21-35 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:rahimzahedi@ut.ac.ir https://doi.org/10.55670/fpll.fusus.3.1.3 https://fupubco.com/fusus r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 22 a city block to a district to an entire city) rather than as single individuals requires simulation and optimization to account for interactions among buildings and between buildings and their surrounding urban environment, and for district energy systems serving multiple buildings with diverse thermal loads across space and time [7]. regulations corroborate the importance of retrofitting existing building stocks or constructing new energy-efficient districts. thus, there is a need for modeling tools to evaluate energy scenarios to manage better and design cities, and numerous methodologies and tools have been developed [8]. research activities in this field have flourished in recent years and have created a stronger urban database that leads to gis, light and range detection, and building hourly energy demand profiles for current and future conditions. this is a testament to the importance of modeling urban buildings. depending on the availability of energy consumption data for historic buildings, a variety of modeling, simulation, and calibration methods, as well as applications, have been proposed [9]. researchers worldwide are working on energy modeling and control to develop strategies that lead to an overall reduction in building energy consumption. one of them is developing control strategies and an efficient computational energy model for the studied building. modeling methods for modeling the energy systems of buildings have been developed and adopted and have shown their ability to provide more accurate and comprehensive information about buildings [10]. 1.2 energy supply and sectors today, the most usable and economical forms of energy are fossil fuels, especially oil products and natural gas [11]. the importance of using renewable energy is improving due to the increasing use of energy and the fact that these forms of energy are not renewable. on the other hand, the means of effective energy use are vastly considered and so are being researched often. this caused broader and more thorough studies of energy use that have led to the study of sectors including residential, hospital, commercial, official, industry, and transportation. 1.3 residential sector the major use of energy in oecd countries belongs to the industry sector. however, in non-oecd countries, the major use of energy is considered for the residential sector [12]. from a different point of view, oil-exporting countries have a lower price of energy use because of the abundance of energy supplies. however, the performance of energy-related machines is not usually optimal. immigration to bigger cities exists because of the location of major facilities in these cities and more work opportunities. so, one of the leading residential solutions to accommodate people is using residential complexes. thus, in non-oecd and oil-exporting countries, the importance of energy use optimization and renewable energy studies are hugely favorable, especially for the residential sector and, in big cities, for residential complexes. 1.4 solar energy solar is one of the renewable energies which, because of numerous advantages, is considered recently to supply the energy need. one of the main advantages of using solar energy is the absence of much pollution that fossil fuels emit [13]. however, there are some disadvantages including timing and climatic limitations, storage, and expensive equipment which caused researchers to study these systems more and more recently. there are multiple parameters to classify solar energy; but mainly, it is divided into two parts of active and passive solar energy. passive solar is when there is no solar energy equipment used and solely by architectural means, the energy is stored and eventually used. however, active solar always has energy-gaining and systematic equipment to procure the energy needed. the active systems can be divided into space heating, domestic hot water heating, electricity supply, desalination, and solar dryers. buker et al. [14] reviewed the applications of building integrated solar thermal collectors in their paper. based on the scenarios reviewed in the paper, passive solar heating combined with building construction and energy-efficient applications can reduce space heating demand by 30%. on the other hand, active solar systems can reduce fuel demand for hot water and space heating from 50% to 70% for hot water and 40% to 60% for space heating. it is also estimated that about 30-40% of global heat demand can be met with solar thermal energy and 20% of europe's heat demand. there are many types of thermal collectors, but their applications remain limited due to reliability, cost, and building integration issues. therefore, significant research is needed mainly in heat absorber design and construction, material and coating selection, energy conversion and effectiveness, cost reduction, performance testing, system control, and building integration facilities. therefore, the use of collectors, along with optimization in their design and usage, can play a significant role in energy efficiency. karami et al. [15] investigated residential buildings as one of the largest energy consumers due to their valuable potential for energy savings. they specifically looked at the combined solar thermal systems that supply the energy needed for domestic hot water and space heating and evaluated their key role in reducing building energy consumption. they investigated the effect of climatic conditions on the thermal performance of a hybrid solar system using dynamic simulation by trnsys. for this purpose, the performance of the system in five different climate zones, including hot-dry, cold-dry, medium-humid, hot-semi-humid, and hot-humid, has been considered. based on the obtained results, the energy needed for hot water consumption in all climatic regions except for the temperatehumid and cold-dry climate regions can be supplied to a large extent through solar energy. their findings confirmed that the energy consumption of the building could be significantly reduced by using the combined solar system as a heating system, resulting in significant energy and economic savings. qerimi et al. [16] investigated the use of solar energy for building hot water supply in kosovo. since the electricity produced in most of the electricity produced in kosovo is produced from fossil fuel, the use of renewable energy, especially in buildings, was considered one of the promising solutions to save non-renewable resources. about 41.4% of the total consumption in kosovo, 15% of this energy is used for domestic hot water. this energy demand can be significantly reduced by using improved building construction techniques and the use of res sources, especially solar heat. for the cases they chose in their work, r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 23 they obtained data related to solar fraction, solar contribution, co2 avoided, collector temperature, financial analysis, etc., using tsol 2018 software. they proposed replacing conventional water heaters with domestic solar water heaters (dswh). the results of this paper show that dswh is economically feasible in pristine and can lead to fuel savings and co2 emission reduction. tang et al. [17] investigated the use of solar energy to heat water in residential buildings. they said that in south africa (sa), up to 40% of household energy consumption is used for water heating, and in this regard, the use of renewable energy, especially solar energy, can help reduce the energy crisis in this country. in their study, they investigated the use of solar water heaters (swh) at the household scale for the first time using climate data for 21 cities in south africa. the technical and environmental evaluation was performed by tsol pro 5.5 on two types of an evacuated tube (et) and flat plate (fp water heater). in addition, these cities were ranked using gams 24.1 and two types of dea methods. the results indicate that the efficiency of evacuated tube swhs is better than flat plate swhs in all cities and if we use an fp water heater, the average solar fraction is 95.93%, which avoids the emission of about 23.5 tons of co2 annually. these values for et water heaters are 99.16% and 24.4 tons per year, respectively. therefore, the results confirmed that the use of solar collectors can make a significant contribution to providing the heat needed by households. supplying sufficient electrical energy while reducing greenhouse gas emissions is one of the major concerns of policymakers and scientists all over the world. in saudi arabia, local authorities are increasingly aware of the necessity of reducing the environmental impact of nonrenewable energy by exploring alternative sustainable energy sources and improving buildings' energy efficiency. recently, building-integrated photovoltaic (bipv) technology has been regarded as a promising technology for generating instantaneous sustainable energy for buildings. to achieve a substantial contribution regarding zero energy buildings, solar energy should be widely used in residential buildings within the urban context [18]. due to the nature of the problem investigated in the present paper, where various technical and economic criteria are discussed, a method to optimize the selection is used. the multi-criteria optimization problem for the solution using the psi (parameter space investigation)-method is formulated as a generalized problem of nonlinear optimization [19]. different attributes of building types, including orientation, size, windows and doors areas, etc., were studied before architecturally. however, the impact of most of these attributes on energy consumption has not been studied. in this study, the impact of five types of buildings on energy consumption and solar micro-generation is investigated. in this research, the simulation, optimization, and analysis are done for different forms of residential complexes and also the possibility of using solar energy is studied. although simple architecture is used for each apartment in all of the buildings, the arrangement of these apartments is different in each case. so, the novelty of this study is that one would be able to decide which type of building is the best to build in terms of energy based on four main parameters of heating load, cooling load, solar fraction, and collector efficiency. 2. literature review wang et al. [20] studied the effect of urbanization on residential energy consumption. using panel data from 136 countries between 1990 and 2015, they examine the impact of urbanization on residential energy consumption around the world, and how the impact varies from region to region, taking into account regional heterogeneity and stages of urbanization. our findings show that the impact of urbanization on residential energy consumption in different areas at different stages of urbanization is very different. most sub-saharan africa is in the process of accelerating urbanization, characterized by rapid population migration to urban areas without economic growth. this feature of urbanization leads to a reduction in total consumption. in contrast, urbanization in developing regions in asia and the middle east, and north africa, coupled with emerging economies, could increase total residential energy consumption. surprisingly, for highly urbanized areas, including the developed regions of the world, latin america and the caribbean, and developing regions in europe and central asia, the impact of urbanization is due to the small gap between urban and rural energy consumption in the residential sector is based on these findings. , we offer four key policy proposals, including evaluating the financial viability of cost-benefit home energy transmission plans, developing a set of custom options for home energy use, and the regular transition process, encouraging bottom-up plans for adoption. clean energy in the residential sector, and sharing a public monitoring and planning platform. accordingly, the importance of using tools such as software modeling of urban residential neighborhoods, which are the main components of cities, becomes more apparent. given that standards are usually observed in the design and construction of any building, what can be further examined is the juxtaposition of several buildings and their impact on the use of natural energy, such as wind and solar. be. therefore, the study of a single building alone cannot provide a correct understanding of the state of energy demand as well as possible optimizations in urban areas. bahgat et al. [21] presented a classification based on the urban characteristics of open spaces (urban valley urban pattern, building distribution, and outdoor shape) and energy consumption and thermal comfort, which also took into account the effect of vegetation and complementary materials. also, the optimal value of the mentioned features was developed to achieve the desired urban features. urban characteristics of open spaces and their optimal values in the five main urban patterns of residential complexes (block, staircase, courtyard, staircase, and linear) in two climatic regions, hot, dry, and hot humid, which can be used as a guidebased urban model. used energy and comfort. urban planners and planners can use this to select the most appropriate urban features according to their preferred weather conditions and urban patterns in residential complexes (such as block, stair, court, stair, and linear). urban valley, density, distribution of buildings, and the shape of space and their subcharacteristics help to achieve energy-efficient and comfortable outdoor spaces. determining these features by observing the values according to the urban design guide, which is based on studies conducted in this field, will guarantee welfare and comfort. in this paper, the effect of r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 24 these factors was examined by quantitative and specific criteria. reinhart et al. [22] reviewed various building energy modeling methods. their findings indicate that significant progress has recently been made toward the development of simulation workflows to estimate the overall energy consumption of operational buildings across neighborhoods. given the insights that can be gained from such simulations for planning, design, and policy decisions, the level of effort required to set up and implement such models seems justifiable. however, several challenges remain for ubem (urban building energy modelling) to differentiate itself as a reliable urban planning tool. the greatest residual uncertainty for ubem simulations is related to the precise definition and description of ancient types that reliably represent a building warehouse. due to the very limited access to building energy consumption measurements and also the general lack of knowledge about the thermal properties of buildings, it is often not possible to estimate the simulation uncertainty nor to calibrate a ubem to reduce the error. to address this problem, model makers need access to building energy audit data as well as measured energy consumption in selected and audited buildings. while privacy concerns often prevent companies from sharing such datasets, some companies have begun to build in-house calibrated ubems to predict future demand profiles. the resulting archetype patterns do not violate anyone's privacy and can, therefore, be shared with the public. some city and state governments, representing another key stakeholder group, have already enacted laws requiring the use of building energy from selected types of buildings to make them public. franco et al. [23] examined india as the world's fastestgrowing economy and home to nearly one-fifth of the world's population to highlight the importance of urbanization to energy consumption. urbanization improves the quality of life of the people and, at the same time, promotes economic growth. however, it also increases energy consumption and can cause an energy crisis. urbanization also has a significant effect on carbon dioxide (co2) emissions. they empirically examined the temporal, dynamic, and causal relationships between urbanization, energy consumption, and emissions. increased energy consumption and greenhouse gas emissions are also being considered in the context of rapid urbanization. to address these problems, the study recommends a set of measures and a set of strategies, including measures to reduce energy intensity and emission intensity through continuous monitoring, information feedback systems, the introduction of industrial energy quota management, and incentives for facilities. energy efficiency is turning off inefficient devices. installation and commissioning of smart residential buildings. reducing distribution and transmission losses by investing in smart grids is also highly recommended. hachem et al. [24] presented a study of ways to increase energy efficiency in multi-story residential buildings. montreal, canada, was selected for this study. energy performance is measured by the balance between consumer demand and electricity generation using integrated pv systems. in this study, the focus was on increasing electricity production by solar cells. in this study, buildings were considered to have very high energy efficiency and comply with the principles of passive solar design. the buildings under study included low-rise (3-5 floors), medium (6-9 floors), and high (up to 12 floors), with eight apartments on each floor. in addition to the roof, pv was used in some of the facades. the simulation results using the energy plus building simulation program showed that the apartments are generally very efficient in terms of cooling and heating, but their use of active solar energy is limited. in this study, they concluded that a three-story building could generate about 96 percent of its total energy consumption if the roof design was optimized for solar energy production. on more than 3 floors, other measures are needed to increase energy production. the implementation of pv systems in 50% of the southern facade and 80% of the eastern and western facades, in addition to the advanced design of the roof surface (folding plate), allows the production of electricity up to 90% of the energy consumption of a 4-story building. this study shows that investing in advanced facade design (such as folding curtain walls) can significantly increase electricity generation and approach zero and surplus net energy status in buildings with eight floors. choi et al. [25] studied the energy consumption characteristics of high-rise apartment buildings through a series of case studies and resident surveys. they reached the following conclusions: (1) high-rise apartment buildings can be classified based on residential or mixed-use residential buildings and the form of the building. (2) in assessing the characteristics of electricity consumption based on building use, residents of mixed-use apartments showed more active heating management behavior and adjusted their indoor stay more actively, but they consumed more electricity, especially in summer than those who live in public residential apartments. (3) for the characteristics of electrical energy consumption, according to the shape of the building, plate buildings consume less energy than tower-type buildings. and the latter consumed 1.48 times more electricity than the former in common areas. (4) when evaluating the characteristics of liquefied natural gas consumption according to the shape of the building, it can be seen that plate buildings consume 10% more gas than high-rise buildings. (5) co2 in mixed-use buildings is higher than emissions in public residential buildings. tereci et al. [26] examined the effects of urban configuration, building typology, and building standards on energy consumption. they concluded that the density and material of the building cover have a significant impact on the energy performance of the town and should be given special attention in the urban design process. one of the most important factors in the energy demand of buildings is their arrangement. they looked at this and found, for example, that a row house in the middle of a block needed 17 percent less heating than a corner house. in addition, the location of the yards is important; yard forms lead to so much mutual shading between buildings that the most deprived apartments with very low solar benefits require up to 80% more heating. if the glazing ratio increases in all facades, the heating demand usually increases by 10 to 20%, while the changes in the southern façade alone do not have a significant effect on the heating demand due to the balancing of profits and losses. in heating-dominated climates, the combined demand for heating and cooling energy increases slightly with increasing site density (6%). in climates with comparable heating and cooling energy demand, the optimal site density r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 25 between completely shadowless open spaces and high density there is a site. for a given fixed-size metropolitan area, multi-family homes have the lowest initial energy demand and co2 per capita, while single-family homes have the highest. due to low density and fewer people in singlefamily urban areas, absolute energy consumption and greenhouse gas emissions are the lowest for this urban structure. in general, it can be said that the results of their work showed that depending on the prevailing heating or cooling needs, the shape of the building blocks, as well as the appropriate type of material, will be different and for the construction of neighborhoods or residential complexes should be considered these topics to be considered. dorer et al. [27] showed in their research that for buildings in an urban environment (compared to independent buildings), urban microclimate can have a significant effect on heat exchange and, thus, on the energy demand of buildings, depending on the geometry and structure of the building. in the case of the presented street valley, the effects of solar radiation and high waves had the greatest impact, followed by the effects of uhi and convective heat exchange on both the surface and the shear layer of the valley to free flow. to model the climate of larger urban areas, a multidimensional approach was proposed, ranging from meteorological scale models to precise modeling of radiant heat exchange and convection at the micro scale, with links to individual buildings and surface elements in building energy simulation it covers the city. the results of their research also confirmed the importance of how buildings are located in an urban area. hong et al. [28] examined the wind environment of the pedestrian surface and the thermal comfort around the buildings, and the wind pressure on the facade with numerical studies by spote. it is generally assumed that apartments in individual buildings experience better ventilation with the experience of wind deflection on one facade and separation of airflow on the other. however, when buildings are grouped in different configurations, the airflow depends on the type of arrangement and their interactions: including the different patterns of building layout and arrangement of trees, as well as the orientation of the building according to the wind. from the simulated results, it is concluded that the high views of the building, which are parallel to the prevailing wind direction, can accelerate the horizontal eddy airflow at the edges, where such a flow can enhance the convective exchange efficiency of hot air. low altitude and cold weather at high altitudes and a pleasant windy environment and thermal comfort are achieved at the pedestrian level. in addition, it has been observed that configurations with a square central space articulated by buildings and oriented towards the prevailing wind can be exposed to airflow and improve air movement. they quantitatively evaluated the outdoor wind environment and thermal comfort of the pedestrian surface around six hypothetical building design patterns and tree arrangements. from another perspective, it reflects the significant impact of architectural design and tree planting on the microenvironment around buildings. it also emphasizes the importance of micro-climate design, for example, conducting an environmental assessment of the options available in the building design phase and greening the landscape in a residential area. in addition, a pleasant outdoor heating environment with the shading of trees and buildings can be used as an additional criterion for assessing the energy efficiency of residential buildings. this article, with the approach of numerical studies, showed that the interactions of adjacent buildings in the designs should be considered and the best layout should be determined according to the intended conditions and objectives. faizi et al. [29] examined the orientation of the building as one of the most important factors affecting the rate of direct energy absorption. they analyzed this issue with ecotect software for four types of residential buildings in mehr housing complexes in tehran, iran, where shadows, solar radiation, access to light, and thermal simulation were analyzed. the results showed that the type 1 building (length width ratio and length orientation in the north direction) has the best performance in terms of shade and type 2 (with an approximately equal length and width and an angle of 30 degrees to the north) has the best in terms of solar radiation. on the other hand, buildings with a large surface area of translucent layers, such as windows in the south and east, can use more daylight to penetrate during the day. in addition, they made the following conclusions regarding the best placement model: • lowest width-to-length ratio along the north • having the maximum level of south-facing walls • design the most transparent layers in the south, east, west, and north. in lateral order • they also suggested genres for different sections 3. methodology in this study, several different residential sites have been considered to simulate the energy model used. a solar thermal system is used in each case to supply the energy demand of domestic hot water. the demand-side simulation is done using design builder software, and the supply-side simulation is done using t-sol software. the location of each building type is edmonton, alberta, canada. figure 1 shows the location of edmonton city. figure 1. location of edmonton city r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 26 the climate in alberta has three different regions. the northern part of alberta is located in region 1, the middle part is located in region 2, and the southern part is in region 4. the city of edmonton is located in zone 2, where the climate is usually cold and dry. also, the wind speed is severe through the winter. so, the main design priorities conclude in protecting from cold air and wind during cold seasons and using natural ventilation in summers. the procedures done in this study are visible in figure 2. as is shown, the study includes two sides of hvac and solar systems. each will be discussed further. 3.1 demand side five different residential sites are considered; each has different properties in some categories, including shape, height, width, and total site area. figure 2. basic schematic of the current study however, the base architecture of every building at each site is the same to distinguish the reason for different energy answer characteristics based on the above categories after simulation. a total number of 320 identical residential units are considered at each site. every single unit is either 141 m2 or 148 m2, and 8 units are used to form a floor of residential buildings. the staircase area is 18 m2, and there are two sets of voids placed in each building, which are 10.43 m2 in case of area. there are four windows located at each orientation of each unit to gain the maximum passive solar energy needed. the basic architecture plan is shown in figures 3-9 show the site view of each type of building and arrangement. the sites are categorized as skyscraper, linear, mixed, towers, and surroundings. r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 27 figure 3. the basic architecture of each floor figure 4. detailed quarter of each floor figure 5. skyscraper type figure 6. linear type figure 7. mixed type figure 8. towers type figure 9. surround type r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 28 3.2 design builder to calculate the energy use of each scenario, all mechanical and electrical simulations should be done to measure the related loads and then the heating and cooling design. heating and cooling loads include heat transfer to or from one or more unconditioned zones to the conditioned zone through the building envelope, walls, ceiling, floor, doors, and windows. they also include infiltration, internal heat gains and losses, hot water gains and losses, solar gains, ventilation, etc. there are numerous types of heating and cooling systems to use in different kinds of buildings. the most common system is a boiler for heating and a chiller for cooling. also, considering the usage of the building, which is residential in this case, scheduling is crucial in different parts of the system, including occupancy, hvac, lighting, etc. [30]. 𝑄𝐻𝑊 = 𝑐𝑝𝜌𝐻𝑊�̇�𝐻𝑊(𝑇𝐻𝑊 − 𝑇𝐶𝑊)/1000 (1) 𝑄𝑆𝐻 = 𝑈𝐴̅̅ ̅̅ (𝑇𝑅−𝑇𝐴) 1000 (2) equations 1 and 2 illustrate the loads calculated where cp is the specific heat coefficient (j/kg.k), ρ is density (kg/m3), v is the volumetric flow rate (m3/h), t is the temperature (k), u is the overall heat transfer coefficient (w/k.m2), and a is the area (m2). subscripts hw, sh, cw, r, and a mean hot water, space heating, cold water, room, and ambient, respectively. 3.3 t*sol modelling to simulate the solar energy parts of the alternatives used in the study, a dynamic simulation is needed. t*sol software is a program that allows one to accurately calculate the yield of a solar thermal system dynamically over the annual cycle. t*sol can optimally design solar thermal systems, dimension collector arrays, and storage tanks. the software is vastly used by researchers and designers in numerous studies and also experimental projects. in t*sol, calculations are performed based on the balance of energy flows and provide yield prognoses according to the hourly meteorological data provided. the solar collector used is a flat plate type, and thus, the equations will be as follows [31]. 𝑆 = 𝐼𝑏𝑅𝑏(𝜏𝛼)𝑏 + 𝐼𝑑(𝜏𝛼)𝑑 (1+cos 𝛽) 2 + (𝐼𝑏 + 𝐼𝑑)(𝜏𝛼)𝑔𝜌𝑔 (1+cos 𝛽) 2 (3) 𝐹𝑠𝑜𝑙 = 1 − 𝑄𝑎𝑢𝑥 𝑄𝑟𝑒𝑞 (4) 𝑄𝑐 = 𝐴𝑐𝐹𝑅[𝐼𝑐(𝜏𝛼) − 𝑈𝑐(𝑇𝑖 − 𝑇𝑎)] (5) 𝜂 = 𝐹𝑅(𝜏𝛼) − 𝐹𝑅𝑈𝑐( 𝑇𝑖−𝑇𝑎 𝐺𝑡 ) (6) where s, q, η, f, i, r, τ, α, β, fr, and gt are solar energy flux collected (w/m2), heat output (w), collector efficiency, solar fraction, solar radiation intensity (w/m2), fraction cosθ.cosβ transmissivity factor, absorptivity factor, tilt angle (°), heat removal factor, and solar irradiance at the collector plane, respectively. subscripts b, d, g, sol, aux, req, c, i and a means beam, diffuse, ground-reflected, solar, auxiliary, required, collector, incoming, and ambient. �̇� = �̇�(ℎ𝑜 − ℎ𝑖) (7) equation 7 demonstrates energy conservation in the solar system. where q, m, ho, and hi are heat rates transferred to the working fluid (w), flow rate (kg/s), and outgoing and incoming fluid enthalpy (j/kg), respectively [31]. 3.4 psi method because buildings may be ranked differently for different parameters, the psi method is used to implement weighting and rank all choices accordingly [32]. equations 8 to 12 illustrate normalized data, standard data deviation, deviation difference, parameter weight, and, finally, weighted data. 𝑅𝑖𝑗 = 𝑥𝑖𝑗 𝑥𝑗 𝑚𝑎𝑥 (8) 𝑃𝑉𝑗 = ∑ [𝑅𝑖𝑗 − �̅�𝑗] 2𝑁 𝑖=1 (9) 𝜑𝑗 = 1 − 𝑃𝑉𝑗 (10) 𝜔𝑗 = 𝜑𝑗 ∑ 𝜑𝑗 𝑀 𝑗=1 (11) 𝐼𝑗 = ∑ (𝑅𝑖𝑗 × 𝜔𝑗)𝑀 𝑗=1 (12) 4. results and discussion 4.1 design builder the simulations are done using logical assumptions at different parts of the software. four people in each apartment unit are considered. their occupancy schedule is defined to be present early morning, late afternoon, and nighttime. temperature preferences are indicated in table 1. table 1. temperature assumptions figure 10 shows the external walls consisting of 30 mm brick, 30 mm cement, 350 mm masonry, 50 mm polyurethane foam, and 50 mm gypsum plasterboard which leads to an rvalue of 3.066 m2-k/w. also, the top floor's roof consists of 20 mm bitumen, 150 mm mw glass wool, 200 mm air gap, and 13 mm plasterboard which leads to an r-value of 4.162 m2k/w. figure 10. external walls structure heating set point °c heating set back °c cooling set point °c cooling set back °c 22 18 25 30 r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 29 windows are double glazed 2×3 mm + 6 mm air gap with no shading and are defined into two groups of 1.5 m and 3 m in length. lighting is considered to be 7.5 w/m2 in all areas while the working plane height is considered to be 0.8 m from the floor. the lighting schedule is also considered when needed. an hvac system is considered for all buildings. fourpipe fan coils, shaped like figure 11, are used in each conditioning zone. heating is supported by a boiler(s), while cooling is supported by an air-cooled chiller(s). mechanical and natural ventilation, domestic hot water, and control systems are other parts of the hvac system. based on the hvac schedule, when there is low occupancy, the hvac system reduces to 50% of the maximum capacity. the heating and cooling loads of each building type are calculated. all other assumptions are considered with the energy code of canada and the software default values. according to figure 12, it can be seen that the heating load is the highest in the case of towers, followed by skyscrapers. figure 11. hvac system diagram figure 12. heating and cooling loads the reason for this issue is the benefit of these two plans from sunlight. it is clear that the middle and back faces of the towers receive the least radiation. the proximity of the towers together helps to reduce the heating requirement to some extent, but benefiting from the energy of the sun's radiation is more effective. the next rank is the cooling load of the linear and surrounding arrangement, which is almost equal to each other due to the same number of floors and the shape of the buildings. the advantage of these two structures compared to towers and skyscrapers is mainly due to the ability to receive more energy from the sun; in addition, the neighborhood of the building also has a positive effect. the combined mode has the lowest cooling load among these 5 modes. this arrangement has the advantages of towers and linear arrangement together. in this way, the combination of four buildings with a lower height in one row and two towers in the other row keeps the amount of solar energy received by all buildings at an optimal level, and their proximity also reduces cooling energy demand compared to a skyscraper. according to figure 12, regarding the required cooling load, the arrangement in the form of towers requires more energy. after that, the environmental arrangement and in the next ranks are linear, combined, and skyscrapers. in a skyscraper, since there is only one roof, much less heat is absorbed through it than in other cases. also, due to its height, during the day, more shade is created on its lower floors on the north side, and this also helps to reduce the need for cooling. in the linear layout, even though more roof surface is exposed to sunlight, the shading of nearby buildings protects many surfaces from direct radiation and reduces the need for cooling. in the combined mode, both the roof level is lower than the linear one, and we have almost the same shading effect compared to the linear one, and for this reason, the cooling load was the lowest in this mode. in the environmental arrangement, unlike the linear arrangement, more parts face direct radiation, and therefore the effect of the proximity of the buildings is less than in other cases, which has increased the need for cooling. arrangement in the form of towers, although the roof area is less than the ambient condition, the side surfaces are more exposed to direct radiation, and for this reason, it requires more energy for cooling. r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 30 figures 13 to 17 illustrate the amount of each fuel and each heating or cooling gain of each building during the year. as shown, the amount of gas used for heating is reduced during warmer seasons. where the electricity demand for cooling increases in the same period. the amount of heating needed is much more than the amount of cooling during the year because of the location of the project, which has a cold climate. towers and mixed-type need higher values of heating in cold climates. figures 13 to 17 also show the gains of each type, and it is obvious that the heating procedure is positive during the year. on the other hand, ventilation and infiltration cause a negative external air to gain all year. this means that the possibility of natural ventilation, especially in summer, is available, which is considered in this study. also, the passive solar gain from exterior widows causes less heating needed in temperate months of the year. thus, having air-sealed windows with no shading in most of the living areas of each apartment could help the heating load needed throughout the year; which is also considered. a b figure 13. fuels (a) and heat gains (b) of skyscraper type a b figure 14. fuels (a) and heat gains (b) of mix type a b figure 15. fuels (a) and heat gains (b) of linear type r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 31 4.2 t*sol in the present study, five alternatives are simulated, and assumptions are indicated in table 2. as shown in figure 18, flat plate collectors are used alongside two storage tanks with volumes of 182 and 29 m3 and a natural gas-burning boiler. the working fluid in the collector loop is a mixture of 60% water and 40% ethylene-glycol. the space heating working fluid temperature is 40 °c before heat exchange and 25°c after heat exchange. the windows' heat flux is considered 5 w/m2. first, the maximum solar fraction is calculated based on the space heating loads. table 3 shows the value of solar fraction for different options. as it is known, skyscrapers have the highest amount. this is because in a skyscraper that has a higher height, more levels of sunlight are received, and there is no building in its vicinity. after that, the linear, environmental, and combined models have the same values, and the towers have a lower solar fraction than the others. in this way, for providing heat, the skyscraper can have better potential and the others are in the next category. however, the problem is that to achieve this fraction, a larger surface is needed to install the collectors. the maximum solar fraction is yielded when there is enough surface area to accommodate the solar collectors. the collector required for this purpose is also calculated. this can be seen in table 4. figure 18. schematic of the solar system used in this table, the level of the collector needed to achieve the maximum fraction is stated: the skyscraper needs the highest amount, and then the towers and other buildings are placed with almost the same values. in terms of feasibility, the level that the building can provide for the installation of collectors is important. in this article, the collectors that can be installed on the roof are desired, and therefore, the roof surface of the buildings is the available space for this work. it is clear that the skyscraper, despite having relatively higher potential, does not give many possibilities to use this potential a b figure 16. fuels (a) and heat gains (b) of surround type a b figure 17. fuels (a) and heat gains (b) of towers type r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 32 due to having only one roof. based on the structure of each building type, the maximum area possible for each case is calculated by the surface area of the rooftop. available surface values for installing solar collectors are listed in table 5. as expected, horizontal arrangements have the largest roof areas, followed by the combined towers and skyscrapers. the above contents are summarized in figures 19 and figure 20. figure 19. solar fraction based on the areas possible and needed figure 20. collector efficiency based on the areas possible and needed based on both area values above for each case, the space heating solar fraction for each case is calculated and shown in figure 19. in this figure, the maximum amount of solar fraction and the amount that can be achieved based on the roof surface of different situations are drawn. according to figure 19, it can be seen that these two values are very close in the linear and surrounding states, and the maximum amount of energy can be absorbed by the solar collectors. however, the distance between these two values is less in the compound and towers and is very large in the skyscraper. also, collector efficiency based on the areas possible and needed is shown in figure 20, in which trends are as expected. because of the reduction of collector efficiency by increasing solar fraction, the optimum amounts possible could be calculated considering the importance of each parameter to the decision-makers. adding heating and cooling loads to the decision-making procedure chooses between scenarios even harder. a psi method of mathematical optimization is considered to choose the building type correctly. the method automatically calculates the best weighting possible for each parameter and then ranks the choices accordingly. the parameters consist of heating load, cooling load, solar fraction, and collector efficiency. the first two parameters are cost values, and the latter are gain parameters. so, in order to correctly use the mathematical method, solar fraction and collector efficiency are changed to be cost parameters in the program. tables 6 to 10 indicate the cost, normal, pv, weight, and result matrices, where parameters of heating load (hl), cooling load (cl), cost of collector efficiency (1-ce), and the cost of solar fraction (1-sf) are located in columns, and building types of sky scrapper (ss), mix (mi), towers (to), linear (li), and surround (su) are located in rows. the amounts stated are calculated with equations 8 to 12. as can be seen in table 10, the skyscraper has won the first rank. after that, there are, in order, the mixed arrangement, linear, towers, and surround. based on this; by weighting the criteria in the multi-criteria ranking and the results, the skyscraper is selected as the optimal option. table 2. t*sol software assumptions consumption usage hot water temperature location climate mean outside temperature min outside temperature residential 50 °c edmonton, ab, canada cold 2°c -35.64°c table 3. maximum solar fraction building type sky scrapper mixed towers linear surround solar fraction (%) 26.9 25.2 24.8 25.2 25.2 table 4. collector area needed to yield maximum solar fraction building type sky scrapper mixed towers linear surround collector area needed (m2) 12865 9752 10413 9878 9878 table 5. maximum area possible for the installation of collectors building type sky scrapper mixed towers linear surround collector area possible (m2) 1157.75 6947 4631 9262 9262 r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 33 table 6. cost matrix table 7. normal cost matrix table 8. pv cost matrix table 9. result weight matrix weight matrix hl cl 1-ce 1-sf 0.251 0.250 0.247 0.252 table 10. result matrix gain rank result matrix hl cl 1-ce 1-sf sum 1 ss 0.25 0.227 0.209 0.245 0.93 2 mi 0.24 0.23 0.241 0.25 0.96 4 to 0.25 0.25 0.23 0.252 0.98 3 li 0.24 0.235 0.247 0.25 0.97 5 su 0.24 0.248 0.247 0.25 0.98 although, decision makers can have different weighting preferences considering the location of the project or fuelrelated and renewable energy policies. thus, different weightings can also be considered. the choice of one could be the most important of heating load and solar fraction. the results are calculated in tables 11 and table 12. as can be seen in table 12, the ranking has been changed, and the skyscraper is second. the first ranks belong to the mixed arrangement. others also changed and respectively are linear, surround, and towers. it shows that according to the condition and priorities in a different situation, in which weights are different, rankings can vary. but by comparing table 10 and table 12 we can see that the two first rankings are similar, but the order is changed which shows that those are most probably the best options. table 11. preference weight matrix weight matrix hl cl 1-ce 1-sf 0.5 0.1 0.1 0.3 table 12. preference result matrix rank result matrix hl cl 1-ce 1-sf sum 2 ss 0.49 0.0907 0.0843 0.292 0.96 1 mi 0.47 0.0922 0.0975 0.298 0.959 5 to 0.5 0.1 0.0932 0.3 0.993 3 li 0.48 0.0941 0.1 0.298 0.969 4 su 0.48 0.0993 0.1 0.298 0.974 5. conclusions in this paper, the issue of energy in the building was investigated. as one of the largest energy consumers and greenhouse gas emitters, the residential sector needs special attention in terms of improving the energy consumption situation. considering the general trend of the world towards the rapid growth of urbanization, which will mainly be in residential complexes, the examination of these complexes has become one of the important matters in the field of energy. in line with the present article, the literature on the subject was reviewed and the various trends that were noticed by the researchers in the design and implementation of the different schemes for complexes were examined. in general, most researchers confirmed that residential complexes are better than detached houses. they also mentioned the use of solar energy as a good solution to reduce the need for fossil fuel consumption. to improve the conditions of energy consumption in buildings, there are various solutions of passive and active methods that can be improved to a great extent by using them. in this article, more than the factors involved in architecture, the focus has been on examining the effect of different types of arrangements on each other. the city of edmonton, which is located in region 2 according to the ashrae classification, was chosen for modeling. this region has a cold and dry climate. also, the wind speed is strong in winter. therefore, the main priorities of the design are to protect the cold air and wind in the cold decision cost matrix hl cl 1-ce 1-sf ss 3620 1666.93 0.741 0.731 mi 3460 1693.13 0.857 0.748 to 3670 1837.31 0.819 0.752 li 3495 1728.2 0.879 0.748 su 3495 1824.72 0.879 0.748 max 3670 1837.31 0.879 0.752 normal cost matrix hl cl 1-ce 1-sf ss 0.986 0.907 0.843 0.972 mi 0.943 0.922 0.975 0.995 to 1.000 1.000 0.932 1.000 li 0.952 0.941 1.000 0.995 su 0.952 0.993 1.000 0.995 mean 0.967 0.953 0.950 0.991 pv matrix hl cl 1-ce 1-sf ss 0.000 0.002 0.011 0.000 mi 0.001 0.001 0.001 0.000 to 0.001 0.002 0.000 0.000 li 0.000 0.000 0.003 0.000 su 0.000 0.002 0.003 0.000 sum 0.002 0.007 0.017 0.000 sum 1pv 0.998 0.993 0.983 1.000 3.973 r. zahedi et al. /future sustainability february 2025| volume 03 | issue 01 | pages 21-35 34 seasons and to use natural ventilation in the summer. these are considered in the modeling. in addition, to actively use solar energy, the usability and improvement rate of solar collectors were also analyzed. therefore, five types of arrangement linear, towers, mixed, skyscraper, and surrounding were proposed, which did not differ from each other in terms of interior design and cooling and heating systems, and the only difference was in the number of floors and their arrangement together. these options were modeled with relevant details in design builder software and the results were investigated. also, modeling of the use of solar collectors was done with the help of t*sol software. the results showed that, for example, the skyscraper option, although it has a favorable situation in terms of the required cooling load and also the potential of receiving solar energy, due to the lack of roof surface that can be used for installing collectors, it cannot use a large part of this energy, of course, it is clear that this is inevitable in engineering matters and it is very difficult or even impossible to optimize all the different criteria, including economic, environmental, operational capability, etc. for this reason, since the problem of determining the optimal option is a multi-criteria problem, to compare the options, the psi optimization method with two weighting methods was used. the results indicated that the first two options are skyscrapers and mixed, and other options are in the next categories. therefore, it can be recommended that the builders of the complex choose one of the two layout types. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of 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[31] kalogirou, s.a., solar energy engineering: processes and systems. 2013: academic press. isbn: 9780123972705 [32] maniya, k. and m.g. bhatt, a selection of material using a novel type decision-making method: preference selection index method. materials & design, 2010. 31(4): p. 1785-1789. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 16 article advancing urban flood mitigation and climate resilience: a gis-based hydrodynamic modeling approach using hec-ras and remote sensing data navid navidpour1, mohammad reza yari2, faraz estelaji3*, amir maleki4, bita rouhi asl5, sahand heidary6 1department of computer engineering, faculty of software engineering, amirkabir university of technology, tehran, iran 2department of construction engineering and management, faculty of civil engineering, iran university of science and technology, tehran, iran 3department of construction engineering and management, faculty of civil engineering, khajeh nasir toosi university, tehran, iran 4department of civil, water, and environmental engineering, shahid beheshti university, tehran, iran 5department of environmental management, faculty of marine science and technology, azad university-north tehran branch, tehran, iran 6faculty of computer engineering, khajeh nasir university, tehran, iran a r t i c l e i n f o article history: received 10 january 2025 received in revised form 15 february 2025 accepted 01 march 2025 keywords: flood hazard evaluation, hydrological modeling, hec_ras modeling, river flow management, climate change *corresponding author email address: faraz.estelaji.1996@gmail.com doi: 10.55670/fpll.fusus.3.2.3 a b s t r a c t over the past decades, significant adverse effects, including the resiliency of critical centers, have emerged. the negative impact has manifested in the vulnerability of critical urban centers during natural disasters and emergencies, leading to their inefficiency, heightened public dissatisfaction, and a breakdown in service delivery during crises. in order to enhance the resilience of key centers, it is essential to first identify and assess the vulnerability of these crucial urban hubs to various risks and threats. in this research, the classification was graded and assessed following the formulation of a questionnaire and the collection of results. utilizing the arithmetic mean of sample opinions, the analytic hierarchy process (ahp) was applied through the expert choice software to assign weights to these criteria and sub-criteria. subsequently, the key urban centers were identified. the hydrology within the city and its surroundings, along with the modeling of rivers during various return periods, were studied using the hec_ras. the results were then integrated into gis to delineate flood risk zones in the city of hamedan. following the input of the arithmetic mean of sample opinions into the expert choice, the value of each indicator was meticulously determined. this delineation indicates that the quantitative level indicator benefits from the maximum weight, while the economics of assets hold the least weight in the assessment. ultimately, by aligning key urban centers with flood-prone zones in the gis framework, vulnerable centers were enumerated. the method used in this study can be extended to all cities based on their river flow modeling and urban zoning. future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.2.3 may 2025| volume 03 | issue 02 | pages 16-25 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:faraz.estelaji.1996@gmail.com https://doi.org/10.55670/fpll.fusus.3.2.3 https://fupubco.com/fusus n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 17 1. introduction major cities, being the most densely populated nuclei, accommodate the highest levels of human resources, investments, economic projects, and infrastructure [1]. due to reasons such as excessive concentration, non-principled land use, disregard for accessibility standards (building and road compatibility), the presence of multiple bridges, neglect of river buffer zones, limited attention to climatic elements like prevailing winds, precipitation in constructions, and even the lack of balanced and standard access distances in the distribution of emergency and rescue centers such as hospitals and fire stations, these cities are exposed to numerous threats and substantial damages [2]. these challenges, especially during crises, can significantly impact the lives of citizens. therefore, taking appropriate measures within the framework of urban management plans and adhering to the principles is imperative [3]. given recent climatic changes and the damages caused by floods and droughts, examining this issue holds great importance [4]. as floods typically affect, areas adjacent to rivers and economic activities, as well as human settlements, are often concentrated near rivers today, studying these regions in terms of flood-prone parameters and preparing flood zoning maps is essential for urban planning [5]. floods are defined when water overflows its natural bed, inundating low-lying areas and riverbank territories, causing financial and human casualties [6]. identifying and grading assets based on their importance for the continuity of urban life and the urban system's resilience in the face of natural and human-made crises facilitate crisis management processes. this resilience enables the urban system to meet city needs during crisis conditions, thereby easing the management of crises resulting from both natural and human-made disasters. the phase of recognizing and prioritizing assets in the case of the city is one of the fundamental steps in this research. 2. literature review considering the principled and scientific design of the surface water collection network is very important as one of the most important components of the social welfare system of citizens, and for this system to function optimally to solve the problem of flooding in one of the rainiest cities in the country, different parts of rasht can be collected and directed to the inlet channel by constructing a structure in appropriate locations that meet the required standard size. the runoff that flows from impervious surfaces can be properly collected and directed to the outlet, thereby solving the problem of localized flooding in most places. of course, this requires the proper design of the urban drainage network along with an examination of the river flood level at the discharge site [7]. in a study aimed at evaluating the hec-ras model in flood prediction of the qorveh watershed in kurdistan province, various effective parameters in the hydrological modeling of this basin were studied. then, using the hecras sub-model and the us soil conservation service (scs) and schneider methods, the basin flood hydrograph was simulated and then calibrated and verified. it was determined that the scs method was more consistent with observational data in simulating the peak discharge of the hydrograph [8]. in this paper, flood zoning was studied using a hydraulic model of river analysis in the manshad watershed of yazd province. in this regard, with the aim of integrating the hec-ras hydraulic model with arcgis software through the hec-ras extension, the flood extent was calculated for return periods of 2 to 200 years in the riverside lands with the help of digitized topographic maps. finally, the area of each of the land uses at risk of flooding with a return period of 200 years was determined, and the most at-risk land use was related to agricultural lands [9]. in the list of most natural hazards, floods are in the first place. increased rainfall has made surface runoff disposal a critical problem in urban areas. various hydraulic models have been developed to measure the amount of runoff in urban areas [10]. the critical crisis areas in the urban structure against floods and inundation were identified, and the damages caused by floods were presented in the form of a damage assessment map [11]. in another investigation, flood zoning was carried out using hydraulic modeling in the province of yazd, specifically in the manshad plain. hec-ras was employed in this study, revealing that the integration of geographic information systems with the hec-ras model facilitates calculations, reduces field operations, and is highly recommended for application in watersheds [12]. ouma et al. [13] utilized building characteristics and their surrounding environment as fundamental information for assessing vulnerability to floods. they establish a direct relationship between the type of construction and building vulnerability. bloemen et al. [14] emphasized the crucial role of planning, decision-making processes, and appropriate technical execution in flood risk management. however, the oftenoverlooked technological aspects of building resilience to floods can significantly contribute to vulnerability reduction and flood risk management. bennett and blamey [15] introduced a novel method that not only studies vulnerability but also incorporates economic assessment and valuation for historical buildings. their approach assesses vulnerability by examining the exposure of historical buildings to floods, considering factors such as architectural form, preservation, and archaeology. albano et al. [16] highlighted the importance of vulnerability analysis for elements exposed to flood risks and the subsequent implementation of hydrological risk reduction strategies. their study focuses on assessing economic and social damages through modeling, examining the intensity trend, the impact on exposed elements, and the physical response of buildings. qiu et al. [17] employed a cellular-based metric system to evaluate urban resilience in dalian city, china, against floods. they simulate floods using the caddies model and identify vulnerable areas within the city's 31 sub-watersheds. their study emphasizes the effectiveness of the new metric in reflecting the system's performance changes, aiding the selection of tailored strategies for enhancing resilience. karber [18] delved into urban design principles for flood resilience in the mekong delta, vietnam. instead of focusing on post-flood damage, they propose alternatives for proactive adaptation to flooding, drawing insights from local ecological knowledge in rural areas and emphasizing the use of local capacities for urban areas. eakin et al. [19] explored the resilience of urban structures in mexico city against climatic hazards, particularly floods. they underline the complexity and n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 18 sequenced nature of building resilience, influenced by social, economic, and institutional conditions. harirchian et al. [20] suggested the use of an intelligent system for assessing and retrofitting buildings prone to flood damage. this system, comprising vulnerability assessment, retrofitting options, and fundamental damage assessment subsystems, aids in calculating the vulnerability of structures and recommending appropriate retrofitting strategies based on the degree of vulnerability. 3. methodology hamedan province spans approximately 19,546 square kilometers, situated in the western mountainous region of iran [21]. its geographical coordinates range from 2 degrees 33 minutes to 2 degrees 38 minutes north latitude and 2 degrees 45 minutes to 2 degrees east longitude. the most populous city within the province is hamedan city, positioned at an elevation of 1,870 meters [22]. the precise geographical location of hamedan city is illustrated in figure 1. figure 1. geographical location for hamedan city the current investigation falls within the realm of applied research, aiming to enhance the state of a phenomenon in hamadan city. the research methodology is rooted in theoretical objectives, adopting a descriptiveanalytical approach. in the descriptive phase, library and documentary studies were employed to compile the necessary information and data [23]. the statistical population encompasses experts, activists, and professionals specializing in the city's natural risks. these individuals were selectively sampled using a purposive sampling method, chosen for their suitability in gathering specialized and precise data on the research subject. a questionnaire was employed with the goal of identifying specific criteria and sub-criteria directly influencing the assessment of endangered assets. expert choice software facilitated the prioritization of these criteria, sub-criteria, and strategies. the integration of these procedures, along with the simultaneous execution of quantitative and qualitative analyses, positions the current study within the realm of mixed research [24]. the assessment of the weight of influential resilience indicators is conducted through a comprehensive five-stage process focusing on flood-vulnerable key centers. 3.1 determination and identification of assets prioritization of key centers in the face of impending threats is accomplished based on criteria and indicators categorized into three levels: life, sensitivity, or importance [25]. quantification of qualitative criteria and indicators for key centers is achieved. table 1 shows criteria, sub-criteria, and indicators. table 1. scores of the main criteria of the grading matrix [26] considerations grade the main criteria no 1 sub-criterion and 5 quantitative indicators 10 fundamental importance 1 3 sub-criteria and 10 quantitative indicators 20 scope of influence 2 1 sub-criteria and 7 quantitative indicators 20 possibility of replacement 3 5 quantitative indicators 6 to be unique 4 3 quantitative indicators 14 role-playing 5 2 sub-criteria and 7 quantitative indicators 5 capital value 6 3 quantitative indicators 10 consequences of injury 7 100 total 3.2 weighting of the main criteria of the ministry for asset leveling and evaluation after selecting the effective criteria in zoning in order to combine them together as information layers, the weight of each criterion must be determined in proportion to their importance according to one of the weighting methods. given that among the selected criteria, some are quantitative, and some are qualitative, we must use a method that allows us to compare and weigh quantitative criteria with qualitative ones, which is one of the problems of weighting in multicriteria decision-making problems. the weight given is given as a number in the evaluation, which indicates the relative importance of that criterion compared to other criteria. this method has found many applications in social and economic issues and has also been used in urban management in recent years. in this research, the analytic hierarchy process (ahp) method was used to weight the criteria. the analytic hierarchy process (ahp) method was founded by saati in 1977. the method is based on performing pairwise comparisons and determining the degree of preference of elements over each other with respect to the desired criteria and is used to solve multi-criteria evaluation problems and determine the priority of multiple options with respect to the desired criteria [27]. utilizing the indicators outlined in table 2. n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 19 the results are classified into one of three categories: critical, sensitive, or important. this classification scheme, proposed by troy et al. [28], provides a comprehensive overview of the criteria used to determine the critical, sensitive, and important classifications for the assessed assets. table 2. classify different levels based on the final score 3.3 using the hec_ras model this model is widely used to model urban drainage channels [29]. gis and hec-ras software have recently been used to display flooded areas [30]. hec-ras software with the hec-georas tool can model and display flooded areas with different return periods [31]. 4. results and discussion the selected assets were those whose removal would impact the provision of services, disrupting the primary functions of the city. to validate the results obtained from the evaluation of key assets in hamadan city, the weighting of asset evaluation indicators becomes crucial. this is because the influence of each index is determined by its weight in defining the significance of an asset. since the indicators listed in table 3 do not carry equal weight, a questionnaire was designed and distributed, and its results were collected. the ahp technique in the expert choice software was then employed to calculate the weights of these indicators. subsequently, the software determined the weight of each index separately based on the arithmetic average of the sample comments. the resulting weights are presented in table 3, providing a comprehensive understanding of the relative importance of each indicator in the asset evaluation process. table 3. weight of asset valuation indicators 4.1 prioritizing important assets adhering to the priority law (80/20), which posits that prioritizing activities based on their importance leads to 80% success with 20% effort, time, and resources, it is crucial to underscore the significance of proper prioritization. neglecting key priorities can result in 80% effort, time, and resources yielding only 20% success in achieving goals. key urban centers should be leveled based on their importance. the implementation of crisis management measures should be prioritized across three grades: 1st grade, 2nd grade, and 3rd grade centers. the quantification of qualitative criteria and indicators is essential for this leveling process. a table designed by the crisis management organization serves as the basis for prioritizing urban infrastructure centers in different areas, categorizing them into three levels: "grade 1, grade 2, and grade 3" (table 3). in this research, after evaluating and assigning scores to each indicator, the total score is recorded in the "score total" column. based on these scores, the level of the relevant key center is determined, categorizing it into one of the three levels: grade 1, grade 2, or grade 3. indicators of effectiveness and performance level, recovery ability (reversibility time recovery level), and 12 consequential effects (losses [human], damages [physical-real], injuries [psychological]. the simulation of river flow and city zoning against floods using the hec_ras model is a critical step in enhancing resilience. identifying threats in a timely manner is essential for implementing intelligent countermeasures, thereby mitigating weaknesses and reducing vulnerability. by developing a rainfall-runoff model, design flood values are determined for different return periods, as shown in figure 2. this comprehensive approach provides a thorough understanding of possible flood scenarios and helps to develop effective preventive measures and urban zoning strategies. leveraging road surface numbers, a digital elevation map of hamedan city was created, integrating it with the elevation digital map of suburban lands to obtain a comprehensive digital elevation map of hamedan city and its surrounding suburban basins. two key considerations are taken into account when determining the watershed boundaries: the first pertains to the area, and the second is related to land use within each sub-basin. design precipitation, a crucial parameter in rainfall-runoff modeling, is tailored to the needs of the selected precipitation-runoff model. four characteristics are established for design precipitation, including the continuity of total rainfall, depth of total rainfall, temporal distribution, spatial distribution of rainfall, and the structure of the rainfall-runoff model. this meticulous approach ensures the accuracy and relevance of the hydraulic modeling process, contributing to a comprehensive understanding of the hydraulic adequacy of the network. to model the basin for calculating design floods at the project site, a rainfall-runoff model was constructed using the hec_ras software. the model incorporates the extra-urban basins of hamedan city with six sources, 24 sub-basins for hamedan city, and 23 waterways representing the city's rivers. the flooding of suburban waterways in the model is considered based on the outcomes of hydrological studies. precipitation loss determination and the conversion of precipitation to runoff are carried out using methods provided by the scs soil protection organization, and river flood routing is conducted using the muskingum cunge method. range of grade rating level 93-100 special 1 83-92 vital 2 71-82 sensitive 3 56-70 important 4 36-55 protective 5 weight asset valuation indicators priority 0.117 functional value 1 0.133 quality level of operation 2 0.416 quantitative level of operation 3 0.188 environmental value 4 0.073 possibility of replacement and repair 5 0.045 dependence on the outside 6 0.022 economic value 7 n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 20 figure 2. structure of rainfall-stream given that water infiltration in the soil depends on factors such as soil type and texture, land use, and vegetation type and density, the amount of rainfall losses can be determined using these data and common methods. for the calculation of design floods, the 6-hour rainfall from hamedan airport station was considered as the representative rainfall. this rainfall was adjusted according to the level of each sub-basin using point rainfall reduction coefficients, aligning with the time distribution pattern of 6-hour rainfall. in this modeling approach, out-of-town areas are treated as a source, and the design rainfall is applied to the urban lands. table 4 provides an overview of the design floods entering the rivers of hamedan city, reflecting the outcomes of this comprehensive rainfall-runoff modeling effort. 4.2 analysis for river modeling some specifications of the river modeling are as follows: a) determination of transverse sections and specifications of existing bridges and culverts along the flow path. b) manning coefficients. c) drop coefficients resulting from the expansion and contraction of the flow. d) flow rate. e) boundary conditions. the analysis of river flow at various times was conducted using hec_ras software. figure 3 illustrates an example of the flow in morad beig and divin river as an outcome of this modeling effort. analysis of the water carrying capacity in different segments of hamedan city rivers was conducted based on the current conditions. the methodology involved considering the downstream section of each river as the zero-kilometer reference point, and distances to other sections were measured accordingly. additionally, the general slope of the ground at each section location was determined using the city's topographical map. the capacity of each section was then calculated using manning's formula. figure 3 illustrates the kilometer plan of the divin river. the horizontal axis represents the distance from the zero section (chainage), while the vertical axis depicts the water-passing capacity of the sections (bankful discharge). notably, the graph reveals that the capacity of river sections does not consistently increase downstream, highlighting the suboptimal water-passing capacity of these channels. it's essential to note that design floods, including a 50-year flood, have also been incorporated into the figure, providing a comprehensive overview of the water-carrying capacity and potential flood scenarios in divin river (figure 4). n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 21 table 4. the modeled floods going to hamedan’s rivers /sec)3modelled flood (m place of entering modelled flood node / sub basin 2-yr 5-yr 10-yr 20-yr 50-yr 100-yr range node 2.20 8.90 14.60 20.30 28.20 34.20 heidare 0.0 a04 9.10 13.20 16.00 18.50 21.90 24.50 abbasabad-01 11240.0 s1 9.50 15.10 19.20 23.20 28.60 32.80 abbasabad-01 2126.7 9c 11.80 24.30 34.30 44.20 57.70 68.00 abbasabad-02 2447.0 17c 11.80 24.60 34.70 44.80 58.60 69.00 abbasabad-02 1210.0 3c 2.80 4.00 4.90 5.60 6.70 19.90 park mardom 1760.9 s5 3.80 5.50 6.60 7.70 9.10 10.20 divin-01 6032.6 s2 3.90 6.40 8.10 9.90 12.30 14.40 divin-01 3424.1 20c 0.30 1.20 1.90 2.60 3.50 4.20 park mardom 868.8 52c 7.70 14.20 19.70 25.20 32.50 38.20 divin-02 3650.7 16c 7.80 15.30 21.10 27.70 36.50 43.40 divin-02 2280.0 21c 8.20 12.00 14.60 16.90 20.00 22.30 moradbeig-01 10937.9 s3 8.50 13.70 17.50 21.10 26.20 30.10 moradbeig-01 6100.0 22c 8.90 15.50 20.30 25.30 32.10 37.30 moradbeig-01 4386.2 25c 9.30 17.20 23.10 29.50 37.90 44.50 moradbeig-01 3286.0 24c 9.40 17.60 23.80 30.10 39.00 45.90 moradbeig-01 1106.0 23c 17.30 33.20 45.50 58.60 76.70 91.00 moradbeig-01 700.1 15c 2.10 3.00 3.70 4.30 5.10 5.60 faqire-01 3664.1 s6 2.30 4.20 5.70 7.20 9.40 11.10 faqire-01 2039.3 50c 0.90 3.50 6.10 8.80 12.30 15.10 etehad 1799.7 k08 3.10 7.70 11.50 15.90 21.60 26.10 faqire-01 2834.4 31c 7.30 10.70 13.00 15.00 17.80 19.90 khezr-01 6848.0 s4 7.50 12.00 15.30 18.30 22.70 26.10 khezr-01 3058.7 26c 10.70 22.80 31.90 40.70 52.90 62.00 khezr-01 1843.3 30c 14.20 31.70 45.20 58.00 76.30 89.80 khezr-02 2234.3 32c 15.30 36.10 52.40 68.10 90.40 106.90 khezr-02 1532.8 33c 15.80 37.80 55.20 71.90 95.50 113.10 khezr-02 0.0 11c n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 22 figure 4. divin river water intake capacity 4.3 results of river hydraulic calculations examination of the longitudinal profiles reveals that in certain segments of hamedan city rivers, the current conditions are inadequate. during designed flood events, water exceeds the channel capacity, leading to road flooding. the insufficient capacity of sections and the inappropriate dimensions of bridges and culverts contribute to the inability of hamedan city rivers to safely convey floodwaters out of the city. figure 5 depicts areas with flood potential based on the conducted modeling. specific sections along each river exhibit inadequate cross-section capacity to accommodate the design flood. notably, significant portions of the divin and khizr rivers are incapable of handling a 50-year flood. however, some segments within these rivers pose even more critical conditions than others. addressing these challenges is crucial to enhancing the overall flood resilience of hamedan city. figure 3. analysis of river crossings at morad beig and divin using hec-ras software n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 23 4.4 integration of assets layer and river modeling output in gis platform the layers containing key assets of hamedan city and the river conditions have been harmonized within the gis platform, and a comprehensive output map has been generated, as illustrated in figure 6. this map encapsulates the calculated results of the adaptation process, offering a visual representation of the interplay between critical city assets and the state of its rivers. figure 5. flood-prone areas with no capacity for water infiltration were identified through hydraulic modelling 5. conclusions the evaluation and mitigation of urban flood vulnerability stand as imperative prerequisites in urban flood management. the vulnerability of key structures during natural disasters can lead to their inefficiency, exacerbating public dissatisfaction and hindering emergency response services. floods, alongside earthquakes and droughts, hold the highest ranks concerning both human and financial losses among recognized natural disasters. urban floods have intensified due to climate change, urbanization growth, and constraints in urban drainage infrastructure. over the past decade, these floods have left significant adverse effects. hence, this study focuses on urban and suburban hydrology, hydraulic network analysis, and modeling of the rivers in hamedan city across various return periods. utilizing the hec-ras software and integrating the results into gis, the flood hazard zone of hamedan city was delineated. key vulnerable centers to floods were identified, emphasizing the necessity for officials to adopt and implement strategies and resilience models to mitigate the cascading impacts of these vulnerabilities. essentially, this research serves as an introduction to proposing resilient solutions for urban structures. in the contemporary era, the convergence of urban life complexities on different fronts, ranging from natural hazards and technological crises to social and security crises, has diminished urban resilience. the primary focus of this research is to elucidate and propose resilient strategies for vital and sensitive urban structures, particularly during natural threats, especially floods. to achieve this, highsensitivity key centers were first identified, and their vulnerability to flood-related risks and threats was examined. criteria and sub-criteria for asset grading and evaluation were established, and, after questionnaire adjustment, results were collected, weighted using the analytic hierarchy process (ahp) technique in the expert choice software. subsequently, key urban centers were determined. the hydrology of both urban and suburban areas, hydraulic network analysis, and river modeling in hamedan city across various return periods were studied using the hec-ras software. figure 6. modification of the asset layer in hamedan city and the flood permeability of various sections of its rivers n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 24 the results were then transferred to gis for flood hazard zoning in hamedan city. finally, by aligning key centers and flood-prone zones within gis, vulnerable centers were identified, and the results were presented. the results indicate that the green-colored zones, representing key centers and assets, intersect with the red lines, indicating inadequate river passage, signifying a critical issue. in this region, key structures and essential infrastructure are not safeguarded against potential future flood hazards. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] kennedy, l., robbins, g., scott, d., sutherland, c., denis, e., andrade, j., ... & bon, b. 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[16] albano, r., l. mancusi, and a. abbate, improving flood risk analysis for effectively supporting the implementation of flood risk management plans: the case study of “serio” valley. environmental science & policy, 2017. 75: p. 158-172. [17] qiu, t., et al., heterogeneous ad hoc networks: architectures, advances and challenges. ad hoc networks, 2017. 55: p. 143-152. [18] karber, p., the indochina chronicles: travels in laos, cambodia and vietnam. 2007: marshall cavendish international asia pte ltd. isbn: 9789814435413. [19] eakin, h., a.m. lerner, and f. murtinho, adaptive capacity in evolving peri-urban spaces: responses to flood risk in the upper lerma river valley, mexico. global environmental change, 2010. 20(1): p. 14-22. [20] harirchian, e., et al., a review on application of soft computing techniques for the rapid visual safety evaluation and damage classification of existing buildings. journal of building engineering, 2021. 43: p. 102536. [21] zehzad, b., kiabi, b. h., & madjnoonian, h. (2002). the natural areas and landscape of iran: an overview. zoology in the middle east, 26(1), 7-10. [22] heydari, a.h., et al., effects of covid-19 disease on electricity consumption of various sectors in iran. case studies in chemical and environmental engineering, 2023: p. 100600. [23] ghorbani, m., et al., evaluating surface water collection infrastructure for management of urban flood risk: integrating hec-ras with gis in overland flow modeling and flood hazard zone mapping within the kan river watershed of tehran. agu24. [24] stallings, r. a. (2003). methods of disaster research. xlibris corporation. isbn: 978-1401079703. n. navidpour et al. /future sustainability may 2025| volume 03 | issue 02 | pages 16-25 25 [25] tallis, h., levin, p. s., ruckelshaus, m., lester, s. e., mcleod, k. l., fluharty, d. l., & halpern, b. s. (2010). the many faces of ecosystem-based management: making the process work today in real places. marine policy, 34(2), 340-348. [26] tallis, h., et al., the many faces of ecosystem-based management: making the process work today in real places. marine policy, 2010. 34(2): p. 340-348. [27] bell, m. l., zanobetti, a., & dominici, f. (2013). evidence on vulnerability and susceptibility to health risks associated with short-term exposure to particulate matter: a systematic review and metaanalysis. american journal of epidemiology, 178(6), 865-876. [28] terwee, c.b., et al., rating the methodological quality in systematic reviews of studies on measurement properties: a scoring system for the cosmin checklist. quality of life research, 2012. 21: p. 651657. [29] wen, j., et al., a computational tool to track sewage flow discharge into rivers based on coupled hecras and dream. water, 2023. 16(1): p. 51. [30] gascon, c. (2007). amphibian conservation action plan: proceedings iucn/ssc amphibian conservation summit 2005. iucn. [31] saeidi, p., mardani, a., mishra, a. r., cajas, v. e. c., & carvajal, m. g. (2022). evaluate sustainable human resource management in the manufacturing companies using an extended pythagorean fuzzy swara-topsis method. journal of cleaner production, 370, 133380. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 26 article developing porous copper/aluminium-chitosan biosorbent hydrogel beads for the removal of phosphate from wastewater panchali dias, md bazlul mobin siddique* faculty of chemical engineering and science, swinburne university of technology, sarawak, malaysia a r t i c l e i n f o article history: received 30 january 2025 received in revised form 06 march 2025 accepted 18 march 2025 keywords: chitosan-based hydrogel, phosphate removal, hydrophilic beads, eco-friendly water treatment *corresponding author email address: msiddique@swinburne.edu.my doi: 10.55670/fpll.fusus.3.2.4 a b s t r a c t excess phosphorus is one of the principal causes of eutrophication, which causes severe ecological imbalance and harm to human health. in this study, several chitosan (cs)/copper and aluminum (cnt, ach) hydrogel beads were created and tested for phosphorus removal. further microcrystalline cellulose and cellulose nano fiber were also used to create stable cs/cnt ach hydrogel beads. the optimized cnt/cs settings with 0.2 mg cnt demonstrated outstanding removal efficacy. it effectively removed phosphate from an aqueous solution with a ph range of 4.5-5.5 using a completely mixed batch of 0.01m sodium dihydrogen phosphate, with 80% phosphate absorption achieved after 48 hours of contact time. the measured maximum adsorption capacity at ph 5.5 solution was 11.39 mg per 0.0206g of the beads (10 beads). the ftir study revealed that all three varieties of synthesized beads have a healthy microstructure. furthermore, the findings of the kinetic study indicated a low absorption rate at 15ºc and a moderate absorption rate at 45ºc. the adsorbent efficiently removed phosphate during 12 hours of contact time, according to a batch adsorption study, using 20 beads weighing 0.0412g. electrostatic attraction and ion exchange can both be responsible for phosphate absorption. furthermore, 10 of the 21 control mcc and cnf beads could remove more than 60% phosphate after 48 hours of contact time with identical solute distributions. this adsorbent might be deployed to effectively treat phosphorus-contaminated water to prevent eutrophication. 1. introduction regardless of the fact that water covers 71% of the earth's crust, we humans manage to endanger the natural equilibrium of water bodies across the world by releasing wastewater. for a multitude of reasons, the earth's limited supply of fresh water, which accounts for around 2.5% of total water content, must be safeguarded. according to the un, approximately 80% of wastewater created by all urban housing projects, big-scale production chains, and even smallscale manufacturing enterprises, among other things, is released into natural water bodies untreated. this research focuses on the chemical component phosphate, which becomes contaminated in natural water bodies by wastewater discharge due to its widespread use in everyday goods. to design a long-term sustainable engineering solution for removing this chemical from a regulated wastewater sample. phosphorous is a nonmetal element having a valency of 5+. when fluorapatite, often known as phosphate rock, is exposed to acid, it creates phosphoric acid. orthophosphate, polyphosphates, and organically bound phosphates are the three types of phosphates. the natural phosphate cycle is critical for animal and plant health, and its imbalance arises when it is released in bulk quantities after human ingestion. all of these kinds are extra phosphate deposits that disrupt the normal chemical equilibrium. phosphorous contributes significantly to water pollution, with negative impacts ranging from eutrophication, ocean acidification, and algae overgrowth to suffocating of some aquatic animal species, shortening their life span. organically bound phosphates are primarily discharged in conjunction with waste solids or organic waste [1]. phosphorous has a noteworthy impact on human health degradation, ranging from dehydration and future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.2.4 may 2025| volume 03 | issue 02 | pages 26-34 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:msiddique@swinburne.edu.my https://doi.org/10.55670/fpll.fusus.3.2.4 https://fupubco.com/fusus p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 27 diarrhoea to renal disease and endothelial dysfunction [2]. the significance of creating technology for chemical removal from effluent wastewater has long been explored and acknowledged. there have been several ways based on its scientific foundation. physical removal methods such as adsorption and magnetic field use, chemical removal methods such as precipitation with lime or aluminium chromate, biological removal methods such as biomass adsorption and reagent use, physical-chemical removal methods, and even chemical-biological removal methods have all been studied and put into practice. this study focuses on the physiochemical removal approach, specifically the inclusion of hydrogel in anion removal. over the last few decades, researchers have created various hypotheses, proposed numerous chemical compositions, and even succeeded in many situations with phosphate removal using the physiochemical removal approach. the first limitation of present techniques appears with phosphate removal utilizing metalimpregnated hydrogels. phosphate anion has a valency of 3, and there haven't been many viable methods for eliminating it at a high percentage. the second limitation is that the effects of additive variations on phosphate absorption are not clearly examined. the majority of investigations use one kind of bead and one set type of additive (metal or non-metal). this makes guessing the absorption levels of a few distinct types of beads prepared for a substantial sort of anion elimination difficult. hydrogel beads prepared in this study are simple structures of the biopolymer 'chitosan' integrated with cationic ions such as copper and aluminium, which can conceive a gel bead-like structure after several experimental steps, with a hollow sponge-like middle sector with hydrophilic abilities due to its surface having water permeable qualities. existing approaches do not generate significant outcomes when adding hydrogel beads in phosphate removal. the research gap is addressed by attempting to synthesize and characterize various types of hydrogel bead structures incorporating copper and aluminium, on their absorbance and ability to absorb targeted anions in a controlled experimentation series, with the hope of also monitoring the beads' response to stimuli changes. 2. literature review 2.1 phosphate in water water is the 'universal solvent' due to its ability to dissolve more substances than any other liquid on earth. phosphates occur in many ways, leading to adverse effects on mankind as well as flora and fauna. depending on its contamination action, they can be listed into three different methods of contamination. 'point source' pollution through phosphates is the way that they end up in natural water bodies in bulk loads without any objection, decay time, or treatment. oil refinery effluents, wastewater from process industries such as dye and acid manufacture, chemical dumping by big-scale laboratories and supply networks, and medical waste from any institution of medicine are the finest examples. phosphate contamination is caused by the late addition of phosphate-rich effluents to water bodies that do not originate from a single source or site. excess fertilizer or weedicides used in agriculture, mine explosions that contaminate ground waterways, and landslides or volcanoes that are natural risks with a large release of phosphates that wash away to water over time are instances of pollution. transboundary pollution is described as contamination that begins in one country but travels to another country's water sources. oil spillage on ocean or river water, chemical deposits (medicine/cosmetics) from accidents on ships/boats traveling by water, and chemical manufacturing fumes carried away by winds or rain are the greatest examples. as previously established, all of these pollution strategies have negative effects on plant and animal species irrespective of water ecosystems. phosphorus is a limiting nutrient needed for all plant development, including aquatic plants and algae. excess concentrations can induce algal blooms, especially in rivers and lakes. a lake with a concentration of less than 0.010 mg/l is considered oligotrophic, whereas one with a concentration between 0.010 and 0.020 mg/l is considered mesotrophy, and concentrations greater than 0.020 mg/l are classified as eutrophic [3]. the acceptable phosphate levels in malaysia are 0.1 mg/l and 0.2 mg/l, according to the national water quality standards, malaysia. these two concentrations are divided into two water classes, and samples with 0.1 mg/l phosphorous content fall into water class iia/iib. the samples with a phosphorus value of 0.2 mg/l fall into the water class iii. to be clear, class iia/iib water is appropriate for water supply after simple treatment, for delicate aquatic species, and for recreational body contact. after considerable treatment, class iii water is appropriate for water supply, common species of fish, and cattle drinking. 2.2 existing methods of phosphate removal 2.2.1 ion exchange this method is applied in small-scale industries, municipal drinking water treatment units, and even in-home water softeners. ion exchange requires passing the water through a specialized ion exchange resin in a closed vessel. the surface of the resin involves active sites, which help remove the constituent of interest in exchange for other feasible, less effective ions. once all the active sites of the resin are used, the resin must be restored or regenerated, and since the used resin is a strong anion resin, nacl can be used for restoration purposes. an example of this application is if a water flow with 5 mg/l phosphate ions is introduced to the ion exchanger, the treated water would contain less than 2 mg/l of phosphate in the system [4]. 2.2.2 magnetic field method here, phosphates are bound to a reagent in the insoluble compound. once the magnetic field is activated with magnetic material addition to the water system, it isolates the phosphate-containing sediment. 2.2.3 electric coagulation method here, electrodes are used to isolate the phosphates inside the water system. electrodes of 2 types can be used, iron-aluminium or steel. this method ensures an easier extraction of phosphates too. 2.2.4 chemical removal methods a) adding aluminium chromate to wastewater in the presence of an alkali generates the following reactions, al2(cro4)3 + 6hco3 − → 2al(oh)3 + 3cro4 2− + 6co2 (1) p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 28 al2(cro4)3. 14h2o + 2po4 3− → 2alpo4 ↓ +3cro4 2− + 14h2o (2) these reactions will fight for the aluminium ions dispersed after the addition of aluminium chromate. the aluminium hydroxide flakes attract the aluminium phosphate particles and colloid particles of solid impurities. b) adding 3 valent iron salts as a coagulant fcl3 + po4 3− → fepo4 + 3cl− (3) in here the ferric phosphate particles sediment. any excess of ferric ions will produce iron hydroxide. iron hydroxide will attract ferric phosphate particles and other particles and sediment itself. c) adding calcium hydroxide as a coagulant ca(oh)2 + hco3 − → caco2 ↓ + h2o + oh− (4) 5𝐶𝑎 + 4𝑂𝐻− + 3𝐻𝑃𝑂4 → 𝐶𝑎5𝑂𝐻(𝑃𝑂4) ↓ +3𝐻2𝑂 (5) in here lime readily reacts with any bicarbonate ions in the water complex. in addition, it also reacts with phosphates. the orthophosphates are precipitated with the help of calcium ions and produce oxyapatite. when the ph value of the water body increases, the solubility of calcium oxyapatite decreases, and the removal of phosphate increases (ph > 9.5 is the ideal). biological methods are said to give the best removal percentage of phosphorous from water complexes. there are different approaches with different efficiencies in the matter, varying the effective removal percentages from 20% 50%. this percentage can be enhanced up to 95% with the current technological maturity. such biological treatment approaches are phostrip, а/о (anaerobic–oxic), and easc (extended anaerobic sludge contact process). however, there are several biological – chemical applications as well [5]. they all pose higher quality compared to chemical treatment and biological treatment separately. they each differ from each other by reagent source and reagent composition. 2.2.5 hydrogel beads hydrogel beads are cross-linked polymers that have hydrophilic traits, and once immersed in aqueous solutions, they swell by attracting water inside the 3d structure. the component must account for at least 10% of the total weight of the material to be called a hydrogel [6]. many alternative theories have been developed over the years to assist in predicting the structural result of hydrogels, which gives us the gel's elasticity value, porosity, and pore size of the hydrogel network. all these theories consider enthalpy, entropy, and other thermodynamic factors in order to establish the structure and pore sizes of hydrogels, and computer modeling methods may then be utilized to accurately create the hydrogel intended. hydrogels are classified as those made from natural polymers, those made from synthetic polymers, and those made by modifying natural polymers with synthetic linkers (semi-synthetic hydrogels) [7]. as a result, hydrogels can undergo structural transformations in response to a stimulus, which can be chemical or physical. chemically prepared gels rely on covalent bonding to introduce the integrity required to form a gel structure [8]. the gels can be cationic, anionic, or neutral depending on the ionic charges on the bonded groups. by stacking various hydrogel layers that each react to a particular stimulus, shape-changing hydrogels may be constructed [9]. hydrogels may also be classed as homopolymer or copolymer based on the different polymerization processes such as suspension, block, solution, and emulsion. homopolymers have just one kind of monomer in their structure, and depending on the nature of the monomer and the polymerization process employed, they may have a cross-linked structure. copolymeric hydrogels are made up of two types of monomers, at least one of which is hydrophilic. an interpenetrating network (ipn) can be formed by joining two polymers, provided that one of them is already present in the solution [6, 10]. hydrogel is found in three different types: resins, films, and nanocomposites, and in an attempt to improve its adsorptive properties, many other chemicals can be integrated into the network. according to the literature survey, it is visible that hydrogels have a high potential to succeed with their applicability in wastewater treatment for intended anion removal [11]. the morphology of hydrogel beads suggests that their size can vary from 20nm – 5mm with porous, rough outer surfaces [12]. their swelling ratio is mainly dependent on the ph of the solution and retention time. biopolymers such as polysaccharides and polypeptides have garnered a serious welcome in the hydrogel bead production industry. 2.2.6 biopolymers there are various biopolymers incorporated in biodegradable research work nowadays. within an organism, these various polymers are made up of numerous individual monomers or units. they are often sourced from plants and animals, making them both biodegradable and easily reusable for different purposes. incorporating this feature of biodegradability came into use after the era of sustainable engineering started. hence researchers have thrived in finding engineering solutions incorporating biodegradable materials. attempting the use of biopolymers in adsorptive studies came into light around the early 2010s. since its application has improved vastly in fields such as tissue engineering. hydrogels are employed in a variety of industries due to their unique architectures and compatibility with various operating conditions. hydrogels are distinguished from other biomaterials by their flexibility, and their versatility is unparalleled since their applications vary from industrial to biological. drug delivery, dye, and heavy metal removal, scaffolds in tissue engineering, and even contact lenses are some of the major uses of hydrogels [6, 10]. biopolymers, as previously discussed, are critical in the development of useful and novel hydrogels with improved biocompatibility [13]. sugar-based polysaccharide biopolymers and protein-based polypeptides have both been used extensively in the development of novel biodegradable and biocompatible hydrogel materials. polysaccharides utilized in the creation of hydrogels include chitosan, cellulose, alginate, and glycosaminoglycans. polypeptides may contain collagen, gelatine, and other proteins [14]. p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 29 2.2.7 hydrogel bead application in wastewater treatment there is a considerable number of works done in the area of hydrogel beads incorporated in wastewater treatment. however, there were some articles which provided an insight for the research. a study on phosphate removal from a complex water environment study incorporated zr-bentonite hydrogels [15]. testing on anion selectivity was further carried out by introducing other multivalent anion salts. another study discusses the application of polyacrylic-based hydrogel beads for heavy metal removal [16]. these acrylic-based polymer hydrogel beads have garnered attention due to their applicability in pollutant adsorption and heavy metal extractions. this research further elaborates on the different approaches that can be taken into consideration when synthesizing acrylic hydrogels. an in-depth analysis of the thermodynamic factor affecting the hydrogel beads is also explained. researchers attempted the removal of boron using modified chitosan hydrogel beads [17]. this was done using a synthesis of manganese chitosan hydrogel beads. this research was done in an attempt to clear freshwater samples entering irrigation systems. results show a potential in commercial application for improving water quality. 2.2.8 materials of application chitosan (cs), copper nitrate trihydrate (cnt), aluminium chloride hexahydrate (ach), microcrystalline cellulose (mcc), and cellulose nanofiber were used in this study to synthesize hydrogel beads (cnf). they are chosen after careful examination of the selected pollutant 'phosphate' in water, its affinity to the metallic ions inside the hydrogel beads, the ability of the biopolymer to absorb and desorb water without hesitation, the adaptability of the biopolymer and enhancers, and the required strength of the hydrogel beads. furthermore, extensive research and theories advanced by other researchers' work on hydrogel beads, such as [8,15,16] and many others, aided in finalizing the proper salts of application for each metal and the methodology of application of each additive and enhancer to the hydrogel prior to bead preparation. chitosan: chitosan is a polysaccharide with high antibacterial properties that is biocompatible, biodegradable, and non-toxic. chitosan, hence, has many uses, including those in medicine, agriculture, food preservation, nutritional supplementation, cosmetics, and wastewater treatment. a polysaccharide generated from chitin is chitosan. copper: copper is a reddish-brown metal with a cubic crystalline structure. it is malleable, ductile, and an extremely good conductor of both electricity and thermal energy. it has a low chemical reactivity and falls under the category of transition metals in the periodic table. the molecular weight of copper is 63.55 g and has a density of about 8.9 gcm-1. the most common ionic form is when the atom releases 2 electrons in the hope of ionic bond formation. therefore, the most abundant cation type is the cu2+ ion. in this research this ion type is used as the metal dispersed in the hydrogel beads. why use copper is due to its high affinity to form an attraction with negatively charged phosphate ions. this has promoted the amount of phosphate removed from the water sample drastically. the copper nitrate trihydrate of 2+ copper was the best choice since it showed very good results during experimentation. aluminium: although it makes up 8.1% of the earth's crust, aluminum is rarely encountered in nature alone. it is typically present in minerals like cryolite and bauxite. these are aluminum silicate minerals. the hall-héroult technique is used to remove the majority of aluminum used in commerce. given that aluminum is not a particularly strong metal on its own, it is frequently utilized as an alloy. copper, manganese, magnesium, and silicon alloys are light but robust. they play a crucial role in the development of hydrogel and is often used in drug delivery and dye removal applications of hydrogel. the introduction aluminum can enhance the hydrogel’s water affinity percentage by high numbers. one of the reasons it is utilized as a crosslinker in the experimentation for some types of beads. microcrystalline cellulose: cellulose (c6h10o5) n is one of the most widely distributed organic polymers in nature. it is a crucial structural component of oomycetes, many kinds of algae, and green plants' main cell walls. the polysaccharide is composed of a linear chain of (1-4) linked d-glucose units numbering from several hundred to several thousand. utilizing various processes, including oxidation, etherification, and esterification, which transform generated celluloses into derivatives of cellulose, many techniques of cellulose extraction have been developed [18]. cellulose nanofiber: emerging nanomaterials called naturally generated cellulose nanofibrils (cnfs) have high strength, large surface area, and variable surface chemistry, enabling regulated interactions with the biological, nanoparticle, small molecule, and polymer materials. while the hydrophilicity of the nanocellulose interface has made it challenging to use cnfs as reinforcing agents in conventional plastics, it has been a significant advantage in the development of reinforced or structured hydrogel composites (or, when dried, aerogels) that exhibit mechanical reinforcement as well as a variety of other desirable properties [19]. the banana pseudo cellulose nanofiber (cnf) used in this research was obtained by a master’s student at swinburne university of technology sarawak. 3. methodology the fabrication procedure was conducted in 4 separate parts, which include the preparation of control cs – cnt/ach beads, the preparation of mcc cs – cnt/ach beads, the preparation of cnf cs – cnt/ach beads, and lastly, the conditioning of the film. the testing procedures include ftir analysis, absorbance performance, temperature sensitivity, and batch adsorption study. all the beakers, flasks, crucibles, and petri dishes were washed with distilled water and dried in an oven for 1 hour at 60ºc prior to use. 3.1 fabrication of hydrogel beads preparation of control cs – cnt/ach beads: 9g of cs were dissolved in 450 ml of 2% (v/v) acetic acid solution to create a chitosan solution of 2% (w/v). following complete cs dissolution, the solution was separated into 9 samples of 50ml given in table 1. the beads were synthesized into 9 different types by using the below additive amounts. p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 30 table 1. distribution of additives for types a – i homogenous distribution was achieved by continuous stirring at 300rpm for 24 hrs of each hydrogel mixture. 18g of sh is dissolved in 900ml of di water to create a 2% (w/v) sh solution and divided into 9 samples of 100ml sh solution. the hydrogel mixtures were added dropwise into each of the sh samples using a micro dropper to form the hydrogel beads. the prepared beads were left at continuous stirring at 300rpm for 24 hrs inside the sh solutions to ensure crosslinking. preparation of mcc cs – cnt/ach beads: the same steps for the hydrogel mixture preparation are carried out for types a – f as control hydrogel beads. then, prior to leaving for continuous stirring, 0.2 g of mcc is added. steps are repeated from then onwards. preparation of cnf cs – cnt/ach beads: the cnf pulp is prepared by soaking 0.3g of cnf in 30ml of di water and letting to soak for 2 hrs. using the sonicator machine, preparation of cnf pulp is done, the settings used are 40% 50% amplitude (gradually increase), elapsed time 8 mins 20 secs, pulse 5/10 and total energy used is 8184joules. the same steps for the hydrogel mixture preparation are carried out for types a – f as control hydrogel beads. then, prior to leaving for continuous stirring 5 ml of cnf pulp is added. steps are repeated from then onwards. conditioning of hydrogel beads: the 21 types of hydrogel beads synthesized were washed with di water till ph 6.5 – 7.5 is reached (tabulated in table 2). the washed beads must be dried in an oven at 60 for 4 hrs. after drying, the beads are stored in a desiccator to avoid contact with air. table 2. twenty-one types of synthesized hydrogel beads 3.2 testing procedure fourier transform infrared analysis: the chemical alterations and bonding of the different types of composite films were analyzed using ftir spectra. the equipment used to conduct the ftir was a perkin-elmer spectrum 400 ftir spectrophotometer. absorbance performance: the absorptive studies were carried out on the percentage weight of water of the soaked beads and the percentage of phosphate removal using titration. a solution of 0.01m sdp is prepared by adding 1.56g of sdp in 1000 ml of di water. sixty-three samples of 15ml, each 0.01m sdp, are distributed, and 10 beads of each of the 21 types of beads are suspended into 3 solutions per type. for water absorbance testing the dry weight before soaking and wet weight after soaking of the hydrogel beads are obtained. for the phosphate removal efficiency testing, the 21 types, each out of the 63, are kept for 12 hrs, 24 hrs, and 48 hrs, respectively. using a 0.1m sh solution the samples of sdp are titrated in the presence of phenolphthalein and ph meter for accuracy. the experiment is repeated for 3 rounds to reduce the error percentage. temperature sensitivity: once the absorbance and phosphate removal efficiencies are calculated, the best type of beads can be identified. a selective experimentation is done to observe the absorbance performance of the beads under temperatures lesser than room temperature and higher than room temperature. the same steps as absorbance testing are carried out for type a control beads to prepare 9 samples of 15ml 0.01m sdp and 10 beads each. three samples are left in the refrigerator set at 15 for 24hrs, 3 samples at room temperature for 24 hrs, and 3 samples sealed inside the oven at 45 for 24 hrs. the same steps of titration are followed at the end of 24 hrs using 0.1m sh. batch adsorption study: using the same selection type, a control, selective experimentation is done to observe the absorbance performance of the beads as a pack of 10 beads, 15 beads, and 20 beads for comparison of the absorbance fluctuations with the varying of no: of beads. the same steps as absorbance testing are carried out for type a control beads to prepare 9 samples of 15ml 0.01m sdp and let 10 beads each of 3 samples for 24 hrs, 15 beads each of 3 samples for 24 hrs, and 20 beads 3 samples for 24 hrs. the same steps of titration are followed at the end of 24 hrs using 0.1m sh. 4. results and discussion 4.1 fourier transform infrared analysis according to the ftir results, figures 1, figure 2, and figure 3 display the ftir spectra of the produced chitosan composite beads packed with copper (ii) particles and the al (iii). the amide (c=o) stretch, the c-n stretch, the bending owing to n-h stretching, and the absorptions due to c-h stretching at around 3000 cm-1 and the c-h bending at around 1300 cm1 are the characteristic peaks for chitosan. the c-o skeletal stretch typical of polysaccharides can be seen at 1100 cm-1, and c-o antisymmetric stretching can be seen at 1000 cm-1. copper and aluminium exhibit absorption bands at 700 cm. figure 1. ftir plot of mcc hydrogel beads p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 31 figure 2. ftir plot for cnf hydrogel beads absorbance performance according to the graph, it is visible that the percentage weight of water absorbed is highest in type f cnf beads. this type consists of cnf and aluminium as additives in the hydrogel mixture. also, the lowest water absorbed is by type a control beads. this type consists of only copper as an additive. these results suggest that the water absorbance when only copper is integrated is very low compared to the other samples with high water affinity moving from types c to f. types c to f are consisted of aluminium, and types c, d, e are consisting of both copper and aluminium. also, it is noticeable that water affinity slightly increases with the addition of mcc into the beads. however, the affinity reduces when cnf is tallied with copper suggesting strong bonds between copper and cnf as a structure more than hollow spaces with lower bonding percentage. figure 3. ftir plot of control hydrogel beads types h and type i show a high affinity towards water due to their high concentration of chitosan compared to type h with the usual chitosan concentration. in testing the percentage removal of phosphate, calculations were done using a simple titration of acid base. the first set of results was tested after 12 hours, and 5 types of beads had a percentage removal higher than 50% already. then, after 24 hours, the results showed that 13 samples had a removal percentage of 50% and above, but already 7 samples showed more than 60% removal efficiency. at the end of 48 hours, 10 samples recorded a removal efficiency of above 60%. this result shows as shown in figure 4, the experiment was indeed a success in recording more than 10 bead types with the effective removal of phosphate from controlled wastewater samples. discussing further, the bead type a had the bestrecorded removal percentage since the beginning of testing. it had a 66.67% removal percentage after 12 hours, a 73% removal percentage after 48 hours, and successful removal of 80% phosphate at the end of 48 hours (figures 5, figure 6, and figure 7). this can be due to the fact that it has the least amount of copper and no other additives blended, ensuring a strong hydrogel network. the fewer the additives, the better the percentage removal across each bead type from a to i. 4.2 temperature sensitivity as the type a control beads showed the best results in the general titrations, it was used to test the effects of the bead when external stimuli changed. temperature fluctuations were chosen for the matter. the same type of bead was distributed into 9 samples and were placed at three different temperatures. the samples at room temperature showed the highest phosphate removal at the end of 48 hours. p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 32 figure 4. plot of percentage weight of water per bead type figure 5. the plot of percentage removal of phosphate after 12 hrs table 3. percentage removal of phosphate at different temperatures figure 6. the plot of percentage removal of phosphate after 24 hrs figure 7. the plot of percentage removal of phosphate after 48 hrs p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 33 the sample set at a lower temperature did not show any progress toward phosphate removal since the percentage was very poor, somewhere around 6.7%. the samples set at a higher temperature still was able to absorb some amount of phosphate. compared to that of the samples at room temperature, it was less. however, the removal of 66.67% shows good numbers. this shows that the beads lose their anion removal efficiency, which is very noticeable at lower temperatures (table 3). anyhow, a slight increment would not affect the case of anion removal as much as low temperatures. this could be due to the gel's tendency to harden at lower temperatures, limiting the amount of water absorbed. further resulting in lesser adsorption of phosphate. however, the best temperature for anion removal is room temperature. 4.3 batch adsorption study similar to section 4.3, the batch adsorption study utilized the same type of bead, type a control, for the study of the effect of the beads per sample. the results showed good progress when compared to one another. when the no of beads increased the absorption, the cap was reached at 12 hours. when using 10 beads, the sample was only able to recover 66.67% of the total phosphates in the solution. however, as expected, when the number of beads was increased by 5, the absorption percentage was increased to 73% (table 4). as per expectation, the sample with 20 beads was titrated with just 0.3 ml of titrant. this means that it reached the absorption cap of 80% over the time period of 12 hours. table 4. percentage removal of phosphate for batch adsorption studies 5. conclusions this experimental research was a success, considering the fact that 10 bead types had a phosphate removal percentage higher than 60%. from the ftir results, the favorable bonding of chitosan to copper and chitosan to aluminum was observed. also, with the introduction of cellulose matter, the rigidness of the beads increased considerably. however, the enhancers did not show any progress towards the affinity of phosphate anion surpassing the control set of beads. the best bead type at the end of the experiment was identified to be type a control, which successfully eliminated 80% of the phosphate in all samples. the same bead was then tested for temperature sensitivity and batch adsorption studies where at room temperature, the beads still showed an 80% removal rate, at 45 celsius, it had lowered its affinity by almost 13%, dropping the percentage of phosphate removal up to 60.67% at 15 celsius the beads did not show any affinity towards the phosphate anions resulting the percentage of removal to be as low as 6.67. in the batch adsorption studies, the same type of bead showed that the maximum adsorption capacity was 80%, where 10 beads in 12 hours resulted in 66.67% absorbance, 15 beads in 12 hours resulted in 73% absorbance, and 20 beads in 12 hours resulted in 80% absorbance. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] banc c, gautier m, blanc d, lupsea-toader m, marsac r, gourdon r. influence of ph on the release of colloidal and dissolved organic matter from vertical flow constructed wetland surface sludge deposits. chemical engineering journal. 2021 aug 15;418:129353. [2] international environmental technology 2022, ‘how do sulphates get into water?’, envirotech online, environmental, viewed 17 june 2022, <https://www.envirotech-online.com/news/waterwastewater/9/breaking-news/how-do-sulphatesget-into-water/48645>. [3] deyab, m., el-adl, m., ward, f., & omar, e. (2021). trophic status, phytoplankton diversity, and water quality at kafr el-shinawy drinking-water treatment plant, damietta. aqua—water infrastructure, ecosystems and society, 70(3), 342-360. [4] almanassra, i. w., mckay, g., kochkodan, v., atieh, m. a., & al-ansari, t. (2021). a state of the art review on phosphate removal from water by biochars. chemical engineering journal, 409, 128211. [5] ruzhitskaya, o. a., & ponomareva, n. s. (2019). modern biological and biological-chemical methods for removing phosphates from wastewater. systems technologies, (3 (32)), 18-22. [6] silva a., richard c., bessodes m., scherman d., merten o. growth factor delivery approaches in hydrogels. biomacromolecules. 2009;10:9–18. doi: 10.1021/bm801103c.  [google scholar] [7] ruso, j. m., & messina, p. v. (2017). application of natural, semi-synthetic, and synthetic biopolymers used in drug delivery systems design. in biopolymers for medical applications (pp. 46-73). crc press. [8] nele v., wojciechowski j.p., armstrong j.p.k., stevens m.m. tailoring gelation mechanisms for advanced hydrogel applications. adv. funct. p. dias & bm. siddique /future sustainability may 2025| volume 03 | issue 02 | pages 26-34 34 mater. 2020;30:2002759. doi: 10.1002/adfm.202002759.  [9] raghavan s.r., fernandes n.j., cipriano b.h. shapechanging tubular hydrogels. gels. 2018;4:18. doi: 10.3390/gels4010018. [10] macaya d., spector m. injectable hydrogel materials for spinal cord regeneration: a review. biomed. mater. 2012;7:012001. doi: 10.1088/17486041/7/1/012001 [11] van tran, v., park, d., & lee, y. c. (2018). hydrogel applications for adsorption of contaminants in water and wastewater treatment. environmental science and pollution research, 25, 24569-24599. [12] yang, y., wu, n., li, b., liu, w., pan, f., zeng, z., & liu, j. (2022). biomimetic porous mxene sediment-based hydrogel for high-performance and multifunctional electromagnetic interference shielding. acs nano, 16(9), 15042-15052. [13] hu x., ricci s., naranjo s., hill z., gawason p. protein and polysaccharide-based electroactive and conductive materials for biomedical applications. molecules. 2021;26:4499. doi: 10.3390/molecules26154499. [14] mahmood, a., patel, d., hickson, b., desrochers, j., & hu, x. (2022). recent progress in biopolymer-based hydrogel materials for biomedical applications. international journal of molecular sciences, 23(3), 1415. [15] xi, h., li, q., yang, y., zhang, j., guo, f., wang, x., ... & ruan, s. (2021). highly effective removal of phosphate from complex water environment with porous zrbentonite alginate hydrogel beads: facile synthesis and adsorption behavior study. applied clay science, 201, 105919. [16] moharrami, p., hazrati, s., shakeri, f., motamedi, e., & ariaeenejad, s. (2024). sodium alginate-and chitosanbased hydrogels with different network charges for selective removal of cationic and anionic dyes from water. water quality research journal, 59(4), 205222. [17] kluczka, j., dudek, g., pudło, w., kazek-kesik, a., & turczyn, r. (2021). boron removal by sorption on modified chitosan hydrogel beads. materials 2021, 14, 5646. [18] gupta, p. k., raghunath, s. s., prasanna, d. v., venkat, p., shree, v., chithananthan, c., ... & geetha, k. (2019). an update on overview of cellulose, its structure and. cellulose, 59. [19] awang wahab, d. n., m. b. m. siddique, n. khairuddin, j. j. chew, and h. t. su. (2024). mechanical, structural and barrier properties of starch-based film reinforced with cellulose microfibres extracted from midribs of musa saba'. food research, 8 (3),117-123. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 18 article design and develop an iot automated nutrient control in a hydroponic system shim lih ching, tay fei siang*, almon chai, chai pui ching faculty of engineering, computing and science, swinburne university of technology, sarawak campus, kuching, sarawak a r t i c l e i n f o article history: received 10 march 2025 received in revised form 18 april 2025 accepted 30 april 2025 keywords: automated system, nutrient control, iot, bak choy, hydroponics *corresponding author email address: fstay@swinburne.edu.my doi: 10.55670/fpll.fusus.3.3.3 a b s t r a c t hydroponics farming is becoming increasingly popular due to its consistent ability to produce healthier plants in a controlled environment and nutrient solution. however, precise and frequent monitoring of the ph, temperature, and nutrient level is required in traditional hydroponic systems, which makes the labor monitoring process more complex and time-consuming. the aim of this study is to present the prototype of an automated nutrient control system that is applied in nutrient film technique (nft) hydroponic systems. the control system combines different sensors to monitor ph and ec levels continuously with the assistance of an arduino uno r3 microcontroller to process real-time monitoring data to adjust nutrient ratios dynamically. meanwhile, the observation of lighting duration on indoor plant growth was recorded to justify the usage of indoor lighting for growing commercial crops. in this study, we used dwarf bak choy (brassica rapa chinensis) to evaluate the effects of various nutrient solution concentrations and lighting on plant growth. 1. introduction hydroponic farming is becoming more popular in farming industries, and it is commonly integrated with sensors for remote monitoring of important nutrient solution parameters, such as ph and ec, which are critical for the growth of the targeted crop. this project aims to develop an automated nutrient control system to eliminate the need for labor-intensive manual intervention and provide long-term solutions to manage these variables in an nft hydroponic system. by addressing the limitations of traditional hydroponics farming during the farmer's manual operations, such as managing large plant populations, nutritional inputs, and controlling nft hydroponic environmental parameters. the proposed iot device collects sensor data and transfers it to a cloud server for analysis and storage. the growing parameters of dwarf bak choy (brassica rapa chinensis) will be used to verify the effectiveness of the proposed automated control system. the proposed approach aims to enhance the growing efficiency and reliability of the bak choy by observing the adjusted environmental and nutrition data. compared with traditional soil farming, hydroponic farming has mitigated challenges of conventional farming, such as soil fertility and climate dependencies. however, it still faces issues in controlling precise ph and nutrient concentrations for promoting plant growth. two common issues related to nutrient concentrations in hydroponic farming are insufficient nutrients and excessive concentrations. insufficient nutrients can hinder the growth of the plant, in which targeted plant parts such as flowers, the plant body, or roots will not grow in time as expected. in contrast, excessive concentrations might induce stress and toxicity to plant growth, which is applied to sensitive crops such as tomatoes, spinach, wasabi, cucumbers, and lettuce [1]. from the result observations in ref [2], for specific tomato species such as rapsodie, moderate increased conductivity increased the maximum photosynthetic rate during the vegetative stage compared with low and high ec treatment. from the study conducted in ref [3], the article found that excessive alkalinity can elevate substrate ph and reduce micronutrient availability to plants. the deployed automating systems for monitoring nutrient concentrations, ph levels, and water regulation offer significant benefits to growers, saving time and effort while providing accurate data during plant growth. the proposed automation enhances hydroponic systems by overcoming the disadvantages of manual nutrient management, thereby contributing to the cultivation of healthier crops. for many developing countries, an effective agricultural system is crucial for their economies to ensure targeted yield productivity. the traditional soil farming methods often require extensive resources such as land, water, and fertilizers, which lead to soil depletion and environmental challenges. food production needs to double future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.3.3 august 2025| volume 03 | issue 03 | pages 18-25 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:fstay@swinburne.edu.my https://doi.org/10.55670/fpll.fusus.3.3.3 https://fupubco.com/fusus sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 19 to meet the high demand from the increasing growth of the global population [4]. this necessitates exploring resilient food production solutions, especially amidst increasing climate instability. hydroponics farming offers a promising solution to these challenges, minimizing land and water usage while maintaining high yields compared to traditional soil farming. from the recent trend, governments are increasingly adopting hydroponic farming in urban areas to enhance food accessibility. for example, singapore has transformed flat house residential and commercial building rooftops into sky farms, which leverage advanced hydroponic farming technologies to strengthen local food production. among hydroponic methods such as wick system, deep water culture, and ebb & flow, nutrient film technique (nft) stands out for its efficiency and common implementation. in nft, a continuous circulated flow of shallow and oxygen-rich nutrient solution across the roots supports the growth of plants on racks. however, due to the cycling flow of the nutrient solution, monitoring and controlling water temperature, oxygen contents, ph levels, and ec become crucial for optimizing plant growth. adjusting nutrient concentrations and ph levels can ensure targeted crops receive adequate nutrition, with verification of the ec sensors, which can indicate nutrient concentration levels necessary for plant health. this experimental methodology can help to propose appropriate adjustments for optimizing hydroponic yields and sustainability. deep knowledge of plant nutrition is crucial to justify the ratio of nutrients and lighting duration for effective automated system implementation. meanwhile, integrating sensor technology for farming automation will help establish a proper system for analyzing crop-specific needs and environmental impacts. this project aims to provide insight into environmental impacts for plant growth by utilizing a proposed iot monitoring system and developing an automated control system for controlling lighting and nutrient distribution. deploying the automation prototype addresses the challenges of implementing precise nutrient management. the system will ensure controllable nutrient distribution during nft hydroponics, which helps to fill current knowledge gaps and offer practical solutions to farmers, empowering them with valuable technological tools and insights. 2. background literature researchers have made significant contributions to automation in hydroponics, particularly through adopting iot technologies aimed at enhancing productivity, sustainability, and crop yields. iot systems facilitate precise monitoring and regulation of critical environmental factors such as ph levels, fertilizer concentrations, humidity, and temperature in hydroponic setups. this capability enables more consistent control overgrowth conditions, potentially boosting crop yields while reducing labor demands. several studies have explored the integration of iot in hydroponic systems to optimize plant growth efficiency. for instance, mapari [5] developed a vertical hydroponic farming system utilizing iot for automated irrigation and real-time ph, tds, temperature, and humidity monitoring. the system, controlled by a node mcu microcontroller, transmits sensor data to a server and a mobile app via wi-fi. it notifies users of anomalies via email, showcasing its novel feature of automated irrigation management and remote monitoring capabilities. similarly, asawari et al. [6] proposed an automated hydroponic system leveraging iot to collect real-time temperature, humidity, and ph data for optimal basil plant growth. their atmega2560 microcontroller-based system demonstrated a significant 58% increase in plant growth height over a 10-day period compared to traditional outdoor cultivation. in another approach, sisyanyo et al. explored hydroponic smart farming using a cyber-physical-social system integrated with telegram messenger [7]. their raspberry pi-based system monitored parameters like light intensity, room temperature, humidity, ph, nutrient temperature, and ec in real-time, enabling farmers to access instantaneous updates on plant conditions. in summary, these studies highlight the recent trend of iot implementation for advancing hydroponic farming, adapting in practical usage through enhanced automation, real-time monitoring, and improvement of agricultural outcomes. in ref [8], the author suggested that the integration of iot with the automated hydroponic systems offers numerous advantages and poses certain limitations, such as the setup cost, which can be unaffordable for small-scale farming, and reliable internet connections are needed to ensure proper monitoring and control in place. in addition, the integration of traditional farming with technology will cause more technological dependencies, which increase vulnerability to technical failures and potentially affect crop yields. specialized knowledge and training may pose challenges for some users in system operation and maintenance. moreover, indoor hydroponic farming demands significant energy resources for 24-hour operation, which could be restricted in areas with limited or costly energy supplies. sisyanto et al. [7] mentioned several limitations of iot hydroponic farming, including the accuracy of nutrient monitoring, which could be potentially compromised due to the installation of multiple sensors for nutrient monitoring. the fault of the ph or ec sensors could affect crop growth. additionally, the monthly subscribed internet connection requirement for iot systems could be impractical or costly in certain regions or applications for continuous monitoring purposes. the study doesn’t integrate output relays for electronics devices like humidifiers to regulate moisture levels. it excludes camera modules for visual plant growth monitoring, which could offer valuable insights into plant growth monitoring. the ec sensor measurement is crucial in hydroponics implementation, as it indicates the concentration of electrolytes in nutrient solutions [9]. these solutions, typically divided into a and b formulations, contain essential macronutrients and micronutrients necessary for plant growth. maintaining optimal nutrient levels is crucial; insufficient nutrients can lead to plant diseases, while excessive levels can foster algae and bacterial growth detrimental to plants [10]. ding et al. conducted studies on bak choy, determining that an ec range of 1.8 to 2.4 in greenhouse conditions resulted in higher photosynthesis rates, productivity, and superior yield compared to other treatments [9]. the ph levels in hydroponic systems, affecting hydrogen ion concentrations, are adjustable using specific chemicals like phosphoric acid for lowering ph and potassium bicarbonate for raising it [11]. optimal ph typically falls sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 20 within the range of 5.5 to 6.5, as highlighted in various studies [12]. maintaining a slightly acidic ph is preferred to prevent the precipitation of essential nutrients like fe, mn, ca, and mg, which occurs at higher ph levels [13]. higher ph levels also reduce the availability of potassium (k) and phosphorus (p) in nutrient solutions. light, consisting of seven different colors, profoundly influences plant growth along with water, air, space, and nutrients. kui et al. emphasize the roles of red and blue light in promoting callus production, assimilate movement, biomass accumulation, phototropism regulation, chloroplast migration, stomatal opening, leaf expansion, and photosynthetic protection [14]. their research demonstrated that lettuce illuminated with rgb (6:2:2) led light at 150 μmol.m−2·s−1 ppfd produced healthier, higher-quality yields compared to plants under singular or mixed blue and redlight conditions. similar studies by li et al. [15] corroborated these findings. additionally, mickens et al. studied red bak choy growth under various led lighting ratios [16], concluding that a 3:1 ratio of red to blue leds yielded the highest biomass and nutrient content over 28 days of growth. 3. methodology the prototype's design involves two key aspects: hardware and software. the hardware design involves installing the nft hydroponic system and selecting appropriate electrical components. on the other hand, the software design focuses on developing an arduino code algorithm to enable automated control of the system. both aspects are critical in ensuring the project's successful implementation and operation. the nft hydroponic system is designed with three shelves, each featuring four rectangular pvc pipes dedicated to plant cultivation. each pvc pipe is equipped with five precisely cut planting holes, totaling 20 holes per shelf and 60 across the entire system. the dimensions of the rack measure 1.83 meters in length, 92.5 cm in width, and 92.5 cm in height. to ensure optimal root oxygenation, the planting holes are precisely 42mm in diameter, accommodating net pots that suspend the upper roots above the nutrient solution. the proposed design promotes efficient nutrient uptake and oxygen absorption from the surrounding air, which is crucial for plant growth. for artificial indoor lighting, 14w led tube lights were installed, emitting red, blue, and white light in a ratio of 3:2:1, which enhances photosynthesis and supports robust plant development by referring to the approach in [17]. the proposed hydroponic system shown in figure 1 includes three separate 20-liter water reservoir tanks, one for each shelf level, allowing separate nutrient solution management and experimentation with different growing conditions. each reservoir is equipped with a motor pump to deliver mixed nutrient water to the targeted plants on shelves. additionally, air pumps with air stones in each reservoir were installed to enhance oxygen content within the nutrient solution, promoting plant yield and health. the wellintegrated sensor module for the nft hydroponic system includes several essential parts. the integrated system included ph sensors, which measure solution acidity or alkalinity based on potential differences detected by the ph meter probe, with proper room temperature control ensuring precise readings. figure 1. front and back views of the nft hydroponic setup moreover, an ec sensor supports arduino integration, measuring the nutrition concentration in the flowing nutrient solution. to monitor reservoir water temperature, we deployed the ds18b20 water temperature sensor, known for its waterproof design and high accuracy (±0.5⁰c). these sensors can be embedded into an arduino mega, and the microcontroller will act as the central processing unit to receive data and control nutrient distribution. for iot monitoring, data visualization, and management, thingspeak was utilized as a cloud platform that enables real-time streaming, data storage, and visualization of sensor data. this solution offers robust integration with arduino for monitoring hydroponic parameters remotely. the integrated arduino mega system consists of an esp8266 wi-fi module, which can provide internet connectivity to support iot applications. the actuator module will control electronics components such as a relay for triggering pumps to adjust the nutrient solution ratio in reservoirs. meanwhile, the ec levels can be managed with common nutrient solutions a and b from lotus farm agritech. the three-level nft hydroponic rack was equipped with 14w led lights, as mentioned earlier. the experiment was conducted in controlled environmental conditions with air conditioning to test the growth responses of bak choy under different lighting durations and nutrition ratio setups. the proposed setup method offers various advantages, including real-time remote monitoring via sensors, streamlined data management with thingspeak, and precise control through the actuator module. however, due to the centralized hvac, environmental temperature control is limited. the proposed experiment will evaluate sensor accuracy, iot integration, standardized experimental conditions, and the impact of the environmental conditions on plant growth. the proposed control system in figure 2 is designed to align with its objective of enhancing plant growth through iot monitoring and controlling key parameters in the nutrient solution. multiple sensors, such as water flow rate, ec, temperature, humidity, and ph, are integrated into the embedded electronic system. these sensors were attached to an arduino mega controller, which enables real-time monitoring and control. dht11 was installed to capture room temperature and humidity, yf-s201 is used to measure the water flow rate, and ds18b20 waterproof probes were used to measure the water temperature. sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 21 figure 2. block diagram of an automated system this environmental data is crucial for monitoring environmental conditions during plant growth. the data collected from these sensors will be uploaded to the online server via thingspeak for data aggregation, visualization, and analysis across six dedicated channels for different lighting and nutrient mix growing monitoring purposes. a part of the approach of monitoring and regulating the nutrient solution will be controlling ph levels in the nutrient solution to maintain between 5.5 and 6.5, which is recommended in ref [12]. the system will trigger a ph down dozer pump using 30% concentrated phosphoric acid to lower the nutrient solution ph back into the optimal range if the ph level exceeds 6.5. this approach controls precise ph control for nutrient availability and plant health. the analog ec sensor is employed to monitor the concentration of electrolytes in the nutrient solution for assessing nutrient concentrations. the proposed automated system manages three water reservoir tanks, which are tested for optimal ec values through controlled mixed a and b solutions as needed. water temperature fluctuations will impact ph and ec values. therefore, the water temperature will be monitored and calibrated using data from the ds19b20 temperature probe every three days, following the manufacturer's guidelines for better ph and ec measurement accuracy. due to the laboratory sensors being adopted for the automated system implementation, the system requires adjustment to address sensor immersion limitations and ensure the reliability of ongoing operation. the calibration routines were set to ensure the sensor system can maintain accurate parameter readings, which ensure the targeted commitment to optimizing hydroponic conditions for robust plant growth and health. as part of the system design, the automated system will regulate light duration parameters within the preexperimental setup, as shown in figure 3. the arduino mega microcontroller is functioning as the principal controller to facilitate precise time management for controlling led tube lights based on the predetermined timer settings. for time duration monitoring, the system employs a ds3231 rtc time stamping module, which will help to enable the activation and deactivation of a 5v relay responsible for managing the lighting system’s operation. in addition, the rtc module will display the current time on an lcd interface connected to the arduino mega. this feature will provide real-time feedback to users and ensure that lighting schedules are maintained accurately according to the specified setup. with the integration of these components, the automated system can improve the efficiency of light regulation in the hydroponic system, which can consistently support the optimal growth and verification of various lighting durations. there are several experimental setups that were conducted to compare and verify the performance of different hydroponic systems, which mainly focus on plant growth index parameters such as height and number of leaves over the growth period. the experiments used seeds of the dwarf bak choy (brassica rapa chinensis) cultivar, germinated uniformly under controlled conditions for 10 days. afterward, 36 seedlings with consistently sized initial leaves were carefully chosen and transplanted into the setup. figure 3. circuit diagram of a light control system the hydroponic system consisted of three shelves and was divided into six sections as shown in figure 4, with two sections per shelf separated by a cardboard divider. each section accommodated six sets of dwarf bak choy plants. the left side of the shelves was exposed to a 12-hour light cycle with alternating 4-hour light and 4-hour dark periods, while the right side experienced continuous 24-hour lighting. all plants were subjected to identical environmental conditions within the same growth room. from day 7 to day 25 of the experiment, leaf number and plant height measurements were taken every three days. figure 5 shows that three different treatments were applied to the racks: i) level 1 rack underwent an ec of 0.8 ms/cm for the first eight days, followed by 1.7 ms/cm for the subsequent 18 days. ii) level 2 rack maintained a constant ec of 1.6 ms/cm throughout the 25-day experiment. iii) level 3 rack started with an initial ec of 2.1 ms/cm for the first eight days, followed by 1.1 ms/cm for the remaining 18 days. on the 8th day of observation, adjustments were made to the water reservoirs of the level 3 rack to address a sudden drop in ec value. water pumps operated continuously, and ph levels were maintained within the range of ph 5.5 – 6.5 throughout the experiment. all data were collected concurrently to ensure consistency and comparability across different growth conditions. sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 22 figure 4. three-level rack divided into six sections for each group of dwarf bak choy figure 5. nft hydroponic setup 4. results and discussion the growth of dwarf bak choy was thoroughly assessed using plant height and leaf count as key parameters, with significant differences observed across different lighting settings. on the level 1 rack, plants subjected to 12-hour led lighting showed average heights ranging from 1.46 cm to 2.48 cm over 25 days, while those under 24-hour lighting exhibited growth ranging from 3.23 cm to 5.4 cm. similarly, on the level 2 rack, plants under 12-hour lighting grew from 1.54 cm to 3.12 cm, whereas those under 24-hour lighting grew from 4.37 cm to 8.23 cm. at level 3, plants under 12-hour lighting grew from 1.34 cm to 3.02 cm, compared to 4.25 cm to 6.68 cm under 24-hour lighting. leaf count variations were minor initially but became significant from day 16 onwards, with plants under 24-hour lighting generally showing greater leaf production by day 25. specifically, plants on 24-hour lighting had an average leaf count of 10 to 12 across all levels, while those under 12-hour lighting averaged 7 to 9 leaves as shown in figure 6. the automated control system effectively managed ph and ec values throughout the experiment, as depicted in figure 7. each rack maintained different ec levels: level 1 started at 0.8 ms/cm for eight days, then increased to 1.7 ms/cm; level 2 maintained a steady 1.6 ms/cm; and level 3 began at 2.1 ms/cm for eight days, then reduced to 1.1 ms/cm. the system generally maintained ec within the specified range, although occasional ph drops below 5.5 indicated overuse of the ph down doser solution. to address this, adjustments in dosing frequency are recommended, possibly incorporating a ph up solution for more balanced ph management. overall, while demonstrating effective regulation of nutrient solution parameters, the system requires fine-tuning to optimize ph control and ensure consistent performance across varied experimental conditions. when comparing the findings of this study to other relevant research in automated control systems for nutrient distribution in hydroponics, it becomes evident that the proposed system demonstrates promising results. in a study by prasetia et al. [18] focusing on iot-based grow light automation, they found that dwarf bak choy grown under led lights showed superior performance in terms of fresh weight, number of leaves, and plant height compared to those grown under sunlight. especially on the 30th day, the result showed the improvement of plant growth, which under led lights averaged 23.6 grams, 11.2 leaves, and 18.1 cm in height, compared to that under sunlight, which averaged 20.2 grams, 9.3 leaves, and 17.1cm. from experimental observation, this underscores the positive impact of an automated hydroponic system on plant growth and its productivity through the controlled environment. the result agreed with the led illumination and iot technology with zigbee in ref [19], which explored a smart hydroponic system implementation. the article's findings discovered improvements over traditional farming methods with a 17.2% increase in leaf yield, 29.85% taller plants, and 14.55% higher in terms of produced weight, which means that harvesting can be earlier by two weeks compared to conventional farming. the outcomes showed that the duration of led lighting can promote plant growth, yield, and efficiency in agriculture. the data collected from the present study aligns with the findings from previous studies, which demonstrate significant differences in plant height and leaf count across different lighting duration settings. moreover, the automated system effectively maintained ph and ec within optimal ranges, which offers optimized growth conditions. with the controlled environment and nutrient management, the automated system not only supports increased yields but also promotes sustainable resource use. for different nutrient settings, the result showed that there is no significant difference between growth in level 1,2, and 3 racks with controlled ec settings. sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 23 figure 6. graphical analysis of plant height and number of leaves of different growth conditions from dap (day after planting) 7 to 25 figure 7. records of ph and ec readings from dap 1 to 25 for three different levels sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 24 it is observed that a high nutrient setting at the beginning of the growth stage will promote the growth of the bak choy, as shown in figure 6, with levels 2 and 3 racks set to have more nutrients mixed in the nft system compared to the level 1 rack. results observed from the level 3 rack showed that high conductivity values in nutrient solutions do not promote significant plant growth. the result agrees with the observation in [2], in which moderate ec treatment increased the conductivity, which in turn increased the maximum photosynthetic rate compared to high and low ec treatments. from the experimental result, this study contributes compelling evidence for the effectiveness of automated control systems in hydroponic farming. with the integration of iot systems and sensor monitoring, the proposed prototype offers pathways to enhance agricultural productivity and sustainability. the findings underscore the potential for future improvements in hydroponics practices for different target crops, which emphasizes the role of technology in driving agricultural innovation and addressing sustainable development goals regarding food security issues. several technological aspects were previously developed by the authors to monitor the growth rate of the plants and their relevant parameters [2023]. 5. conclusions this paper demonstrated the impact of the different lightning settings on the bak choy growth through an automated iot control system for nutrient and ph control in nft hydroponic systems. the findings indicated that plants exposed to 24 hours of lighting showed a significant increase in plant growth indices, such as height and leaves, compared to those under 12 hours of lighting duration, with variations in nutrition distributed across different rack levels. the automated system successfully maintained the ph and ec levels within the suggested ranges through minor fluctuations in ph, which emphasized the need for fine-tuning in dosing adjustments or earlier predictions in the ph rising trend. the experimental results aligned with the previous studies, which support the moderate increase of ec value and will help promote higher plant yields, improved growth rates, and efficient resource utilization. with the integration of iot monitoring and control, the study suggests the potential of automation implementation in enhancing hydroponic farming approaches in terms of efficiency. the future work of this project should focus on refining ph stability, optimizing nutrient dosing strategies, and expanding the automated system's adaptability to diverse targeted plants. in the past, the team had developed various technological solutions for supporting and monitoring plant growth. eventually, these automation implementations contribute to sustainable agricultural practices, supporting the sustainable development goals and innovation in smart farming technologies. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] m. sakamoto and t. suzuki, "effect of nutrient solution concentration on the growth of hydroponic sweetpotato," agronomy, vol. 10, no. 11, p. 1708, 2020. 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[7] r. sisyanto, s. suhardi, and n. b. kurniawan, "hydroponic smart farming using cyber physical abbreviations dht22 temperature & humidity sensor ds18b20 water temperature sensor ec electrical conductivity havc heating, ventilation, and air conditioning iot internet of things lcd liquid crystal display led light-emitting diode mcu micro-controller unit nft nutrient film technique ph potential of hydrogen pvc polyvinyl chloride tds total dissolved solids ppm parts per million ppfd photosynthetic photon flux density rtc real-time clock sl. ching et al. /future sustainability august 2025| volume 03 | issue 03 | pages 18-25 25 social system with telegram messenger," in 2017 international conference on information technology systems and innovation (icitsi), 2017, pp. 239-245. doi: https://doi.org/10.1109/icitsi.2017.8267950. 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[online]. available: https://www.dpi.nsw.gov.au/__data/assets/pdf_file/ 0007/385576/leafy-asian-veg-final-low-res.pdf. [12] f. c. gomez-merino and l. i. trejo-tellez, "nutrient solution for hydroponic systems," in hydroponics: a standard methodology for plant biological researches, rijeka: intech, 2012. doi: https://doi.org/10.5772/37578. [13] h. singh, b. dunn, m. payton, "hydroponic ph modifiers affect plant growth and nutrient content in leafy greens," journal of horticultural research, vol. 27, no. 1, pp. 31-40, 2019. doi: https://doi.org/10.2478/johr-2019-0004. [14] l. kui, h. zhi, y. yong, "influence of light quality and intensity on biomass and biochemical contents of hydroponically grown lettuce," hortscience, vol. 53, no. 8, pp. 1157-1163, 2018. doi: https://doi.org/10.21273/hortsci.53.8.1157. 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[18] y. prasetia, a. g. putrada, and a. rakhmatsyah, "evaluation of iot-based grow light automation on hydroponic plant growth," *jurnal ilmiah teknik elektro komputer dan informatika, vol. 7, p. 314, 2021. doi: https://doi.org/10.26555/jiteki.v7i2.21424. [19] p. bugayong, j. casalla, j. lopez, and m. c. pacis, "smart hydroponic system with hybrid switching mechanism, led illumination, and iot using zigbee technology," in 2022 ieee 14th international conference on humanoid, nanotechnology, information technology, communication and control, environment, and management (hnicem), pp. 1-6, 2022. [20] g. w. michael, f. s. tay, and y. l. then, "development of automated monitoring system for hydroponics vertical farming," journal of physics: conference series, vol. 1844, no. 1, p. 012024, mar. 2021, doi: 10.1088/1742-6596/1844/1/012024. [21] f. tay, s. b. a. kashem, and w. c. y. seng, "automated miniature greenhouse," adv. sci. lett., vol. 23, no. 6, pp. 5309–5313, jun. 2017, doi: 10.1166/asl.2017.7365. [22] m. a. z. m. rafique, f. s. tay, and y. l. then, "design and development of smart irrigation and water management system for conventional farming," journal of physics: conference series, vol. 1844, no. 1, p. 012009, 2021, doi: 10.1088/17426596/1844/1/012009. [23] j. e. j. fong, f. s. tay, and y. l. then, "vision-based monitoring (vbm) for plant quality and control system," advanced science letters, vol. 23, no. 6, pp. 5309–5313, jun. 2017, doi: 10.1166/asl.2017.7365. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://doi.org/10.1088/1755-1315/166/1/012025 https://doi.org/10.1088/1755-1315/166/1/012025 https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 37 article research on safety risk assessment of polyimide foam production line based on ahp-fce method ripeng gao1, liang jiang2, yiting li2, xinuo fang2, xiaohong gui2* 1aerospace research institute of materials & processing technology, beijing, beijing 100076, china 2china university of mining and technology, beijing, beijing 100083, china a r t i c l e i n f o article history: received 19 september 2025 received in revised form 10 november 2025 accepted 01 december 2025 keywords: polyimide foam, safety risk assessment, analytic hierarchy process, fuzzy comprehensive evaluation, index system, risk management *corresponding author email address: gxhbox@sina.com doi: 10.55670/fpll.fusus.4.1.4 a b s t r a c t polyimide foam, as a high-performance sandwich composite material, is widely used in high-tech manufacturing industries such as aviation and aerospace. nevertheless, its production process involves numerous hazardous chemicals and sophisticated machinery, which is extremely hazardous to the system itself. today, the overall assessment tools for multidimensional safety risks on the production line are unsatisfactory. to address this, this paper developed a safety risk assessment system comprising five dimensions: equipment, materials, personnel, environment, and management. the study applied the analytic hierarchy process (ahp) to calculate indicator weights and the fuzzy comprehensive evaluation method (fce) to assess safety risk in a polyimide foam line. the results show that the overall risk level of this production line is relatively high, and the main sources of risk are equipment factors and processmaterial factors. simultaneously, personnel and safety management factors should also be considered. based on the evaluation findings, specific risk control measures are offered, with both theoretical background and methodological underpinning for the safety design and operational management of polyimide foam production lines. 1. introduction polyimide foam material possesses extensive opportunities of application in aviation, aerospace, and other high-end equipment manufacturing industries because it has excellent high-temperature resistance, light weight, high strength, and good chemical stability [1-4]. as highperformance sandwich composites are in demand for model products, the industrialization of polyimide foam is advancing rapidly [5,6]. nevertheless, its manufacturing process requires numerous hazardous chemicals and equipment, including flammable solvents (tetrahydrofuran and methanol) and hazardous processes (high-temperature, highpressure foaming, microwave radiation, and dust crushing). this puts the production line at several safety risks during operation, such as fire, explosions, poisoning, and mechanical injuries. currently, studies on polyimide foam materials are conducted at both the local and international levels, with the main emphasis on maximizing performance and expanding applications [7-10]. on the contrary, studies on assessing system safety risks and control measures in the production process are lacking. the possible deficiency of systematic evaluation techniques and technical assistance in the overall assessment of safety risks across the entire process and its many dimensions is particularly relevant to realizing largescale industrialization at the domestic level. current safety evaluation systems are not without problems, such as the use of incomplete indicators, subjective weighting distributions, vague evaluation outcomes in the application to production systems with complex process characteristics, and numerous risk couplings. in a bid to overcome this, this study aims to discuss the construction of a polyimide foam production line. by incorporating relevant technical documentation, we created a safety risk assessment framework comprising five dimensions: equipment, materials, personnel, environment, and management. the weights of all risk factors were decided using the analytic hierarchy process (ahp). simultaneously, the fuzzy comprehensive evaluation method (fce) was applied to address uncertainties and indeterminate information during the evaluation process, yielding a similar quantitative analysis of the production line's safety risks. this study will provide scientific foundations and risk management methods for safety in polyimide foam production lines and, thereby, contribute to the safe, controlled industrial development of these high-risk process lines. future sustainability open access journal https://doi.org/10.55670/fpll.fusus.4.1.4 february 2026| volume 04 | issue 01 | pages 37-44 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:gxhbox@sina.com%20 https://doi.org/10.55670/fpll.fusus.4.1.4 https://fupubco.com/fusus ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 38 2. research methods to systematically and scientifically evaluate safety risks in polyimide manufacturing lines, this study uses a complex assessment tool combining qualitative and quantitative evaluation. specifically, the analytic hierarchy process (ahp) is initially used to create an evaluation index for safety risks and to compute the weights of each indicator, reflecting the relative significance of various factors in the comprehensive risk. based on this, the fuzzy comprehensive evaluation (fce) technique is presented to address the inherent twosidedness and uncertainty in safety risk assessment and to convert the expert's experience and judgment into quantitative assessment outcomes. the combined use of ahp and fce can not only ensure the scientific validity and consistency of indicator weights but also provide an opportunity to conduct a thorough quantitative assessment of complex risk factors and to support the methodological support for further risk analysis and decision-making [11]. 2.1 hierarchy analysis method the analytic hierarchy process (ahp) is a multi-criteria decision-making technique that uses both quantitative and qualitative methods to compare the relative significance of elements, assign weights at various levels, and rank and select the best alternative [12,13]. this method was proposed by the american operations researcher, t. l. saaty. it has found extensive application across most fields and has been demonstrated to be effective and universal in making complex decisions [14]. the steps for implementing the ahp analysis method are shown in figure 1. figure 1. steps in the analytic hierarchy process (ahp) analysis it is possible to divide the ahp weighting process into four steps: (1) build a hierarchical organization: compare the relationships between the elements of evaluation to create a hierarchical system. based on a precise grasp of the essence of the problem, clarify the decision-making objectives, decompose the problem into different levels, and determine the target level, criterion level, and solution level. (2) constructing the judgment matrix: using the 1-9 proportional scale [15] as shown in table 1, pairwise comparisons are conducted between elements within the same level, with appropriate scale values selected based on their relative importance. judgment matrices are then constructed for each criterion level according to the pairwise comparison results. (3) determine the maximum eigenvalue λmax and its corresponding eigenvector ω of the judgment matrix. (4) consistency check. calculate the consistency index ci as shown in equation (1). 𝐶𝐼 = 𝜆𝑚𝑎𝑥−𝑛 𝑛−1 (1) here, λmax denotes the maximum eigenvalue of the judgment matrix, while n represents the matrix's order. the consistency index (ci) measures the internal consistency of the matrix. then calculate the random consistency ratio (cr) as shown in equation (2). 𝐶𝑅 = 𝐶𝐼 𝑅𝐼 (2) relative importance (ri) represents the average random consistency index of the judgment matrix at the corresponding order. the consistency ratio (cr), typically set at 0.1, is used to assess whether the matrix demonstrates acceptable consistency. the cr < 0.1 implies that the matrix satisfies the consistency requirements. when this happens, the eigenvector ω, which is the eigenvalue of the largest eigenvalue λmax, is scaled to get the evaluation index weights. on the other hand, when cr is greater than 0.1, it indicates high levels of inconsistency in the judgment matrix, requiring that the pairwise comparisons be re-examined and tweaked iteratively until a tolerable level of consistency is attained. table 1. meaning of the 1-9 scale 2.2 fuzzy comprehensive evaluation method the fuzzy comprehensive evaluation method (fce) is a quantitative measurement based on fuzzy mathematics. it is practical in nature, as it applies the principle of fuzzy relation synthesis to measure factors whose boundaries in the system are unclear, thereby providing a complete evaluation [16,17]. the basic steps of the fuzzy comprehensive evaluation method are as follows: scale definition 1 the i factor is as important as the j factor. 3 the i factor is slightly more important than the j factor. 5 the i factor is more important than the j factor 7 the i factor is significantly more important than the j factor. 9 the i factor is absolutely more important than the j factor. 2，4，6，8 the comparison result between the i and j factors falls within the median of the adjacent judgments listed above. count backwards compare factor j with factor i to obtain the judgment value 𝑎𝑗𝑖 = 1/𝑎𝑖𝑗 . ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 39 (1) determine the set of evaluation factors: identify all evaluation factors for the subject. assuming n factors influencing safety assessment, the critical factors set is obtained: 𝑈 =（𝑢1, 𝑢2, . . . 𝑢𝑛） (3) (2) determine the evaluation level set: set evaluation levels, typically divided into multiple categories such as severe, relatively severe, moderate, relatively weak, and no impact. these evaluation levels form a set: 𝑉 =（𝑣1, 𝑣2, . . . 𝑣𝑛） (4) (3) determine the weight set: in fuzzy evaluation of various factors, the determination of weight is the key to evaluation. according to the importance of evaluation factors, the weight of evaluation indicators is determined to form a weight set: 𝐴 =（𝑎1, 𝑎2, . . . 𝑎𝑛） (5) the value ∑ 𝑎𝑖 𝑛 𝑖=1 𝑎𝑖𝑢𝑖 of 1 represents the weight of the evaluation factor, which can be determined through the analytic hierarchy process (ahp). (4) establish the fuzzy relation matrix r: the membership degree reflects the extent to which an evaluated object belongs 𝑟𝑖𝑗𝑢𝑖𝑣𝑖to a specific evaluation level under a given factor, denoted as, where represents the membership degree of the factor in the level. all factor membership degrees collectively form a fuzzy evaluation matrix: 𝑅 = [ 𝑟11 𝑟12 𝑟21 𝑟22 ⋯ ⋯ 𝑟1𝑛 𝑟2𝑛 ⋮ ⋮ ⋱ ⋮ 𝑟𝑚1 𝑟𝑚2 ⋯ 𝑟𝑚𝑛 ] (6) (5) fuzzy comprehensive evaluation: the fuzzy comprehensive evaluation result b is: 𝐵 = 𝐴𝑅 = (𝑎1, 𝑎2, . . . 𝑎𝑚) [ 𝑟11 𝑟12 𝑟21 𝑟22 ⋯ ⋯ 𝑟1𝑛 𝑟2𝑛 ⋮ ⋮ ⋱ ⋮ 𝑟𝑚1 𝑟𝑚2 ⋯ 𝑟𝑚𝑛 ] = (𝑏1, 𝑏2, . . . 𝑏𝑚） (7) here, b denotes the membership vector, with bi representing the membership degree of the comprehensive evaluation result in the i-th evaluation level. (6) processing of evaluation results: based on the fuzzy comprehensive operation result b, the final rating of the evaluated object can be determined using either the maximum membership principle or the weighted average method. the maximum membership principle selects the highest corresponding rating in bi as the evaluation result, while the weighted average method calculates the weighted average of all evaluation ratings to obtain the final result. in practice, the ahp and fce methods can be implemented effectively using specialized software tools for efficient, accurate computation and analysis. the implementation platform of this study was yaahp software. first, we prepared a survey questionnaire based on the hierarchical structure of the ahp, in which we invited experts to make pairwise comparisons and score indicators at each level. after collecting the data from the questionnaires, the data were processed in yaahp to obtain judgment matrices, calculate indicator weights, and test consistency. based on this, we have integrated the software's fuzzy overall analysis capability. to determine the final assessment results, we multiplied the experts' scores for subordinate factors by the weights derived using ahp. all calculations of weight and the total fce evaluation process went along smoothly with the assistance of yaahp. such an approach was not only the most effective in enhancing research efficiency and standardization but also in rendering risk assessment results scientifically valid and reliable. 3. construction of the safety evaluation index system science and a rational risk assessment system are the basis of accurate safety risk analysis. to make the assessment results effectively and impartially illustrate the safety situation in the production lines of polyimide foams, this study systematically analyzed the production process, the properties of hazardous substances, and the types of accidents that may occur in the manufacturing lines. our analysis of project documentation and related literature enabled us to develop a multi-level, multi-dimensional system of safety risk evaluation indices. 3.1 basis and principles of indicator system construction to develop a comprehensive and precise evaluation index system for safety risks in polyimide foam production line, it must be grounded in solid theoretical foundations and clear design principles [18]. this study, after comprehensively examining domestic and international chemical process safety standards (e.g., gb 45673-2025) and the characteristics of polymer material synthesis processes, established the following four core principles to guide the scientific construction of the index system: (1) systematic principle: the index system should be able to comprehensively cover the key safety dimensions, such as "people-machine-material-method-environment", ensure that the factors are relatively independent and have internal logical connections, and constitute a hierarchical and complete organic whole, to avoid the omission or repeated evaluation of important risk sources. (2) scientific principle: the selection, definition, and hierarchical attribution of each indicator must have a solid theoretical basis (such as accident causation theory, system engineering principles) or come from the clear support of industry standards and technical specifications, to ensure that it can accurately and objectively reflect the essence and impact path of a specific risk. (3) operability principle: indicators must be observable, measurable, and comparable. the required data for evaluation should be obtained through feasible methods, such as on-site inspections, reviewing equipment operation records, querying safety management archives, and expert on-site assessments, to ensure the evaluation work can be effectively implemented. (4) the principle of dynamism and orientation: the index system is not only used for static risk status assessment, but also should pay attention to the dynamic process of risk management, guide enterprises to pay attention to the continuous improvement of safety management, and provide directional guidance for future risk early warning and prevention and control priorities. 3.2 construction of safety evaluation index system first, by systematically reviewing domestic and international literature on chemical process safety and polymer production process safety, we identified common risk factors, including equipment reliability, hazardous ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 40 chemical management, and personnel safety behavior [1922]. secondly, we conducted an in-depth analysis of safety design documents, operating procedures, and safety management regulations related to polyimide foam production lines. this enabled us to identify specific risk points unique to polyimide foam manufacturing, including radiation control in microwave foaming processes, fire/explosion risks associated with solvents like tetrahydrofuran, and interlock controls during high-pressure vulcanization. building on this foundation, we applied the analytic hierarchy process (ahp) methodology to decompose complex safety risk issues into three hierarchical levels: objectives, criteria, and indicators. this resulted in a clear hierarchical structure model. the specific risk evaluation index system for polyimide foam production lines is detailed in table 2. 4. risk assessment 4.1 indicator weighting this study developed an expert survey questionnaire on risk indicators for polyimide foam production lines, based on the established risk assessment framework. industry experts were invited to complete the questionnaire. using the collected data, judgment matrices were constructed in yaahp software to aggregate expert opinions through group decision-making, ultimately determining the final weights of each indicator. first, based on the risk index evaluation system for polyimide foam production lines, a hierarchical model was constructed in the yaahp software, as shown in figure 2. the expert data was then imported into the yaahp software to construct judgment matrices for each expert. all matrices demonstrated a consistency ratio (cr) below 0.1, passing the consistency test to ensure the scientific validity and rationality of the weight distribution. the final weight allocation results are presented in table 3. as shown in table 3, the key risk points with higher weights constitute the primary risk profile of this production line. the top three factors are all equipment-related: b11 core equipment stability and reliability design (0.1068), b12 safety interlock and protective device effectiveness (0.0994), and b14 electrostatic protection and grounding system reliability (0.0780). following closely are b42 safety layout of hazardous materials production facilities (0.0557), b13 compliance of special equipment safety accessories (0.0547), b21 management of hazardous chemical storage and usage (0.0450), b51 coverage of safety education and specialized training (0.0405), and b31 management of workers' physical and mental health status (0.0407). this clearly identifies the priority areas for risk control resource allocation. 4.2 fuzzy comprehensive evaluation after determining the weights of each indicator, experts were invited to rate the relevance v= {low risk 1, relatively low risk 2, general risk 3, relatively high risk 4, high risk 5} of all secondary indicators in the evaluation set. the results were imported into the yaahp software, which performed fuzzy calculations to generate a comprehensive safety risk assessment score for the polyimide foam production line. the final evaluation report is shown in figure 3. the overall safety risk assessment score for the polyimide foam production line is 3.7246, as shown in figure 3. this score is considered a relatively high risk according to the set-out evaluation scale. this means the entire safety scenario in the production line is critical, and the management should take urgent action and implement effective measures. the most significant factors were equipment-related (b1) and process material (b2), with scores of 4.05 and 3.98, respectively, and were all considered high risk. this not only confirms the findings of the ahp weight analysis but also establishes these two dimensions as the main factors contributing to high overall risk levels. the scores for personnel factors (b3), safety management factors (b5), and environmental risk factors (b4) were 3.46, 3.30, and 3.2,5, respectively, which are within the upper band of general risk and on the border of relatively high risk. these results reveal a significant lack in these fields that cannot be ignored. 4.3 recommendations for countermeasures this section will present a detailed safety risk analysis of the polyimide foam production lines and an indicatorweighted fuzzy overall assessment. it will offer specific riskprevention and improvement suggestions in five main areas: equipment and facilities, process materials, personnel management, safety management, and environmental control. these are measures to improve overall safety management capabilities and mitigate systemic risks. (1) strengthen the inherent safety of equipment and facilities, focusing on high-weight risk points 1. enhancement of the reliability of core equipment: to develop and actively introduce a preventative maintenance and life cycle maintenance system for major equipment (such as high-temperature pressure tanks and microwave foaming furnaces), as well as the implementation of equipment-based monitoring technology, to detect the trend of equipment deterioration in advance. 2. assurance of the functionality of combustible gas alarm interlocks and mechanical protective devices: the functionality of combustible gas alarm interlocks and mechanical protective devices should be regularly checked and inspected to be responsive and effective. create an interlock system management ledger that has wellestablished maintenance responsibilities and cycles. 3. comprehensive electrostatic protection system: have periodic tests and maintenance of the grounding resistance of all equipment and pipelines that carry any of the flammable and explosive media to offer continuous and dependable grounding. the use of anti-static materials and humidification in processes is likely to generate static, such as during crushing and conveying. (2) optimize the risk control of process materials and strictly prevent the loss of control of hazard sources 1) accurate control over hazardous chemicals: introduce the one book one label system (safety data sheets and safety labels) of all substances, standardize storage and usage conditions of solvents, including tetrahydrofuran and methanol, and enhance integrity checks in leak prevention facilities. ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 41 table 2. risk assessment index system for polyimide foam production line evaluation goal primary indicator secondary indicator subdivide secondary indicators polyimide foam wire production line safety risk assessment a device factor b1 core equipment stability and reliability design b11 design life, failure rate, and maintenance cycle of hightemperature pressure tanks, microwave foaming furnaces, vulcanizing machines, etc., as well as material selection and system design for pressure-bearing pipelines safety interlock and protective device effectiveness b12 the combustible gas detector is interlocked with the emergency ventilation system, while the fire damper is interlocked with the corresponding air conditioner. protective measures are implemented for mechanical processing equipment such as vulcanizing machines and cutting machines. special equipment safety accessories compliance b13 pass rate of pressure gauge, safety valve, and quick-opening interlock device inspection electrostatic protection and grounding system reliability b14 electrostatic grounding of crushing equipment, pipelines, fans, etc. explosion-proof electrical equipment selection and installation compliance b15 explosion-proof marking, explosion-proof clearance, and cable sealing devices meet the standards completeness of the equipment online monitoring and early warning system b16 coverage of real-time electrical fire monitoring, vibration monitoring, and temperature/pressure collection process material factor b2 hazardous chemicals storage and use management b21 storage conditions and anti-leakage measures for polyimide resin, tetrahydrofuran, methanol, alcohol, isocyanate, etc. asphyxiation gas risk prevention and control b22 nitrogen leak detection, accident ventilation and alarm interlock control of combustible gas and dust concentration b23 dust and steam concentration monitoring and control in crushing, foaming and oven processes high-temperature and high-pressure interlock control b24 temperature and pressure dual-limit interlock and overlimit protection for pressure vessels and other equipment fire prevention in cleaning operations b25 fire and explosion prevention facilities, anti-static flooring, and ventilation in alcohol consumption areas waste gas and harmful substance control b26 hydrogen fluoride, methanol, and cyclopentadiene emissions purification and compliance monitoring personnel factor b3 workforce health management b31 health examination and fatigue monitoring before high temperature, high altitude and confined space operations compliance with operating procedures and violation control b32 violation of regulations and operation job qualifications and skill set b33 certification rates for special operations, explosion-proof electrical maintenance, and pressure vessel operation job standard compliance rate b34 the wearing rate of work protective equipment, the implementation rate of the "three certificates" in confined spaces, and the orderly arrangement of items and tools in the workplace security awareness and risk identification ability b35 can you identify the risks of chemicals, poisoning, explosion and other risks specific to this process emergency response capability b36 emergency response proficiency for on-site fires, leaks, and explosions environmental risk factor b4 noise hazard control b41 noise levels of vacuum pumps and cooling systems ≤85 db, along with the proportion of ear protection worn. safety layout of hazardous materials production facilities b42 the location, evacuation distance, and fire prevention distance of class a operation area comply with the specifications fire protection facilities: configuration and effectiveness b43 the completeness rate of fire hydrants, fire extinguishers, fireproof roller shutters, and fire water sources microwave radiation control b44 microwave oven cavity shielding effect pass rate evacuation corridor accessibility b45 no items in the channel. the indicator light is working properly. ventilation and dust removal system performance b46 local exhaust and accident ventilation air volume compliance rate environmental temperature and humidity and chemical stability b47 the temperature and humidity control records in the storage and production areas meet the process requirements safety management factor b5 safety education and specialized training coverage rate b51 training ratio for high-temperature, high-pressure, confined space, explosion-proof areas, and chemical operations safety responsibility system implementation b52 workplace safety responsibility signing rate and assessment results emergency plan development and drill b53 fire, explosion, leakage, electric shock and other special plans and exercise frequency operational procedures and system completeness b54 update and operability of core equipment and hazardous work procedures closed-loop management of safety inspections and hazard rectification b55 monthly inspection frequency and closed-loop rectification rate ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 42 figure 2. hierarchical structure model figure 3. comprehensive evaluation report ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 43 2) enhanced process safety parameter interlock: re-examine and optimize alarm and interlock settings for critical process parameters (temperature, pressure, concentration) to ensure automatic downgrading or shutdown procedures when limits are exceeded, preventing accident escalation. (3) improve personnel safety literacy and behavioral norms 1) special training and capacity building: develop special training modules for the risks of the polyimide foam production process and adopt the combination of case teaching and practical exercise to improve the risk identification and emergency response ability of employees. 2) operation process supervision and behavior correction: promote the "behavior safety observation" activity, and use video surveillance and other technical means to strengthen remote supervision of high-risk operations (such as limited space, high temperature cleaning), timely intervention in violation of rules, and analysis of root causes. (4) improve the safety management system and promote closed-loop management 1) link the implementation of the responsibility system with performance assessment: include safety performance indicators (such as the rate of hidden danger rectification and the number of violations) into the annual assessment of departments and individuals, clarify the rules of rewards and punishments, and enhance the safety responsibility awareness of all staff. 2) closed-loop optimization of hazard identification and management: through digital systems (e.g., mobile inspection apps), the entire process of hazard reporting, rectification, and verification is tracked, ensuring timely resolution and feedback for each identified issue, thereby forming a closed-loop management system. (5) improve working environment and emergency support conditions 1) layout optimization and emergency facility maintenance: regularly review fire separation distances between class a zones and adjacent facilities to ensure unobstructed evacuation routes. establish a monthly inspection system for fire protection facilities to maintain their readiness at all times. 2) improvement of local environmental control ability: optimize the airflow organization of local exhaust hood for dust (gas) production processes, such as foaming and crushing, and regularly measure the air volume and air speed to ensure that the capture efficiency meets the occupational exposure limit requirements. 5. conclusion this paper mathematically constructs a multidimensional assessment model that includes five aspects, such as equipment, materials, personnel, environment, and management, to evaluate the degree of safety risks in polyimide foam manufacturing lines. the paper uses the analytic hierarchy process (ahp) and the fuzzy credibility evaluation (fce) method to provide quantitative risk assessment and classification. the key findings are as follows: (1) through ahp weight analysis, the identification of key risk factors such as the stability and reliability design of core equipment, the effectiveness of safety interlock and protective devices, and the reliability of the electrostatic protection and grounding system are the priority areas of risk control. (2) the comprehensive evaluation based on fce indicates that the production line's overall risk is classified as "relatively high risk". the highest scores were attributed to equipment and process material factors, which are the primary contributors to the elevated risk level. (3) although the personnel, environment, and safety management factors are at the level of "general risk", they are still close to the threshold of "relatively high risk", indicating that there are obvious shortcomings in the risk prevention and control system, which need to be strengthened systematically. table 3. weight ranking of risk indicators risk indicator weight b11 core equipment stability and reliability design 0.1068 b12 safety interlock and protection device effectiveness 0.0994 b14 static protection and grounding system reliability 0.0780 b42 safety layout of hazardous materials production facilities 0.0557 b13 compliance of safety accessories for special equipment 0.0547 b21 management of storage and use of hazardous chemicals 0.0450 b31 personnel physical and mental state management 0.0407 b51 safety education and special training coverage 0.0405 b41 noise hazard control 0.0346 b15 explosion-proof electrical equipment selection and installation compliance 0.0345 b16 equipment online monitoring and early warning system completeness 0.0295 b22 asphyxiating gas risk prevention and control 0.0295 b52 safety responsibility system implementation 0.0279 b26 waste gas and harmful substance control 0.0269 b44 microwave radiation control 0.0254 b32 compliance with operating procedures and violation control 0.0252 b53 emergency plan preparation and exercise 0.0245 fire prevention in b25 cleaning operations 0.0238 b54 operational procedures and system completeness 0.0225 b23 combustible gas and dust concentration control 0.0213 b43 fire protection facilities and effectiveness 0.0213 b46 ventilation and dust removal system performance 0.0212 b24 high-temperature and high-pressure interlock control 0.0188 b34 work specification compliance rate 0.0182 b33 job qualifications and skill set 0.0164 b45 evacuation channel accessibility 0.0162 b47 environmental temperature and humidity and chemical stability 0.0127 b55 closed-loop management for safety inspection and hazard rectification 0.0106 b35 safety awareness and risk identification 0.0103 b36 emergency response capability 0.0080 ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 44 (4) based on the evaluation results, specific risk prevention and control measures are put forward from the aspects of equipment inherent safety, process parameter control, personnel behavior management, closed-loop system operation, and environmental emergency support, which provide an operational practice path for the safe operation and continuous improvement of the polyimide foam production line. this study provides methodological support for risk identification, classification, and the formulation of control strategies in high-risk production systems. future research may further incorporate dynamic risk-monitoring data and intelligent early-warning technologies to improve the realtime and prospective character of risk assessment. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] wu haitao, liu tiantian, pan li, et al. research and application of polyimide foam. chemical new materials, 2023,51(10):231–234,238. 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[22] li tingbo. development and application of chemical safety production risk assessment system. chemical management, 2024, (28):98–101. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 32 article regression analysis and classification of temperature modulated metal oxide semiconductor gas sensors responses on flue gas elvina chu qing heng, nikko leo, ting soon ling, hong siang chua, hui en lee* swinburne university of technology sarawak campus a r t i c l e i n f o article history: received 01 june 2025 received in revised form 10 july 2025 accepted 20 july 2025 keywords: air quality monitoring, electronic nose (enose), metal oxide semiconductor (mos) sensors, regression analysis, gas sensors, flue gas detection *corresponding author email address: helee@swinburne.edu.my doi: 10.55670/fpll.fusus.3.4.4 a b s t r a c t industrial emissions, particularly from flue gases, pose significant risks to environmental sustainability and public health. conventional air quality monitoring systems often suffer from high costs, delayed reporting, and limited detection capabilities. this study presents a cost-effective, real-time air quality monitoring solution using an electronic nose (enose) system integrated with metal oxide semiconductor (mos) gas sensors. these sensors target key pollutants, such as carbon monoxide (co) and carbon dioxide (co2), which also serve as indicators of transformer faults in industrial settings. the enose system leverages machine learning for both regression and classification tasks, enabling accurate quantification of pollutant levels and categorization of air quality into defined categories. principal component analysis (pca) is employed to optimize feature extraction, enhancing model precision and efficiency. notably, the system integrates digitally controlled buck converters for automatic temperature regulation, reducing sampling time from 390 to 130 seconds. additionally, a redesigned airtight sensor chamber and optimized airflow design, along with the use of tedlar bags, improve sample integrity and minimize interference. hardware development involved prototyping on breadboards using lm2575, lm2576, and lm2574 ics, followed by the creation of a compact 10 cm × 10 cm pcb for efficient power management. multimeter testing verified reliable electrical connections. experimental validation showed the system achieved over 91% accuracy in distinguishing between "good" and "bad" air quality levels. strong correlations between sensor output and pollutant concentrations confirm system reliability. this research demonstrates a scalable, efficient tool for real-time air quality monitoring and fault detection in industrial environments. 1. introduction air pollution poses a critical global challenge, significantly affecting public health and environmental sustainability. industrial processes—especially the combustion of fossil fuels—emit flue gases containing harmful pollutants, including nitrogen oxides (nox), sulfur oxides (sox), carbon monoxide (co), carbon dioxide (co₂), volatile organic compounds (vocs), and particulate matter. these pollutants degrade air quality, contribute to climate change, and lead to severe health risks [1]. the world health organization (who) estimates that outdoor air pollution is linked to approximately 4.2 million deaths annually, underscoring the urgent need for accurate, real-time air quality monitoring systems [2]. in response to these challenges, this study employs the metal oxide semiconductor (mos) gas sensor module previously developed in our earlier work [3–5]. in that study, temperature modulation was applied to the mos sensors by varying the heater voltage to influence each sensor's gas selectivity, also referred to as its sensitivity profile. this technique significantly increased the dimensionality of sensor data. by exploring the multi-dimensional nature of the generated data, this study aims to identify the optimal heater voltage setting that enables precise selectivity toward specific future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.4.4 november 2025| volume 03 | issue 04 | pages 32-46 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:helee@swinburne.edu.my https://doi.org/10.55670/fpll.fusus.3.4.4 https://fupubco.com/fusus ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 33 flue gas components. flue gas, also referred to as exhaust gas, is the byproduct of burning fossil fuels like coal, oil, or gas in industrial applications such as boilers and engines [6]. these gases, mainly composed of co₂ and co, are generated from sectors such as energy, transportation, and manufacturing [2]. while these activities are essential for industrial operations, they contribute substantially to air pollution and climate change. in malaysia, this issue has become increasingly serious, especially in urban areas with intense industrial activity and heavy traffic. rapid urbanization has worsened the situation by increasing industrial production and vehicle emissions, further deteriorating air quality. in addition to air pollution, transformer faults are a growing concern. faults such as overheating and insulation breakdowns can lead to the release of co₂ and co into transformer oil. these issues can result in expensive equipment damage, unplanned operational downtime, and disruptions to the power supply. effective monitoring of these gases is crucial for early fault detection in transformers and to control pollution levels in urban areas. traditional gas monitoring technologies like continuous emission monitoring systems (cems), gas chromatography (gc), and mass spectrometry (ms) provide precise results but are often expensive, complex, and unsuitable for large-scale deployment due to their reliance on specialized equipment and trained personnel. furthermore, these methods typically lack real-time capabilities, making them inefficient for continuous air quality assessment [7]. to address these limitations, this study explores the development of an improved metal oxide semiconductor (mos)-based gas sensor system, commonly referred to as an electronic nose (enose). these sensors mimic the human olfactory system, offering a cost-effective, compact, and scalable solution for detecting gas compositions, such as co and co₂, in both flue gases and transformer environments. integrated with regression analysis, principal component analysis (pca), and machine learning classification algorithms, the enose can accurately quantify pollutant concentrations and classify air quality levels in real time [8,9]. despite their potential, mos sensors face challenges, particularly with manual temperature modulation. this process involves adjusting the sensor’s temperature to improve selectivity and sensitivity. however, manual control often results in delays between temperature adjustments and sensor response, reducing measurement reliability [10,11]. inconsistent readings due to air leaks in non-airtight sensor chambers and time-consuming sample collection methods further compromise accuracy and efficiency. automating the temperature modulation process can enhance sensor precision and consistency, enabling more reliable gas differentiation in complex mixtures like flue gases. additionally, improving air sampling methods to reduce collection time and ensure airtight conditions will further streamline the system’s performance. ultimately, this study aims to design a mos-based gas sensor system that delivers accurate, efficient, and real-time detection of co and co₂ for both environmental monitoring and transformer fault detection. through advanced regression analysis and classification techniques applied to enose sensor data, the initiative seeks to improve the accuracy and responsiveness of air quality assessments. by addressing the current limitations of sensor-based technologies, this system presents a scalable and practical alternative to conventional monitoring methods, enabling more effective air quality control and transformer fault diagnostics. 2. methodology 2.1 sensor case design for gas sampling figure 1 illustrates that the sensor chamber case has been thoughtfully designed to ensure accurate and reliable gas sampling. it features an airtight seal and a controlled gas inlet system, which allows only the intended gas mixture to enter the chamber, thus preventing contamination from outside air and enhancing the precision of the sensor readings. to minimize the risk of leaks, silicone gaskets are used, ensuring that the results remain consistent and accurate. additionally, the chamber case includes a manual valve, as shown in figure 2, along with a tedlar bag, providing precise control over the flow rate and composition of the gas sample, which gives greater confidence in the collected data. furthermore, the chamber's compact and lightweight design, made possible through 3d printing, makes it cost-effective and easy to use in a variety of settings. figure 1. solidworks 3d model of the chamber case with central inlet for controlled gas flow figure 2. designed and printed gas sampling chamber case for gas detection ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 34 2.2 digital temperature modulation design by using a buck converter figure 3 represents the design process for digital temperature modulation. before proceeding to full-scale testing and pcb design, each buck converter was first assembled on a breadboard, as shown in figure 4, to ensure proper functionality. this approach allowed for easy adjustments and troubleshooting within a flexible setup. for the 1a temperature control system, we utilized the lm2575 ic in conjunction with a digital potentiometer to adjust the output voltage, which ranged from 4.0v to 5.0v. the 3a converter, designed for the pneumatic system and based on the lm2576 ic, was tested to confirm a stable 5v output under a 3a load, with an oscilloscope monitoring for any voltage fluctuations. finally, the 500ma sensor array converter, using the lm2574 ic, provided a consistent 5v output, with careful observation of voltage stability and thermal performance. this prototyping phase confirmed that all converters met the required specifications prior to moving forward with the pcb design. figure 3. process of designing the digital temperature modulation figure 4. buck converter breadboard prototyping with the lm2574 500ma ic for troubleshooting after successfully testing individual buck converters on a breadboard, the next step was to combine all three circuits into a single pcb design. figure 5 displays the backend pcb layout for combined buck converters. this design aimed to efficiently manage power for the mos sensor module, pneumatic system, and sensor array. the pcb design process involved converting the schematic into a compact and functional layout. key considerations included footprint design, component placement, and routing. accurate pad layouts were created to ensure proper alignment of components and to minimize assembly errors. components were strategically arranged to reduce wiring complexity while maintaining adequate spacing for airflow and heat dissipation. routing was done with care, using 1 mm traces for power lines and a copper-filled ground zone to enhance current flow and cooling. the final pcb design measures 10cm x 10cm, a standard size that facilitates easy manufacturing, testing, and future modifications. figure 5. backend pcb layout for combined buck converters once the pcb is prepared, the next step is to solder the components. figure 6 demonstrates the circuit board with polarized capacitors (highlighted) that require careful orientation during assembly. first, gather the necessary tools: a soldering iron, solder wire, flux, and tweezers. clean the pcb pads to ensure a smooth soldering process, and then apply flux to help the solder adhere. carefully place the components in their correct positions, paying special attention to polarized parts like capacitors and diodes. start by soldering one pin of each component to hold it in place, and then secure the remaining pins. after soldering, inspect the joints to ensure they are clean and solid. use a multimeter to test the circuit. finally, clean off any excess flux and add any finishing touches, such as heatsinks, to complete the process. this ensures everything is securely connected and ready for testing. 2.3 troubleshooting and resolving inductor overload in the buck converter circuit inductors have a maximum current rating, and when this limit is exceeded, they can overheat and fail. in this case, the original inductor was unable to handle the 3a current, leading to its failure. figure 7 illustrates the replacement process of the 100 μh inductor in the circuit to address the overload ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 35 issue. after replacing it with a 100μh inductor rated for 3a, the system functioned correctly again. this experience underscores the importance of selecting components that are properly rated for the system’s current demands to ensure reliable performance and prevent damage. figure 6. circuit board with polarized capacitors (highlighted) that require careful orientation during assembly figure 7. replace 100μh inductor rated for 3a in the buck converter circuit 2.4 air sampling process flue gas samples were collected using a redesigned metal oxide semiconductor (mos) gas sensor, a 5v motor pump, and tedlar bags. figure 8 illustrates the collection of 75 samples distributed across three air quality categories: good, moderate, and poor. the samples were sourced from clean forested areas, vehicle exhaust points, and gardens with vehicle presence. the motor pump ensured consistent sampling, while the tedlar bags helped maintain gas purity. table 1 summarises the distribution of air samples collected across three air quality categories: bad, moderate, and good, with 25 samples gathered for each category, totalling 75 samples. for the bad air quality category, samples were directly collected from the exhausts of four different vehicles: alza, bezza, van, and myvi, to represent highly polluted environments. the moderate category involved sampling air from four separate areas within the malaysia-china friendship park, a location with a mix of natural and urban influences. for the good category, air was sampled from four locations along the 7th mile haji baki bamboo trail, a clean forested area with minimal pollution. all samples were properly labeled and stored for no more than 24 hours to maintain their integrity before analysis. figure 8. sample collection using tedlar bags with a total of 75 air samples table 1. air sampling locations and sample distribution table 2 outlines the timeline and actions involved in the sampling procedure for data collection. before collecting air samples, the gas sensors are allowed a 30-minute warm-up period to stabilize. during this time, the heater voltage is set to 4.0v, and the system is calibrated to ensure accurate readings. this process is both safe and non-invasive, while the temperature control further enhances sensor sensitivity. the sensors operate with a built-in heater powered by a 5v supply, starting at 4.0v and increasing by 0.1v every 10 seconds until reaching 5.0v at 120 seconds. after that, the voltage drops back to 4.0v, which helps the sensors respond accurately to the air samples. the updated sampling procedure has streamlined the process, reducing the total sample time from 390 seconds to 130 seconds through fully automated voltage adjustments. this improvement enhances efficiency, allowing for more samples to be collected in less time. the 10-step voltage change creates multiple data points, air quality category sampling location number of samples store time bad directly collect air from 4 different car exhausts (alza, bezza, van, and myvi). 25 not over 24 hours good 7th mile haji baki bamboo trail (jungle), from 4 areas. 25 moderate malaysia china friendship park, from 4 areas. 25 ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 36 providing richer and more detailed information, which also improves sensor sensitivity for more accurate detection of pollutant levels. table 2. sampling procedure timeline and actions for data collection time actions connecting sample connect the tube from the tedlar bag to the chamber. open the valve from the tedlar bag first, not the valve from the chamber. pre-sampling the heater automatically sets to 4.0v. switch the calibration button to "open." the system adjusts the sensors until their output stabilizes at 1.00 ± 0.02v. once stable, switch the calibration button "off." 0 – 10s ensure the output voltage of the sensors is at a steady state at the baseline value, which is around 1.00 ± 0.05v, for 10s. 11s – 20s start from 11s, open the chamber valve and gently press the tedlar bag to let air into the chamber for 10 seconds. close the chamber valve after 10 seconds. 21s – 120s the heater voltage automatically steps up to 4.1v at 21 seconds, increasing by 0.1v every 10 seconds until reaching 5.0v at 120 seconds. 121s – 130s at 121 seconds, the heater voltage automatically steps back down to 4.0v. post – sampling start the purging process to clear the chamber. turn on the vacuum valves and air pump until the sensor output stabilizes at 1.00 ± 0.05v. perform a final check to ensure a steady reading around 1.00 ± 0.02v and get ready for the next sample. 2.5 data collection the data collection process involves acquiring raw sensor data from diverse environments with varying air quality conditions. the dataset is systematically divided into two subsets: a training set for model development and a validation set for performance evaluation. to create the training datasets, a total of 60 air samples were collected and categorized as follows: • 20 samples of bad air, • 20 samples of good air, and • 20 samples of moderate air. for model validation, an additional 15 air samples were collected, distributed evenly among the categories: • 5 samples of bad air, • 5 samples of good air, and • 5 samples of moderate air. the electronic nose (enose) system equipped with metal oxide semiconductor (mos) sensors was used to capture sensor output voltages over specific time intervals. for regression analysis, a commercial carbon dioxide (co2) detector is used to measure and collect co2 concentrations, in parts per million (ppm), with five readings at each sampling point. 2.6 data extraction table 3 presents the mos sensors used in this study, along with their respective targeted gases. sensor data is recorded continuously from 0 to 130 seconds. however, for analysis, sensor data is extracted from the time intervals between 25 seconds and 115 seconds, in 10-second increments, as shown in figure 9. this approach selects sensor readings at ten key intervals, capturing critical temporal variations in the sensor's response to different gas concentrations. the extracted data from these intervals is then fed into matlab to train and validate the classification models. table 3. mos sensors and targeted gas figure 9. sensors' instantaneous response extracted at 10-time intervals of the sampling process 2.7 data analysis the machine learning classification process, as illustrated in figure 10 (a), involves a series of steps designed to accurately categorize air quality levels based on sensor data collected from the enose system. this project will utilize the matlab classification learner application, which offers 30 classification models. the classification models and their respective model categories are tabulated in table 4. the process begins with principal component analysis (pca), which reduces the dimensionality of the raw sensor data while retaining critical features. this step enhances types of mos sensors targeted gas tgs2600 hydrogen (h2), carbon monoxide (co), methane (ch4) tgs2602 vocs, ammonia (nh3), hydrogen sulfide (h2s) tgs2620 alcohol, vocs tgs2611 methane (ch4) ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 37 computational efficiency and improves the overall performance of the classification models. the reduced dataset is utilized to train machine learning models using matlab’s classification learner application, where algorithms such as decision trees, support vector machines, and ensemble methods are assessed to determine the most effective model. 𝐴𝑐𝑐𝑢𝑟𝑎𝑐𝑦 (%) = ( 𝐶𝑜𝑟𝑟𝑒𝑐𝑡 𝑝𝑟𝑒𝑑𝑖𝑐𝑡𝑖𝑜𝑛𝑠 𝑇𝑜𝑡𝑎𝑙 𝑝𝑟𝑒𝑑𝑖𝑐𝑡𝑖𝑜𝑛𝑠 ) × 100 (1) once the models are trained, data validation is performed using a separate validation dataset to ensure the generalizability and robustness of the models when applied to new, unseen data. the accuracy of each model is then computed using metrics such as training and validation accuracy. equation (1) is used to compute the accuracy of each model. following this, the fine-tuning process begins, where hyperparameters are optimized, and the bestperforming models are recalibrated to further enhance their performance. finally, the optimized models are evaluated to confirm their reliability and readiness for deployment in realworld air quality monitoring applications. (a) (b) figure 10. (a) workflow for the machine learning classification process (b) workflow for the regression analysis process the regression analysis workflow, depicted in figure 10 (b), outlines the steps involved in quantifying pollutant concentrations based on sensor output voltages. the process begins by plotting sensor output voltage (vout) against commercial reference pollutant concentrations (in ppm). next, the data is cleaned to remove outliers and inconsistencies, ensuring the integrity of the analysis. a line of best fit is then generated using linear regression to model the relationship between vout and pollutant concentrations. finally, the best-performing regression plots are evaluated for accuracy and reliability, with metrics such as r-squared values used to validate model performance. table 4. classification models and model categories 3. results and discussion 3.1 digital temperature modulation output voltage testing after integrating the buck converters onto the pcb, voltage regulation testing was conducted to verify their output voltages. the voltage regulation test of lm2575 buck converter on pcb was setup as shown in figure 11. lm2576 provided a stable 5.07v, suitable for high-current applications, while lm2574 delivered 5.05v for low-current applications. the lm2575, controlled by an arduino, adjusted its output from 4.0v to 5.0v in 0.1v increments, decision tree 1.linear svm 4.cosine knn 1.narrow neural network 1. fine tree 2.quadratic svm 5. cubic knn 2.medium neural network 2.medium tree 3.cubic svm 6.weighted knn 3.wide neural network 3. coarse tree 4.fine gaussian svm ensemble classifiers 4.bilayered neural network discriminant analysis 5.medium gaussian svm 1.boosted trees 5.trilayered neural network 1.linear discriminant 6.coarse gaussian svm 2.bagged trees kernel approximation classifiers naïve bayes classifier nearest neighbour classifiers 3.subspace discriminant 1. svm kernel 1.gaussian naïve bayes 1. fine knn 4.subspace knn 2.logistic regression kernel 2.kernel naïve bayes 2.medium knn 5.rus boosted trees support vector machines (svm) 3.coarse knn neural network classifiers ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 38 demonstrating precise voltage control for temperature modulation. table 5 summarises the output voltage testing results of the lm2576, lm2574, and arduino-controlled lm2575 buck converters. these results confirm the successful integration and reliable performance of all three converters. figure 11. voltage regulation test of the lm2575 buck converter on the pcb setup table 5. output voltage testing results of lm2576, lm2574, and arduino controlled lm2575 buck converters 3.2 evaluating the digital temperature modulation sensor response in a graph this test evaluated the performance of the digital temperature control system, which is designed to improve sensor accuracy, consistency, and efficiency. the performance of this system is presented in figure 12. during the test, the heater voltage was gradually increased by 0.1v every 10 seconds, starting at 4.0v and reaching a peak of 5.0v, before smoothly returning to 4.0v. the response curve indicated that the sensors (tgs2600, tgs2602, tgs2620, and tgs2611) produced stable and consistent outputs throughout the process. the updated process improved sampling consistency and reduced sampling time. while the previous design took 390 seconds to complete each sample, the automated system now accomplishes this in just 130 seconds. this threefold reduction not only saves time but also allows researchers to collect more samples, ultimately increasing overall efficiency and productivity. the gradual voltage adjustments ensured that the sensors responded steadily, resulting in accurate and uninterrupted data collection. furthermore, the system’s capability to adjust voltage without delays or fluctuations underscores its reliability. these results demonstrate that the automatic temperature control system effectively enhances sampling performance while making the process faster and more efficient. figure 12. performance of the digital temperature control system 3.3 sensor performance and stability in different air quality the response curves offer valuable insights into how the metal oxide semiconductor (mos) gas sensors react to different air quality conditions, highlighting their effectiveness in identifying and classifying pollutant levels. figures 13 and figure 14 show the response curves for bad air quality samples, where sensors (tgs2600, tgs2620, and tgs2611) react strongly to high concentrations of co₂ and co. the voltage rises rapidly, reaching between 3v and 5v within the first 10 seconds after flue gas is introduced into the chamber. tgs2600 and tgs2620 maintain steady performance throughout the sampling period. however, tgs2611 shows less reliable behavior after 20 seconds, with its voltage dropping to a range of 2.5v to 4v by 120 seconds. this decline is likely due to changes in air saturation and temperature variations, which impact pollutant levels and sensor accuracy. buck converter ic input voltage (v) time (s) output voltage (v) 3a current lm2576 12 5.07 500ma current lm2574 12 5.05 1a current lm2575 12 0-19 4.02 20-29 4.11 30-39 4.21 40-49 4.31 50-59 4.41 60-69 4.50 70-79 4.60 80-89 4.74 90-99 4.82 100-109 4.94 110-119 5.03 120-129 4.02 ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 39 for good air quality samples, as shown in figure 15, the sensors maintain stable voltage levels below 2.5v, reflecting low concentrations of co₂ and co in the clean air. this steady performance indicates the sensors’ reliability in detecting minimal pollutant levels. in figure 16, moderate air quality samples also exhibit steady voltage responses, like good air quality. the voltages remain below 2.5v, placing all moderate samples in the clean air category. a clear distinction emerges when comparing bad air samples to good and moderate ones. bad air samples produce significantly higher voltage responses due to the higher concentrations of co₂ and co, while good and moderate samples yield much lower and more stable outputs. these findings confirm the sensors’ ability to reliably differentiate between varying air quality conditions, providing consistent and accurate responses for classifying pollutants. 3.4 sensor accuracy analysis table 6 presents the accuracy of four gas sensors: tgs2600, tgs2602, tgs2620, and tgs2611, in detecting gases at various time intervals ranging from 25 to 115 seconds. the results indicate that optimal performance occurred between 45 and 65 seconds, where all sensors achieved their highest accuracy levels. tgs2602 recorded the highest accuracy of 65.33% at both 45 and 65 seconds, followed closely by tgs2600, which peaked at 62.67% at 55 and 65 seconds. figure 13. shape of sensor response curve showing instability and voltage drop over time in bad air quality (sample 2) figure 14. shape of sensor response curve showing instability and voltage drop over time in bad air quality (sample 8) ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 40 tgs2620 reached its maximum of 60.00% at 65 seconds, while tgs2611 performed best at 45 seconds with an accuracy of 58.67%. after 75 seconds, the accuracy of most sensors either declined or stabilized, with tgs2602 notably dropping to a consistent 52.00% from 85 seconds onward. these findings suggest that the 45to 65-second window is the most effective period for capturing accurate gas detection data, underscoring the importance of timing in optimizing sensor performance. table 7 presents the refined analysis of gas sensor accuracy for four sensor models: tgs2600, tgs2602, tgs2620, and tgs2611, measured across time intervals from 25 to 115 seconds. the results show a notable improvement in detection performance compared to the initial analysis. tgs2600 maintained a high and consistent accuracy of 92.86% from 25 to 55 seconds before stabilizing at 91.43% for the remainder of the test. tgs2602 improved to 91.43% from 45 seconds onward, while tgs2620 demonstrated consistent accuracy, peaking at 92.86% at 25 seconds and maintaining 91.43% throughout most subsequent intervals. tgs2611 maintained an accuracy of 91.43% across nearly all time points, with a slight increase to 92.86% at 105 seconds. overall, all four sensors exhibited strong and stable performance with minimal fluctuation after 45 seconds, indicating improved system stability and sensor reliability under refined testing conditions. at 25 seconds, tgs2600 and tgs2620 recorded the highest accuracy of 92.86%, effectively detecting and classifying air quality as good or bad. tgs2602 and tgs2611 followed closely with accuracies of 90.00% and 91.43%, respectively. over time, all sensors stabilized at 91.43%, demonstrating reliable and consistent detection capability. these findings confirm the sensors' ability to accurately differentiate between air quality conditions. tgs2600 and tgs2620 showed superior early figure 15. shape of sensor response curve showing stable voltage over time in good air quality (sample 24) figure 16. shape of sensor response curve showing stable voltage over time in moderate air quality (sample 56) ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 41 detection performance, making them particularly well-suited for both short-term and long-term air quality monitoring in real-world applications. table 6. the accuracy of the gas sensors in correctly detecting gases (initial analysis) tgs2600 tgs2602 tgs2620 tgs2611 time (s) accuracy (%) 25 53.33 60.00 50.67 52.00 35 50.67 61.33 48.00 49.33 45 54.67 65.33 54.67 58.67 55 62.67 64.00 57.33 56.00 65 62.67 65.33 60.00 52.00 75 58.67 53.33 58.67 49.33 85 56.00 53.33 54.67 52.00 95 54.67 52.00 54.67 54.67 105 57.33 52.00 56.00 54.67 115 61.33 52.00 56.00 52.00 table 7. the accuracy of gas sensors in correctly detecting gases (refined analysis) tgs2600 tgs2602 tgs2620 tgs2611 time (s) accuracy (%) 25 92.86 90.00 92.86 91.43 35 92.86 90.00 91.43 91.43 45 92.86 91.43 91.43 91.43 55 92.86 91.43 91.43 91.43 65 91.43 91.43 91.43 91.43 75 91.43 91.43 91.43 91.43 85 91.43 91.43 91.43 91.43 95 91.43 91.43 91.43 91.43 105 91.43 91.43 91.43 92.86 115 91.43 91.43 90.00 91.43 the sensor response to different air quality samples categorized as "bad," "good," and "moderate" is illustrated in figure 13, figure 14, figure 15, and figure 16, respectively. these graphs correspond to sample 2, sample 8, sample 24, and sample 56. each graph plots the sensor output voltage over time (in seconds) for the four metal oxide semiconductor (mos) sensors used in the study. for the bad air sample (sample 2 & 8), the sensor output voltage rises sharply and stabilizes at high levels, reflecting strong detection of high pollutant concentrations typical of poor air quality. for the good air sample (sample 24), voltage readings are significantly lower, stabilizing at low levels, indicating reduced pollutants and cleaner air. for the moderate air sample (sample 56), voltage readings fall between the bad and good samples, showing a moderate rise and stabilization, effectively capturing intermediate air quality conditions. these results confirm the sensors’ ability to differentiate between varying pollution levels. 3.5 classification results the best-performing classification models and their corresponding validation and classification accuracies are summarized in table 8. the table highlights the topperforming classification models: bagged trees, tri-layer neural network, svm kernel, and logistic regression kernel. all models achieved a classification accuracy of 100%, correctly classifying all training data without misclassification. for validation accuracy, each model recorded 93.33%, indicating strong generalization and consistent reliability when applied to unseen data. the confusion matrices for the four best-performing models (bagged trees, tri-layer neural network, svm kernel, and logistic regression kernel) are shown in table 9. these matrices provide a detailed view of each model’s ability to classify air quality samples into “bad,” “good,” and “moderate” categories. among the models, bagged trees demonstrated the best performance, with minimal misclassifications. specifically, only one “good” sample was classified as “moderate,” and one “moderate” sample was classified as “good,” reflecting high reliability and robustness. the tri-layer neural network also achieved strong results, but it exhibited slightly more errors, misclassifying three “bad” samples as “good” and one “moderate” sample as “good,” suggesting reduced sensitivity in identifying poor air quality. the svm kernel model performed consistently, with balanced classification across categories. however, it struggled with borderline cases, misclassifying two “bad” samples as “moderate” and one “good” sample as “moderate.” logistic regression kernel showed the highest misclassification rates, with two “bad” samples classified as “good” and one “moderate” sample classified as “good,” indicating reduced robustness when differentiating between similar air quality categories. despite all models achieving 100% classification accuracy during training, their validation accuracy – 93.33% for each model – reveals differences in their ability to generalize to unseen data. bagged trees stood out as the most reliable model for distinguishing air quality levels, followed closely by the tri-layer neural network and svm kernel. logistic regression kernel, while effective, exhibited more challenges in handling nuanced distinctions between air quality categories. these results confirm bagged trees as the most effective and robust model for this classification task. table 8. best performing classification models types of classification models best performing models validation accuracy (%) classification accuracy (%) bagged trees 93.33 100 trilayer neural network 93.33 100 svm kernel 93.33 100 logistic regression kernel 93.33 100 ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 42 table 9. confusion matrices of best-performing models confusion matrix bagged trees svm kernel tri-layer neural network logistic regression kernel table 1. co2 concentrations at kampung haji baki collection points kampung a kampung b kampung c kampung d co2 concentrations (ppm) 4525 3735 3100 1930 4045 3670 3155 1885 4430 3880 1880 1745 4310 4115 1835 1580 4270 3845 1855 1359 average (ppm) 4316 3849 2365 1699.8 ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 43 3.6 linear regression results for air samples with co₂ concentrations exceeding the 5000 ppm detection limit of standard sensors (e.g., car exhaust), measurements were capped at 5000 ppm for regression modelling. this simplifies analysis by standardizing maximum values while acknowledging the sensor’s limitations. although variability above 5000 ppm is not captured, this approach ensures meaningful insights without introducing bias from non-detectable values. the regression analysis was performed to quantify co₂ concentration levels (in ppm) across different collection points using sensor output voltages. the analysis focused on two key locations: kampung haji baki and the malaysia-china friendship park, with the results summarized in table 10 and table 11, respectively. table 10 shows co₂ concentrations at kampung haji baki, categorized as “good air,” with averages ranging from 1,699.8 ppm to 4,316 ppm, reflecting low pollutant levels. table 11 presents co₂ concentrations at malaysia-china friendship park, categorized as “moderate air,” with averages between 459 ppm and 565 ppm, indicating slightly higher pollutant levels. the sensor output voltage was plotted against commercial ppm values across 10 time intervals (25s to 115s). the r-squared values, indicating the goodness of fit for the linear trendline, were calculated for each sensor (tgs2600, tgs2602, tgs2620, tgs2611). higher r-squared values (closer to 1) signify better consistency and reliability of the data. outliers were removed by identifying significant deviations from mean values and overlapping points to prevent skewed regression analysis. this process improved regression accuracy, increased r-squared values, and enhanced the predictive reliability of the models. as shown in table 12, outlier removal significantly improved the rsquared value, indicating better consistency in the data. for further analysis, three intervals – 25s, 45s, and 75s – were selected due to their relatively high r-squared values. these intervals demonstrated strong linear relationships across all sensors, ensuring robust and reliable trends for interpreting results and discussion. tgs2602 sensor consistently achieved the highest r-squared values across the selected time intervals (25s, 45s, 75s), as shown in table 13. table 11. co2 concentrations at malaysia–china friendship park collection points china a china b china c china d co2 concentrations (ppm) 440 595 410 470 430 575 410 505 420 550 680 525 455 555 465 545 550 550 415 540 average (ppm) 459 565 476 517 table 12. comparison of vout vs. commercial (ppm) at 25-th second interval for tgs2602 sensor before outlier removal: after outlier removal: ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 44 these intervals exhibit the strongest linear relationships between vout and commercial ppm values, establishing tgs2602 as the most reliable sensor for regression analysis in this study. furthermore, while commercial co₂ sensors are limited to a maximum concentration of 5000 ppm, the mos gas sensors used in this study demonstrate the capability to measure beyond this range, highlighting their extended detection potential. for moderate and bad samples, tgs2602 and tgs2620 recorded the highest r-squared values among the four sensors at the selected time intervals (25s, 45s, 75s), as shown in table 14. to highlight the most reliable data, this paper presents the vout vs. ppm plots for tgs2620 at the 25s interval and tgs2602 at the 45s and 75s intervals. these intervals demonstrate the strongest linear relationships, making them ideal for regression analysis. referring to table 10 and table 11, co₂ concentrations differ between "good air" and "moderate air" quality levels. at kampung haji baki (table 10), average co₂ concentrations range from 1699.8 ppm to 4316 ppm, categorized as good air. in contrast, malaysia-china friendship park (table 11) shows averages from 459 ppm to 565 ppm, reflecting moderate air quality. these variations highlight the impact of location on co₂ levels. forests like kampung haji baki have higher co₂ due to soil respiration, microbial activity, and restricted airflow from dense vegetation. urban parks, such as malaysiachina friendship park, benefit from photosynthesis, better airflow, and aquatic co₂ absorption, resulting in lower co₂ levels (400–700 ppm). table 13. plot of vout vs. commercial (ppm) for good and bad samples at 25s, 45s and 75s time interval plot of vout vs commercial (ppm) 25s 45s 75s table 14. plot of vout vs. commercial (ppm) for moderate and bad samples at 25s, 45s and 75s time interval plot of vout vs commercial (ppm) 25s 45s 75s ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 45 4. conclusions this research demonstrated the development and effectiveness of an advanced enose system, equipped with metal oxide semiconductor (mos) sensors, for real-time air quality and flue gas monitoring. by addressing key limitations of traditional gas sensing systems, the study introduced a more efficient, accurate, and cost-effective solution for detecting pollutants such as carbon monoxide (co) and carbon dioxide (co₂). key advancements included precise temperature control, improved sensor chamber design, and optimized sampling methods, all of which enhanced the performance and stability of the mos sensors. the integration of automatic digital buck converters significantly reduced the sampling time from 390 seconds to just 130 seconds, while maintaining consistent and reliable operation. the redesigned sensor chamber ensured improved airflow, maintained airtight conditions, and minimized external interference, resulting in more accurate gas detection. the system successfully quantified pollutant concentrations and classified air quality into "good," "moderate," and "bad" categories with over 91% classification accuracy. machine learning models, such as bagged trees and svm kernel, further improved classification reliability, while linear regression models demonstrated strong correlations, confirming the accuracy of sensor outputs. analysis of sensor behavior revealed that poor air quality was characterized by rapid voltage increases (3v–5v), while good to moderate air conditions showed stable voltages below 2.5v. notably, 45second sampling intervals provided an optimal balance between sensor response stability and classification accuracy. additionally, outlier removal significantly improved data quality and model performance. effective strategies, such as the use of tedlar bags for sample preservation and automated voltage adjustments, enhanced the consistency of air sample collection. looking ahead, future research should explore the enose’s performance under varied environmental conditions, including fluctuations in temperature and humidity, to ensure greater robustness. refining sampling methodologies for moderate and high-pollution scenarios, incorporating advanced sensors with extended detection ranges, and conducting long-term field deployments will further align the system with conventional air monitoring standards. in conclusion, the enose system represents a scalable, portable, and reliable tool for environmental monitoring and industrial fault detection. its high efficiency, adaptability, and real-time capabilities make it a valuable asset for modern air pollution management strategies. acknowledgements the author would like to express sincere gratitude to ir. a/prof. dr. chua hong siang and dr. lee hui en for their exceptional mentorship, guidance, and unwavering support throughout the project. their expertise and insightful feedback were instrumental in shaping the research and enhancing its overall quality. appreciation is also extended to swinburne university of technology sarawak for providing the essential resources—funding, facilities, and software— that made this project possible. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the authors declare no potential conflict of interest. references [1] rabia, r., et al., "impact of industrial processes on air quality and public health," journal of environmental science, vol. 29, no. 4, pp. 215–223, 2021. [2] h. ritchie. "deaths from air pollution are high, but the data contains hope." clean air fund. https://www.cleanairfund.org/news-item/deathsair-pollution-datahope/#:~:text=the%20world%20health%20organi zation%20estimates,from%20burning%20wood%20 and%20charcoal (accessed 29 november 2024, 2024). [3] h. e. lee, h. s. chua, z. j. a. mercer, s. m. ng, and m. shafiei, "fraud detection of black pepper using metal oxide semiconductor gas sensors," in 2021 ieee sensors, 31 oct.-3 nov. 2021, pp. 1-4, doi: 10.1109/sensors47087.2021.9639658. [4] h. e. lee, z. j. a. mercer, s. m. ng, m. shafiei, and h. s. chua, "metal oxide semiconductor gas sensors-based e-nose and two-stage classification: authentication of malaysia and vietnam black pepper samples," in 2022 ieee international symposium on olfaction and electronic nose (isoen), 29 may-1 june 2022 2022, pp. 1-4, doi: 10.1109/isoen54820.2022.9789618. [5] hui en lee et al., "temperature modulation of metal oxide semiconductor gas sensors and machine learning for geo-tracing of food products and classification of transformer oil quality," vol. 1, exploring engineering: an anthology of multidisciplinary undergraduate research, colin choon lin tan and b. t. lau, eds., sarawak, malaysia: swinburne sarawak sdn. bhd., 2023, pp. 104 119. [online]. available: https://swinburne.librarynet.com.my/angka.sa2/swi nburne/opacbibdetail.htm?bibid=742488 [6] a. raihan, r. a. begum, m. n. mohd said, and j. j. pereira, "assessment of carbon stock in forest biomass and emission reduction potential in malaysia," forests, vol. 12, no. 10, p. 1294, 2021. [online]. available: https://www.mdpi.com/19994907/12/10/1294. [7] a. cavaliere et al., "development of low-cost air quality stations for next generation monitoring networks: calibration and validation of pm2.5 and pm10 sensors," sensors, vol. 18, no. 9, p. 2843, 2018. [online]. available: https://www.mdpi.com/14248220/18/9/2843. [8] sun, w., et al., "discriminative detection of different cigarette brands using a fast-response electronic nose," acs omega, vol. 8, pp. 46034–46042, 2023. ecq. heng et al. /future sustainability november 2025| volume 03 | issue 04 | pages 32-46 46 [9] karim, s 2021, 'train and evaluate a classification model in machine learning!', medium, viewed 12 june 2024, < https://medium.com/@sarakarim/train-andevaluate-a-classification-model-in-machine-learning18fbd6504da3>. [10] h. e. lee, z. j. a. mercer, s. m. ng, m. shafiei, and h. s. chua, "metal oxide semiconductor gas sensors-based e-nose and two-stage classification: authentication of malaysia and vietnam black pepper samples," in 2022 ieee international symposium on olfaction and electronic nose (isoen), 29 may-1 june 2022 2022, pp. 1-4, doi: 10.1109/isoen54820.2022.9789618. [online]. available: https://ieeexplore.ieee.org/abstract/document/9789 618 [11] a. sudarmaji and a. kitagawa, "application of temperature modulation-sdp on mos gas sensors: capturing soil gaseous profile for discrimination of soil under different nutrient addition," (in english), journal of sensors, article p. na, 2016 annual // 2016. [online]. available: https://link.gale.com/apps/doc/a513009155/aone ?u=anon~e45f8757&sid=googlescholar&xid=90bef4 d5 this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 1 article the role of infrastructure in enhancing urban resilience to natural hazards: a case study of tehran navid navidpour1*, ali mokhtarzadehaghdam2, mohammadreza yari3, samiyeh ghanbili4, ramin makarinezhad5, sahand heidary5 1department of computer engineering, faculty of software engineering, amirkabir university of technology, tehran, iran 2department of construction engineering and management, faculty of civil engineering, iran university of science and technology, tehran, iran 3department of civil engineering, faculty of hydraulic structures, university of tehran, tehran, iran 4department of civil engineering, international islamic azad university of parand, tehran, iran 5faculty of computer engineering, khajeh nasir university, tehran, iran a r t i c l e i n f o article history: received 10 february 2025 received in revised form 18 march 2025 accepted 31 march 2025 keywords: resilience, gis modeling, worn-out urban texture, urban planning, risk assessment, crisis management *corresponding author email address: nav1370@gmail.com doi: 10.55670/fpll.fusus.3.3.1 a b s t r a c t urban resilience is paramount in mitigating the vulnerability of worn urban fabrics to natural hazards and safeguarding cities against irreparable damage. this study focuses on worn-out areas of tehran city, analyzing their social and physical resilience dimensions. adopting a descriptive-analytical approach, the research employs statistical methods such as one-sample t-tests, pearson correlation, and regression coefficient analysis using spss and gis. the statistical population comprises 230 randomly selected citizens residing in the study districts. the findings show that the physical dimension, with a score of 3.31, is more important than the social dimension, with a score of 2.81, which emphasizes the need to strengthen urban resilience. according to the results of this study, the studied areas do not have sufficient stability and resilience against natural disasters. prospective analyses conducted using geographic information system (gis) and the mic mac strategic studies model indicate the complexity of factors affecting urban resilience. these analyses reveal the high impact of variables and the interrelationships between them. in particular, it has been found that indicators related to infrastructure and management have a more significant impact in region 7 compared to region 15, which emphasizes the need to develop targeted intervention strategies. this comprehensive study provides a better understanding of urban resilience mechanisms and emphasizes the importance of coordinated planning and preventive measures to strengthen vulnerable urban areas. ultimately, the results of this study show that adopting appropriate and coordinated measures is essential to ensure the safety and sustainability of cities. 1. introduction earthquakes have increased both the probability and consequence of natural disasters such as floods, storms, and droughts [1]. infrastructure resilience must be increased to reduce the harmful effects of natural disasters [2]. most urban management programs emphasize the high resilience of infrastructure networks before a disaster occurs [3]. infrastructure must be developed in such a way that, first, it suffers minor damage during disasters, and second, it can return to its previous state in the shortest possible time. the term resilience is often left to debate and does not have a general definition or consensus, although it is more used in future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.3.1 august 2025| volume 03 | issue 03 | pages 01-11 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:nav1370@gmail.com https://doi.org/10.55670/fpll.fusus.3.3.1 https://fupubco.com/fusus n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 2 integrated urban drainage management [4]. the concept of resilience is widely applied in many fields of study (economics, engineering, psychology, sociology). in economics, resilience is the ability to quickly recover from a shock. in earthquake engineering, resilience is the ability to reduce hazards and do retrieval activities in ways that minimize social disorders and reduce the effects of future earthquakes [5]. in social science, resilience is the ability of groups or communities to deal with anxiety and external disturbances due to social, political, and environmental changes. the community's resilience is the ability of a society to be resilient against disaster, which refers to the ability to prevent or protect against major threats. in general, resiliency indicates the capacity of an urban system or society at risk of compliance with resistance or change to reach an acceptable level of performance, organization, and structure. the growing pace of urbanization around the world has brought unprecedented challenges to human societies. this paradigm shift has created complex issues, especially in the context of future urbanization in developing countries [6]. these challenges cover various areas, including urban sustainability, infrastructure development, the urban environment, and the resilience of aging structures. with the increasing pace of urbanization, the need to adopt a forwardlooking approach to confront these challenges is becoming increasingly apparent [7]. urban managers and policymakers are forced to develop strategies to create sustainable urban systems, especially in metropolitan areas that face the complexities of sustainable growth and development. the conceptual framework of resilience, first proposed in 1973 by holling in the field of bioecological sciences, has become the basis for numerous subsequent definitions over time. in this context, resilience does not simply mean the ability to survive but includes broader concepts such as sustainable livelihoods, the ability to resolve crises, and building resilient communities [8]. researchers have defined resilience as the ability of a city to cope with and adapt to a wide range of shocks and stresses, such that the structures critical to maintaining urban function remain efficient in crisis conditions [9]. in the specialized field of dilapidated urban textures, resilience has emerged as an independent concept and plays a central role in contemporary urban planning literature. this aspect of resilience is not only a physical feature but also a mentalspatial category that requires a fundamental review and modernization of urban structures to provide targeted services tailored to the needs of citizens. in the context of the increasing global population, especially in urban areas, the complexities and challenges in different sectors are also intensified [10]. therefore, risk management in urban planning and design is particularly important and requires adopting strategic measures for crisis management, reducing vulnerabilities, promoting safety, and improving the quality of life. in this regard, the city acts as a dynamic platform for various events and highlights the vital role of urban planning in predicting, preventing, and managing crises [11]. the dilapidated areas in district 7 of tehran are an example of the social, economic, and political challenges that have arisen due to the migration of the original residents to other parts of the city, the arrival of immigrants with diverse economic and cultural backgrounds, the lack of social solidarity and the weakness in citizenship education. one of the fundamental issues in this area is the lack of a sense of belonging among the residents, which exacerbates the problems of this urban context. given the historical importance of tehran, this city has a special place for studying urban resilience, and analyzing this issue in district 7 is of particular necessity [12]. this research seeks to conduct a comprehensive analysis of resilience measures in the dilapidated urban fabric of district 7 of tehran, focusing on social and cultural dimensions. using a mixed approach that includes quantitative and qualitative methods, this study aims to assess social and physical resilience [11]. in addition to identifying key driving forces in each dimension, this research will propose practical and effective solutions to strengthen the resilience of dilapidated urban fabrics in district 7 of tehran. in this way, the present research will contribute to the broader discourse of urban resilience and provide insights and suggestions for increasing the adaptive capacity of urban spaces against natural disasters and other disruptive events [8]. 2. theoretical concepts resilience, a concept that was first introduced in biology, is known as a tool for analyzing the ability of systems to cope with shocks and recover from them. this concept is particularly important in the urban context, as modern cities have become the focus of attention and resilience studies due to their social, economic, and environmental complexities [11]. in fact, resilience and adaptation in cities mean their ability to manage unexpected challenges and environmental pressures so that these spaces are able to cope with crises and return to stable and efficient states. global studies have shown that the vulnerability of urban communities depends on several factors, including demographic diversity, socioeconomic status, and physical and infrastructural conditions. crises are not limited to physical damage but also have widespread economic and social impacts [12]. this situation requires urban planners and officials to take a comprehensive and strategic approach to strengthening resilience and reducing damage. resilience can be examined from different angles [13]. the three main approaches in this field include sustainability, recovery, and transformation. each of these approaches emphasizes specific dimensions of resilience and represents different ways to analyze and improve the capacity of cities to face crises. in the sustainability approach, resilience is defined as the ability of a system to maintain the status quo in the face of crises and return to its initial conditions after the crisis occurs [14]. communities with high tolerance can overcome severe pressures and quickly return to their previous state. this approach is particularly useful in assessing the capacity of communities to deal with environmental and social challenges. in the recovery approach, resilience emphasizes more on the timing and quality of the return to a stable state. resilient communities are able to quickly and efficiently return to their original state, and this characteristic indicates their capacity to absorb and adapt to change. this aspect of resilience is particularly important in urban planning and interventions, as it can provide solutions to reduce the effects of crises and accelerate the reconstruction of communities. in the transformation approach, resilience is seen not only as a return to the previous state but also as a process of adaptation n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 3 and acceptance of change. in this view, change is inevitable and a positive force that can lead to the transformation and evolution of societies [15]. resilient communities in this approach can exploit crises as an opportunity to grow and evolve into new and more stable states. finally, these different approaches to resilience, especially at the urban level, provide a comprehensive and comprehensive framework for the analysis and management of urban crises. these concepts practically help urban officials and planners design appropriate policies and strategies to strengthen resilience and address upcoming challenges [16]. by embracing resilience as a dynamic concept that encompasses sustainability, recovery, and transformation, urban planners and policymakers can formulate adaptive strategies to enhance the resilience of urban spaces against a spectrum of shocks and tensions. table 1 shows the definition of resilience in the literature. 2.1 social resilience the concept of social resilience, rooted in understanding dynamic systems and their intricate interplay with the environment, offers profound insights into the complexities of societal responses to unforeseen events. this perspective is particularly valuable for decoding the decisions and adaptations related to natural resources management, spotlighting the inherent characteristics of how different social classes navigate unexpected challenges. social resilience is multifaceted, encompassing three vital aspects: resistance, recovery, and creativity. these elements collectively define a society's ability to not only withstand shocks but also to rebound and innovate in the aftermath [26]. the intricacies of social resilience parallel the broader concept of resilience but introduce an added layer of complexity due to the diverse components that constitute society—natural, social, and economic environments. similar to resilience, social resilience operates at different levels, reflecting the interconnected nature of societal elements. in the contemporary world, where societies are consistently exposed to a spectrum of risks, social resilience emerges as a critical imperative. achieving social resilience necessitates the mobilization of various forms of capital, with social capital playing a pivotal role in fortifying communities' adaptive capabilities and comprehensive crisis response [27]. 2.2 economic resilience economic resilience, a cornerstone of societal well-being, entails society's capacity to adapt strategically and minimize losses stemming from risks [28]. this adaptability is manifested across the five pillars of resilience: anticipation, resistance (sustainability), absorption, response, and adaptation and recovery. economic resilience isn't merely reactive; it is a proactive endeavor aimed at preserving the structure and functionality of the economy, even in the face of uncertainty. the economic resilience of a society is intricately connected to the foundational principles of economic stability and equilibrium [29]. 2.3 institutional and organizational resilience within the dimension of institutional and organizational resilience, the physical attributes of organizations play a pivotal role in shaping a society's ability to withstand and recover from crises. the number of local institutions, access to timely information, the preparedness of forces and volunteers, adherence to crisis management guidelines, and the effectiveness of laws and regulations—all contribute to the resilience of institutions. additionally, the satisfaction of local residents with institutional performance, especially in areas like housing construction, determines the overall robustness of the societal response to crises [30]. table 1. resilience definition in literature author resilience definition bahrami et al. [14] (2014) the ability of a system to absorb disruptions, adapt during changes, and reorganize itself is crucial for preserving its core principles, functions, identity, structure, and feedback mechanisms. jutidharabongse et al. [15] (2024) the capacity of a system to uphold its function and structure amidst internal and external changes. hall et al. [16] (2011) the system's capacity to endure environmental shocks while retaining its effective resource allocation capability. palik et al. [17] (2002) sustaining structure and function in the aftermath of disturbances is imperative for ongoing and continuous development. rodríguez et al. [18] (2007) it encompasses the capability to recuperate and deliver essential life, business, industry, government, and societal functions in the face of calamities and various risks. madni et al. [19] (2009) it denotes the capability of a system or society to endure encountered challenges and dangers, adapt proactively, and efficiently mitigate adverse effects, all the while preserving its fundamental structure and functionality. leichenko [20] (2011) the capacity to endure a diverse range of shocks and stresses. desouza and flanery [21] (2013) it represents the city's capacity to absorb disruptions while preserving its function and structure. folke [22] (2006) the system's capability to revert to its initial state following a natural disturbance or an issue induced by human activities. zahedi et al. [23] (2023) the system's capability and capacity to persist in functioning amid challenges and adverse conditions. shi et al. [24] (2021) the capability to adapt to and respond effectively to changes within urban systems. estelaji et al. [25] (2024) it embodies an organization's capacity to adapt to changes within its economic and institutional environment. n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 4 preserving ancient values is a primary goal for resilient societies, and historical contexts and old neighborhoods serve as tangible repositories of identity and culture. mosques, cisterns, baths, cells, markets, and historical houses embody the spirit of a community and are deemed invaluable. unfortunately, inefficient urban planning and management policies jeopardize the potential for reusing and maximizing these historical assets. this not only compromises the preservation of cultural heritage but also contributes to the gradual deterioration of central core tissues in cities, intensifying conflicts within urban contexts [31]. in this research, a focal point has been the exploration of social resilience, especially concerning the challenges faced by cities and worn-out urban tissues. social resilience, as a core dimension of broader societal resilience, empowers positive responses to changes, the maintenance of essential functions, and the preservation of societal fabric despite external pressures. the examination of social resilience is crucial in understanding and fortifying societies against the multifaceted challenges of the modern world. in conclusion, the augmentation of resilience, stability, and adaptability against tensions, risks, and dangers represents a transformative pathway toward revitalizing the capacities and potentials of a society. a more flexible social system correlates with diminished societal vulnerability to crises and tensions. social resilience, extending beyond mere responsiveness to social, political, and environmental changes, emerges as an indispensable determinant in a society's ability to confront external pressures and disturbances. 2.4 worn texture and urban dilapidation urban decay has a special place in the urban landscape, bringing signs of disorder, imbalance, and neglect [32]. this phenomenon is considered a narrative of urban history that shows the developments and changes in neighborhoods and urban spaces over time. worn-out textures that were once alive and dynamic have now become serious urban problems due to neglect, for which physical restoration alone is not enough, and special attention should be paid to preserving cultural identity and social cohesion [33, 34]. the distinctive features of worn-out buildings include various elements, including architectural features and the quality of urban infrastructure. these buildings are often associated with historical monuments and show signs of non-compliance with technical standards. the old facade of these buildings and the use of traditional materials such as brick, wood, and iron, in addition to their own beauty, indicate an inability to comply with modern construction principles. narrow streets and irregular accesses contribute to the sense of disorganization and highlight the need for a comprehensive strategy for urban renewal. the challenges of these contexts go beyond aesthetic aspects and are rooted in the structural deficiencies of these buildings [35]. the lack of proper earthquake resistance and inadequate maintenance have accelerated their deterioration. this necessitates the need for strategic measures to strengthen these buildings and ensure the safety of their residents. also, the lack of infrastructure and services in these areas has created additional problems for residents, including the lack of open spaces and a lack of cultural and educational facilities [36]. the dilapidated buildings in district 7 of tehran are emblematic of larger problems in urban development. historical neglect and spatial disorganization have exposed these areas to natural and unnatural hazards and pose a threat to the health of the community. these problems are not only visible in physical deterioration but also in the decline of social and cultural values [37]. loss of social dignity and disregard for cultural values exacerbate the problems of these urban spaces and make them vulnerable to various threats. a comprehensive and multidimensional approach is needed to revitalize these contexts. while physical reconstruction is essential, revitalizing the social and cultural aspects is equally important. urban planning and management must go beyond infrastructure renovation to preserve culture and strengthen social cohesion [38]. the renovation process must aim to restore a sense of identity and social pride in addition to restoring physical structures. 3. methodology this research uses a qualitative approach to examine the challenges and resilience strategies in districts 7 and 15 of tehran and considers comparative and applied case analyses as its main approach. for data collection, a semi-structured questionnaire is used as the main tool, which allows for a detailed analysis of the resilience indicators related to these areas. in this research, purposive sampling is carried out among long-term residents, especially people who have lived in these areas for more than 15 years, so that the data is rich in real experiences and long-term perspectives. this methodology allows the research to comprehensively and accurately examine the specific challenges and resilience strategies of each area and provide a better understanding of urban resilience. the research will include all residents of districts 7 and 15 to gather a wide variety of experiences and opinions related to urban resilience. the sample size was calculated using the cochran formula, resulting in the selection of 230 residents of the atabek neighborhood as a representative sample of the community. this method ensures that the research results are statistically accurate and fully reflect the opinions and experiences of the majority of residents in these areas. 3.1 district 7 of tehran the population recorded in the last census of 2015 was approximately 330,000 people living in 91,000 households. the district is demarcated by districts 3, 8, 6, 12, and 11 on its various sides and is recognized for its vulnerability due to an aging urban infrastructure. data from the reconstruction organization [37] indicates significant urban renewal efforts, with 639 building permits issued over the past decade, leading to the renovation of over 83,671.1 square meters of deteriorated fabric. the deteriorating state of buildings in these areas, particularly in neighborhoods like armenians, poses a safety risk and highlights the need for extensive redevelopment. approximately 15.52% of the district's area is considered deteriorated, housing a population of 86,788, which underscores the critical challenges facing district 7 and justifies its selection for a focused study on urban resilience and revitalization. figure 1 likely presents a detailed map of district 7, delineating its division into 5 zones and 14 neighborhoods, offering an essential overview of its geographical and administrative layout. this map is n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 5 foundational for visualizing the district's spatial organization and aids in the identification of specific areas for focused study or intervention. figure 1. zones and neighborhoods 3.2 gorgan neighbor gorgan neighborhood, covering 60 hectares with 22.8 hectares of deteriorated urban fabric, hosts a population of 21,390, reflecting a slight growth since 2010. this area exhibits a balanced gender ratio and an average household size of 2.7, showcasing a predominantly young demographic, with the largest age group being 30 to 34 years. historically a migrant hub during tehran's expansion in the 1930s, gorgan's diverse population and physical landscape have evolved significantly, incorporating both residential and commercial zones. despite its urban advancements, gorgan maintains a strong residential character, with over 80% of its plots dedicated to housing. the quality of neighborhood buildings is shown in table 2. table 2. the quality of neighborhood buildings buildings quality number of buildings percentage newly constructed 586 buildings 21.4% under construction 64 buildings 2.3% maintainable 854 buildings 31.2% dilapidated/destructible 1206 buildings 44.1% vacant/non-essential structures 23 buildings 0.8% unspecified 2 buildings 0.07% total 2733 buildings 100% urban planning in gorgan faces challenges, particularly in traffic management and accessibility, due to narrow streets, primarily less than 6 meters wide. the neighborhood's development strategy emphasizes the creation and enhancement of east-west passageways to improve traffic flow and access. this approach underlines the ongoing need for urban renewal that prioritizes improved living conditions, infrastructure enhancements, and the addition of green spaces. 3.3 shahed neighbor shahed is the largest neighborhood in district 7's zone 1, covering approximately 130 hectares, with 62 hectares classified as deteriorated fabric. the neighborhood has a population of 42,153, reflecting a slight increase since the 2010 census and constituting 55% of the zone's population. the gender ratio is balanced, with 98.4 males per 100 females and an average household size of 2.8, aligning with regional averages. the social fabric comprises middle-class, educated residents, primarily employed in government and private sectors. a significant number of immigrants contribute to the area's social diversity. established in the 1920s and 1930s, the neighborhood has experienced substantial transformations due to demographic shifts and urban development. notable landmarks include tavakoli garden and behrami children's hospital. challenges include residential congestion, inadequate north-south connectivity, and a network of narrow alleyways, exacerbated by the construction of the imam ali highway, causing spatial disconnection. 3.4 nezam abad nezam abad covers approximately 58 hectares, with 34 hectares classified as deteriorated fabric. the population stands at 12,264, with a balanced gender ratio and an average household size of 2.8. the demographic composition indicates a young population, with a majority in the 20-40 age group. the neighborhood evolved post-1930s, initially housing workers and later accommodating armenian, zoroastrian, and jewish communities, whose presence has since declined. urban development has been affected by the imam ali highway, creating a spatial divide. the area features residential, commercial, and industrial activities but faces accessibility challenges due to narrow streets and limited urban renewal. the neighborhood consists of three superblocks with distinct characteristics. older buildings typically have one to two stories, while newer structures, post-1980s, include up to six stories. facilities such as imam hossein hospital significantly influence the area's urban fabric. 3.5 atabak atabak is characterized by significant commercial activities along its main streets and mixed residential zones with multi-story buildings. historically, the neighborhood has evolved from its early settlement by residents from the city gates area, many of whom were involved in land trading businesses from the 1960s. previously known as atabak, the area encompassed neighborhoods from bisim to hashem abad, while its current boundaries extend from civil street to besat highway. urban challenges include balancing commercial expansion with residential needs and addressing n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 6 the infrastructural gaps resulting from historical development patterns. 3.6 valiasr (bisim) valiasr neighborhood, also known as bisim, is characterized by a lack of educational facilities due to recent urban development. the demolition of three schools for the construction of imam ali highway has left the northern part of the neighborhood devoid of educational facilities. the neighborhood's residents are primarily government and municipal workers, and the area also includes the notable tavakoli garden and behrami children's hospital. 3.7 minabi minabi neighborhood occupies an area of 78 hectares and has a population density of 323 people per hectare. it has a balanced gender ratio and a relatively young population, with active individuals constituting the largest demographic segment. the neighborhood has seen extensive urban development since 2005, particularly with the construction of imam ali highway. its demographic changes have been significant due to the displacement and resettlement caused by the highway construction. 4. results and discussion in this chapter, following an understanding of the study area and employing the methods outlined in section 3, the collected data is analyzed, and the research findings are presented. initially, resilience indicators in both the social and physical dimensions, derived from theoretical foundations, are extracted. the reliability of the researcher-created questionnaire is then ascertained using cronbach's alpha method. standard deviation and the impact of variables on social resilience in both districts 7 and 15 are determined through one-sample t-tests in each social and physical dimension separately. convergent validity (ave) is utilized to ensure the research model's suitability for social resilience in both districts. pls software outputs are employed to conclude whether the model is fit for purpose in terms of resilience indicators for deteriorated urban textures. subsequently, the evaluation of resilience indicators for social and physical dimensions for districts 7 and 15 is derived through onesample t-tests, after which the overall resilience in social and physical dimensions is established. the relationship between social and physical resilience dimensions with overall resilience is analyzed for each district. pearson correlation tests are used to assess the correlation between variables due to the interval nature of the questions and the use of a fivepoint likert scale for indexing. in assessing the physical dimension, optimized boundary methods for form and texture indices and other physical dimension indicators are evaluated using spatial analysis, geographical data statistics, and network analysis tools in gis software. for futureoriented analysis of social and physical resilience in districts 7 and 15, questionnaires and impact matrices are formulated to analyze the final results. influential and influenced factors are identified and analyzed within the micmac software framework. the research findings for district 7 show that internal reliability calculated through spss using cronbach's alpha was significant, as indicated in table 1, with a cronbach's alpha of 0.74 for the questionnaire items, confirming the study's reliability. for district 15, one-sample t-tests with a test value of 3 were conducted. it was found that if the mean variable for social interactions, neighborhood identity, sense of belonging, social participation, civic education, security, and social resilience is statistically less than 3, these variables, and ultimately social resilience, are in a state of disorder. the fundamental research model is assessed for fit, with essential statistics such as the average variance extracted, composite reliability (c.r), and cronbach's alpha examined. with the pls output, table 3 and table 4 confirm that the model is suitable in terms of fit indices. figures 2 through 8 depict the over 30year-old buildings, the number of floors in deteriorated fabric, and the granularity of deteriorated fabric in district 7, zone 1. these figures highlight areas requiring renovation, the current state of urban aging, and the granularity of deteriorated textures. figure 2. buildings over 30 years old in zone 1 of district 7 figure 3. buildings over 30 years old in zone 1 of district 7 n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 7 figure 4. the number of floors in the deteriorated fabric of zone 1 of district 7 figure 5. the number of floors in deteriorated fabric figure 6. the granularity of deteriorated fabric in the neighborhoods of zone 1, district 7 figure 7. particle size distribution of the deteriorated fabric in the neighborhoods of zone 1, district 7 figure 8. percentage of renewal in the deteriorated fabric block of zone 1, district 7 table 3 and table 4 details the mean and standard deviation of social resilience variables in district 15, while tables 2 provide one-sample t-tests for satisfaction levels with social and physical resilience indicators, respectively. to evaluate social resilience, 15 indicators were selected from theoretical and research backgrounds and assessed using single-sample t-tests, with significance set at the 0.95% confidence level. the findings revealed that most social resilience indicators showed low satisfaction levels among residents of zone 1, district 7 in tehran, indicating overall low social resilience. exceptions include indicators related to voluntary cooperation to reduce vulnerability, institutional, and awareness of potential accident damages, which scored medium to high. critical areas identified for improvement include first aid training, emergency response familiarity, and trust in official media, which recorded the lowest resilience levels. table 3 in the study details citizens' satisfaction levels with these social indicators. n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 8 for the assessment of physical resilience, 14 indicators were selected based on theoretical underpinnings and research background, evaluated through single-sample t-tests, with all indicators considered significant at the 95% confidence level. the results indicated that all the physical resilience dimension indicators are at a low level of satisfaction. hence, it can be inferred that the satisfaction of residents living in the neighborhoods of zone 1, district 7, regarding physical resilience indicators, averages at a very low level. a closer look at the physical indicators revealed that the quality of streets and alleys and the quality and durability of residential buildings were identified as having the lowest levels of resilience. table 4 details the citizens' satisfaction levels with physical indicators. for the hypothesis testing of the research, single-sample t-tests were conducted with a test value of 3. this means that if the mean of variables such as the level of social interactions, neighborhood identity, sense of place belonging, social participation, civic education, security, and social resilience is statistically less than 3, these variables, table 3. single sample t-test satisfaction level for social indicators indicator t-value mean mean deviation degrees of freedom (df) p-value awareness of natural disaster risks -13.83 2.118 -1.450 229 0.001 residents' awareness of safe places map -19.15 2.764 -1.671 229 0.001 residents' awareness of housing safety regulations -13.75 2.223 -0.450 229 0.01 residents' awareness of emergency facilities -23.67 1.112 -1.471 229 0.001 level of first aid training & familiarity with actions like transferring injured, injections, bandaging -31.45 2.310 -0.890 229 0.000 residents' skills in providing first aid -28.15 2.211 -1.763 229 0.001 mental peace during and after an incident -18.80 1.568 -0.870 229 0.000 trust in official media news -37.56 2.406 -0.218 229 0.000 collaboration in crisis problem solving -14.43 1.807 -1.910 229 0.001 willingness to volunteer for reducing vulnerability 11.32 1.340 0.450 229 0.01 sense of place belonging -13.87 2.674 -1.781 229 0.01 mutual trust between people and organizations -19.56 2.809 -1.568 229 0.000 trained and volunteer forces -21.45 2.561 -0.740 229 0.000 awareness of reactions and proper behavior in times of crisis -24.34 2.452 -1.430 229 0.001 table 4. single sample t-test satisfaction level for physical indicators indicator t-value mean mean deviation degrees of freedom (df) p-value access to medical centers -18.32 2.756 -0.433 229 0.000 access to educational centers -12.65 2.562 -1.874 229 0.001 condition of neighborhood water piping -17.67 2.561 -1.564 229 0.001 access to temporary housing -21.12 2.760 -0.430 229 0.001 access to public transportation -15.35 2.432 -0.989 229 0.01 access to green spaces and evacuation routes -18.45 2.542 -1.874 229 0.001 access to main road network -21.67 2.654 -1.438 229 0.001 distance from natural hazard zones -23.89 2.876 -0.211 229 0.000 access to fire stations -11.80 2.234 -1.870 229 0.001 quality and durability of residential buildings -31.14 2.639 -0.890 229 0.000 condition of electricity and electrical installations -23.34 2.333 -0.675 229 0.000 presence of evacuation route maps -20.05 2.843 -0.963 229 0.001 durability of public services -18.11 2.564 -0.780 229 0.000 quality of alleys and neighborhood streets -34.23 2.245 -1.460 229 0.001 n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 9 and ultimately, social resilience, are considered to be in a state of disarray. the significance level of the t-test indicates that the means for the level of social interactions, neighborhood identity, sense of place belonging, social participation, civic education, security, and overall social resilience are below 3. according to table 5, the mean for social interactions is 2.30, for neighborhood identity is 2.41, for a sense of place belonging is 2.58, for social participation is 2.33, for overall social resilience is 2.25, for civic education is 2.23, and for security is 2.18. these results confirm the primary hypothesis and the related sub-hypotheses, indicating lower levels of social interactions, identity, belonging, participation, resilience, civic education, and security than the benchmark level of 3. for testing the main hypothesis, structural equation modeling was conducted. initially, the fit of the measurement model was examined. model fit refers to the extent to which a model is consistent with and agrees with the observed data. therefore, the research's proposed model fit was further analyzed to ensure its compatibility with the research data, ultimately aiming to derive answers to the research questions. table 5. mean and standard deviation of social resilience variables in district 15 type count mean standard deviation sense of place belonging 200 2.58 0.6723 neighborhood identity 200 2.41 0.8761 social participation 200 2.33 0.9321 level of social interactions 200 2.30 0.7645 social resilience 200 2.25 0.6132 civic education 200 2.23 0.9831 security 200 2.18 0.6549 the examination of the conceptual model's fit was carried out in two stages: first, evaluating the fit of the model's measurement part and second, assessing the fit of the model's structural part, which is discussed in detail subsequently. table 6 shows the questionnaire indicators and their reliability coefficients. the description of the table below demonstrates that the impact of indicators such as the level of social interactions, sense of place belonging, social participation, and neighborhood identity on the resilience of deteriorated fabric in district 15 is statistically significant at the 0.001 level with a 95% confidence interval. furthermore, according to the priority of each indicator in the friedman test, it was shown that the sense of place belonging has the most significant impact, with social interactions and social participation ranking second and third, respectively. therefore, based on the obtained results, it can be said that the researcher's hypothesis regarding the impact of social resilience indicators on deteriorated fabrics in district 15 is confirmed. in other words, factors like sense of place belonging, level of social interactions, social participation, and neighborhood identity have a significant effect on the social resilience of deteriorated fabrics in district 15. single sample t-test by priority of variable impact is shown in table 7. table 6. questionnaire indicators and their reliability coefficients (district 15) index number variable α value 1 sense of place belonging 0.84 2 social participation 0.68 3 civic education 0.72 4 level of social interactions 0.87 5 social resilience 0.78 6 neighborhood identity 0.69 7 security 0.81 table 7. single sample t-test by priority of variable impact (district 15) variable df sig. (2tailed) mean difference 95% confidence interval of the difference upper lower sense of place belonging 198 0.001 0.5634 0.7400 0.3871 social resilience 198 0.001 0.3341 0.7659 0.7843 social participation 198 0.03 0.2343 0.5943 0.1562 level of social interactions 198 0.05 0.7765 0.4983 0.1875 neighborhood identity 198 0.05 0.3421 0.3290 0.1245 civic education 198 0.067 0.4351 0.7840 0.1670 security 198 0.76 0.4565 0.7847 0.4312 n. navidpour et al. /future sustainability august 2025| volume 03 | issue 03 | pages 01-11 10 5. conclusions in the research's conclusion, the discourse on resilience emerges as a contemporary subject within urban management. it addresses the gap between theoretical foundations of resilience and their practical application, highlighted by the lack of comprehensive studies on social and physical resilience. natural disasters have led to a reconsideration of the approach to urban spaces, underscoring the necessity of creating resilient cities. this study aimed at a comparative analysis and evaluation of social and physical resilience in the deteriorated urban fabrics of tehran's districts 7 and 15. the findings reveal that the physical dimension of resilience scored highest, with a rank of 3.31, followed by the social dimension at 2.81. conceptual views on urban space recovery and spatial sustainability exhibit a thorough understanding of resilience concerning deteriorated fabrics. by integrating the physical and social dimensions, the study faced challenges in data collection. the simultaneous examination of social and physical resilience required comprehensive observations of the inhabitants' connection with their living spaces, impacting the depth of the study. despite these challenges, the study successfully employed various methods and techniques to enrich the data collection process. through the deployment of appropriate variables and methodology aligned with the realities of urban resilience in the target fabrics of districts 7 and 15, the research presented distinct outcomes compared to frequently repeated scientific approaches, which often yield similar results. the thorough analysis of research indicators, combined with approaches for identifying drivers and scenarios, allowed for the presentation of various strategies as part of a multifold strategy in subsequent phases. the study confirmed the second hypothesis, suggesting that a lack of neighborhood belonging and social participation are principal components in the disordered state of social resilience within the deteriorated fabric of district 15 of tehran. the research process's reliability and validity were assured through meticulous data evaluation at various stages. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] v. mega, "a planet of cities at a time unlike any other: towards the 2030 sustainable development agenda," in human sustainable cities: towards the sdgs and green, just, smart and inclusive transitions: springer, 2022, pp. 1-40. 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(2006). resilience: the emergence of a perspective for social–ecological systems analyses. global environmental change, 16(3), 253-267. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 1 review regulatory and standard insights on transboundary co2 in the context of mrv mohammad nurizat rahman* energy markets and strategy, energy systems, dnv technology centre, 118227 singapore a r t i c l e i n f o article history: received 10 april 2025 received in revised form 18 may 2025 accepted 02 june 2025 keywords: transboundary co2, eu ets, iso, verra, regulatory *corresponding author email address: izat.rahman@dnv.com doi: 10.55670/fpll.fusus.3.4.1 a b s t r a c t as transboundary carbon capture, utilisation, and storage (ccus) projects gain momentum globally, the need for a coherent, robust, and verifiable system for measurement, reporting, and verification (mrv) of cross-border carbon dioxide (co₂) flows becomes increasingly critical. this paper reviews and synthesises key regulatory frameworks and technical standards, namely, the eu emissions trading system (eu ets), iso 27914 and iso 27915, and the verra vm0049 methodology, to assess their applicability to mrv across the co₂ capture, transport, and storage chain. the eu ets, under its 2024 consolidated implementing regulation, sets a high benchmark for uncertainty management and data integrity in co₂ accounting; however, it lacks specific prescriptions for advanced or smart metering technologies. iso 27914, while focused on geological storage, provides essential guidance for long-term containment and injection site monitoring, relevant to the final stages of the ccs chain. iso 27915 provides a comprehensive framework for quantifying and verifying ghg emissions and reductions, establishing a direct link between co₂ flow measurement and emissions reporting. the verra vm0049 methodology, although designed for voluntary carbon markets, provides comprehensive procedures for quantifying and monitoring emissions across transport and storage stages, with practical relevance to transboundary co₂ transfers. while none of these instruments independently address all aspects of cross-border co₂ movement, their combined insights highlight both foundational strengths and critical gaps, such as the absence of unified custody transfer protocols and limited treatment of fugitive emissions in transitional zones. this paper aims to consolidate these insights to inform future mrv frameworks tailored to the unique technical, regulatory, and jurisdictional challenges of transboundary co₂ flows. 1. introduction the paris agreement, along with an increasing number of national and regional commitments to carbon neutrality, underscores the critical importance of deploying carbon mitigation technologies [1-4]. among these, carbon dioxide (co₂) capture and storage (ccs) emerges as a pivotal solution in addressing the global climate challenge. ccs encompasses a suite of technologies designed to capture co₂ emissions from industrial and energy-related sources, preventing their release into the atmosphere. once captured, the co₂ is either transported to a suitable geological formation for long-term storage or, in cases where co-location allows, injected directly into storage reservoirs beneath the capture facility [5]. in addition to storage, captured co₂ can be utilised in various co₂-derived products and services, including synthetic fuels, industrial chemicals, mineralised construction materials, and enhanced oil recovery (eor). these utilisation pathways form the basis of carbon capture, utilisation, and storage (ccus), a broader concept that incorporates both storage and the commercial use of captured co₂ [6, 7]. ccs and ccus technologies are central to the global effort to limit temperature rise to well below 2°c above pre-industrial levels, in line with the objectives of the paris agreement. recognising their climate mitigation potential, the united nations framework convention on climate change (unfccc) formally accepted ccs under the clean development mechanism (cdm) of the kyoto protocol in 2011 [8]. looking forward, ccs may also serve a key role in carbon dioxide future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.4.1 november 2025| volume 03 | issue 04 | pages 01-11 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:izat.rahman@dnv.com https://doi.org/10.55670/fpll.fusus.3.4.1 https://fupubco.com/fusus mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 2 removal (cdr) strategies, enabling net-negative emissions by capturing co₂ directly from the atmosphere and storing it securely [6]. although technical and economic challenges persist, multiple studies have confirmed the feasibility of ccs/ccus with existing technologies [9]. in the context of ongoing reliance on fossil fuels, particularly coal and natural gas, ccus provides a critical pathway for mitigating emissions from both energy production and heavy industry [10-12]. large-scale deployment of ccus systems necessitates integration with existing energy infrastructure, as capture, compression, transportation, and injection processes all require significant energy inputs [13, 14]. in light of the limited availability of alternative decarbonisation technologies for hard-to-abate sectors, ccus remains indispensable for addressing both current and legacy emissions [15-18]. despite its recognised potential, the global rollout of ccs remains limited. as of 2023, operational ccs facilities collectively capture over 50 million tonnes (mt) of co₂ per year, a modest fraction of the estimated 37.4 gigatonnes (gt) of global annual co₂ emissions. currently, around 45 commercial-scale projects are active across sectors such as industrial manufacturing, fuel transformation, and power generation. while early progress was slower than anticipated, recent years have seen renewed momentum. over 700 ccus projects are now at various stages of development across the full value chain, indicating a growing recognition of the technology’s role in supporting climate targets. in 2023, the projected co₂ capture capacity for 2030 increased by 35%, while announced storage capacity saw a substantial 70% growth. these developments position the anticipated co₂ capture capacity for 2030 at approximately 435 million tonnes (mt) annually, with the announced storage capacity reaching around 615 mt per year. despite these advancements, the current trajectory remains insufficient to meet the scale outlined in the net zero emissions by 2050 (nze) scenario, which requires the capture and storage of 1 gigatonne (gt) of co₂ per year [7]. the announced capacities represent only 40% and 60% of the targets, respectively, highlighting the urgent need for accelerated action and investment to close this gap. although the projected co₂ capture capacity for 2030 shows a 35% increase, as of 2022, there were only 137 ccs projects in operation globally. the majority of these projects are concentrated in developed regions: 36 in north america (14 operational), 65 in europe (6 operational), and 8 in australia (1 operational). figure 1 illustrates the geographical distribution of the estimated co₂ capture capacity of these facilities by country, assuming all ccs projects proceed as planned and reach their projected operational capacities. this data has been sourced and adapted from the global ccus projects database maintained by the international association of oil and gas producers [19]. most ccs projects operate within the boundaries of a single nation, with co₂ capture, transport, and storage occurring entirely under the jurisdiction of one state. however, for a global alignment of co₂ sources with suitable storage reservoirs, the widespread deployment of ccs projects is essential. expanding ccs efforts beyond developed countries is key to achieving this objective. research suggests that many developing nations possess significant potential for co₂ storage [20]. this storage capacity could be pivotal for countries lacking sufficient geological storage options but still seeking to leverage ccs as a tool for emissions reduction [21]. figure 1. estimated co₂ capture capacity by countries despite this potential, several barriers prevent the widespread adoption of ccs in developing nations. these include the technical complexity of the required technologies, the substantial investment and resources needed for risk assessment and management, and the absence of robust regulatory frameworks to regulate ccs facilities. consequently, participation by developing nations remains limited, as illustrated in figure 1. the internationalisation of ccs projects, where co₂ is captured in one nation or region and transported to another for permanent storage, introduces significant regulatory challenges, particularly in the areas of transboundary transport and storage. developing a ccs supply chain that spans multiple jurisdictions necessitates the creation of comprehensive regulatory frameworks at both international and domestic levels to effectively manage associated risks and incentivise technological investment [22, 23]. these regional and domestic frameworks play a crucial role, as they can either facilitate or hinder the widespread implementation of such a supply chain. literature consistently emphasises the importance of strong policy support for ccs, especially in regions that serve as both sources and sinks for co₂ [24]. a critical element in the development of a comprehensive regulatory framework for the transboundary shipment and storage of co₂ is the establishment of effective monitoring, reporting, and verification (mrv) systems. this requires a robust carbon accounting system specifically designed to monitor transboundary co₂ flows. given the absence of a centralised mrv framework for such transboundary co₂, this paper seeks to analyse existing standards and regulatory frameworks related to carbon management, evaluate the key criteria essential for a future mrv system, and propose best practices and lessons learned from these frameworks to guide the future development of mrv systems for transboundary co₂ flows [25]. 2. monitoring, reporting, and verification (mrv) mrv of emissions is fundamental to the credibility of any emissions trading system, whether within compliance carbon markets, such as the european union emissions trading system (eu ets), or voluntary carbon markets (vcms), like the gold standard marketplace and the verra registry. although these systems differ in structure, the eu ets, being based on carbon allowances, and vcms, on carbon credits, both rely heavily on robust mrv frameworks. within the eu ets, mrv underpins transparency, facilitates compliance tracking, and strengthens enforcement. a comprehensive, consistent, accurate, and transparent mrv system fosters trust in emissions trading by ensuring that operators fulfil their obligation to surrender the correct number of allowances. as the world’s first international emissions mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 3 trading scheme, the eu ets has developed mature and reliable mrv guidelines over time, providing a robust framework for emissions measurement and reporting. in the vcm, carbon credits are issued based on the reduction or removal of one metric tonne of co₂-equivalent greenhouse gas (ghg) emissions through specific projects. these credits are quantified using detailed carbon accounting methodologies and mrv guidelines. for instance, verra’s verified carbon standard (vcs) is the world’s most widely used ghg crediting programme. it enables individuals, companies, or organisations to purchase credits that support emission-reducing activities. verra’s methodologies ensure the accurate quantification of ghg benefits and the issuance of verified carbon units (vcus). these methodologies define project boundaries, establish baselines, assess additionality, outline monitoring parameters, and quantify ghg emission reductions or removals, thus reinforcing rigorous metering and measurement practices. specific methodologies, such as vm0049, are dedicated to ccs projects. mrv guidelines in both compliance and voluntary frameworks are grounded in extensive scientific research, incorporating carbon accounting, remote sensing, and environmental monitoring techniques. they are aligned with international standards, including iso 14064 (greenhouse gases – part 1: specification with guidance at the organisation level for quantification and reporting of greenhouse gas emissions and removals) and iso 14065 (requirements for greenhouse gas validation and verification bodies). for ccs applications, standards such as iso 27915 (carbon dioxide capture, transportation, and geological storage quantification and verification) provide further specificity, ensuring that monitoring and verification processes are rigorous, consistent, and internationally standardized. therefore, critical insights from these standards and existing regulations can be used to propose key measures for the future establishment of mrv systems for transboundary co₂ flows. in this paper, table 1 summarises the international standards and regulations reviewed. in all of these standards and regulations, the review was conducted by focusing on the key aspects considered essential for establishing a robust mrv framework for transboundary co₂ flows. these aspects serve as the evaluation criteria outlined below. while this list is not exhaustive, it captures the most critical elements deemed vital for addressing the unique challenges posed by the international shipment and storage of co₂. a clear understanding and alignment on these aspects are crucial to ensure consistency, transparency, and reliability across different jurisdictions. the key aspects are as follows: 1. co₂ receipt metering and monitoring requirements: proper metering and monitoring at the point of co₂ receipt is fundamental to ensuring that the quantity and quality of co₂ being transported and stored are accurately recorded. this includes: o selection of metering technologies: an evaluation of the technologies recommended or required by the standards and regulations, including their suitability for different co₂ conditions. o co₂ operating conditions: consideration of technical parameters that impact metering and monitoring accuracy, including pressure, temperature, flowrate, composition (including levels of impurities), phase state (gaseous, liquid, supercritical), environmental conditions, and operational limits. o calibration procedures: requirements for metering equipment to be calibrated in accordance with recognised national or international standards, ensuring traceability and accuracy across different measurement points. o accuracy and uncertainty levels: specification of the allowable error margins and required uncertainty levels for measurement systems to maintain credibility and precision in reporting. o additional guidelines: any supplementary procedures or considerations that support effective measurement and reporting but may not fall directly under the above categories, for example, redundancy measures or backup metering protocols. table 1. standards and regulations reviewed details reference eu ets • directive 2004/87/ec • directive 2009/31/ec • commission implementing regulation (eu) 2018/2066 • commission implementing regulation (eu) 2018/2067 • commission implementing regulation (eu) 2024/2493 • commission implementing regulation (eu) 2023/2122 • others policy/technical papers related to ccs, referencing the eu ets [26] iso • 27914 • 27915 [27, 28] verra’s vcs • ccs overarching methodology: vm0049 carbon capture and storage • transport module: e.g. vmd0057 (project emissions from co2 transport for ccs projects) • storage module: e.g. vmd0058 (project emissions from co2 storage in saline aquifers and depleted hydrocarbon reservoirs) [29-31] 2. co₂ metering and monitoring points: it is essential to clearly define where metering and monitoring must occur along the co₂ value chain to maintain a complete and verifiable record of co₂ movements. this includes: o identification of critical points: such as the point of capture, before and after compression, at the point of entry and exit in transport systems (pipelines, ships, etc.), and at the injection point into storage sites. o specification of requirements: including the technical specifications needed at each monitoring point to ensure consistent data collection and compatibility across jurisdictions. 3. leakage/reversal management: leakage or reversal events, where stored co₂ is unintentionally released back into the atmosphere, pose significant risks to the environmental integrity of transboundary ccs operations. as such: o best practices for management: the standards and regulations are assessed for their recommended practices in detecting, reporting, mitigating, and remediating leakage or reversal incidents. o requirements for contingency planning: including the development of monitoring plans, corrective action mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 4 measures, and financial assurance mechanisms to address potential liabilities. 4. digital and smart solutions: the integration of digital technologies can significantly enhance the efficiency, accuracy, and transparency of mrv systems. therefore: o recommendations for digital tools: evaluation of guidance on the use of smart metering, real-time monitoring systems, blockchain for data integrity, remote sensing technologies, and digital platforms for automated reporting and verification. o data management practices: standards for data security, transparency, and accessibility to ensure that data collected across different jurisdictions can be reliably used for regulatory reporting and carbon accounting. an overall traffic light assessment was performed for each of the identified standards and regulations. the colour coding used in this assessment is as follows: • green: the standard or regulation provides a comprehensive definition or coverage of the topic, and it is fully applicable to the case of transboundary co₂ flows. • yellow: the evaluation criteria are covered within the standard or regulation, but the coverage is either partial or not fully applicable to the specific requirements of the current case. • red: the evaluation criteria are not covered or addressed within the standard or regulation. detailed discussions on how each of these standards and regulations align with the evaluation criteria, together with justification for their respective traffic light ratings, are provided in the following chapters. 3. eu ets the overall traffic light assessment of the relevant eu ets regulations is presented in table 2. adapted from eu regulation 2018/2066 pursuant to directive 2003/87/ec (consolidated 2024), the monitoring and reporting regulation (mrr) outlines two primary methodologies for quantifying ghg emissions: the calculation-based methodology and the measurement-based methodology. the calculation-based approach estimates emissions based on fuel and material inputs, using emission factors and activity data. this method is generally simpler and more commonly applied across european installations. in contrast, the measurement-based methodology directly determines emissions by continuously measuring the concentration of relevant ghgs, primarily co₂, in the flue gas, along with the volumetric flow rate of that gas. table 2. relevant eu ets regulations criterion remarks metering technology no specific information is provided regarding recommended metering technologies. co₂ operating conditions related to metering and monitoring the regulations mainly focus on co₂ quantities (flows) and concentrations, without detailed specifications on operating conditions such as pressure, impurities, or phase state. calibration procedures traceable to national or international standards a generic explanation is provided, requiring calibration to national or international standards, but without specific protocols or references. accuracy and uncertainty levels of metering systems a notable feature is the use of a tiered approach for uncertainty requirements in the monitoring system. additional measurement and monitoring guidelines for accounting and regulatory reporting the eu ets provides best practices to address potential data loss in co₂ metering, particularly under article 45. it also introduces flexibility to measure co₂ at either the transferring or receiving installation. this is particularly relevant to the current co₂ value chain planned in malaysia, where metering will occur at the receiving station. to ensure data integrity, operators must reconcile co₂ quantities across the value chain and provide technical justifications for any discrepancies, such as uncertainties or operational deviations. identification and specification of critical metering and monitoring locations generic guidance is provided, emphasising flexibility to install metering points at transferring or receiving facilities, but without specifying detailed sitting criteria across the full value chain. leakage/reversal any co₂ leakage (including fugitive emissions, venting, or incidents) must be accounted for in the installation’s emissions report. biogenic co₂ leakages are treated as fossil emissions. in-transit corrections are permitted (typically reconciled at year-end). reversals are addressed according to the standard eu ets rules for transferred co₂. digital/smart solutions to enhance co₂ data collection, management, and analysis no specific recommendations or requirements for digitalisation or smart solutions are provided. overall remarks the eu ets (particularly commission implementing regulation (eu) 2018/2066, pursuant to directive 2003/87/ec and its 2024 consolidation) establishes important requirements for uncertainty management and data handling in co₂ metering across the ccs supply chain. it offers relevant guidance for co₂ measurement and monitoring applicable to the current transboundary co₂ flow scenario. however, it lacks detailed recommendations on specific metering technologies and the integration of digital or smart metering solutions, which would need to be supplemented through project-specific practices or by referencing additional standards. mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 5 this approach is also applied to monitor co₂ transfers between installations, whereby both the concentration and flow of the transferred gas must be accurately measured. this is particularly relevant in the context of ccs, where the transport and storage of co₂ demand a higher degree of accuracy than conventional combustion-based emission sources. although the use of continuous emission measurement systems (cems) for monitoring flue gas emissions is relatively uncommon in europe due to the prevalence of calculation-based methods, cems becomes essential in ccs applications. in such scenarios, calculating emissions based on fuel input is often impractical or inaccurate. as a result, the ccs-specific mrv, which amends the broader mrr framework, places a strong emphasis on cems as a critical tool for real-time co₂ stream monitoring, especially at transfer points. continuous monitoring of co₂ stream composition is expected to be a standard requirement to ensure reliable accounting of transferred volumes in ccs chains. one of the defining features of the eu ets regulatory framework is the tiered system used to define the accuracy and uncertainty requirements for emission measurements. for measurement-based methodologies, tier 4, the highest level, must be applied for transferred co₂, requiring an uncertainty of no more than ±2.5%. the selection of tiers depends on the scale of the installation. for example, largescale co₂ capture installations handling more than 50,000 tonnes per year are typically classified as category b or c, thus requiring adherence to tier 4 for both co₂ flow and concentration measurements. however, the regulation provides flexibility in its application. where achieving the highest tier is technically infeasible or would result in disproportionate costs, operators may request approval to use a lower tier, subject to justification and acceptance by the relevant competent authority. this approach maintains a balance between regulatory rigour and operational practicality, particularly for installations facing technical limitations. table 3 summarises the applicable guidance for installations under the mrr, based on the eu ets reference [32]. the eu ets also provides best practices to address potential data loss in co₂ metering, as outlined in article 45. another significant aspect is the flexibility to measure co₂ at both the transferring and receiving installations. this is highly relevant to the transboundary value chain. to ensure accuracy, the measured co₂ quantities throughout the value chain must align. if discrepancies occur, operators must provide technical explanations, such as measurement uncertainties or deviations, to justify the differences. 4. relevant iso standards the overall traffic light assessment for the iso 27914:2017 is presented in table 4. moreover, the overall traffic light assessment for the iso 27915:2017 is presented in table 5. according to iso 27915, ghg reporting for ccs projects is conducted annually, while the actual measurement of co₂ flow is performed continuously, with data typically aggregated on a monthly basis. at the point of capture, the co₂ stream is monitored using physical measurement devices such as flow meters and sensors. these instruments are used to record key parameters, including co₂ concentration, flow rate, pressure, and temperature, as the gas enters the transportation system. for storage operations, metering is carried out at both the plant gate, marking the custody transfer point, and at the injection wellheads, ensuring comprehensive coverage of co₂ flows into subsurface formations. to reduce calibration errors and improve overall accuracy, iso 27915 allows for data aggregation at centralised collection points rather than relying solely on individual wellhead measurements. the standard outlines clear methodologies for calculating the annual co₂ mass handled in a ccs system. one common approach is to sum the quarterly co₂ concentrations, expressed either as weight or volume percentages, and multiply these by the corresponding mass or volumetric flow recorded during each quarter. alternatively, where co₂ concentration data are available, they can be combined with density values (expressed in metric tons per standard cubic meter or derived from the total stream mass) and volumetric flow data to calculate accurate annual totals. table 3. mrr guidelines for various installation categories installation category emission source category tier required minimum tier (if tier required technically not feasible or unreasonable costs) if not at least tier 1 is possible category c (>500kt) major highest tier in annex viii highest tier in annex viii minus 1 (minimum tier 1) fall-back approach minor highest tier in annex viii tier 1 category b (50kt<x≤500kt) major highest tier in annex viii highest tier in annex viii minus 2 (minimum tier 1) minor highest tier in annex viii tier 1 category a (≤50kt) major tier 2 tier 1 minor tier 2 tier 1 installation with low emissions (<25kt) major tier 1 unless higher tier is achievable without additional effort (not applicable for n2o) minor mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 6 table 4. traffic light assessment iso 27914:2017 criterion remarks metering technology no specific information is provided regarding the types of metering technology to be used. co₂ operating conditions related to metering and monitoring the standard addresses the composition of the co₂ stream and outlines expected ranges for pressure, temperature, and flow rate at the receiving storage facility. it also includes injection rate and design specifications, though these are primarily intended for storage site operations. calibration procedures traceable to national or international standards general reference is made to calibration procedures, but specific traceability requirements are not detailed. accuracy and uncertainty levels of metering systems no explicit information or thresholds regarding accuracy or uncertainty levels are included. additional measurement and monitoring guidelines for accounting and regulatory reporting the quantity of co₂ injected must be recorded for purposes of accounting, engineering, and regulatory compliance. however, guidance remains high-level. identification and specification of critical metering and monitoring locations the standard recommends individual meters be installed at each injection well, downstream of the custody transfer meter, to ensure detailed tracking at the point of storage. leakage/reversal general guidelines are provided on leakage management. these include requirements for primary seals, assessment of potential leakage pathways, installation of secondary containment barriers, and the use of flow modelling to evaluate potential leakage scenarios. digital/smart solutions to enhance co₂ data collection, management, and analysis no specific information is provided regarding digitalisation or smart solutions. overall remarks iso 27914 is focused on geological storage of co₂ and is most applicable to the storage phase of the ccs value chain. it is highly relevant when the transported co₂ is intended for long-term containment in geological formations. while the standard does not explicitly address transportation metering and monitoring, it does cover essential requirements for injection site monitoring, safety assurance, and leakage prevention. it provides a useful reference for evaluating monitoring approaches at the point of co₂ injection. table 5. traffic light assessment iso 27915:2017 criterion remarks metering technology the standard mentions the use of mass and volume flow meters for co₂ measurement, in addition to chemical analysis systems (e.g. sampling and laboratory testing) and general leakage detection technologies, such as laser and infrared systems, particularly relevant for storage applications. co₂ operating conditions related to metering and monitoring key parameters prioritised for measurement and monitoring include co₂ concentration, flow rate, pressure, and temperature. the standard also highlights the importance of pre-treatment systems to remove impurities (e.g. annex gases, minor components, organics) before capture or transport, which affects monitoring requirements. calibration procedures traceable to national or international standards to minimise calibration errors, the standard recommends data aggregation at centralised collection points rather than relying exclusively on wellhead meters, particularly in storage contexts. however, specific traceability requirements are not extensively detailed. accuracy and uncertainty levels of metering systems the tier 3 methodology is introduced, involving flow metering during gas loading and discharge. this method relies on site-specific or plant-level data, including direct measurements and modelling, to enhance measurement accuracy. additional measurement and monitoring guidelines for accounting and regulatory reporting the standard discusses aggregation methodologies for ccs systems, which involve combining co₂ measurements across different points within the supply chain to calculate the total co₂ captured, transported, and stored, crucial for both accounting and regulatory reporting. identification and specification of critical metering and monitoring locations measurement and monitoring points across the ccs value chain are outlined for quantification and verification (q&v) of co₂ flow and emissions. these include capture outlets, transport interfaces, and injection points. leakage/reversal the standard provides general guidance on leakage management, primarily in the context of emissions quantification. accurate leakage estimation is essential for reliable ghg accounting. digital/smart solutions to enhance co₂ data collection, management, and analysis no specific recommendations are provided regarding the application of digital or smart metering technologies. overall remarks iso 27915 offers guidelines for the q&v of ghg emissions and reductions from ccs activities. it covers all elements of the ccs chain, capture, transport, and storage, with a particular emphasis on ensuring the accuracy of emissions reporting. while its focus is on ghg q&v, it offers valuable guidance on co₂ metering and monitoring, especially because leak rates must be measurable. thus, the standard creates a direct link between co₂ flow measurement and broader ghg reporting across the ccs chain. mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 7 by integrating chemical analysis techniques, either inline or through periodic sampling and laboratory testing, with flow measurements, operators can obtain a detailed understanding of the co₂ stream’s composition and quantity. this precision is essential not only for reporting but also for operational efficiency and regulatory compliance. in addition to pure co₂, the gas stream often contains annex gases such as nitrogen (n₂), oxygen (o₂), hydrogen (h₂), and argon, as well as minor components like methane (ch₄), carbon monoxide (co), and water. trace impurities, including sulfur dioxide (so₂), nitrogen oxides (noₓ), hydrogen sulfide (h₂s), mercury, various metals, and volatile organic compounds like benzene, may also be present. iso 27915 emphasises the importance of removing these substances prior to co₂ transport or injection through dedicated treatment units integrated within the conversion and separation process. although the standard does not delve into the direct impacts of these impurities on surface infrastructure or storage formations, it recommends that monitoring plans account for the associated risks. the concept of data aggregation is another critical aspect of iso 27915, particularly in the context of complex ccs networks. aggregation enables project developers to combine co₂ measurements taken at different points along the value chain to calculate the total amount captured, transported, and stored. two primary aggregation methods are identified. the first, known as post-segregation aggregation, involves summing the co₂ mass values recorded by separate meters at key points throughout the system. the second, presegregation aggregation, calculates total annual co₂ mass by subtracting the sum of internal co₂ uses or losses, measured downstream, from the upstream total captured at the main flow meter. this approach is useful for tracking and accounting for process-related co₂ consumption or losses before final storage. leakage detection and management are also addressed through a multi-faceted approach. iso 27915 recommends the use of pressure monitoring, regular visual inspections, and advanced detection technologies such as laser-based and infrared systems to identify leaks in buried pipelines or storage infrastructure. these techniques are essential for ensuring the long-term containment of co₂ and maintaining environmental safety. furthermore, iso 27915 aligns with key elements of the u.s. environmental protection agency’s (epa) greenhouse gas reporting program (ghgrp), specifically subpart rr, which pertains to geologic sequestration. under subpart rr, facilities injecting co₂ underground are required to develop and implement a robust mrv plan approved by the epa. required data points include the mass of co₂ received for injection, the amount injected into subsurface formations, any co₂ produced back to the surface, surface leakage, and emissions from equipment leaks or venting. additionally, emissions occurring between production flow meters and wellheads must be reported, along with the mass of co₂ successfully sequestered and the cumulative total reported over time. in cases where co₂ is transported by ship, iso 27915 introduces a tier 3 methodology for accurately metering gas quantities during loading and discharge. this methodology is consistent with the 2006 ipcc guidelines (volume 2, section 3.3), which describe three tiers of accuracy for estimating emissions from energy systems. tier 3 methods are the most precise, relying on site-specific or facility-specific data derived from direct measurements, real-time monitoring, and tailored modelling approaches. these methods are particularly suitable for high-integrity ccs operations involving transboundary co₂ transport and storage. 5. verra ccs-related methodology/modules the overall traffic light assessment for the verra ccsrelated methodology and modules is presented in table 6. under the verra ccs methodology vm0049 , the eligibility of a co₂ stream for storage is contingent upon its purity and compliance with relevant regulations. specifically, the captured co₂ must be at least 95% pure and must meet all applicable national, regional, or local standards concerning co-injected substances. this ensures that the stream is suitable for geological storage and minimizes environmental risks. to measure the flow of co₂, the methodology provides two main options: mass flow meters and volumetric flow meters. for supercritical co₂, where impurities can distort volumetric readings, project proponents must either use mass flow meters while accounting for all impurities exceeding 0.25% mole fraction, or use volumetric meters while accurately determining both co₂ density and concentration. importantly, the cumulative mole fraction of unmeasured impurities cannot exceed 2%. when using mass flow meters, the total mass flow is multiplied by the co₂ concentration (mass fraction), which is derived from sampled mole fractions. these measurements are carried out continuously, with data captured at least every 15 minutes. commercially available technologies such as coriolis, thermal, impeller, and twin turbine meters are recommended by the methodology as well. similarly, volumetric flow measurement at stp requires multiplying the total volumetric flow by the co₂ concentration (volumetric fraction) and its density at stp. devices like rotameters, turbines, wedges, ultrasonic, and vortex meters are recommended to be used, with the same 15-minute monitoring interval. pressure and temperature at the flow meter must also be recorded continuously under operating conditions using digital or analog instruments such as pressure transducers, thermocouples, or thermistors. sampling of the gas stream focuses on components exceeding a mole fraction of 0.5% under standard conditions or 0.25% under supercritical conditions. two options are offered: option a involves gas chromatography with data aggregated weekly, while option b adds ir spectroscopy and aggregates monthly. calibration of all metering and monitoring equipment must adhere to either manufacturer specifications, national/local standards, or international benchmarks (e.g., iec, iso), ensuring traceability and data reliability. equipment must operate within specified conditions and undergo routine maintenance. the transport module (vmd0057) defines its boundary at the custody transfer point and includes intermediate storage and all transport legs. each leg is considered separately when different transport modes are involved or when crossing borders, enabling clear attribution of emissions across jurisdictions. the methodology underscores the importance of emissions monitoring at each intermediate storage site and transport leg, identifying these as critical metering points. mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 8 table 6. traffic light assessment verra ccs methodology vm0049 criterion remarks verra ccs methodology vm0049 verra transport module vmd0057 verra storage module vmd0058 metering technology the modules vmd0057 and vmd0058, based on methodology vm0049, outline that co₂ measurements must be conducted using commercially available devices. • mass flow: measured using coriolis, thermal, or impeller meters and multiplied by the co₂ concentration (mass fraction). • volumetric flow: measured using rotameters, turbine, ultrasonic, or vortex meters at standard temperature and pressure (stp), multiplied by co₂ concentration (volumetric fraction) and co₂ density. • measurements must be continuous, with a minimum reading every 15 minutes. co₂ operating conditions related to metering and monitoring the co₂ stream must meet the following requirements: • minimum purity of 95% co₂. • compliance with applicable national/regional/local regulations regarding co₂ purity and concentrations of coinjected substances. calibration procedures traceable to national or international standards metering equipment must be installed and calibrated in line with local/national standards or manufacturer specifications. if these are unavailable, international standards (e.g., iec, iso) must be used. equipment must operate within the manufacturer’s operating conditions and be routinely calibrated, inspected, and maintained. accuracy and uncertainty levels of metering systems no specific levels for accuracy or uncertainty are defined. however, a statistical approach is required for quantifying overall uncertainty in emission reductions and removals, considering potential measurement errors. additional measurement and monitoring guidelines for accounting and regulatory reporting pressure and temperature must be continuously monitored at the flow meter under operating conditions using recordable electronic signals (e.g., pressure transducers, thermocouples, or thermistors). sampling requirements: • applies to components with >0.5% mole fraction at standard conditions or >0.25% under supercritical conditions. • sampling is done with commercially available devices: o option a: gas chromatography, data aggregated weekly. o option b: gas chromatography + ir spectroscopy, data aggregated monthly. • minimum monitoring frequency: every 15 minutes. identification and specification of critical metering and monitoring locations no direct specification. the modules emphasise the need to measure emissions at each intermediate storage site and transport leg – deemed critical for co₂ measurement. mandatory monitoring points are required for co₂ injection downstream of all intermediate storage, compression, and conditioning units, both onshore and offshore. leakage/reversal no specific procedures outlined for leaks or reversal under transport modules. (note: verra defines leakage as an unintended increase in ghg emissions outside project boundaries because of project activities). fugitive or vented emissions from transported co₂ are acknowledged, but quantification or measurement details are not provided. the storage module includes quantification methods for both intentional and unintentional leaks from surface and subsurface. digital/smart solutions to enhance co₂ data collection, management, and analysis a working group has been established to advance digital measurement, reporting, and verification (dmrv) technologies. the initiative is ongoing and under development. overall remarks the verra methodology vm0049 provides a framework for quantifying ghg reductions from ccs projects within the vcm, using a baseline-versus-project approach across the co₂ capture, transport, and storage chain. modules vmd0057 and vmd0058 specifically address emissions from transport and storage, which is highly relevant for transboundary co₂ activities, such as shipping or pipeline transfer between countries. while the methodology does not explicitly define transboundary protocols, its detailed provisions on co₂ stream purity, metering technologies, and leakage quantification provide valuable technical insights. mn. rahman /future sustainability november 2025| volume 03 | issue 04 | pages 01-11 9 for certain transport scenarios, particularly when using ships, trucks, or rail, the methodology allows emissions estimation using default values and measured co₂ mass. when co₂ is transported in detachable containers, the total weight, including the container, must be monitored using flow meters or weighing scales. fugitive emissions during transport are acknowledged but not comprehensively quantified. while ch₄ emissions from fuel use are considered, co₂ fugitive emissions are referenced only in terms of likely sources like valves or connectors, with limited calculation guidance. conversely, the storage module (vm0058) provides more detailed treatment. the storage site boundary includes all surface facilities, injection and monitoring wells, and subsurface areas up to the extent of the co₂ plume. mandatory monitoring points must be located downstream of intermediate storage, compression, and any conditioning units, both for onshore and offshore wells. the methodology addresses both intentional and unintentional co₂ releases. surface venting may result from maintenance (e.g., blowdowns) or safety mechanisms (e.g., pressure relief valves) and must be quantified using one of three approaches: direct measurement, estimation for isolated volumes, or estimation for non-isolated volumes. subsurface venting, often associated with injection well maintenance, must follow approach 1 (direct measurement). unintended surface leaks (e.g., pipeline leaks) are quantified using emission factors, with a default value of 0.26 kg co₂/hr/km provided. subsurface leakage from the storage complex requires modelbased estimation using reservoir and monitoring data. across all modules, metering and weighing devices must remain within operational specifications and be regularly calibrated. for co₂ and fuel-related measurements, cross-verification with energy balances and purchase documentation is recommended to ensure data consistency. 6. conclusions this paper has examined the eu ets, iso 27914 and 27915 standards, and the verra vm0049 methodology to assess their technical provisions, practical relevance, and regulatory applicability to future transboundary co₂ mrv frameworks. each instrument brings valuable strengths. the eu ets, through its 2024 implementing regulation, provides a robust compliance regime with strong provisions on uncertainty management and data handling, although it lacks detailed direction on digital and advanced metering technologies, which will be vital for cross-border integration. iso 27914, while limited to geological storage, offers critical insight into injection site monitoring and leakage prevention, making it especially relevant at the receiving end of transboundary co₂ flows. iso 27915 enhances the chain-wide accountability of ccs by linking accurate flow measurement with broader ghg quantification and verification requirements. it reinforces the importance of consistent metering and monitoring across all ccs components, especially when emission reductions are claimed across jurisdictions. the verra vm0049 methodology contributes significantly to the technical definition of project boundaries, stream purity, emissions accounting, and leakage quantification. modules vmd0057 and vmd0058 are particularly applicable to shipping and pipeline-based transboundary movements. however, as a voluntary mechanism, verra does not explicitly address governance structures or liability allocation across borders, which will be critical for enforceability in a regulated international context. taken together, these standards and methodologies offer critical building blocks for the development of future transboundary co₂ mrv frameworks. they highlight both the technical rigour already available and the systemic gaps that must be addressed. among these are the absence of standardised protocols for custody transfer, underdeveloped quantification of fugitive emissions during crossjurisdictional transport, and insufficient integration of digital monitoring technologies. this paper seeks to bring coherence to the fragmented landscape of current standards and regulations by identifying how each addresses (or overlooks) the specific challenges posed by transboundary co₂ flows. the analysis offers a consolidated knowledge base to guide regulators, project developers, and policymakers in shaping a credible, transparent, and internationally harmonised mrv system. such a system will be fundamental to supporting the scalability of cross-border ccus projects, enabling their contribution to global net-zero targets. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the author declares no potential conflict of interest. references [1] d’amore, f., lovisotto, l., bezzo, f., 2020. introducing social acceptance into the design of ccs supply chains: a case study at a european level. j. cleaner prod. 249, 119–337. https://doi.org/10.1016/j.jclepro.2019.119337 [2] zhang, d., alhorr, y., elsarrag, e., marafia, ah., lettieri, p., papageorgiou, lg., 2017. fair design of ccs infrastructure for power plants in qatar under carbon trading scheme. int. j. greenhouse gas 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https://creativecommons.org/licenses/by/4.0/ m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 12 review evaluating the impact of economic policies on solar energy growth in iran mahshid noorollahi1, shahab eslami2, hossein yousefi2*, arash shahee3, mahmood abdoos2 1faculty of economics, university of tehran, tehran, iran 2energy modelling and sustainable energy system (metsap) research lab, school of energy and sustainable energy resources, college of interdisciplinary science and technologies, university of tehran, tehran, iran 3school of energy and sustainable energy resources, college of interdisciplinary science and technologies, university of tehran, tehran, iran a r t i c l e i n f o article history: received 15 april 2025 received in revised form 19 may 2025 accepted 03 june 2025 keywords: photovoltaic, renewable energy, policy instruments, techno-economic assessment, sustainable development *corresponding author email address: hosseinyousefi@ut.ac.ir doi: 10.55670/fpll.fusus.3.4.2 a b s t r a c t this paper explores the techno-economic implications of iranian policy instruments designed to promote large-scale photovoltaic (pv) power plants. as global energy demands rise and environmental concerns intensify, transitioning from conventional fossil fuels to renewable energy sources has become imperative. this study investigates the current state of iran's electricity market and the effectiveness of its power purchase policies in facilitating pv development. despite possessing substantial solar energy potential, iran faces significant challenges, including financial constraints and inconsistent energy policies, which hinder the swift adoption of renewable technologies. the research utilizes a comprehensive approach to assess these barriers and proposes strategic financial solutions to enhance investor confidence and participation in the solar energy sector. notably, this study contributes to the existing literature by providing a detailed analysis of iran's unique socioeconomic context and its impact on the implementation of renewable energy policy. the findings underscore the necessity for cohesive governmental support and innovative financing mechanisms to unlock iran's vast solar resources, ultimately paving the way for sustainable energy solutions that align with global carbon neutrality goals. 1. introduction as energy consumption has risen, humanity has encountered a progressive decline in fossil fuel reserves in recent years. this has prompted the adoption of alternative and sustainable energy sources, such as wind, water, and solar power. simultaneously, the escalating human need for energy has resulted in the excessive utilization of fossil fuel resources. consequently, this has led to environmental degradation and damaging pollution, imposing substantial financial burdens on governments to combat ecological contamination. the depletion of fossil fuel reserves served as the primary impetus for governments to transition towards clean and renewable energy, progressively shifting their focus towards natural sources such as wind and solar power. undoubtedly, the sun is universally recognized as the primary energy source for humans. throughout history, humans have harnessed their heat and light for various purposes. even in modern times, with cutting-edge technology, it is feasible to construct cost-effective solar power plants. furthermore, it is imperative to ensure energy provision without incurring exorbitant expenses associated with the extraction and utilization of fossil fuels and the emission of detrimental gases. in the sun belt, iran has significant potential for solar energy generation. among these, qazvin is a prominent province in developing and constructing solar power plants. qazvin's favorable conditions for building a power plant and installing solar panels stem from its geographical location and high elevation, which result in a fall in air temperature at higher altitudes. the efficiency of the panels increases. however, solar radiation may be a contributing factor. in certain regions, the elevated temperature diminishes the panels' effectiveness. the expansion of trade and energy use, emerging from technological growth and changing lifestyles, are the most significant factors in global warming and future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.4.2 november 2025| volume 03 | issue 04 | pages 12-20 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:hosseinyousefi@ut.ac.ir https://doi.org/10.55670/fpll.fusus.3.4.2 https://fupubco.com/fusus m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 13 environmental changes seen and reported by the researchers [1]. new investigations have revealed a higher trend in electricity demand due to industrial improvement in developing nations. this increasing trend proposes that energy consumption in developed nations will be surpassed by use in developing countries due to the enhancement of socio-economic factors [2,3]. different methods have been developed to harness solar energy, with thermal and photovoltaic systems being the predominant ones. both options offer several benefits, including providing pure and inexhaustible energy, which is also cost-free. despite the vast potential, this energy usage is significantly limited [4]. the iranian economy relies heavily on petroleum due to its abundant fossil fuel sources. the sluggish transition towards renewable energy, a key challenge, can be attributed to governmental policy and iran's prevailing social conditions. understanding the role of governmental policy in this transition is crucial for informed decision-making. at this point, acquiring solar energy is difficult without government support and encouragement. the feed-in tariff scheme is the most broadly approved policy instrument to promote pv [5]. the iranian government has opted for this strategy to enhance the development of renewable energy power facilities. extensive research has identified the optimal hybrid systems for residential applications [6]. numerous studies have also examined the impact of government initiatives on the cost and effectiveness of solar energy supply systems and power plants. notably, a recent study outlined a practical and straightforward method for effectively controlling the ideal scale of renewable energy systems for residential use during the conceptual phase, providing reassurance and confidence in its application [7]. public policy substantially influences the progress of technologies in the renewable energy industry, mainly through tax incentives, production quotas, and tradable certificates [8]. several studies have been conducted in developing countries, such as india, to evaluate policy instruments and long-term planning for photovoltaic (pv) development. the most effective instruments include various state policies, such as different tariff fits [9, 10]. additionally, similar research has been conducted in the us to identify the most effective policy solution for rapidly developing renewable energy [11]. due to the different parameters in this article, the approach proposed for this optimization was based on the ret screen software. in this paper, this policy instrument has been investigated to determine the technoeconomic impact of this policy on a large-scale photovoltaic power plant. for a better understanding, the market and situation of the electricity market in iran have been analyzed [12]. despite the significant potential of renewable energy sources, iran continues to rely on fossil fuel resources to meet its energy needs. the country has faced significant financial difficulties and has generated substantial greenhouse gas emissions [13-14]. moreover, the nation has faced numerous challenges in establishing alternative renewable energy sources and formulating consistent energy policies in recent years. to examine the source of these barriers, this study initially provides a comprehensive analysis of previous energy policy initiatives in iran. it demonstrates that sufficient commitment to long-term energy planning may have significantly mitigated these challenges. nevertheless, past studies have shortcomings in applying individual planning tools through technical assessment. 2. the islamic republic of iran's electricity context despite possessing the world's second-largest oil and gas reserves, iran uses renewable energy resources in its energy mix. this decision is based on the following justifications: • to conform to global initiatives aimed at mitigating climate change and reducing the use of fossil fuels. • the objective is to enhance energy availability in remote and isolated areas of the country by implementing decentralized energy generation. • to facilitate the management and mitigation of the escalating levels of urban air pollution. • to increase the energy security of iran's energy supply through a mix of technologies. to sustain and guarantee the current amount of nonrenewable energy exports, as of 2008, approximately 84.5% of iran's electricity was generated by thermal power plants that utilized natural gas and heavy fuel oil as their primary fuel sources. these power plants had a combined capacity of around 53 gw. during the un climate change conference in paris, iran committed to reducing its greenhouse gas (ghg) emissions by twelve percent by 2030. iran has experienced a recent upswing in its economic growth, expanding by 3% in 2015. growth is forecast to increase to 5.8% and 6.7%, respectively, in 2016 and 2017. the share of different sources of an electric power plant and their situation should be specified to investigate the energy policy. in the next part, the electricity generation in iran is briefly discussed [15-17]. 3. electricity generation in iran electricity in iran is generated by a combination of stateowned power plants, such as those managed by tavanir and affiliated regional electric companies, hydroelectric power plants under the control of the deputy of water and sewage of the ministry of energy (moe), privately-owned power plants, and the nuclear power plant managed by the atomic energy organization. privatization began with the implementation of energy conversion agreements (ecas). it progressed through the establishment of build-operatetransfer (bot) and build own operate (boo) projects in collaboration with private investors [18]. in 2013, tavanir conducted a competitive bidding process and sold a portion of its power plants, resulting in a 41% rise in the electricity generated from remote locations compared to the total installed capacity. this information is supported by the studies conducted by zandi et al. [5], aryanpur et al. [19], and tabasi et al. [20]. within every regional electric business exists a department known as the "deputy of power transmission" or "deputy for operation." this department is responsible for maintaining, operating, and enhancing transmission lines and substations. because tavanir owns and manages all 16 regional electric firms, the transmission industry is still regarded as a regulated monopoly [21]. why a large-scale pv power plant in iran? in 2012, iran initiated its feed-in tariff scheme to promote the creation of renewable energy. however, according to bloomberg new energy finance, by the end of 2015, the country had only installed 35 mw of solar photovoltaic (pv) and 195 mw of wind energy. in collaboration with the renewable energy organization of m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 14 iran (satba), the government has recently introduced guaranteed twenty-year power purchase contracts. these contracts provide developers with a fixed and appealing price for electricity generated from renewable sources [22]. the study "enabling pv iran," commissioned by the german government and conducted by the german solar industry association, emphasizes iran's favorable solar irradiation and significant electricity demand as essential factors indicating the considerable growth potential of iran's solar energy sector. this is despite iran's abundant reserves of hydrocarbons [23]. the survey stated that iran has the potential to be one of the most suitable areas for solar energy. the country benefits from three hundred sunny days annually, covering two-thirds of its area. given these circumstances, the paper proposes that photovoltaic electricity generation (solar power) in iran has the potential to increase by double compared to certain established european nations [24, 25]. at the beginning of 2016, the iranian ministry of energy announced its intention to authorize contracts for 1 gw of wind and solar energy projects. a key feature of this initiative is the feed-in tariff program, which offers substantial benefits to projects incorporating domestic content. these projects can potentially enjoy a tariff rise of up to 30% under the fit program, a significant boost. notably, the advantageous tax rates associated with this program will remain in effect until 21 march 2017, providing a clear timeline for stakeholders to plan their investments [26]. the ppa proposed under this fit regime will be a 20-year agreement supported by a government agreement to secure the ppa payment regime. the ppa further reduces the tariffs for all power plants under this fit regime by 30% after the first ten years until the conclusion of the contract. the tariff is also linked to fluctuations in the euro exchange rate against the rails in table 1. fft of the solar pv plant is presented [27]. table 1. fit of solar pv plant in iran technology capacity price (irr per kwh) solar pv >30 mw 3200 10 mw<and ≤30 mw 4000 100 kw<and ≤10 mw 4900 20 kw<and ≤10 kw 7000 ≤20 kw 8000 4. iranian sanctions iran has faced international sanctions for an extended period. in 2014, certain restrictions on trade, known as sanctions, imposed by the european union (eu) were partially repealed. these sanctions, specified in regulation 42/2014, targeted specific sectors such as petrochemicals. the us secondary sanctions were suspended as part of the joint comprehensive plan of action, which was agreed to by iran, china, france, russia, the uk, the usa, and germany on 14 july 2015. additional relaxation of sanctions would be provided once the international atomic energy agency (iaea), a trusted international body, confirms that iran has fulfilled its obligations regarding nuclear activities. in january 2016, following a thorough secondary examination, the iaea declared that iran had fulfilled its nuclear-related obligations, and the eu and us had officially lifted sanctions [3]. eu sanctions have, since the announcement, been mostly lifted, including the following: the unrestricted movement of funds the restoration of swift services in iran the majority of individuals and organizations on the list were removed, but a few well-known names remain the restrictions on most forms of commerce were withdrawn the us secondary sanctions were suspended, which included: the us would no longer seek to penalize non-us persons and entities who enter business in specific sectors in iran (e.g., oil and gas, automotive, etc.) the us still seeks to prohibit non-us persons and entities from entering into business with persons and entities who remain on the sdn list (terrorism, human rights abuse, wmd, irgc) the critical remaining sanctions are that the us primary sanctions remain in place, which implies: persons and entities subject to us jurisdiction will continue to be prohibited from entering into iran-related transactions in principle, this would include non-us subsidiaries owned or controlled by us persons or entities. following the lifting of eu and us secondary sanctions, business with iran for eu companies has been largely normalized as of january 2016. however, practical difficulties continue to be encountered in iran, primarily due to the ongoing reluctance of international banks to re-enter the iranian market [28]. however, under growing pressure from business, some banks are actively working on returning to the iranian market. recent announcements from the japanese, italian, and chinese governments have committed them to supporting business finance in iran. 5. fippa and foreign investment protections and incentives iran has been trying to attract foreign direct investment into the country since the implementation of sanctions with some success. since the lifting of primary sanctions, some of the legislation passed has opened the way for foreign investment with protections, most notably the fippa legislation, iran's foreign investment promotion and protection act. the investment organization administers the act to the foreign investment council. each company seeking its protections must apply for the incentives, and it receives such protections through a permit being issued to the company. wishing to invest in iran: the following guarantees and protections are afforded to companies who make use of the fippa incentives: foreign capital is at risk of being nationalized and dispossessed. in such situations, the foreign investor will be allowed to obtain coverage. if laws or authorities decide to prohibit or temporarily halt authorized financial transactions under this act, the authority will assume responsibility for and compensate for any resulting damages. m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 15 the purchase of assets and producer services in international investment is facilitated when a state-run entity is the sole client or provider of products or producer services at a subsidized price. fippa further provides the following rights to companies: international investments subject to this act shall use the same protections and tools as possible for national assets in a non-discriminatory way. the exterior investment and its interests may be given in foreign money or assets. approval of international investments in all the product, manufacturing, farming, transport, information, and services areas, as well as in fields linked to water and energy. the reference to investment-related discussions in international courts. the possibility of land purchase in joint ventures in the company's name (registered in iran). issuance of permits for three years in iran for foreign investors, directors, specialists, and their direct families, and the chance of visa renewals. the investors are informed of the last settlement of their applications within 45 days. having an opportunity to pick the investment process and method. approval of expenditures by any actual or legal non-iranian or iranian person using the capital of a foreign source and investing the equipment envisaged in fippa to them. the international investor needs to choose an audit institute from the audit institutes approved by the iranian authority. in this article, new strategies are reviewed according to the feedin tariff policy, which encourages the application of largescale photovoltaic power plants in the power sector. these policies have not been studied in earlier articles. the economic factors, such as the irr of the assets, the simple, and the equity payback, are analyzed together for assessment. in this article, a 30 mw pv power plant is investigated. the project site is about 220 kilometers from the iranian capital, tehran, the country's largest electricity user. the other project site is about 55-hectare land at 35th km of the tehranqom old road after ikia. both sites have been simulated in pvsyst software, and the economic parameters have been analyzed in ret screen software. all the results are presented. 6. site condition in this article, we will examine qazvin province regarding solar energy potential. in terms of days of radiation, this province has 280 days of radiation throughout the year, which means it has a capacity of 1800 to 1900 kilowatt hours of solar energy radiation. in this sense, it is one of the best areas to use and benefit from the sun's energy to produce electricity. the best place to construct solar power plants in qazvin is the plain land. although all regions of the province are prone to the construction of this type of power plant, in terms of cost, the installation of structures and panels will naturally be expensive in mountainous areas such as alamut, lower tarem, and auj. at the same time, qazvin is prone to using renewable energies, including solar and wind power, in two ways: the location of parts of the province, including siahposh and kahek, on the way to the wind tunnel, as well as the benefit of all its areas in terms of water purity. the weather and being above sea level for installing solar panels have made the province a special place in this field. however, for the construction of wind power plants, particular windy areas are considered, to the extent that in qazvin, only limited areas such as siahposh and kohek are suitable for doing this work, or for the construction of scattered production power plants, areas that benefit from gas should be considered. naturally, these power plants cannot be built in any region. however, in the solar power plant section, it must be said that all parts of this province are prone to benefit from this issue, and installing and operating them anywhere is possible. he installed solar panels in it. the electricity generated from solar power plants can be installed in transmission lines all over the province. this problem also increases the efficiency of electricity, and at the same time, they can be installed at low power, such as 5 or 10 kilowatts. the annual average temperature at the site is a low 14.1°c with maximum monthly summer temperatures of between 32°c and 36°c and average monthly minimum temperatures in winter of below 10°c (figure 1). figure 1. average annual temperature 7. modelling the priest software is widely used and continues to be developed at the university of geneva, switzerland. this software designs and simulates solar power plants connected to the grid, off-grid, solar pump, and dc microgrid at kilowatt and megawatt levels. overall, this software is a robust and comprehensive program with many features. 7.1 design of grid systems (grid connect) in pvsyst software with the help of this section, you can design and simulate all types of power plants connected to the grid on different scales. in iran, systems connected to the grid have only one use: transmitting and injecting all electricity produced by solar panels. meanwhile, in european countries, electricity can be fed into the grid simultaneously, and the energy created from the panels can be used to supply electricity to domestic consumers. pv system software is a well-known and leading software in the world. there are no actual high wind speeds in the region. however, the wind does blow consistently year-round, ranging between 1.0 m/s to 2.0 m/s all year round. the level of direct sunlight is low from november to march, where we see only 5–6 hours of direct sunlight. in contrast, 9 – 11 hours of direct sunshine are experienced in summer. figure 2 reflects the annual average hours of daylight the project site receives. m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 16 figure 2. hours of daylight the observed irradiation in qazvin is relatively low in winter but very high in summer, with the annual average global horizontal irradiation [kwh/m2] of the area at a moderate 1852 kwh/m2. according to table 2, from the point of view of solar energy production in 1852 kw hours per square meter, the highest amount is in july and june, which has the best efficiency and the most increased production, which is 225and 227-kw hours per square meter, respectively, and the lowest the value is for january, which is equal to 79 kw hours per square meter. the characteristics of pv modules are presented in table 3. it is a mono-silicon panel from the canadian solar company. according to table 3, the efficiency of this panel is 20.5 to 21.5%. this panel type is perc, its dimensions are 182 x 182 mm, and its power tolerance is 10 watts. monocrystalline solar panels are made of a single crystal structure, usually silicon, which allows for higher efficiency and better low-light performance than other solar panels. this makes them popular for residential, commercial, and industrial solar installations. the design of this panel utilizes advanced solar cell technology and perc (passively emitted rear cell) technology, which helps improve light absorption and energy conversion. the characteristics of the inverter are presented in table 4. to design the inverter for this power plant, we tried to use the best inverter available in the market, which is also economical. this inverter has characteristics that distinguish it from other inverters: its standard pv power is equal to 78 kw, and the maximum panel power supports up to 113 kw. 8. results and discussion an actual annual normalized production (per installed kwp) pattern for a 30 mw pv power plant in qazvin is shown in figure 3. figure 4 is the result of pvsyst software. qazvin is one of the iranian states with great solar potential, and there is a plan to install a 200 mw renewable energy power plant, mostly pv and wind. the production of a 30 mw pv power plant in qazvin and its main results are shown in table 5. as shown in table 5, the annual production of the pv plant is about 53497 mwh. utilizing table 1 data, economic calculations can be made. in this regard, we used retscreen software. the results of the financial analysis are shown in table 6. table 2. monthly solar resource data table 3. the characteristics of pv modules table 4. the characteristics of the inverter month gh (kwh/m2) dh (kwh/m2) bn (kwh/m2) ta °c td °c ff m/s jan 79 34 110 -1 5.4 0.9 feb 103 37 131 3.6 4.3 1.6 mar 149 58 161 9.1 2.9 1.9 apr 171 59 175 13.4 3 1.8 may 207 70 202 18.3 5.7 1.6 jun 227 68 230 23.8 7.5 1.9 jul 225 72 221 26.4 9.6 1.9 aug 215 61 230 26 8.2 1.7 sep 176 45 214 21.9 6.1 1.6 oct 133 47 157 16 3.5 1.3 nov 94 31 145 8 0.2 1.1 dec 74 31 107 2.8 2.9 1.2 year total 1852 613 2083 14.1 2.3 1.5 nom power 305 voc 45.2 isc 8.84 vmpp 36.6 minimum mpp voltage 460 maximum mpp voltage 820 frequency 50/60 nominal pv power 78 kw maximum pv power 113 kw maximum pv current 255 a m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 17 figure 3. the normalized production (per installed kwp) the 23 million$ is the initial cost for this project. 23000$ is considered for operation and maintenance costs. the financial viability is presented in table 6, which demonstrates the application of economic calculations using the software. the cumulative cash flow graph in the mentioned situation is shown in table 7. metrics are used to measure the rate of roi and allow an investor to evaluate and compare investment performance. this rate measures a company's profitability; the higher the pace of the index, the better the company can utilize its capital, and profitability is improved. according to the mentioned conditions, the loan capital return period will be short, and the irr for the overall project will be approximately 34.8 percent. figure 5 illustrates the development of large-scale pv power plants across iranian states. most of the power plants installed after 2016 demonstrate the impact of sanctions on the development of renewable energy in iran. five provinces, yazd, hamedan, kerman, and fars, hold the largest share. in 2017, the new fees in the tariff system applied to investors' interest in pv power plans increased. table 6. financial parameters table7. the financial viability of a 30mw pv power plant inflation rate % 15.0% project life yr 25 debt ratio % 70% debt interest rate % 4.00% debt term yr 10 pre-tax irr equity % 34.8 pre-tax irr assets % 20.5 simple payback yr 10.6 equity payback yr 5 pre-tax irr equity yr 10 table 5. balances and main results for 30 mw pv, qazvin globhor t amb globeinc(kwh /m2) globeeff(kwh/ m2) earray (mwh) e_grid(mwh) effarrr % effsysr % jan 83.1 0.03 134.3 131.4 3809 3670 15.02 14.47 feb 99.6 3.38 142.5 139 3964 3828 14.74 14.23 mar 140.9 9.14 171.6 166.9 4565 4405 14.09 13.6 apr 169.1 13.11 177.6 171.2 4613 4452 13.76 13.28 may 205.3 18.27 192.4 185 4879 4711 13.44 12.97 jun 221.4 23.33 197 189.2 4879 4651 12.95 15.51 jul 220.2 26.41 200.6 192.6 4815 4675 12.79 12.35 aug 207.8 25.91 210.5 203.4 4840 4884 12.71 12.29 sep 168.9 21.47 196.7 191 5051 4667 13 12.57 oct 126.6 16 173.9 169.8 4826 4312 13.6 13.14 nov 91.9 7.86 149.3 146.2 40534464 3915 14.39 13.89 dec 74.3 2.71 127.7 124.7 3619 3493 15.02 14.49 year 1809.1 14.03 2074.2 2010.3 53497 51663 13.67 13.2 m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 18 figure 4. results obtained by retscreen software for cash flow figure 5. pv power plant development by the states in iran 9. conclusions the pv power plant project has been sized at 30 mwdc to benefit from the favorable tariff for such a project size. we have further assumed an annual escalation of 6% each year based on the combined euro to rial exchange and cpi indexation. the ppa also provides a 30% reduction in the valid ppa tariff applicable from year 11 to 20. the results show that, although from a technical point of view, iran has excellent potential for a pv power plant, financial problems do not allow investors to enter the market quickly. the currency exchange rate has recently become the main problem; new sanctions pose a higher risk to foreign investors. it seems a new policy instrument requires a bank guarantee and different insurance policy instruments to encourage more investors. the decrease in the costs of photovoltaic modules will help the authority to implement further investment impulses in this field as electricity costs increase and address the fundamental values in iran. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the authors declare no potential conflict of interest. m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 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(2019). review of two decade geothermal energy development in iran, benefits, m. noorollahi et al. /future sustainability november 2025| volume 03 | issue 04 | pages 12-20 20 challenges, and future policy. geothermics, 77, 257266. [28] alimohammadlou, m., & bonyani, a. (2019). iran's energy policy after the nuclear deal for cooperation with foreign oil and gas companies. international journal of procurement management, 12(2), 199-218. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 26 article unifying thermodynamic and mechanical stability in perovskites: a computational approach for advanced applications coskun firat* istanbul technical university, energy institute, istanbul, türkiye a r t i c l e i n f o article history: received 25 march 2025 received in revised form 07 may 2025 accepted 15 may 2025 keywords: perovskite stability, thermodynamic-mechanical integration, combined stability index, computational analysis, material design for durability *corresponding author email address: coskun.firat@itu.edu.tr doi: 10.55670/fpll.fusus.3.3.4 a b s t r a c t perovskite materials hold immense potential for advanced technologies, yet their practical deployment is hindered by an insufficient understanding of the interplay between thermodynamic and mechanical stability. this study bridges this critical gap by developing a unified computational framework that integrates both stability dimensions, enabling the rational design of perovskites for demanding applications. leveraging pre-computed density functional theory data from the materials project and aflow databases, 44 perovskite materials are analyzed. thermodynamic stability is assessed via formation energy and energy above hull, while mechanical stability is quantified through bulk modulus, shear modulus, and pugh’s ratio. a novel combined stability index is introduced, employing geometric mean aggregation of normalized metrics to prioritize balanced performance. key findings reveal that ba-based perovskites exhibit superior thermodynamic stability and mechanical resilience. this work provides a computational blueprint for synthesizing perovskites tailored to applications requiring durability under thermal and mechanical stress, such as photovoltaics and catalysis. by correlating composition-structure-property relationships, the study advances the design of next-generation materials, emphasizing the necessity of holistic stability metrics. 1. introduction perovskite materials, with their general formula abx3, have emerged as a cornerstone of modern materials science due to their exceptional optoelectronic, catalytic, and mechanical properties [1]. these materials underpin advancements in solar cells, light-emitting diodes, solid oxide fuel cells, and piezoelectric devices, among others. however, their practical implementation is often hindered by challenges related to stability under operational conditions. thermodynamic stability [2-4] in perovskites has been widely studied using metrics such as formation energy and energy above the hull. for instance, ba-based perovskites are renowned for their superior thermodynamic stability [5-7], whereas materials with high energy above hull values are prone to decomposition [8]. however, these studies have focused mainly on isolated thermodynamic properties [9-11], neglecting how mechanical stability [12-14] influences overall performance. conversely, mechanical stability metrics like bulk modulus [15], shear modulus [16], and pugh’s ratio (b/g) [12,17] have been used to classify perovskites as brittle or ductile [18-20], with k-based perovskites [21] demonstrating excellent mechanical properties. yet, the interplay between thermodynamic and mechanical stability remains poorly understood, limiting the rational design of perovskites that can withstand real-world stresses such as thermal cycling or mechanical loading [22-23]. previous studies have made significant strides in exploring thermodynamic or mechanical stability in isolation, but few have considered these aspects together in a cohesive framework [24-27]. this disconnect is problematic for applications where both forms of stability are critical. for example, a material with excellent thermodynamic stability but poor mechanical properties may fail under stress, while a mechanically robust material with poor thermodynamic stability may decompose during operation [28]. bridging this gap requires a holistic approach that integrates thermodynamic and mechanical stability metrics, enabling the design of perovskites with balanced properties. in this future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.3.4 august 2025| volume 03 | issue 03 | pages 26-34 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:coskun.firat@itu.edu.tr https://doi.org/10.55670/fpll.fusus.3.3.4 https://fupubco.com/fusus coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 27 study, three key questions are addressed: how can thermodynamic and mechanical stability be unified into a single framework for perovskites? what compositionstructure-property relationships govern their combined stability? and which materials exhibit optimal stability profiles for advanced applications? to answer these questions, pre-computed dft data from both the materials project and aflow for 44 perovskites with different crystal systems are analyzed [29,30]. thermodynamic parameters (formation energy, energy above hull) and mechanical properties (bulk modulus, shear modulus) are evaluated using python-based computational tools. a combined stability index is introduced to unify these metrics, enabling systematic identification of materials with optimal stability profiles. this work makes several key contributions. first, a unified stability framework is established, which integrates thermodynamic and mechanical metrics, providing a holistic view of perovskite stability. second, the compositionstructure-property relationships are revealed, showing that ba-based perovskites excel in thermodynamic and mechanical stability. notably, tantalum-containing compounds consistently outperform their niobium counterparts in combined stability metrics. third, promising candidates such as ktao3 (high mechanical strength), ba2taino6 (exceptional thermodynamic stability), and ba2taino6, banbo3 (balanced stability) are identified. these findings offer a computational blueprint for designing nextgeneration perovskites, with implications for energy conversion, catalysis, and electronics. the practical relevance of this work lies in its ability to guide the synthesis of stable perovskites for applications requiring both durability and performance. for instance, thermodynamically and mechanically robust perovskites could enhance the longevity of solar cells, improve catalytic efficiency in harsh environments, or develop reliable high-temperature sensors. 2. methodology this study analyzes a dataset of 44 perovskite materials with abx3 and related stoichiometries, leveraging precomputed density functional theory (dft) [31] data from the materials project and aflow databases. the dataset comprises materials with cubic, pseudo-cubic, tetragonal or trigonal symmetry [32], spanning diverse compositions of asite cations (ba, sr, ca, k, na) [33,34] and b-site cations (ti, zr, nb, ta) [35,36], enabling systematic exploration of composition-stability relationships. the dft calculations were performed using the vienna ab initio simulation package (vasp) [37] with the perdew-burke-ernzerhof (pbe) exchange-correlation functional [38], ensuring consistency with widely accepted computational standards. the dataset includes the following key parameters: • material identification: chemical formula, standardized formula notation, and unique material id. • crystal structure: space group, lattice parameters, and atomic positions. • electronic properties: bandgap and electronic structure classification (metal, semiconductor, or insulator). • thermodynamic stability: formation energy per atom, energy above hull (relative to the convex hull), and stability classification. • mechanical properties: voigt-reuss-hill (vrh) averaged bulk modulus, shear modulus, and elastic constants where available. python-based computational tools (pandas, numpy, matplotlib, seaborn) were employed to process and analyze the dataset [39]. derived mechanical properties, including pugh’s ratio (b/g), poisson’s ratio, and vickers hardness, were calculated using empirical relationships. a combined stability index was developed to unify thermodynamic and mechanical stability metrics, enabling quantitative comparison of materials. statistical methods, including correlation analysis and classification algorithms, were applied to identify trends in composition-structure-property relationships. to ensure reproducibility, all computational workflowsfrom data retrieval to visualizationwere structured using open-source libraries, with custom functions validated against reference calculations. the methodology emphasizes transparency in parameter derivation and error handling, particularly for entries with anomalous mechanical properties (e.g., negative shear moduli). 2.1 thermodynamic and mechanical stability analysis thermodynamic stability was evaluated using two key metrics: the formation energy per atom (𝐸𝑓) and the energy above hull (𝐸ℎ𝑢𝑙𝑙). the formation energy, defined as [30]: 𝐸𝑓 = 𝐸𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑−∑ 𝑛𝑖𝐸𝑖𝑖 𝑁 (1) eq (1) quantifies the energy released or required to form a compound from its constituent elements. here, 𝐸𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 is the total energy of the perovskite, 𝑛𝑖 and 𝐸𝑖 represent the number of atoms and reference energy of element i in its standard state, and n is the total number of atoms in the compound. the energy above the hull (𝐸ℎ𝑢𝑙𝑙), calculated as [30]: 𝐸ℎ𝑢𝑙𝑙 = 𝐸𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 − 𝐸𝑐𝑜𝑛𝑣𝑒𝑥 ℎ𝑢𝑙𝑙 (2) eq (2) measures the energy difference between a compound and the most stable phase(s) at its composition, where 𝐸𝑐𝑜𝑛𝑣𝑒𝑥 ℎ𝑢𝑙𝑙 corresponds to the lowest-energy configuration of stable phases. materials were categorized into stability classes based on 𝐸ℎ𝑢𝑙𝑙 values: • stable: 𝐸ℎ𝑢𝑙𝑙 = 0 • very likely stable: 0 < 𝐸ℎ𝑢𝑙𝑙 < 0.025 ev/atom • likely stable: 0.025 ≤ 𝐸ℎ𝑢𝑙𝑙 < 0.05 ev/atom • potentially metastable: 0.05 ≤ 𝐸ℎ𝑢𝑙𝑙 < 0.1 ev/atom • likely unstable: 𝐸ℎ𝑢𝑙𝑙 ≥ 0.1 ev/atom. statistical analyses, including mean, standard deviation, and extreme values, were applied to characterize the distribution of thermodynamic parameters. correlation studies further identified relationships between composition and stability metrics. mechanical stability is assessed using bulk modulus (b), shear modulus (g), and derived parameters. the voigt-reuss-hill (vrh) averaging scheme has been employed to compute isotropic values of b and g from the anisotropic elastic tensor for data in the databases. pugh’s ratio (𝐵 𝐺⁄ ) classifies materials as ductile (𝐵 𝐺⁄ > 1.75) or brittle (𝐵 𝐺⁄ < 1.75). derived mechanical properties included: young’s modulus [40,41]: 𝐸 = 9𝐵𝐺 3𝐵+𝐺 = 2𝐺(1 + 𝜈) (3) poisson’s ratio [40,41]: 𝜈 = 3𝐵−2𝐺 2(3𝐵+𝐺) (4) coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 28 vickers hardness [42]: 𝐻𝜈 ≈ 0.92 ( 𝐺 𝐵 ) 1.137 𝐺0.708 (5) simplified elastic anisotropy index (derived from the universal anisotropy index [43]): 𝐴𝑎𝑝𝑝𝑟𝑜𝑥 = 5𝐺 𝐵 + 𝐵 5𝐺 − 6 5 (6) statistical distributions of mechanical properties were analyzed, and correlation matrices were constructed to explore relationships between composition and mechanical behavior. 2.2 combined stability assessment to holistically evaluate both thermodynamic and mechanical stability, a combined stability index integrating normalized values of 𝐸ℎ𝑢𝑙𝑙 , b, g, and pugh’s ratio is developed. this index enables systematic ranking of materials based on their ability to balance competing stability requirements, critical for applications demanding both long-term phase persistence and mechanical resilience. the assessment framework follows four key steps: normalization: each parameter (𝐸ℎ𝑢𝑙𝑙 , b, g, b/g) was scaled to a 0–1 range using min-max normalization to eliminate unit dependency and ensure equal weighting. for a parameter x, the normalized value 𝑋𝑛𝑜𝑟𝑚 is calculated as: 𝑋𝑛𝑜𝑟𝑚 = 𝑋−𝑋𝑚𝑖𝑛 𝑋𝑚𝑎𝑥−𝑋𝑚𝑖𝑛 (7) where 𝑋𝑚𝑖𝑛 and 𝑋𝑚𝑎𝑥 represent the minimum and maximum values of 𝑋 across the dataset. for 𝐸ℎ𝑢𝑙𝑙 , lower values indicate greater stability, so the normalization was inverted (1 − 𝑋𝑛𝑜𝑟𝑚). weighting: parameters were assigned weights reflecting their relevance to specific applications. for general-purpose evaluation, equal weights (𝜔𝑖 = 0.25) were applied to all parameters, ensuring unbiased prioritization of thermodynamic and mechanical stability. aggregation: the weighted parameters were combined using the geometric mean to compute the stability index (𝑆𝑖𝑛𝑑𝑒𝑥) for each material [44]: 𝑆𝑖𝑛𝑑𝑒𝑥 = (∏ 𝑋𝑖,𝑛𝑜𝑟𝑚 𝜔𝑖𝑛 𝑖=1 ) 1 ∑ 𝜔𝑖 ⁄ (8) unlike arithmetic averaging, the geometric mean penalizes materials with extreme weaknesses in any stability dimension, favoring balanced performance. classification: materials were categorized into four stability classes: for classification, thresholds were defined for each property (𝐸ℎ𝑢𝑙𝑙 , 𝐸𝑓, b, g, and pugh’s ratio). these thresholds are used to classify materials into different stability categories. a categorization function was defined to evaluate each material based on the defined thresholds. the function first categorizes the material based on 𝐸ℎ𝑢𝑙𝑙 . then, it adjusts the stability category based on mechanical properties (b, g, and pugh’s ratio). finally, it considers 𝐸𝑓 to provide a holistic assessment. the combined stability category will be like: stable (strong mechanical properties) (low formation energy), very likely stable (moderate mechanical properties) (moderate formation energy), likely stable (brittle) (low formation energy), potentially metastable (brittle) (low formation energy), likely unstable (weak mechanical properties) (high formation energy), unknown (for materials with missing data). 3. computational details and the results the dataset for this study originated from the materials project and aflow databases, from which 1070 cubic perovskite materials with abx3 and related stoichiometries were initially extracted. however, only 44 of these materials contained complete mechanical property data (bulk modulus, shear modulus, etc.), necessitating a focused analysis on this subset to unify thermodynamic and mechanical stability metrics. all computational workflows, including data processing, statistical analysis, and visualization, were implemented in python 3.8 using the following libraries: • pandas and numpy for data manipulation and numerical computations. • matplotlib and seaborn for generating visualizations. • custom functions for specialized calculations, such as the combined stability index and normalized parameter aggregation. key visualization techniques were employed to elucidate structure-property relationships: a. scatter plots to examine correlations between thermodynamic and mechanical parameters. b. heatmaps to visualize multivariate relationships across stability metrics. c. bar charts to compare key properties (e.g., formation energy, bulk modulus) across materials. d. radar plots for multi-parameter comparison of topperforming candidates. the computational workflow was designed for reproducibility: • data processing steps were systematically documented, including handling of missing values and normalization procedures. • validation against reference calculations (e.g., crosschecking dft-derived properties with literature values) ensured robustness. • the final dataset of 44 materials, along with analysis scripts, is archived to facilitate reproducibility. this approach enabled the integration of thermodynamic stability (formation energy, energy above hull) and mechanical stability (bulk modulus, shear modulus, pugh’s ratio) into a unified framework. by focusing on materials with complete datasets, the combined stability index could be rigorously applied to identify candidates with balanced performance for advanced applications. the results for the first five stable materials are given in table 1. in figure 1, the thermodynamic stability distribution of 44 perovskite materials based on their 𝐸ℎ𝑢𝑙𝑙 values are illustrated. the distribution shows a sharp decline in frequency as 𝐸ℎ𝑢𝑙𝑙 increases, indicating that most materials are stable or very likely stable, with fewer materials being metastable or unstable. the dashed lines provide clear visual thresholds for the stability categories, aiding in the quick assessment of material stability. figure 2 indicates the pugh’s ratio distribution of 44 materials. it can be seen that most materials have a pugh’s ratio clustered around 2, indicating a tendency towards ductility. the red dashed line at 1.75 clearly marks the boundary between ductile and brittle materials, making it easy to identify the classification of each material. the distribution shows a sharp peak around the ductile region, with a rapid decline in frequency as the ratio increases, indicating that most materials are ductile. a few materials have significantly higher pugh’s ratios, suggesting they are exceptionally ductile. coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 29 figure 1. thermodynamic stability distribution of perovskites based on 𝐸ℎ𝑢𝑙𝑙 figure 2. distribution of pugh’s ratio of the perovskite materials figure 3 illustrates the relationship between pugh's ratio (b/g) and elastic anisotropy for various materials. in figure 3, the red dashed line at b/g = 1.75 separates ductile materials (right) from brittle ones (left). most stable materials have low anisotropy and are near the ductile-brittle threshold. a few outliers show significant anisotropy or extreme pugh's ratios. figure 4 shows the relationship between the bulk modulus (b) and shear modulus (g) for various materials. figure 3. relationship between pugh's ratio (b/g) and elastic anisotropy for various materials figure 4. the relationship between the bulk modulus and shear modulus for various materials most materials are clustered between 100-200 gpa for bulk modulus and 50-150 gpa for shear modulus. a few outliers have significantly higher or lower values, indicating unique mechanical properties. stable materials tend to have higher values of both moduli, indicating good mechanical resilience. the correlation between bulk and shear moduli suggests that materials with high resistance to compression also resist shape changes well. figure 5 shows the combined stability of the materials. table 1. thermodynamic, mechanical properties, and combined index for some stable materials code formula crystal system ehull (ev/atom) ef (ev/atom) b (gpa) g (gpa) pugh’s ratio combined index m7 ca2ta2o7 cubic 0.000789 -3.4826 148.2 97.79 1.5155 78 m13 batio3 cubic 0.014788 -3.4775 160 106.6 1.5009 74 m18 ktao3 cubic 0 -3.0716 184.6 121.3 1.5218 44.5 m19 bazro3 cubic 7.17e-05 -3.6392 147.6 91.03 1.6214 78 m28 srfeo3 cubic 0 -2.223 128.6 80.35 1.6004 99.5 coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 30 most materials are clustered near the origin, indicating both high thermodynamic stability and ductility. a few outliers show distinct properties, for example, batio3 (m26) having high ductility and ba2nbo (m17) being less stable thermodynamically. stable and ductile materials are near the origin with low 𝐸ℎ𝑢𝑙𝑙 and high pugh’s ratio. stable and brittle materials have low 𝐸ℎ𝑢𝑙𝑙 but lower pugh’s ratio. this index is useful for identifying materials that balance both thermodynamic and mechanical stability, which is crucial for applications requiring durability and resilience. figure 6 shows the radar plot for ktao3 (m18), which provides a visual representation of its key properties. bulk modulus vrh (gpa) indicates the material's resistance to uniform compression. the plot shows a moderate to high value, suggesting good mechanical stability. shear modulus vrh (gpa) reflects resistance to shape changes. the value is also moderate, supporting mechanical resilience. energy above hull (ev/atom) represents thermodynamic stability. the plot shows a relatively low value, indicating good stability. pugh's ratio indicates ductility. the plot shows a moderate value, suggesting a balance between ductility and brittleness. the plot is fairly balanced, with no extreme values, indicating that the material has a good balance of properties. the shaded area represents the overall performance across these parameters, with a larger area generally indicating better combined stability. figure 7 shows the grid radar plot for material indices 14, 23, 35, and 39, as well as other candidates with good combined indices. figure 6. radar plot of the combined index for ktao3 4. discussion integrating thermodynamic and mechanical stability metrics into a unified framework has revealed critical insights into the design of perovskites for advanced applications. by analyzing 44 perovskites with complete datasets, this study demonstrates that materials such as ktao3, ba2taino6, and banbo3 exhibit balanced stability profiles, positioning them as promising candidates for applications requiring both durability and performance. figure 5. combined thermodynamic and mechanical stability of materials coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 31 the combined stability index successfully identifies materials that excel in both thermodynamic and mechanical stability. for instance, ktao3 (m18) achieves low energy above hull (0 ev/atom) and moderate mechanical properties (bulk modulus = 184.6 gpa, shear modulus = 121.3 gpa), reflecting its resistance to decomposition and mechanical stress. this balance is critical for applications like solar cells, where operational stresses (e.g., thermal cycling) demand materials that remain structurally intact over time. the dominance of ba-based perovskites (e.g., batio3, bazro3) in the top candidates aligns with prior studies highlighting the stabilizing role of large a-site cations like ba²⁺, which reduce lattice distortions and enhance mechanical resilience [5,7]. tantalum-containing perovskites (e.g., ba2taino6) consistently outperform their niobium counterparts (e.g., banbo3) in combined stability metrics. this is attributed to ta⁵⁺’s higher electronegativity and stronger metal-oxygen bonding, which enhances both thermodynamic stability (lower 𝐸ℎ𝑢𝑙𝑙) and mechanical properties (higher bulk/shear moduli) [26]. these findings underscore the importance of b-site cation selection in tailoring stability. the pugh’s ratio distribution (figure 2) reveals that most materials (∼70%) are ductile (b/g>1.75), a desirable trait for flexible electronics. however, brittle materials like ca2ta2o7 (m7) still rank highly due to exceptional thermodynamic stability (𝐸ℎ𝑢𝑙𝑙 = 0.0008 ev/atom), illustrating that application-specific requirements should guide material selection. for instance, brittle but thermodynamically stable perovskites may suffice for rigid photovoltaic panels, while ductile materials are preferable for wearable devices. the geometric mean-based combined index penalizes extreme weaknesses in any stability dimension, favoring balanced performance. figure 7. the grid radar plot for material index-14, 23, 35 and 39 coskun firat /future sustainability august 2025| volume 03 | issue 03 | pages 26-34 32 for example, srfeo3 (m28) achieves the highest combined index (99.5) due to its moderate 𝐸ℎ𝑢𝑙𝑙 (0 ev/atom) and exceptional mechanical properties (b=128.6 gpa, g=80.35 gpa). however, outliers like batio3 (m13) with higher 𝐸ℎ𝑢𝑙𝑙 (0.0148 ev/atom) but superior ductility (b/g=1.62) highlights the need for customizable weighting schemes in the index to prioritize specific properties for targeted applications. 5. limitations and future work this study offers valuable insights into the stability of perovskite materials, yet several limitations must be acknowledged: the analysis does not account for the influence of temperature and pressure on material stability, which can be significant in real-world applications, the impact of defects, which can greatly affect stability, is not included in this study, the dataset is limited to a few materials, restricting the exploration of other potentially stable structures. expanding the dataset to thousands of perovskites using highthroughput dft could uncover novel candidates with rare stability profiles, such as materials combining ultralow 𝐸ℎ𝑢𝑙𝑙 and extreme ductility. while dft-derived metrics provide valuable insights, experimental validation of mechanical properties (e.g., nanoindentation for hardness) and thermodynamic stability (e.g., calorimetry) is essential to confirm computational predictions. training machine learning models on stability metrics could accelerate the discovery of composition-structure-property relationships, particularly for non-cubic perovskites [12]. customizing the combined index weights (e.g., prioritizing mechanical stability for aerospace materials or thermodynamic stability for high-temperature catalysts) would enhance its practical utility. 6. conclusions this comprehensive investigation into perovskite materials has provided valuable insights into the interplay between composition, structure, thermodynamic stability, and mechanical properties. through systematic computational analysis of 44 distinct perovskite compositions, several promising candidates for technological applications were identified. the analysis highlights the superior stability profiles of tantalum-containing materials, suggesting that 5d transition metals may enhance both thermodynamic and mechanical stability due to stronger and more directional bonding characteristics. this trend underscores the potential advantages of incorporating such elements into perovskite structures. the observed relationships between formation energy and mechanical properties, such as bulk modulus, suggest fundamental structure-property correlations that can guide future material design. materials with more negative formation energies tend to exhibit higher elastic moduli, indicating that stronger bonding contributes to both thermodynamic and mechanical stability. this work lays the groundwork for targeted experimental validation of the identified promising compositions. future efforts should focus on synthesizing and characterizing these top candidates, particularly those containing tantalum, to verify the predicted properties and assess their performance under application-relevant conditions. additionally, extending this computational framework to include dopants and defects could further enhance the stability and functional properties of these promising perovskite materials. by this work, the combined stability assessment approach has successfully identified materials that balance thermodynamic and mechanical stability, providing a rational basis for the development of next-generation perovskite materials for diverse technological applications. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the author declares no potential conflict of interest. references [1] l. sanga, c. lalengmawia, z. renthlei, s. t. chanu, l. hima, n. s. singh, a. yvaz, s. bhattarai, d.p. rai, (2025). a 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[44] i. h. siegel, (1942). index-number differences: geometric means. j. of the american statistical association, 37:218, 271–274, doi.org/10.1080/01621459.1942.10500636. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 35 review a comprehensive review of alkaline fuel cells saad bin abul kashem* business management & information systems programme, university aberdeen, qatar a r t i c l e i n f o article history: received 05 february 2025 received in revised form 11 march 2025 accepted 24 march 2025 keywords: alkaline fuel cell, cathode material, catalyst *corresponding author email address: saad.kashem@afg-aberdeen.edu.qa doi: 10.55670/fpll.fusus.3.2.5 a b s t r a c t the alkaline fuel cell is known as the “bacon” fuel cell. it generates electricity through the chemical reaction without the emission of greenhouse gases. this will allow it to replace fossil fuels in the future. it produced only the water for the final product. it operates at a temperature of 25˚c to 250˚c, which is relatively low compared to the internal combustion engines. it has wide application in the modern industry. this is due to the system's high efficiency, reaching up to 60%. however, the alkaline fuel cell has several disadvantages, which affect to popularize. this paper contains a review of alkaline fuel cells, an extensive study of the components that make up the fuel cells, as well as the future applications and challenges of fuel cells. a comparison of alkaline fuel cells and other types of fuel cells has also been discussed in the paper. in addition to the research paper, future trends and forecasts will also be able to accurately predict the viability of implementing this technology in the near future. 1. introduction the alkaline fuel cell is called the ‘bacon’ fuel cell. named after its british inventor, it is one of the most developed fuel cell technologies with a wide range of heat, electricity, and water production applications. with its numerous advantages, which include (but are not limited to) an abundance of hydrogen, non-hazardous by-products, and a quiet and clean source of energy that is more efficient at all levels of use, this technology shows great prospects in the gradual but inevitable replacement of fossil fuel. the ability of fuel cells to directly convert chemicals to electrical energy is what scientists believe will be a key component of future energy sources. alkaline fuel cells are made up of an alkaline electrolyte. it is usually a potassium hydroxide liquid in which hydroxide ions (oh-) travel from the cathode to the anode in water and are generally fueled with pure hydrogen. catalysts also speed up reaction rates at the anode and cathode. operating temperatures of these cells can range from 25˚c to 250˚c. alkaline fuel cells are currently capable of producing 14% more electricity with 23% less emissions. due to the high rate of reactions, efficiencies of up to 60% can be reached in some applications. current drawbacks of this fuel cell technology are the cost of production, the small amounts of energy that can be stored at a time, and the diseconomies of large-scale application. much research still must be done to determine the plausibility of wide-scale application, which researchers still call a “fairy tale”. in this research, the team will perform an in-depth analysis of the current alkaline fuel cell technologies as well as their advantages and drawbacks. the team will also examine the current efforts by scientists to put this technology to wide-scale use. in addition, future trends and forecasts will be looked into to accurately forecast the viability of implementing this technology in our fastchanging and technologically driven world. the goal of the research on alkaline fuel cells is to investigate the application and mechanism of energy production of the fuel cell. secondly, the possibility of alkaline fuel cells as a future source of energy supply will also be studied and analyzed. this research will discuss different aspects of the alkaline fuel cell, including its components, advantages and disadvantages, and importance. the research is more about experimental procedures, and a handful of simulations are involved as well. however, experiments are carried out in the laboratory. in addition, every member is exposed to hands-on experience when experiments are carried out in the laboratory. moreover, results obtained in the laboratory can be compared with similar experiments that have been done for accuracy and improvement. for a better understanding of the benefits of alkaline fuel cells, there will be a comparative analysis done with the following types of fuel cells: • proton exchange membrane fuel cells • direct methanol fuel cells • phosphoric acid fuel cells • molten carbonate fuel cells • solid acid fuel cells future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.2.5 may 2025| volume 03 | issue 02 | pages 35-46 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:saad.kashem@afg-aberdeen.edu.qa https://doi.org/10.55670/fpll.fusus.3.2.5 https://fupubco.com/fusus sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 36 2. background 2.1 alkaline fuel cells 2.1.1 definition of alkaline fuel cells fossil fuel combustion, such as coal, jet fuel, and gasoline, falls under the non-renewable energy category. this releases harmful emissions into the environment and increases the greenhouse effect. on the other hand, many other environmentally friendly alternative energy sources, such as solar, wind, geothermal, and hydroelectric power, can be used only in particular environments. according to viswanathan [1], fuel cells as a potential electrical energy conversion scheme are now being used worldwide. the reason for developing fuel cells is that they can have near-zero emissions while being quiet and efficient. similarly, fuel cells use hydrogen and oxygen as reaction sources, which are abundant and environmentally friendly. a chemical reaction between the hydrogen ions with oxygen as an oxidizing agent. the reaction directly converts chemical energy into electrical energy [2]. fuel cells are classified according to their electrolyte type. thus, alkaline fuel cells (afc) use an alkaline electrolyte. in common practice, alkaline fuel cells use liquid potassium hydroxide (koh) as the electrolyte. in addition, alkaline fuel cells are categorized as “lowtemperature fuel cells” as their operating temperature ranges from 50 – 100 degrees celsius [3]. similarly, the electrical efficiency of an alkaline fuel cell ranges between 60 – 70 percent. on the other hand, afc systems have been said to have the advantage of good electrochemical stability [4]. 2.1.2 energy production in alkaline fuel cells an alkaline fuel cell comprises two electrodes: a cathode and an anode. they are separated by an electrolyte. as for the electrolyte solution, potassium hydroxide (koh) solution is used as it can penetrate the porous electrode similar to the reaction gases. since potassium hydroxide has a higher ionic conductivity and higher solubility than sodium hydroxide, it is feasible to use koh as the electrolyte [5]. in addition, adjacent to the electrolytes, a porous coating of a catalyst is used. since oxygen reduction reaction in alkaline media is easily achieved when compared with acidic media, the catalyst increases the electrical efficiency of the fuel cell [2]. the catalysts used in most common applications of fuel cells are silver, nickel, metal oxides, or noble metals [6]. as shown in figure 1, in an alkaline fuel cell, hydrogen gas is pumped into the anode, and oxygen is pumped into the cathode. the anode and cathode are electrically connected. when hydrogen gas hits the catalyst, the hydrogen atoms are oxidized. this triggers a reaction with oxygen whereby hydroxyl ions are produced at the cathode of the alkaline fuel cell [7]. these ions travel to the anode side of the fuel cell, where they react with hydrogen to form water continuously. hydrogen gas combines with the hydroxyl ions at the anode to form water and electrons during the process. in the meantime, the water formed at the anode diffuses back to the cathode, where it interacts with oxygen while returning electrons to revive the hydroxyl ions [8]. the overall reaction of the fuel cell produces heat and water as by-products and generates four electrons per mol of oxygen. since the four electrons are not capable of passing through the electrolyte, they are forced out at the anode, producing a current that flows through an electric circuit [2]. in contrast, an electrical current is produced when the flow of electronic charge within the circuit is balanced by the movement of ionic charge through the electrolyte [9]. on the other hand, the behavior of the cathode is directly related to the lifetime and power output of alkaline fuel cells. since the oxygen reduction reaction at the cathode is a slower reaction when compared with the hydrogen oxidation reaction at the anode, losses are incurred [5]. moreover, carbon dioxide affects the fuel cell, where the formation of carbonate species affects the performance of the alkaline electrolyte [10]. this carbonate is formed when carbon dioxide reacts with the electrolyte. the formation of carbonate decreases the ionic conductivity of the electrolyte and blocks the pores in the electrode. ultimately, oxygen flow to the reacting sites is reduced as the pores are blocked, which causes the electrode to flood [9]. hence, the oxygen solubility and electrode activity are vastly reduced. however, if an anion exchange membrane (aem) is used as a solid electrolyte, the carbon dioxide issue is minimized greatly as there is a scarcity of mobile cations in the membrane [11]. figure 1. schematic diagrams of an alkaline fuel cell 2.1.3 alternate material for hydrogen in fuel cells methanol and ethanol are some of the alternative materials used instead of hydrogen in alkaline fuel cells [12]. a direct alkaline methanol fuel cell is a type of alkaline fuel cell that uses methanol. similarly, a direct alkaline ethanol fuel cell is another type of alkaline fuel cell whereby ethanol is used. water management at the anode is caused by carbonation, where carbon dioxide is permanently produced during operation [13]. regarding this, an anion exchange membrane is introduced as an electrolyte in the direct alkaline methanol fuel cell [14]. as for the catalysts used, a direct alkaline methanol fuel cell uses nickel as the anode catalyst for methanol oxidation in the alkaline media as a common practice [15]. in contrast, palladium, a pure metal, catalyzes the ethanol oxidation reaction in a direct alkaline ethanol fuel cell [16]. according to [15], because of the high overpotential for the electrochemical oxidation of the ethanol at low temperatures, direct alkaline ethanol fuel cells have a lower performance when compared to direct alkaline methanol fuel cells. however, when the energy densities of sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 37 methanol and ethanol are compared, the energy density of ethanol is greater than that of methanol, provided a complete oxidation to carbon dioxide is attained. moreover, ethanol and its oxidation products are less toxic than methanol and its oxidation products. 2.1.4 review of cathode material the efficiency and general overall performance of any fuel cell are largely due to the methods applied in fabricating the layer structures from carbon and ptfe of the gas diffusion electrode. all developed fuel cells utilize identical porous electrode structures, similar to the electrodes used in metalair batteries. the overall power of the cell and the lifetime of the alkaline fuel cells are directly linked to cathode behavior, and an in-depth look into cathode development is necessary. most of the afc's polarization losses occur at the cathode, much more so than at the anode. this phenomenon can be explained by the speed of the oxygen reduction reaction, which takes place at the anode and is much slower and more limiting than the hydrogen oxidation reaction that takes place at the anode. two types of designs exist for the afc. they are the monopolar and bipolar stack designs. the monopolar stack design has several advantages, such as lower cost; it achieves this by avoiding the expensive materials needed for bipolar stack plates [17,18]. furthermore, stack thickness decreases due to the presence of only one type of gas chamber between the two electrodes. apart from these, the need for additional mechanical pressure is eliminated since the parts are mostly glued or welded together. finally, the disconnection or interruption of a bad cell in this situation will facilitate the maintenance of the entire stack. however, some drawbacks are associated with this design. currently, the monopolar design has a limited density of up to 100 ma cm-2. this is due to current collection losses at each side of the electrode. the bipolar design shows a steadier current density throughout the entire surface of the electrode and even has a terminal voltage of higher value and less power limitation. this geometry will be preferred for high-power applications, but its cost is a major drawback [17]. 2.1.5 design of electrodes alkaline fuel cell electrodes are made up of many bonded polytetraflouraethylene (ptfe) carbon-black layers (figure 2). these three-layer structures have many functions. they consist of an active layer, a gas diffusion layer, and a backing (support) material [19]. figure 2. design of a double-layer electrode in a bipolar stack design this design is used more often than a single-layer electrode, although more complex designs are currently in use depending on the scope of the application. a good doublelayer electrode should have a backing material that easily allows gases to permeate it, as well as good electrical conductivity and high strength. due to the nature of the monopolar design, backing materials also play the role of the current collector, and as such, metal screens and meshes that are comprised mainly of nickel are used. in the case of bipolar designs, the backing material comes in direct contact with the bipolar plate. this implies that carbon cloth or porous carbon paper can be used for it [20]. the gas diffusion layer plays a very important role. it supplies gases that undergo the reactions to the active layer. in addition to this, it prevents electrolytes from passing through the electrode. a phenomenon termed ‘flooding’. most monopolar designs use a ptfe gas diffusion layer. bipolar designs require a gas diffusion layer that is capable of electronic conduction. ideally, a gas diffusion layer should be completely hydrophobic and have satisfactory metal conductivity [21]. 2.1.6 materials used in the fabrication of electrodes a wide variety of materials is used to make alkaline fuel cell electrodes. recently, most alkaline fuel cell electrodes used carbon-supported catalysts with a large surface area for ptfe to obtain the necessary three-phase boundary elaborated on earlier in the report. the key parameter here in electrode performance and catalytic activity is the surface area of the catalysts used on the electrode rather than its weight [22]. ptfe has been a very popular binding agent since its introduction. some other alternatives include wax and polyethylene. it is present as globular particles or porous substrates with thin films and fibrils. when combined with carbon black, it permeates the carbon subsurface. sintering, which involves melting ptfe to provide a thin covering over the carbon black, is usually necessary [17]. carbon black has some particular chemical and electrical properties that make it ideal for afc electrode use. carbon black consists of carbon in the form of globular particles obtained through decomposing carbon by heat application. its high surface area characteristic is achieved by treating it with steam at high temperatures as the steam passes through the carbon black’s inner core, which has more entropy than the outside; a large number of pores form while the particle does not completely disintegrate [23]. 2.1.7 operational mechanism by altering or adjusting the various input layers and structures, scientists can control the electrochemical behavior of the afc. control can be achieved if the ratio of hydrophobic and hydrophilic pores inside the carbon structure is altered. two structures in the electrode play vital roles in its operation. the first is the macrostructure created due to the incomplete covering of the carbon particles by ptfe. this is responsible for the skeletal structure and ensures electrical conductivity and mechanical support [24]. the secondary microstructure is a result of the pore system inside the carbon black particle, and this is also dependent on the nature of the pore, its structure, and the surface area of the carbon used. micro pores are hydrophilic, while macro pores are hydrophobic. hydrophobic micropores are essential in gas mass transport because they mimic the sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 38 behavior of gas supply channels. on the other hand, oxygen reduction reaction mechanisms occur in hydrophilic pores and are filled with electrolytes. 2.1.8 cathode catalyst materials a variety and range of materials exist and can be considered for use as the cathode catalyst. these include, but are not limited to, non-noble metals, noble metals, perovskites, spinels, etc. in evaluating the catalyst chosen, it is necessary to factor in the effect that the type of carbon used has on the catalyst. the supporting carbon particle, which has a range of physical and chemical characteristics, directly impacts the catalyst support system [19]. if we plan on building and sustaining a pollution-free world in the future, the world will have to bank on low-temperature fuel cells like polymer electrolyte fuel cells and alkaline fuel cells. in addition to its relatively cheaper cost, the system has advantages in its working principle; no gas humidification is required, in the case of pefc. in addition to this, the temperature of the afc can be managed with only its electrolyte. it will be established in the course of this report that afcs are a promising alternative to polymer electrolyte fuel cells (pefc) and other forms of energy generation and storage [22]. the key aspect of this attractiveness goes down to the cathode part of the electrode, which is used in the oxidation-reduction reaction, as has been established previously. to use afcs in the long term will require a longterm behavioral analysis of these components. the lifetime of the entire cell is based on the degradation of the electrodes. since the cathode in a fuel cell can be easily replaced, most of the focus will be on it. for this research, a few variations will be considered, described in detail below. 2.1.9 silver cathodes in alkaline fuel cells this cathode consists of catalysts made of silver and polytetraflouraethylene as a binder roll-formed into a metal web-like structure. silver can be used in this situation because of the less corrosive nature of the alkaline fuel cells compared to the acid fuel cell environments. this presents a big cost advantage over other types of cells and also a much higher commercial use potential [25]. the solubility of silver in a completely alkaline fuel cell can affect the overall performance if it gets dissolved and transferred to the anode part. this resulting plating of the anode component may destroy the catalysts present at the anode. a study investigated this degradation during the oxygen reduction reaction (orr) at a constant load. according to a study performed on silver electrodes in alkaline cells, the electrodes were investigated by observing the structure and the changes that electrochemical stressing induces. this was achieved using a scanning electron microscope. measurements were performed with a topcon ds130 and a zeiss gemini leo microscope. this device was equipped with a noran voyager 3000 edx system. in addition, a variation of the microscopic beam energy in the range of 1-40 kev was performed. the results showed that the performance of the silver cathode used decreased during operation time at a constant rate. also, because of the declining roughness of the surface, the surface area of the catalysts decreases, and the pore system is altered. during the orr, a reduction in electrochemical performance is observed. a direct implication is that in an operating period of about 5000 hours, the total voltage loss will be about 100mv [22]. this result will be more suitable for mobile than stationary applications. 2.1.10 bipolar gas diffusion layer: polytetraflouraethylene bonded carbon black layer as per a study on this bipolar electrode, nickel was selected as the conductor because it is a cheap alternative and has good characteristics of mechanical strength, high porosity, specific surface area, corrosion resistance, low density, and electrical conductivity. new electrode designs are also possible due to its three-dimensional structure. the diagnostic technique used to test the efficiency and source of losses of the cathode is called electrochemical impedance spectroscopy (eis). the nickel used in this experiment had 99.9% pure, 110 pores per inch, a thickness of 1.7 mm, and an average pore size of 590nm [24]. in the preparation of each electrode, the gas diffusion layer mixture was rolled and formed into a thickness of 0.5mm with a calendaring machine, and it was done on top of the glass-proof paper. excess liquid is finally removed by pressing at constant pressure, and then the resultant cathode coalesced in the air at 255 c for 30 minutes. the liquid electrolyte utilized in this study was strong potassium hydroxide synthesized from deionized water and potassium hydroxide pallets. trapped air was avoided in the cell throughout the experiment by properly circulating the electrolyte from top to bottom. this new cathode design that had been developed over time for the oxygen reduction cathode reaction in an alkaline fuel cell showed promising results from the experiment conducted. based on the study, cathode performance was significantly improved, especially at high potentials of 130 ma cm2 at 25 c and 0.8 v. this is compared to about 35 ma cm2 of previous designs in the same testing conditions. this insight will allow us to relate the micro and macrostructure of the electrode to its kinetics, which offers exciting opportunities for further cathode evolution and development [26]. 2.2 future innovations for alkaline fuel cells technological change does not just happen from nothing. it evolves, and therefore, the history of its evolution matters. early scientists discovered that just as electricity could be used to split water into its component elements, the reversal process can be done to generate electricity. originally, platinum was used as the electrode, while sulphuric acid was used as the electrolyte. this was very expensive and impractical; hence the idea was shelved temporarily [27]. further attempts by other scientists to revive this idea will involve them changing the acidic sulphuric acid electrolyte to an alkaline fluid to reduce the cost. for this new fuel cell, nickel could be used as an electrode much cheaper than platinum. energy systems around the world are trying to switch to cleaner energy sources to reduce the rate of co2 emissions. this unilateral action is necessitated by the fact that climate change, scarcity of fossil fuels, and uneven distribution of traditional energy sources are becoming a growing concern [1]. although it is expected that this change will be costly and technically difficult, the burden of innovation will lie in the hands of government institutions and industry entrepreneurs. analyzing the trends in sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 39 innovation will serve as a means of evaluating the success so far and predicting the pace at which future innovations will take place [2]. a study focused on technological innovations in practice explained that the united states is currently one of the world’s largest energy consumers. though its government is sluggish in implementing radical climate and energy policies, it has introduced two changes in the energy sector to enhance the country’s competitiveness in the energy sector and encourage innovation. the energy policy act of 2005 and the energy security and independence act of 2007 are the two policies and significant reasons behind the country's massive investment in fuel cell technology research [4]. despite these investments, commercialization of this relatively new technology has been slow. at this stage, it is uncertain how much public acceptance this technology will gain in the future. currently, fuel cell technology firms are developing many prototypes and pre-commercialization products at fast speeds to try and ease the technology into the very aggressive energy market. a few innovations, however, show good prospects [27]. 2.2.1 nano gold hybrid materials for oxygen reduction reaction a review by umsa et al. [29] investigated the use of novel nano gold hybrid materials for use in the oxygen reduction reaction of an alkaline fuel cell. the study highlighted that the successful application of these materials would rely on parameters such as the size and crystallographic orientations of nanogold materials in the electrodes. this parameter is very critical and determines, to a large extent, the overall performance of the fuel cell [28]. while this gold technology might not be up to standards yet with the more expensive platinum electrode, it proved from the study that it could be a reliable and reasonable alternative. it has been discovered that nano particulate gold has good catalytic activity for oxidation-reduction reactions [29]. the performance of nanoparticulate catalysts is directly influenced by their size and support. although catalytic activity usually cannot be observed at characteristic sizes more than 5 nm. the unique structure and properties of these au nanoparticle hybrid materials are responsible for their current and growing applications in the field of fuel cells. despite all the prospects and successes recorded by the nanoparticle gold electrode, fuel cells based on this technology have still not been fully understood by scientists. their surface chemistry is still somewhat elusive; hence, they have still not yet been able to replace the traditional fuel cells. these nanoparticle fuel cells have many possible permutations; this, combined with the dynamic surface chemistry, makes them an attractive option for future study and application [30]. 2.2.2 alkaline direct ethylene glycol fuel cells alkaline direct ethylene glycol cells represent what can be said to be the most promising source of power for portable stationary and mobile applications. this is because this fuel cell stack runs on sustainable fuel, and the key components that make up the overall design are relatively inexpensive [31]. ethanol is very suitable for alkaline cell use because it is a carbon-neutral transportation fuel. however, an issue exists with difficulty in breaking down its bonds at temperatures lower than 100o c. 2.3 advantages of alkaline fuel cell 2.3.1 environmentally friendly characteristics hydrogen is a sustainable green energy. the final product of hydrogen combustion is the water, which is the cleanest energy and pollution-free [32]. hydrogen combustion will not emit greenhouse gases. hydrogen can be produced through a different process. hydrogen can be obtained from fuel processing, biomass, and water. the fuel processing of methane is the primary hydrogen production method used in factories today [33]. only 2%-6% of commercial hydrogen production is from electrolysis, and over 95% is from fossil fuel conversion [32]. nowadays, more research is being done to obtain hydrogen through a cleaner process from biomass and water. biomass used for the production can be obtained from different types of organic resources such as agricultural wastes, sawdust, corn, and others. 2.3.2 high energy efficiency besides that, the alkaline fuel cell is used as an essential energy storage for the spacecraft. it converts the excess electrical energy into storage through electrolysis. hydrogen and oxygen are stored in a tank and supplied to the fuel cell when needed. the fuel cell will not be affected by the carnot factor, which will allow it to have high efficiency [34]. a fuel cell is more efficient than the combustion of fuel, which produces heat and electricity [35]. this is because a fuel cell is not a heat engine. conventional combustion power plants usually have an efficiency of 33% to 35%, whereas the fuel cell is able to reach an efficiency of 65% [36]. 2.3.3 low maintenance cost the alkaline fuel cell has proven that the maintenance cost is cheaper than the conventional diesel energy generator, which allows it to be used in remote areas [37]. the initial cost of the alkaline fuel cell is higher, but the alkaline fuel has a low maintenance cost. a fuel cell is used in the vehicle as the fuel cell's energy source. fuel cell vehicles can be considered zeroemission vehicles [38]. alkaline fuel cells run at lower temperatures compared to the normal engine, which deals less damage to the engine. the alkaline fuel cell operated at 60 °c to 140 °c with the highest efficiency [34]. conventional engines will operate at high temperatures, so a cooling system is needed. more operating parts means higher maintenance costs. 2.3.4 non-toxic hydrogen is a non-toxic substance that is uncommon for a fuel source. unlike nuclear energy, the power plant's failure is catastrophic and will harm human beings. in the various accidents that occurred, radioactive substances released caused the death of thousands of people, and the area around it was quarantined. this can be seen in the various nuclear power plant accidents: the three mile island, chornobyl, and fukushima [39]. hydrogen is unique compared to other fluids, which have high solubility and are easily diffused with other materials at room temperature [40]. this reduced the chance of affecting the health of the human body. sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 40 2.4 disadvantages of alkaline fuel cells 2.4.1 high difficulty in storage storage of the hydrogen for the alkaline fuel cell is an issue. the hydrogen is stored in three types: compressed gas, adsorbed gas, and cryogenic liquid gas [41]. commonly, hydrogen is stored using compressed gas and cryogenic liquid gas. the high pressure of the hydrogen storage caused the design of the cylinder storage tank to be bulky. besides that, metals will become brittle when consistently in contact with hydrogen gas. this is known as the hydrogen embrittlement [42]. 2.4.2 fossil fuel still needed hydrogen production commercially nowadays mainly uses fossil fuels, including natural gas, petroleum, and carbon [43]. hydrogen is not considered renewable energy when it is produced from fossil fuels. hydrogen gas production will still cause the emission of greenhouse gases and the depletion of fossil fuels. this production method is not the long-term production method for hydrogen. although hydrogen can be produced through water electrolysis, only 4% of the total production of hydrogen gas is produced by water electrolysis [44]. 2.4.3 flammable oxygen gas and hydrogen gas may not be toxic, but they are flammable. the pure hydrogen will not explode, but it will burn if not handled with care. hydrogen flame is almost invisible under daylight. this is because the wavelength of the flame is similar to ultraviolet, which is about 311nm [41]. the hydrogen can produce more than 2,000 degree celsius when burning in the air which is considered low in the combustion of the fuel. 2.4.4 costly to use the fuel cell contains no moving parts and should have a lower production cost. however, the materials, catalysts, and sealing of the alkaline fuel cell are the main costs of the fuel cell, which will be extremely expensive to achieve high efficiency [45]. more research needs to be done to increase the performance, reliability, and durability, which means more cost for the research. this will increase the cost to produce the fuel cell. various problems are faced during the scaling-up of the fuel cell, including degradation, uneven chemical reaction, reduction of active area, and others [46]. the lifecycle cost of the fuel cell is higher than the internal combustion engine and hybrid engine due to the high initial cost [47]. therefore, large production is needed to reduce the cost of the fuel cell. 2.5 comparison with other fuel cells alkaline fuel cells are fuel cells with an alkaline electrolyte that consumes hydrogen and pure oxygen and produces water, heat, and electricity (figure 3). they are among the most efficient fuel cells, reaching 70% [48]. in the last decade, energy-related problems are on the rise. one of the means of renewable energy conversion is via alkaline fuel cells. these fuel cells are used to produce electrical energy [49]. alkaline fuel cells can be compared with a number of other fuel cells some of those fuel cells are mentioned as follows: • direct methanol fuel cells (dmfc) • molten carbonate fuel cells (mcfc) • phosphoric acid fuel cells (paf) • proton exchange membrane fuel cells (pemfc) • reversible fuel cells (rfc) • solid oxide fuel cells (sofc) figure 3. process of alkaline fuel cells 2.5.1 direct methanol fuel cells dmfc is a promising alternative for reinforcement control frameworks and the power supply of convenient gadgets. although dmfc has complex electrochemistry, it is promising as a power hotspot for compact and uninterruptable power supply applications. it is attractive in terms of high energy density liquid fuel, quick recharging by refilling, and low operating temperature [50]. during the process, both methanol and water can undergo a phase transition from liquid to gas phase, as shown in figure 4. h2o (gas) ↔ h2o (liquid) (1) ch3oh (gas) ↔ ch3oh (liquid) (2) figure 4. the schematic process diagram of direct methanol fuel cells 2.5.2 molten carbonate fuel cells mcfc utilizes liquid salts as fuel for energy devices (figure 5). electrolyte membrane constituted by a liquid carbonate eutectic and a lithium aluminate solid support attractive. liquid carbonates are non-toxic and very conductive salts. at a regular working temperature of 650oc, sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 41 heat and electrical power are generated. the liquid carbonate goes about as whatever other dissolvable, for example, water [51]. the separation produces acidic-fundamental properties, which control the conduction. the condition of equilibrium is written below: m2co3 (l) ↔ m2o (s) + co2 (g) (3) figure 5. process of molten carbonate fuel cells 2.5.3 phosphoric acid fuel cells pafc is the most industrially propelled innovation among the hydrogen-oxygen fuel cells (figure 6). pafc is distinct from the other energy conversion systems because the electrolyte operates at 160-220oc. co poisoning of the platinum catalyst is additionally diminished. pafc is discovered to be valuable in stationary power distribution, defense, and military applications. because of the utilization of valuable metal electrocatalysts, it is expensive. the chemical energy of the reaction is converted into electrical energy [52]. the equations of the process at the electrodes are shown below: anode: h2 → 2h+ + 2e (4) cathode: ½ o2 + 2h+ + 2e → h2o (5) overall: h2 + ½ o2 → h2o (6) figure 6. process of phosphoric acid fuel cells 2.5.4 proton exchange membrane fuel cells pemfcs are the cells where electrochemical reactions occur to produce electrical power (figure 7). proton conducting film comprises catalyst layers and gas diffusion layers. these segments are manufactured independently and, after that, squeezed together at high temperatures and pressure. the equations of the electrodes are shown below: anode: ½ o2 + 2h+ + 2e → h2o (7) cathode: h2 → 2h+ + 2e (8) the flow of ionic charge through the electrolyte must be balanced by the flow of electronic charge through an outside circuit, and this balance produces electrical energy [53]. figure 7. process of proton exchange membrane fuel cells 2.5.5 reversible fuel cells rfc offers an answer for creating fuel using surplus power and reconverting this into power utilizing a similar device (figure 8). rfc system in electrolysis mode can be utilized to make hydrogen and oxygen, which are put away in tanks. on the off chance that there is an absence of vitality, then the put away hydrogen and oxygen are utilized as working fuel to produce power. hydrogen and oxygen are both naturally well-disposed and economical [54]. the overall reaction of water electrolysis is expressed as: h2o (g/l) + electrical energy + heat → ½ o2 + h2 (9) figure 8. process of reversible fuel cells sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 42 2.5.6 solid oxide fuel cells sofc is a device that allows the prompt change of substance vitality into electrical vitality at high temperatures, using an all-strong state cell equipped with ceramic materials (figure 9). these frameworks can, on a basic level, accomplish productivity levels higher than customary advancements used to make power. the responses included are fundamental and undefined to those incorporated into the interior burning engine. sofc includes three segments gathered together to shape like a sandwich. a thick electrolyte is sandwiched between two penetrable terminals, the cathode and anode [55]. the following equations are involved in the anode and cathode, as shown below: anode: o2(s) + h2 (g) = h2o (g) + 2e (10) 4o2(s) + ch4 (g) = 2h2o (g) + co2 (g) + 8e (11) cathode: ½ o2 (g) + 2e= o2(s) (12) figure 9. process of solid oxide fuel cells 2.6 fuel cell applications 2.6.1 maritime activities shipping is a significant activity that contributes massively to the global emissions of greenhouse gases, volatile organic compounds, particulate matter, hazardous air pollutants, and oxides of nitrogen and sulphur. 3.5% of co2 emissions and over 5% of sox emissions worldwide are the result of shipping activities. despite introducing modern propulsion technology, the shipping industry has failed to reduce emissions. this puts them behind the road transport. the absence of strict environmental regulations at sea can also be a major factor in why shipping has a poor environmental emissions record [56]. fuel cells have the potential to be of use onboard ships. application of fuel cells in different vessels includes emergency power supply, electric energy generation, especially in waters and harbors prescribing environmental regulations; small-scale power output for propulsion at unique operating modes (e.g., very quiet run); and generation of electrical power to satisfy the needs of the ship. the fuel cell is used in submarines to achieve air-independent propulsion, and the proton exchange membrane fuel cell system was utilized on german navy submarines [57]. 2.6.2 stationary power generation molten carbonate fuel cell (mcfc) is the most promising high-efficiency and sustainable power generation technology, as demonstrated by the current availability of several commercial units in the market. stationary power generation utilizing mcfc technology offers an efficient alternative to power plants fueled by coal. mcfcs have emerged as the preferred technology for commercialized stationary power generation. various companies around the globe are conducting tests on big-scale power generation systems that consist of kilowatt to megawatt-class systems. some companies are expanding their systems to hospitals, hotels, data centers, and other industries with lower power demands, including wastewater treatment plants [58]. 2.6.3 space programs the alkaline fuel cells (afc) utilized in space shuttle programs of the united states are unable to withstand co2. the polymer electrolyte fuel cell (pefc) was developed initially for use in space and was used for quite some time until its sensitivity to co was discovered. in terrestrial applications, fuels that contain hydrocarbon compounds had to be used in various applications, and the presence of carbon monoxide and dioxide was detrimental to the systems. in order to overcome this hurdle, the phosphoric acid fuel cell (pafc), the molten carbonate fuel cell (mcfc), and the solid oxide fuel cell (sofc) were developed [59]. 2.6.4 transportation and portable energy polymer electrolyte fuel cells (pemfcs) and direct methanol fuel cells (dmfcs) have been seen as compatible sources of power generation for electric cars. in theory, methanol possesses greater specific energy density (6000 wh/kg) when compared to the best rechargeable battery in the market, lithium polymer, and lithium-ion polymer (theoretical, 600 wh/kg) systems. this advantageous efficiency trait can be utilized to enable longer battery life in cell phones, laptop computers, and other consumer electronics. these fuel cells can also increase the battery's lifetime, thereby giving longer hours before replacement [60]. 2.6.5 automotive applications in the automobile market, carmakers have made significant efforts to switch to more efficient and sustainable fuels to power vehicles. various laws have been enforced on automobile manufacturers that force them to adhere to strict emission standards as well as fuel consumption margins. hence, there are continuous efforts in this industry to develop technology that meets these requirements. fuel cell technology can be the answer as it gives the manufacturers what they need: environmental compatibility, consumer profit, costs of maintenance, and efficiency [20]. alkaline fuel cells can be used in the automotive industry and have high power density requirements. however, when compared to the pefc, the simplicity of afc technology enables the utilization of affordable materials for catalysts, electrolytes, and other parts needed for the cell and the system. pefcs could be the future of automotive applications, but only after implementing a method of reducing the costs significantly. this puts afcs at a big advantage compared to the pefc [61]. sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 43 2.7 the future of fuel cells 2.7.1 direct methanol fuel cells to reduce greenhouse gases and avoid the violation of current environmental rules and regulations, a system with high efficiency combined with economic feasibility must be created. this energy conversion system with the abovementioned benefits is seen in dmfcs [60]. 2.7.2 hybrid systems solar and wind energy are the types of energy sources preferred these days due to their natural abundance and unlimited supply. however, due to the various geographical limitations, such as the need for low cloud cover for solar energy and high-speed wind areas for windmills, harnessing energy consistently has been a challenge. results from various experiments showed that by combining solar energy, wind energy, and fuel cells, a hybrid system can be designed that will prove to be a plausible solution for applications hindered by geographical limitations. these systems, known as hybrid power systems, will considerably increase the energy supply [62]. studies conducted in the past support using a fuel cell as another energy source to overcome such problems. 2.7.3 direct oxidation of alkaline fuel cells direct oxidation alkaline fuel cells (doafcs) have recently gained attention due to their potential to solve problems encountered in the proton exchange membrane fuel cells. a polymer electrolyte made up of an anion exchange membrane has been found to reduce carbonate build-up from the co2 released. the electro-oxidation of fuels enables the utilization of cheaper metals such as palladium, silver, and nickel as well as perovskite-type oxides in alkaline fuel cells, which will decrease the catalyst cost considerably compared to catalysts made of platinum [63]. 2.7.4 electric vehicles the benefits of running electric vehicles on fuel cell power plants are an established technological fact. pem and pafc systems are tested, their results are studied, and viability is assessed. a significant factor in deciding the use of a fuel cell type is the economics associated with that cell. similarly, the fuel needed to power these cells is also significant in automotive applications. ammonia is a key ingredient in most fuel cells as it is available all around the globe and has the added use of being a gasoline additive to clear the presence of nitrogen oxide from exhaust gases, as suggested by renault [64]. 3. results analysis 3.1 challenges the challenges facing fuel cells are quite simply that of efficiency and costs associated with the manufacturing and running of those fuel cells. future research will focus on these aspects, and once plausible solutions have been found, fuel cells can finally answer energy requirements in particular industries [65]. solid oxide fuel cells (soecs) are operable on natural gas and gasoline fuels. they are also compatible with alternative or green fuels such as hydrogen and biofuels. the only obstacles facing it are reduced operating temperature and cost [66]. pemfcs are believed to have great potential for use in the transportation sector. high cost is a significant factor slowing down the progress and entry into commercial use [67]. a low-power system constructed using afcs will compete with a pemfc system regarding running costs. afcs are cost-efficient and hence preferable over pemfc systems [68]. 3.2 importance of alkaline fuel cells in the future a fuel cell system is an advanced power device for the future that is sustainable, environmentally friendly, and clean. fossil fuel storage is limited and will be replaced in 70-150 years. persistent utilization of non-renewable energy sources will produce greenhouse gases, prompting environmental change and an earth-wide temperature increase. alkaline fuel cells produced the power for nasa's gemini and apollo space containers, giving the group drinking water. the technology of the alkaline fuel cells will contribute essentially to a reduction in environmental impacts, improved vitality security, and the formation of new vitality businesses. basic energy components can be used in transportation, distributed heat and power generation, and energy storage systems [69]. technical improvements are dependable on increments in overall car advertising. dramatic restrictions on emissions as well as the regiment of fuel consumption by legislation. the technology of fuel cells offers the likelihood to exceed expectations as far as environmental compatibility, consumer benefit, cost of maintenance, and efficiency. the alkaline hydrogen energy components framework with flowing koh electrolyte and minimal effort-catalyzed carbon cathodes could be a promising alternative [70]. alkaline direct methanol fuel cells are a type of alkaline fuel cell that converts the chemical energy stored in ethanol directly into electricity. this produced electricity can be utilized in automobiles because these alkaline fuel cell components keep running on carbon-neutral, sustainable fuel, and the electro-catalyst and membrane materials that constitute the cell are relatively inexpensive [3]. daihatsu is a big name when it comes to automobiles. they are one of the biggest automobile names in japan. daihatsu motor company developed a fuel cell that eliminates the need for platinum. this alkaline fuel cell runs on easily handled hydrazine hydrate. it is safe to use as polymer technology developed by the company [71]. electricity generation is another significant factor in the future of alkaline fuel cell components. electricity generation from macro-algae utilizing alkaline fuel cells. this renewable power source innovation can relieve the energy crisis emergency and significantly reduce global warming emissions [72]. algae stand out amongst the most encouraging supportable wellsprings of sustainable power sources since they have higher growth rates, require less earth's surface, and don't contend with other food productions [73]. electricity is additionally generated from refillable glucose alkaline fuel cells with methyl viologenimmobilized activated carbon-nickel anode. the electricity produced by alkaline fuel cells has a lot of advantages, such as less pollution, high efficiency, and adaptability to deal with various fuel sorts. glucose is abundant, cheap, nonpoisonous, simple to get and store, and convenient to transport; it is a potential positive fuel for energy components. the only issue confronted is the high cost [74, 75]. sba. kashem /future sustainability may 2025| volume 03 | issue 02 | pages 35-46 44 4. conclusion research on alkaline fuel cells is conducted by only a few segments of researchers based primarily in europe. the most common problems hindering the use of afcs have been solved, and new and innovative ideas for developing systems have been developed. overcoming the challenges of cost and efficiency will make fuel cells the answer to the global population's demanding and increasing energy requirements. acknowledgment the author is grateful to dr. jaka sunarso for his constant support. this work would not have been possible without his kind help. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data 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[75] e. gülzow, "alkaline fuel cells: a critical view," journal of power sources, vol. 61, no. 1–2, pp. 99-104, 7// 1996. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 21 article analysis of fatigue of construction workers based on electromyographic signals xiaohong gui*, xinuo fang, mengting li, mingjun dai, lianbin su china university of mining and technology, beijing, beijing 100083, china a r t i c l e i n f o article history: received 25 may 2025 received in revised form 01 july 2025 accepted 14 july 2025 keywords: electromyographic signals, construction workers, time-frequency analysis, fatigue monitoring *corresponding author email address: gxhbox@sina.com doi: 10.55670/fpll.fusus.3.4.3 a b s t r a c t aiming to address the fatigue issue of construction workers resulting from highintensity physical labor, this paper proposes a fatigue analysis method based on surface electromyographic signals (semg), focusing on the handling operation as the research object, to explore the fatigue characteristics of construction workers' muscles and significant monitoring indices. by collecting semg signals under different fatigue levels, we analyze the trends of time-frequency domain indicators (root mean square value rms, integral emg value iemg, median frequency mf, mean power frequency mpf, and over-zero rate zcr). the experimental results show that with the increase of fatigue, the rms and iemg of brachioradialis and erector spinae increase significantly, while the mf and mpf decrease significantly, which reflects the physiological mechanism of the decrease of muscle contraction efficiency and the enhancement of neural drive. the changes in the indexes of erector spinae are more significant than those of brachioradialis due to the higher stability load and the activation characteristics of fast muscle fibers. through the test of intergroup variability, rms, iemg, mf, and mpf are selected as the core indicators for fatigue monitoring. this study provides an objective, quantitative basis for labor protection in the construction industry and lays a theoretical foundation for the real-time monitoring of occupational fatigue and the optimization of work efficiency. 1. introduction as a vital pillar of the national economy, the construction industry plays a crucial role in driving high-quality economic development [1]. however, due to the high labor intensity and poor working environment faced by construction workers, the safety accident rate in the construction industry has long been higher than that of other industries [2]. construction workers are often required to perform physically demanding tasks in awkward working postures for extended periods, making them prone to occupational fatigue [3]. this condition can lead to the occurrence of unsafe behaviors that increase the risk of safety accidents and other occupational health problems [4]. fatigue has been recognized as one of the main causes of safety accidents in the construction industry, so research on fatigue in construction workers is very important. most of the fatigue produced by construction workers is physiological fatigue, and the reason for this fatigue is due to the lack of metabolic capacity of the body caused by prolonged labor or strenuous exercise, resulting in a significant accumulation of lactic acid and carbon dioxide and other metabolites in the muscle, this local acidic environment will interfere with the process of calcium ions and calponin binding in the myocyte, which will inhibit the normal contraction of the muscle, and ultimately lead to the physiological fatigue state of the organism [5]. at present, numerous scholars have conducted research on human fatigue. bai wei et al. [6] proposed a method of judging driver fatigue by testing surface electromyographic signals through electromyography experiments for the problem of muscle fatigue and injury that can be easily caused by the process of drivers getting into the car. yang yanpu et al. [7] effective identification of upper limb muscle fatigue state in hand-overhead operation based on support vector machine by collecting surface emg signals of the subjects as well as subjective fatigue state. xin yunsheng et al. [8] analyzed the muscle fatigue of monorail crane drivers by conducting electromyographic testing studies on 16 muscles prone to fatigue. liang zhanhun et al. [9] analyzed and researched the local muscle fatigue of climbing workers through surface emg signals, explored the characteristic pattern of change of future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.4.3 november 2025| volume 03 | issue 04 | pages 21-31 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:gxhbox@sina.com https://doi.org/10.55670/fpll.fusus.3.4.3 https://fupubco.com/fusus x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 22 surface emg signals and its relationship with the subjective fatigue evaluation value in the process of operation, and provided data support for objectively evaluating the local muscle fatigue of climbing operation and preventing workrelated musculoskeletal disorders. xu zhao et al. [10] introduced semg signal recognition and motion capture technology into the process of fatigue state monitoring, proposing a fatigue analysis method that integrates an improved emg fatigue threshold algorithm and biomechanical analysis. wang hongpeng et al. [11] selected a typical road section of the pamir plateau in xinjiang to conduct a real driving test to investigate the fatigue characteristics of the neck muscles of plateau highway drivers under the effect of continuous driving time and altitude by means of surface electromyographic signals. antwi-afari et al. [12] analyzed the loading conditions of different body parts of the workers in carrying out a study related to manual material handling operations, which showed that reasonable control of lifting weight, improvement of working posture, and reduction of repetitive operations can effectively reduce the probability of fatigue. wang et al. [13] conducted a study on roofing operations and found that different working postures and frequency of operations can cause significant changes in the electromyographic activity level of the lower back muscles of the workers, which suggests that the effect of the mode of operation on the muscular fatigue should not be ignored. shariatzadeh et al. [14] designed and manufactured a novel wearable sensor system with semg electrodes and motion tracking sensors for monitoring dynamic muscle movements in the human body. currently, there are few studies on the analysis of operational fatigue of construction workers, and few studies for the analysis of physiological fatigue of construction workers. therefore, this paper analyzes the operation fatigue of construction workers based on emg signals and combined with subjective fatigue perception, to explore the intrinsic connection between fatigue perception and emg signals, to reveal the dynamic change law of the fatigue state of construction workers, so as to improve the efficiency of construction workers, to reduce the unsafe behaviors triggered by physical fatigue, and to reduce the probability of safety accidents. 2. experimental design and method 2.1 subjects since construction workers are predominantly male and generally have good physical fitness, 12 healthy adult male construction workers were selected as subjects in this study. all subjects have high physical fitness and typically exercise for more than 1 hour per day. the specific physical data are as follows: age 22-26 years old, height 170-182cm, weight 6580kg, bmi 22.02-24.17. before the experiment, to ensure that all the subjects can experiment with the best physical state, the subjects are required to maintain sufficient sleep, prohibit alcohol, coffee, sports drinks and other beverages, and the experimental time is selected in the morning or the afternoon, to maximize the experimental time was chosen in the morning or afternoon to maximize the simulation of the construction time in the building construction site. 2.2 research methods adopting the research method of laboratory simulation, the above research objects were selected to simulate the work of construction workers in the laboratory. the manual handling operation was chosen as the experimental task, which has lower requirements for the laboratory environment and can be carried out in a controlled setting. the noraxon ultium emg wireless surface emg instrument was used to monitor emg signals during the experiments, and the borg scale was used to quantify the physical state objectively. 2.3 electrode arrangement of emg equipment emg signals are measured by electrodes placed on the surface of the skin, which are capable of recording the signals of electrical activity of the muscles in response to nerve stimulation, thus reflecting the physiological state and functional changes of the muscles. based on the results of related research [15-17], the brachioradialis and erector spinae muscles are selected as the target muscle groups in this paper. the electrode arrangement position of emg signals is shown in figure 1, and only one side of the muscle can be measured in the measurement, so the right half of the muscle of the subject is chosen to be measured. figure 1. myoelectric electrode arrangement (① is the brachioradialis muscle, and ② is the erector spinae muscle) 2.4 experimental procedure before the beginning of the experiment, wear the physiological monitoring equipment for the subject correctly and make sure that the physiological monitoring equipment can work normally. then, the subjects entered the resting session and kept sitting still for 10 minutes in order to bring their physiological status to the basal level. at the end of the resting period, the experiment began with subjects lifting a 25 kg weight from point "a" and stacking five weights to point x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 23 "b" according to the diagonal path shown in figure 2. after completing each set of tasks, the subjective fatigue perception according to the borg scale was filled in, and then the weights were carried from point "b" to point "a" one by one. this process was repeated until the subject felt completely exhausted and signaled the termination of the experiment. physiological indexes of the subjects were recorded throughout the experiment. figure 2. manual handling simulation operation 2.5 data collection and recording 2.5.1 subjective fatigue scale the borg perceived exercise intensity scale (rpe) was used in the experiment, which ranges from 0-10, indicating the subject's perception of fatigue in accomplishing a specific task, from "no feeling" to "maximum effort". the borg scale score was recorded once after each subject completed five lifting tasks until the fatigue level reached its limit. in order to systematically analyze the fatigue of construction workers and reflect the subjective fatigue state of the subjects in a more detailed way, the borg scale scores of the subjects in the process of lifting and carrying tasks were divided into three fatigue levels: 0-3 points were divided into the low-fatigue group, 4-6 points were divided into the moderate-fatigue group, and 7-10 points were divided into the severe-fatigue group. 2.5.2 pre-processing of emg signals the emg signal will be interfered by the measurement environment noise, inherent noise of the equipment and baseline drift in the process of acquisition and recording, so to accurately extract the surface emg signal that can reflect the fatigue state of the body, it is necessary to use the corresponding filtering method to preprocess the original emg signal. (1) inherent noise of the acquisition instrument: in the process of emg signal acquisition, the inherent noise of the measuring instrument is one of the main sources affecting the signal quality. in order to minimize the noise interference in signal acquisition, the skin surface where the target muscle group is located is cleaned as necessary before the experiment, and the distance between the electrodes on the paired surfaces is reasonably controlled. (2) measurement of environmental noise: environmental noise refers to the noise pollution introduced by the peripheral electrical equipment during the signal acquisition process, of which industrial frequency interference is the most important form of interference. according to china's power system standards, the operating frequency of the ac power supply network is set to 50hz, which causes the spectral energy of industrial frequency interference to show significant aggregation characteristics near the 50hz frequency point. therefore, this paper adopts a butterworthtype bandpass filter to suppress the industrial frequency interference, and the filter parameters are set to a 4951hz passband range. (3) time-frequency domain feature index extraction: in order to comprehensively evaluate the change rule of emg signals under fatigue state, this paper calculates the root mean square (rms) and integral electromyography (iemg) of the filtered emg signals of the brachioradialis and erector spinae through the average value of the sliding window of 500 milliseconds. meanwhile, the median frequency (mf), mean power frequency (mpf), and zero-crossing rate (zcr) were derived after calculating the power spectral density using the scipywelch function. in addition, the time-domain features of emg, rms, and iemg were normalized by the corresponding values of maximum muscle force (mvc) of the respective muscles. these feature indicators reflect the degree of muscle fatigue from multiple dimensions, such as signal intensity, total activity, and frequency distribution, respectively, and have good sensitivity and stability in muscle fatigue detection. the specific calculation process of each feature index is as follows: rms: it is a kind of feature indicator reflecting the overall amplitude of the signal, mainly used to assess the intensity of muscle activity, commonly used in fatigue monitoring and action recognition. the calculation formula is shown in equation (1). 𝑅𝑀𝑆 = √1 𝑁 ∑ 𝑖=1 𝑁 𝑥𝑖 2 (1) where xi is the signal value of the ith sampling point; n is the total number of sampling points. iemg: it is a feature that sums the absolute values of the signals and is used to assess the overall output of the muscle activity, which is suitable for the analysis of muscle fatigue over a long period of time. the calculation formula is shown in equation (2). 𝐼𝐸𝑀𝐺 = ∑ 𝑖=1 𝑁 |𝑥𝑖| (2) mf: is the frequency in the power spectrum that divides the total power into two equal parts, commonly used in fatigue monitoring. mf usually drifts to lower frequencies as the muscle fatigues. the formula is shown in equation (3). ∫0 𝑀𝐹 𝑃(𝑓)𝑑𝑓 = ∫𝑀𝐹 𝑓𝑚𝑎𝑥 𝑃(𝑓)𝑑𝑓 (3) where p(f) is the power spectral density of the signal, fmax is the maximum frequency. mpf: is the weighted average of the frequency distribution of the signal, similar to mf, used to assess muscle fatigue. the calculation formula is shown in equation (4). 𝑀𝑃𝐹 = ∫0 𝑓𝑚𝑎𝑥𝑓⋅𝑃(𝑓)𝑑𝑓 ∫0 𝑓𝑚𝑎𝑥𝑃(𝑓)𝑑𝑓 (4) x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 24 zcr: is the number of times the signal passes through the zero point within a certain time window and is used to analyze the frequency changes of emg signals, especially the frequency dynamics during rapid muscle contraction and relaxation. the calculation formula is shown in equation (5). 𝑍𝑅𝐶 = ∑ 𝑖=1 𝑁−1 1((𝑥𝑖 ⋅ 𝑥𝑖+1) < 0) (5) 3. results and discussion 3.1 subjective fatigue according to the statistical results, there were 57 low fatigue groups, 262 moderate fatigue groups, and 141 severe fatigue groups, and the difference between the three groups was statistically significant (p< 0.05). with the progress of the handling task, the subjective fatigue perception of the subjects gradually deepened, and the borg score showed a significant upward trend. the mean value of the scores in the low fatigue group remained at a low level, approximately in the range of 1-3 points, reflecting that the subjects' fatigue perception was relatively light at this fatigue level; whereas the scores in the moderate fatigue group were in the range of 4-6 points, showing an increase in fatigue perception; the mean value of the scores in the severe fatigue group was significantly higher than that of the previous two groups, usually in the range of more than 7 points, showing that the fatigue perception of the subjects reached the peak in the state of severe fatigue, as shown in figure 3. figure 3. mean values of scores of different subjects at three levels of fatigue 3.2 emg signal analysis 3.2.1 descriptive analysis of emg signal characteristics indicators based on the three different fatigue groupings, the mean values of the characteristic indexes of the subjects under different fatigue levels were calculated. the changes of the mean values of the physiological indexes of the 12 subjects from low fatigue to severe fatigue states are shown in figure 4 (a, b, c, d, e). from figure 4 (a) to (e), it can be seen that as the fatigue level rises, the time-frequency domain indexes of emg signals of brachioradialis and erector spinae, such as rms and iemg indexes, show an upward trend; such as the mf and mpf indexes, show a downward trend; and the trend of change of the zcr indexes is not obvious, and the trend of change of each subject is not consistent. specifically: (1) rms of brachioradialis muscle increased from low fatigue (0.05± 0.30) to severe fatigue (0.08± 0.04), and iemg low fatigue (0.06± 0.07) to severe fatigue (0.09± 0.10). (2) the rms of the erector spinae muscle increased from low fatigue (0.46± 0.67) to severe fatigue (1.05± 1.73), and iemg from low fatigue (0.10± 0.08) to severe fatigue (0.22± 0.26). (3) mf of the brachioradialis muscle decreased from low fatigue (0.13± 0.11) to severe fatigue (0.11± 0.09), and mpf decreased from low fatigue (0.15± 0.12) to severe fatigue (0.13± 0.11). (4) mf decreased from low fatigue (0.93± 0.31) to severe fatigue (0.74± 0.22), and mpf decreased from low fatigue (0.89± 0.27) to severe fatigue (0.72± 0.18) in the erector spinae muscle. (5) the zcr of the brachioradialis and erector spinae muscles showed a small increase in their mean values, although the trend was not significant. zcr increased from low fatigue (0.10± 0.02) to severe fatigue (0.11± 0.03) for brachioradialis, and from low fatigue (0.10± 0.02) to severe fatigue (0.11± 0.03) for erector spinae. as above, the trend of rms vs. iemg suggests that as the lifting operation progresses, the subjects' muscle fatigue builds up, resulting in less efficient muscle contraction and higher neural drive is required to maintain force output.the trend of mf vs. mpf suggests that as the muscle fatigue builds up, the muscle's fast muscle fibers (type ii) take the lead in fatigue due to lactic acid buildup and energy depletion, and the slow muscle fibers (type i) dominate the contraction, resulting in a slowing of action potential conduction and an increase in the proportion of low-frequency components. the trend of zcr shows that fatigue results in a widening of the action potential waveform, a decrease in highfrequency oscillations, and a decrease in the number of times the signal crosses the baseline (zero point) per unit time. among them, by comparing the change amplitude of the characteristic indexes in the time-frequency domain of the erector spinae and brachioradialis, it can be found that the change amplitude of the characteristic indexes of the erector spinae is significantly larger than that of the brachioradialis. the mechanism can be summarized as the following three points [18,19]: (1) biomechanical load differences: the erector spinae muscle is continuously subjected to spinal compression and shear forces during handling operations, and the muscle fibers (especially type ii fast muscle fibers) are more prone to fatigue; (2) distribution of muscle fiber types: the vertical spine muscle has a higher proportion of fast muscle fibers (about 60%), which enter anaerobic metabolism earlier under sustained loading, leading to lactic acid accumulation and left shift of the frequency spectrum; (3) recruitment pattern of motor units: the erector spinae muscle needs to maintain postural stability, and the motor units showed high-threshold synchronized activation, with greater central nervous system drive intensity. x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 25 a) rms change trend chart for test subjects b) iemg change trend chart for test subjects c) mf change trend chart for test subjects d) mpf change trend chart for test subjects x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 26 in summary, although some subjects, due to individual differences, have outstanding anti-fatigue ability of the muscle groups of their forearms or erector spinae, and the trend of the time-frequency domain characteristic indexes is not obvious, the overall trend is the same as the findings obtained by the previous research [20,21], which confirms that the standard emg acquisition equipment used in this paper can effectively capture muscle fatigue under dynamic operating environments, and further verifies the reliability of the experimental data. 3.2.2 screening of fatigue significant indicators of emg signals by statistically analyzing the characteristic indicators of the emg signals of the brachioradialis and erector spinae muscles, the significant indicators under different fatigue levels were screened. since the data in this paper belongs to the relevant samples, the normality test was firstly performed on the above characteristic indexes. for the data that satisfy the normality test, single-group repeated-measures anova and bonferroni post-hoc two-by-two comparisons were carried out. for the data that do not satisfy the normality test, friedman's test and wilcoxon signed-rank test were carried out to carry out post-hoc two-by-two comparisons. a normality test was done for the dependent variable as shown in table 1, and due to the small sample size, the shapiro-wilk test results were chosen to be used. from the results of the shapiro-wilk normal distribution test, it can be seen that the p value of rms and zcr indexes of brachioradialis muscle and mf, mpf, and zcr indexes of erector spinae muscle in different fatigue groups were all greater than 0.05, obeying normal distribution; the rest of the indexes did not obey normal distribution. a single-group repeated-measures anova was performed on the above indexes that obeyed normal distribution, and mauchly's test of sphericity was performed on the dependent variable, and the results are shown in table 2. mauchly's test of sphericity showed that the data of rms and zcr indexes of the brachioradialis muscle, and the data of mf and mpf indexes of the erector spinae muscle, did not satisfy the assumption of sphericity (p1=0.000＜0.05, p2=0.001＜ 0. 05, p(3)=0.001< 0. 05, and p(4)=0.001<0. 05, and p(4)=0.001< 0. 05, p3=0.012＜ 0.05, p4=0.021＜ 0.05), when the dependent variable violates the conditions of the spherical assumption needs to be epsilon (ε) correction, as can be seen in table 2, the huynh-feldt method was chosen to be more effective in the correction, and after the correction of ε1=0.553, ε2=0.559, ε3=0.672, ε(4)= 0.702. the data of the zcr index for the erector spinae muscle satisfied the spherical assumption (w=0.654, p=0.120＞ 0.05), so the results under the spherical assumption were read directly. the results of the within-subjects effect test for each level of the dependent variable are shown in table 3, and combined with the results of the analysis above, it can be seen that by the shapiro-wilk test, the dependent variables in each group of the rms and zcr indexes for the brachioradialis muscle and the mf, mpf, and zcr indexes for the erector spinae muscle obeyed a normal distribution (p＞0.05). the dependent variables of rms (brachioradialis), zcr (brachioradialis), mf (erector spinae), and mpf (erector spinae) indexes did not satisfy the assumption of sphericity by mauchly's sphericity hypothesis test, and ε1= 0.553, ε2= 0.599, ε3= 0.672, and ε4= 0.702 after correction by huynhfeldt's method. after correction, f(1)(1.105,12.160) = 12.958, p1= 0.003＜ 0.05, i.e., the difference is statistically significant; f2(1.197,13.171) = 0.736, p2= 0.430＞ 0.05, i.e., the difference is not statistically significant; f3(1.344,14.787) = 9.843, p3= 0.004＜ 0.05, i.e., the difference is statistically significant; f4(1.403,15.437) = 11.738, p4= 0.002＜ 0.05, i.e., the difference is statistically significant. the dependent variable of zcr (erector spinae muscle) index satisfies the assumption of sphericity, and under the degree of sphericity, f (2,22) = 4.082, p=0.031＜ 0.05, i.e., the difference is statistically significant. the results of the bonferroni correction for the above statistically significant indicators are shown in table 4. figure 4. changes in the mean values of physiological indicators under different fatigue states of the subjects (left figures: brachioradialis muscle, right figures: erector spinae muscle) e) zcr change trend chart for test subjects x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 27 as can be seen from table 4, rms (brachioradialis muscle), mf (erector spinae muscle), and mpf (erector spinae muscle) indices were found to be statistically significant in the low fatigue group versus the moderate fatigue group (p1=0.012＜0.05, p2=0.035＜0.05, and p3=0.017＜0.05), and in the low fatigue group versus the severe fatigue group (p1=0.011＜0.05, p2=0.018＜0.05, p3=0.011＜0.05), moderate fatigue group versus severe fatigue group (p1=0.022＜0.05, p2=0.032＜0.05, p3=0.015＜0.05) differed significantly, indicating that rms (brachioradialis muscle), mf (erector spinae muscle), and mpf (vertical spine muscle) indexes were significantly different between different fatigue groups, and the effect on fatigue zcr (erector spinae) indexes no significant difference between different fatigue groups (p＞0.05), which means that they were not significant for fatigue. friedman's nonparametric test was performed on the indicators of iemg (brachioradialis), mf (brachioradialis), mpf (brachioradialis), rms (erector spinae), and iemg (erector spinae) that did not obey normal distribution, and the results of the test are shown in table 5. the p-value of a certain indicator in friedman's test is less than 0.05, indicating that at least one group of the indicators between different fatigue grades has a significant difference. as can be seen from the table, iemg (p=0.000＜0.05), mf (p=0.000＜0.05), mpf (p=0.000＜0.05) for brachioradialis muscle, and rms (p=0.000＜0.05), iemg (p=0.000＜0.05) for erector spinae muscle indicated that at table 1. normality test of characteristic indexes of emg signals characteristic index fatigue level kolmogorov-smirnov a shapiro-wilk statistic df sig. statistic df sig. rms (brachioradialis) low fatigue .123 12 .200 .960 12 .785 moderate fatigue .106 12 .200 .986 12 .998 severe fatigue .102 12 .200 .986 12 .998 iemg (brachioradialis) low fatigue .296 12 .005 .717 12 .001 moderate fatigue .329 12 .001 .660 12 .000 severe fatigue .301 12 .004 .696 12 .001 mf (brachioradialis) low fatigue .287 12 .007 .740 12 .002 moderate fatigue .305 12 .003 .704 12 .001 severe fatigue .343 12 .000 .712 12 .001 mpf (brachioradialis) low fatigue .268 12 .017 .763 12 .004 moderate fatigue .285 12 .008 .730 12 .002 severe fatigue .326 12 .001 .736 12 .002 zcr (brachioradialis) low fatigue .170 12 .200 .948 12 .606 moderate fatigue .174 12 .200 .908 12 .199 severe fatigue .211 12 .145 .890 12 .119 rms (erector spinae) low fatigue .378 12 .000 .539 12 .000 moderate fatigue .384 12 .000 .525 12 .000 severe fatigue .433 12 .000 .558 12 .000 iemg (erector spinae) low fatigue .273 12 .014 .752 12 .003 moderate fatigue .311 12 .002 .654 12 .000 severe fatigue .367 12 .000 .628 12 .000 mf (erector spinae) low fatigue .170 12 .200 .963 12 .825 moderate fatigue .142 12 .200 .942 12 .521 severe fatigue .110 12 .200 .972 12 .934 mpf (erector spinae) low fatigue .157 12 .200 .937 12 .458 moderate fatigue .203 12 .187 .955 12 .708 severe fatigue .104 12 .200 .986 12 .998 zcr (erector spinae) low fatigue .127 12 .200 .961 12 .802 moderate fatigue .152 12 .200 .937 12 .456 severe fatigue .139 12 .200 .930 12 .377 table 2. mauchly's test of sphericity for each indicator withinsubjects effect indicator mauchly's w approximate chi-square df sig. epsilon greenhousegeisser huynh-feldt lower limit fatigue rms (brachioradialis) .149 19.040 2 .000 .540 .553 .500 zcr (brachioradialis) .260 13.465 2 .001 .575 .599 .500 mf (vertebrae) .410 8.912 2 .012 .629 .672 .500 mpf (vertebrae) .463 7.708 2 .021 .650 .702 .500 zcr (vertebrae) .654 4.245 2 .120 .743 .832 .500 x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 28 least one group had significant differences between different fatigue levels. to further screen the indicators that were significant for fatigue among different fatigue groups, the wilcoxon signed rank test was performed to compare the above indicators two by two, as shown in table 6. all indicators in the table have significant differences between different fatigue groups (p＜0.05), indicating that the indicators in the table are significant for fatigue. table 3. within-subjects effect test for each indicator indicator type iii sum of squares df mean square f sig. η² rms (brachioradialis) sphericityassumed .004 2 sphericityassumed .004 2 12.958 .000 .376 greenhousegeisser .004 1.080 .004 12.958 .003 .376 huynh-feldt .004 1.105 .004 12.958 .003 .376 lower limit .004 1.000 .004 12.958 .004 .376 zcr (brachioradialis) sphericityassumed .000 2 .000 .736 .490 .033 greenhousegeisser .000 1.150 .000 .736 .425 .033 huynh-feldt .000 1.197 .000 .736 .430 .033 lower limit .000 1.000 .000 .736 .409 .033 mf (erector spinae) sphericityassumed .222 2 sphericityassumed .222 2 9.843 .001 .314 greenhousegeisser .222 1.258 .177 9.843 .005 .314 huynh-feldt .222 1.344 .166 9.843 .004 .314 lower limit .222 1.000 .222 9.843 .009 .314 mpf (erector spinae) sphericityassumed .178 2 sphericityassumed .178 2 11.738 .000 .353 greenhousegeisser .178 1.301 .136 11.738 .002 .353 huynh-feldt .178 1.403 .127 11.738 .002 .353 lower limit .178 1.000 .178 11.738 .006 .353 zcr (erector spinae) sphericityassumed .131 2 .066 4.082 .031 .159 greenhousegeisser .131 1.486 .088 4.082 .047 .159 huynh-feldt .131 1.664 .079 4.082 .040 .159 lower limit .131 1.000 .131 4.082 .068 .159 x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 29 table 4. post hoc tests for each indicator (bonferroni correction) indicators (i) fatigue group (j) fatigue group mean difference (i-j) standard error significance 95% significant interval lower limit upper limit rms (brachioradialis) low fatigue moderate fatigue -.015* .004 .012 -.027 -.003 severe fatigue .027* -.007 .007 .011 -.048 -.006 moderate fatigue severe fatigue -.012* -.004 .004 .022 -.022 -.002 mf (erector spinae) low fatigue moderate fatigue .120* .042 .035 .000 .239 severe fatigue .191* .056 .018 .032 .349 moderate fatigue severe fatigue .071* .026 .032 -.002 .144 mpf (erector spinae) low fatigue moderate fatigue .094* .027 .017 .017 .172 severe fatigue .172* .047 .011 .040 .304 moderate fatigue severe fatigue .078* .029 .015 -.004 .159 zcr (erector spinae) low fatigue moderate fatigue .017 .033 1.000 -.077 .111 severe fatigue .136 .060 .137 -.034 .306 moderate fatigue severe fatigue .119 .057 .188 -.043 .281 table 5. friedman non-parametric test for each indicator indicator χ² df sig. kendall's w iemg (brachioradialis) 24 2 .000 .727 mf (brachioradialis) 24 2 .000 .727 mpf (brachioradialis) 24 2 .000 .727 rms (erector spinae muscle) 24 2 .000 .727 iemg (erector spinae) 22.167 2 .000 .671 table 6. wilcoxon signed rank test for each indicator indicator fatigue level z sig. r iemg (brachioradialis) moderate fatigue-low fatigue -3.059 .002 -.883 severe fatigue-low fatigue -3.059 .002 -.883 heavy fatigue-moderate fatigue -3.059 .002 -.883 mf (brachioradialis) moderate fatigue-low fatigue -3.059 .002 -.883 severe fatigue-low fatigue -3.059 .002 -.883 heavy fatigue-moderate fatigue -3.059 .002 -.883 mpf (brachioradialis) moderate fatigue low fatigue -3.059 .002 -.883 severe fatigue-low fatigue -3.059 .002 -.883 heavy fatigue-moderate fatigue -3.059 .002 -.883 rms (erector spinae) moderate fatigue-low fatigue -3.059 .002 -.883 severe fatigue-low fatigue -3.059 .002 -.883 heavy fatigue-moderate fatigue -3.059 .002 -.883 iemg (erector spinae) moderate fatigue-low fatigue -2.824 .005 -.815 severe fatigue-low fatigue -3.059 .002 -.883 heavy fatigue-moderate fatigue -3.059 .002 -.883 x. gui et al. /future sustainability november 2025| volume 03 | issue 04 | pages 21-31 30 4. conclusions in this paper, the fatigue state of construction workers was analyzed using emg signals, and the fatigue significant indicators of emg signals were screened and the following conclusions were drawn: (1) the brachioradialis and erector spinae muscles are common. during lifting operations, indicators of brachioradialis and erector spinae such as rms and iemg increased with increasing fatigue level, whereas mf and mpf decreased with increasing fatigue level, reflecting that as fatigue builds up, the muscle contraction efficiency decreases, resulting in the need for subjects to exert greater neural drive to maintain force output. among them, the erector spinae muscle showed more obvious changes in emg signal characteristics than the brachioradialis muscle, which was mainly attributed to the greater stability and strength support demands assumed in the lifting operation, and the percentage of fast muscle fibers and the activation pattern of highthreshold motor units made its response to fatigue more significant. (2) significant indicator screening. by statistically analyzing the characteristic indexes of emg signals of brachioradialis and erector spinae, the rms, iemg, mf, and mpf indexes of brachioradialis and erector spinae had significant differences between different fatigue groups (p＜ 0.05), indicating that they can be used as core indexes for fatigue monitoring when evaluating emg characteristics. the study in this paper not only verifies the feasibility of emg signals in occupational fatigue monitoring but also provides a scientific basis for the quantification of labor intensity, the optimization of operating posture, and the management of occupational health of construction workers. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the authors declare no potential conflict of interest. references [1] choudhry rm, fang d. why operatives engage in unsafe work behavior: investigating factors on construction sites. safety science, 2008, 46(4): 566584. 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[21] kim j-y, jung m-c, haight jm. the sensitivity of autoregressive model coefficient in quantification of trunk muscle fatigue during a sustained isometric contraction. international journal of industrial ergonomics, 2005, 35(4): 321-330. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 1 article analysis and forecast of renewable energy production and investment development in the republic of kazakhstan mukhtar saltayevich yerzhanov, alma mukhtarovna yerzhanova* turan university, higher school of finance and accounting, almaty, kazakhstan a r t i c l e i n f o article history: received 10 july 2025 received in revised form 20 august 2025 accepted 01 september 2025 keywords: renewable energy, energy investment, government support, republic of kazakhstan *corresponding author email address: al.yerzhanova@turan-edu.kz doi: 10.55670/fpll.fusus.4.1.1 a b s t r a c t this study examines the structural, financial, and policy dimensions of renewable energy development in the republic of kazakhstan between 2022 and 2024, offering projections through 2030. drawing on national legislation, statistical datasets, international benchmarks, and qualitative field insights, it evaluates production dynamics across solar, wind, hydro, and bioenergy systems. quantitative analysis reveals a 42.8% increase in renewable electricity output over the three-year period, reaching a 6.43% share of total electricity generation by the end of 2024, yet still below the nationally mandated targets for 2030 and 2050. the paper examines the evolving legal framework that supports both utility-scale and distributed energy initiatives, highlighting incentives such as auction-based feed-in pricing, tax exemptions, extended power purchase agreements, and individual producer rights. it identifies systemic barriers, including tariff indexation delays, currency risks, limited access to concessional finance, and infrastructure bottlenecks. financing structures dominated by debt instruments and international capital flows are mapped through institutional profiles. comparative policy analysis and stakeholder feedback from events like qazag green fest inform a set of integrated recommendations, including expanding energy storage systems, modernizing grid infrastructure, deploying green taxonomies and investor safeguards, and scaling technical education and public awareness campaigns. the findings underscore kazakhstan’s pivotal opportunity to transition toward energy sovereignty and climate resilience through coordinated public–private strategies, regulatory clarity, and robust investment mechanisms. 1. introduction renewable energy is energy obtained from natural sources (sunlight, wind, etc.) that are replenished at a rate exceeding their consumption. renewable energy sources provide a large amount of energy and are associated with much lower emissions. currently, renewable energy sources are a cheaper alternative in many countries than fossil fuels (coal, oil, and gas). renewable resources include solar energy, wind energy, geothermal energy, ocean energy, and bioenergy. the sustainable development of the global economy is closely tied to the effective utilization of the advantages of renewable energy. renewable energy sources have become a magnet for innovation and investment. most developed countries have included principles for the development of renewable energy sources in their national development strategies. annual investments exceeding $750 billion have proven the profitability of the future sector. the rapid growth of solar, wind, and other types of renewable energy has positively affected the sustainability triad: economy, social sphere, and ecology. this allows us to consider this phenomenon as a factor in creating a new energy system and future economy. just three decades ago, the global community considered achieving 10% electricity production from renewable energy sources in the total energy balance to be an excellent result. at present, this is no longer sufficient to ensure energy security and conserve financial resources at the macro level. the goal of our research is to analyze and assess the level of development and production of renewable energy in the republic of kazakhstan. based on this goal, the following research tasks have been addressed in this article: • an analysis of the production and development of renewable energy in kazakhstan over the past three years has been conducted. future sustainability open access journal https://doi.org/10.55670/fpll.fusus.4.1.1 february 2026| volume 04 | issue 01 | pages 01-09 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:al.yerzhanova@turan-edu.kz https://doi.org/10.55670/fpll.fusus.4.1.1 https://fupubco.com/fusus ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 2 • issues of state support and investment in the development of renewable energy in the republic of kazakhstan have been examined. • a forecast of further development of renewable energy sources (res) in kazakhstan until 2030 has been provided. currently, the entire world is facing the challenge of climate change, which is one of the most important issues for the energy sector. renewable energy is becoming a viable alternative, driven by the growing trend of decreasing construction costs for renewable energy stations, which is fueled by increased investor demand. the main growth drivers are the new strategy, according to kazakhstan’s concept for transition to a green economy: • 10% share of renewable energy sources in total electricity production by 2030 • 50% share of alternative and renewable energy sources in total electricity production by 2030 [1] in matters of government policy on production and financial support for the republic of kazakhstan, the experience of leading countries such as china and türkiye is noteworthy. the relevance of this study is confirmed by the analysis, forecasts, and strategic perspectives for developing renewable energy production and promoting investments from both the public and private sectors. according to the international consulting company pwc, investment in renewable energy sources is especially significant for the oil and gas and energy sectors. studying the foreign experience of countries using renewable energy sources, in the uk, over five years, investments in the green economy yielded 75% annual returns, while at the same time, fossil fuels yielded 8.8%, and in the usa, the figures were 200% and 97.2%, respectively [2]. thus, it is relevant to involve all necessary participants in implementing green energy projects, particularly small-scale renewable energy projects. this study provides a comprehensive analysis and assessment of the development level and production of renewable energy in the republic of kazakhstan. the study methodically examines the sector's recent performance and future potential, providing a clear and evidence-based outlook. the primary research objectives addressed in this article are: • to analyze the production and development of renewable energy in kazakhstan over the past three years. • to examine the key issues of state support and investment in kazakhstan's renewable energy sector. • to provide a quantitative forecast for the development of res in kazakhstan through 2030. the relevance of this study is underscored by the global challenge of climate change and the increasing economic viability of renewable energy projects. by analyzing recent data, evaluating government policy, and forecasting future growth, this research offers strategic insights for public and private sector stakeholders. the findings contribute to the broader discourse on green energy transitions in resourcerich nations and provide a crucial framework for accelerating the implementation of sustainable energy projects in kazakhstan. 2. literature review the issues of development prospects, government support, investment, and financing of projects in the renewable energy sector have been studied by well-known foreign scholars [3-13]. in the republic of kazakhstan, several articles have been published in recent years on the challenges of developing renewable energy [14,15], including analyses of policy and governance hurdles [16-18], financial and investment processes impacting renewable projects [19], and scenario planning for coal exit and renewable energy transitions [20]. additional studies have explored multicriteria decision-making systems for spatial renewable energy development in kazakhstan [21] and evaluated renewable versus nuclear resources for electricity generation [22]. in determining the stage of emergence and development of renewable energy in kazakhstan, as well as in assessing the world experience of leading countries in the use of renewable energy, the works of american and european scientists were considered. for instance, references [3, 4, 6] examine the development of renewable energy and mechanisms for stimulating its growth in the usa. features of targeted innovative stimulation of renewable energy use in european countries are considered in reference [5]. several researchers emphasized the importance of financial support mechanisms for stimulating investment in renewable energy. one of the key financial support mechanisms is the use of preferential tariffs, tax benefits, and tradable “green” certificates [23]. these mechanisms provide financial incentives for the development of renewable energy sources and help to offset the higher costs associated with renewable energy technologies [10]. recent reviews highlight additional innovative financing models, such as concessional finance, blended finance, and auctions, which mitigate risks and enhance the attractiveness of renewable projects in developing countries [24,25]. policy insights from comparative studies in brazil and nigeria further underscore the role of targeted incentives in overcoming barriers to renewable energy financing [26]. additionally, financial investments from both the public and private sectors are crucial for expanding renewable energy production capacity [9]. such investments help fund research and development, infrastructure development, and the implementation of renewable energy projects. empirical evidence from global samples suggests that green bonds, a form of green finance, significantly enhance renewable energy production by providing dedicated capital flows [27]. the role of financial markets in supporting renewable energy projects is also significant. financial market investors, including pension funds, insurance companies, and mutual funds, utilize renewable energy stock indices to evaluate and manage their investments. these indices provide information on the financial performance and potential risks associated with renewable energy projects, enabling investors to make informed decisions [11]. green finance influences the investment behavior of renewable energy enterprises, facilitating better capital allocation and risk management [28]. studies on renewable energy investment and green economies show that green finance enhances firm-level investments, particularly in asia [29]. furthermore, the creation of a “green” financial system is essential for financing green energy projects [12]. the green financial system ensures that funds are directed toward sustainable and environmentally friendly projects, including renewable energy. such a system can help reduce environmental degradation and facilitate investments in clean technologies ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 3 for renewable energy projects. research demonstrates that green finance not only supports renewable energy development but also contributes to climate change mitigation by reducing emissions [30,31]. bibliometric analyses reveal evolving trends in energy transitions and green finance, emphasizing their interconnected roles in sustainable development [32]. the success of renewable energy projects depends not only on financial indicators but also on non-financial performance measures, such as environmental impact, social benefits, and long-term sustainability. assessing these non-financial indicators alongside financial ones allows for a more comprehensive evaluation of the success and viability of renewable energy projects. critical reviews of competitiveness indicators for energy projects stress the need for multi-disciplinary key performance indicators (kpis) that encompass environmental, social, and governance factors beyond economics [33]. empirical studies confirm that non-financial measures, such as community engagement and ecological footprints, significantly influence project outcomes [13]. financial support systems are crucial for the development and implementation of renewable energy projects. mechanisms such as preferential tariffs, tax benefits, and tradable green certificates provide financial incentives for the development of renewable energy sources. to expand renewable energy production capacity, financial investments are required from both the public and private sectors [9]. the role of financial markets in managing investments in renewable energy is significant. additionally, the development of a green financial system and the consideration of non-financial performance measures are crucial to the success of renewable energy projects. for instance, segmentation analysis of support mechanisms for green hydrogen highlights the efficacy of offtake support and infrastructure funding in reducing investment risks [34]. studying the strategies of global leaders in the application of renewable energy and in-depth research by prominent scholars will help formulate recommendations for adapting foreign experience to the development of kazakhstan’s green economy. 3. methodology 3.1 research design this study utilizes a mixed-methods research design, combining both qualitative and quantitative approaches. this design is most suitable for providing a data-driven and factual analysis of the multi-level impact of renewable energy on kazakhstan's economy, foreign policy, and energy security. the methodology is specifically structured to answer the central research question: how can kazakhstan enhance its capabilities in developing renewable energy? it is also designed to test the guiding hypothesis that kazakhstan’s efforts to introduce renewable energy can become a strategic turn that will enhance its national influence and security. 3.2 data collection and sampling data was gathered using a combination of primary and secondary research tools to ensure a comprehensive and triangulated perspective. primary data: • expert interviews: we interviewed specialists, such as government officials, energy company executives, and researchers. these interviews helped us understand what influences kazakhstan's renewable energy plans and how diplomacy attracts investment. • surveys: a structured questionnaire was distributed to a sample of stakeholders in the energy sector. a purposive sampling strategy was employed to target individuals with direct experience in renewable energy projects. the survey aimed to collect quantitative data on perceived investment risks, policy effectiveness, and growth prospects. secondary data: • statistical data: national statistics on energy production and investment were collected from official government sources of the republic of kazakhstan. • document analysis: policy documents, legal acts, and reports from international organizations like irena were systematically reviewed to provide context and quantitative benchmarks. 3.3 data analysis the collected data were analyzed as follows: • qualitative analysis: thematic analysis was the method used to analyze data from expert interviews and policy papers. this process involved identifying, coding, and understanding recurring ideas and trends related to kazakhstan's energy diplomacy, foreign relations, and its utilization of renewable energy in its policies. • quantitative analysis: the study used descriptive statistics like frequencies, means, and percentages to analyze survey responses and national data. trend analysis was also applied. this quantitative method helped find key patterns in renewable energy growth and supported the qualitative results with statistical backing. by integrating the findings from both qualitative and quantitative analyses, this study provides a robust and multifaceted response to the research question. 4. analysis and discussion the pathways and prospects for developing renewable energy sources in the republic of kazakhstan are defined by the ministry of energy of the republic of kazakhstan. the law of the republic of kazakhstan on the support of renewable energy sources provides definitions and types of renewable energy sources. renewable energy sources (res) are sources of energy that are continuously renewed by naturally occurring processes. they include the following types: solar radiation energy, wind energy, hydrodynamic energy of water, geothermal energy (heat from soil, underground water, rivers, and reservoirs), and anthropogenic sources of primary energy resources, such as biomass, biogas, and other fuels derived from organic waste used for producing electricity and/or heat. the legislative acts of kazakhstan play a significant role in the development of renewable energy sources. the existing legislation is attractive for investors, including private investors and international financial institutions. however, to stimulate the electricity market, it is necessary to consider several additional recommendations and proposals from experts and scientists. to achieve the goals set under the paris agreement by 2050, the installed capacity of renewable energy facilities must increase by a factor of 10. this is the forecast provided by the international renewable energy agency (irena). despite commitments made by countries to limit the rise in global average ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 4 temperature, current investments in construction and development of green technologies may be insufficient to reach stated objectives. an indispensable part of a country's green ecosystem is its green taxonomy. the green taxonomy has several priority tasks, as highlighted in the undp information package for implementing small-scale renewable energy projects in kazakhstan. figure 1 illustrates these main objectives [2]. renewable energy projects are included in the list of priority investment projects. previously established investment preferences have been supplemented with benefits, including exemptions from the following taxes: land tax, property tax, and corporate income tax. in kazakhstan, the duration of contracts for guaranteed electricity buyback by the res operator has been extended to 20 years. a comprehensive analysis of kazakhstan’s renewable energy market was performed, drawing on research by the international auditing firm pwc. project-level evaluations indicate that the predominant financing structure for renewable energy projects in kazakhstan follows a 70/30 split, with 70% of costs funded through debt financing, primarily loans. development banks play a pivotal role in financing these projects, as detailed in table 1. banks involved in renewable energy financing, which outlines the key financial institutions supporting the sector’s growth. despite the active development of the res market in the republic of kazakhstan and strong legislative support, renewable energy still faces many challenges that restrict sector growth. one of the key limiting factors is investment risk. several major reasons that hinder investment growth in the sector have been identified. the most critical among them are shown in figure 2. this study examined how investment in kazakhstan's renewable energy sector affects electricity production from renewable sources. the renewable energy facilities in kazakhstan include wind (wpp), solar (spp), small hydro (hpp), and biofuel power plants (biopp). table 2 shows data on electricity production from renewable energy sources in kazakhstan. table 1. banks involved in renewable energy financing from table 2, it can be seen that by the end of 2024, the share of electricity generated from res in kazakhstan’s total production was 6.43%. the growth in res share compared to 2022 was 42.8%. if such growth rates are maintained, the 2030 target is achievable. electricity production from res in kazakhstan is generated by small hydro plants, wind farms, solar farms, and biogas installations. detailed breakdown by source is provided in table 3. table 2. res electricity production in kazakhstan, 2022–2024 [16] year total res production share of res in energy structure (%) 2022 5,110.7 4.5 2023 6,675.5 5.92 2024 7,581.33 6.43 bank amount (billion kzt) ebrd (european bank for reconstruction and development) 162 dbk (development bank of kazakhstan) 67 china development bank 29 dbk leasing 22 adb (asian development bank) 21 gcf (green climate fund) 10 edb (eurasian development bank) 15 aiib (asian infrastructure investment bank) 14 green climate fund 10 icbc 6 figure 1. the main objectives of the “green” taxonomy [2] figure 2. reasons hindering investment growth in res [1] ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 5 according to table 3, kazakhstan had 148 res installations by the end of 2024, with a combined capacity of 3,032.11 million kwh. this includes: • 59 wind energy facilities with 1,520.05 million kwh capacity • 46 solar energy facilities with 1,222.61 million kwh capacity • 40 small hydro facilities with 287.68 million kwh capacity • 3 bioenergy facilities with 1.77 million kwh capacity in 2024, amendments were made to the law of the republic of kazakhstan regarding support for the use of renewable energy sources and energy. according to this law, the population, farming households, and small and medium-sized enterprises are now allowed to generate electricity independently and sell it. every citizen of kazakhstan is permitted to install renewable energy systems with a capacity of up to 200 kilowatts and sell any surplus electricity generated by these systems. when evaluating the profitability of installing such renewable energy systems, several factors are essential: • location for solar panels (intensity of solar radiation and number of sunny days per year) • location for wind turbines (wind availability and speed) • cost of the renewable energy installation • household electricity consumption patterns all of these factors determine how much surplus electricity can be supplied to the grid. based on kazakhstan’s legislative acts and academic research, we identified the following additional recommended support measures for res: • mandatory connection of renewable energy installations to transmission or distribution grids • priority and compulsory transmission of electricity generated from res • mandatory purchase of electricity produced using res by individual consumers through the unified settlement center • exemption of res producers from paying transmission taxes and elimination of licensing requirements for electricity production table 3. electricity production by res type in kazakhstan (2022– 2024) (millions of kwh) [16] practices from developed countries for supporting res could be adapted and implemented in kazakhstan. however, this requires a comprehensive approach: • evaluation of energy output from res and associated costs • development of subsidy mechanisms and investment attraction strategies for sector development, considering the country’s limited resources • creation of special investment funds to support subsidies in kazakhstan’s case, the low energy efficiency of many buildings and the aging energy infrastructure, much of it from the soviet era, must be considered, as it requires modernization. therefore, evaluating locations where active use of small res installations by individuals and their electricity contributions to the grid would not overload the system is crucial. to effectively use small-scale res installations, individuals need basic technical knowledge. thus, res distribution programs should include training and awareness initiatives on the operational features of such energy systems. kazakhstan’s res sector receives active government support. currently, government support includes: • guaranteed electricity buyback at auction price • annual indexation of tariffs • exemption from grid fees • investment preferences these policies foster a favorable investment climate, support the development of new projects, and ensure the sustained growth of green energy in the country’s overall energy balance. to enhance government support for res projects, a scientific approach is needed in their implementation and development. a transparent and predictable tariff policy is essential, as is creating conditions for broader private-sector participation in res construction and operation. kazakhstan’s government has stressed the inadmissibility of administrative barriers that deter investors and hinder project realization. kazakhstan has committed to achieving a 15% share of electricity production from res by 2030 and increasing that share to 50% by 2050. the country has a vast territory, it’s the ninth largest in the world, and possesses 77% of central asia’s solar energy potential and 90% of the region’s wind energy potential. however, much of this potential remains underutilized, as kazakhstan still relies heavily on soviet-era energy infrastructure geared toward fossil fuels. for example, in 2024, the country’s electricity was generated as follows: • 66% from coal • 21% from natural gas • 6.6% from hydroelectric power • only 6.4% from res this scenario demands substantial investment in res development and modernization of the grid infrastructure. several kazakh researchers emphasize the importance of developing renewable energy, as res plays a crucial role in addressing global challenges—such as energy, environmental, and food security [3,5-8]. res project support systems are essential for successful development and implementation. these include: • banking initiatives: energy loans and project financing • the role of financial institutions and investment companies in backing res • public-private partnerships in res financing • challenges and opportunities for financial support of res enterprises year small hpp # wpp # spp # biopp # 2022 260,00 37 948,00 46 1148,00 44 1.77 3 2023 269.61 39 1394.6 57 1202,60 45 1.77 3 2024 287.68 40 1520,05 59 1222.61 46 1.77 3 ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 6 kazakhstan’s commitment to using renewable energy sources is reinforced through the national action plan for renewable energy development. this comprehensive strategy outlines ambitious targets and policy frameworks to facilitate res deployment. preferential tariffs and other incentive schemes have attracted investment and created a supportive environment for renewable energy projects. furthermore, regulatory frameworks shed light on government investments and subsidies that drive sector growth. securing financial support is the cornerstone of renewable energy projects. banks were the first to offer energy loans and project financing options, aiding res implementation. financial institutions and investment companies now collaborate to provide innovative funding models. public-private partnerships have emerged as a viable pathway, highlighting the collaborative approach needed for a sustainable energy transition. nevertheless, challenges in securing financial backing remain, necessitating strategic solutions for overall sector development. 5. project financing, foreign investment, and risk mitigation in kazakhstan, the primary financing scheme comprises approximately 70% debt financing. in terms of the number of projects, nearly two-thirds are implemented by kazakhstani investors. however, around 60% of all installed res capacity is financed by foreign investors, since they tend to be more interested in undertaking large-scale projects. kazakhstan is actively developing international cooperation and attracting investments in the res sector, particularly in solar and wind energy projects. this supports the successful implementation of large-scale res projects across various regions of the country. currently, the main investors in res projects in kazakhstan are development banks and foreign investors. foreign investors aim to stabilize the legislative framework and contractual conditions as they stood at the time investment obligations were undertaken. such stability allows them to clearly understand and confidently assess their future commitments, responsibilities, and risks. res projects in the republic of kazakhstan frequently utilize project finance structures, which combine debt and equity financing. this enables investors to share risks and participate effectively in the implementation of projects. renewable energy projects require significant upfront investment. because most of these projects are financed through loans from international organizations in foreign currency, currency fluctuations can result in substantial cost increases in the local currency, the tenge (kzt). this is precisely why the tariff indexation mechanism was introduced to make projects more attractive to investors. however, there remains a risk of delayed tariff indexation, which may result in losses for investors, particularly if production costs rise and the tariff remains unchanged after project launch. res projects often have long payback periods, which raise risks for investors, especially in volatile economic conditions. project financing is vulnerable to political interference. additionally, legislative changes may significantly affect a project's financial outlook. therefore, investors need to account for political risk before committing to obligations. such factors represent serious challenges for investors, especially when planning and implementing renewable energy projects. in general, kazakhstan’s renewable energy sector presents several unique features and opportunities that make it attractive for project financing. 6. proposals and recommendations analysis of actual data for the years 2022–2024 and forecast analysis through 2030 has shown that there are several problems and challenges in implementing and developing res in the republic of kazakhstan: • dependence on weather conditions • legislative framework • generation instability • outdated coal-fired power plants • shortage of professional specialists • financial risks for investors restraining factors in the development of res in kazakhstan’s energy market were thoroughly discussed at the 3rd international business festival (qazag green fest). as a result of this forum, a number of recommendations were provided, which we also support: • review and adopt a strategy for the development of the electricity sector in kazakhstan through 2030 • expand joint training and retraining programs with foreign universities for specialists in the energy sector • develop markets for bilateral renewable energy contracts • promote further incentives for small-scale res • improve the tariff indexation mechanism for res projects • strengthen informational support for res development • exclude res installations from the list of terroristvulnerable facilities in our view, possible solutions for advancing production and investment in the renewable energy sector include: i. development of energy storage capacities and systems: to stabilize the energy system, energy storage systems should be developed and implemented. these systems will accumulate excess electricity generated by res and release it into the grid during peak consumption periods. ii. regulatory mechanisms: introduce step-by-step regulatory mechanisms governing the integration of new res installations into the national energy system and determine the priority order for electricity transmission from various generation sources during peak loads and demand drops. iii. infrastructure and technology development: in order to make res a competitive sector of the economy, it is necessary to have not only natural resources and sales markets. development of related industries, such as manufacturing, transportation, and electricity sales, is also crucial. attention should be given to creating industrial clusters that provide a full cycle: from design and component manufacturing to recycling of decommissioned res equipment. developing domestic infrastructure and technologies for solar and wind generation will help reduce dependence on imports, lower production costs through scale effects, reduce electricity tariffs, and make res more accessible, while also creating new jobs and contributing to kazakhstan’s economic growth. iv. investor protection mechanisms: to protect investors from risks (e.g. delayed indexation, electricity price drops, or increases in capital and operating costs during res project implementation), there is a need to create governmentbacked or private guarantee systems. ms. yerzhanov & am. yerzhanova /future sustainability february 2026| volume 04 | issue 01 | pages 01-09 7 v. implementation and expansion of educational programs and specialist training in the res sector: introducing relevant educational programs and training a sufficient number of res specialists is a key task for industry development. such specialists include solar and wind energy designers, operations engineers, and meteorological energy analysts. currently, kazakhstan’s ministry of science and higher education funds 18 programs in energy and energy efficiency. eight of these programs are specifically focused on the development of renewable energy. promoting green energy disciplines among young people will foster the development of renewable energy in kazakhstan and help achieve global goals related to climate change and environmental protection. 7. conclusion we have presented information about various financial support systems available for renewable energy projects in kazakhstan. with a clear understanding of these support mechanisms, potential investors can make informed decisions, contributing significantly to the country’s goals in renewable energy and a sustainable future. although challenges remain, the future of renewable energy in kazakhstan is optimistic. by addressing regulatory difficulties, investing in research and development, and improving financial support mechanisms, kazakhstan can overcome its obstacles and continue progressing toward a sustainable energy future. through collective efforts of government bodies, private enterprises, and the public, the republic can not only achieve its renewable energy targets but also become one of the leading countries in the res sector, paving the way for a greener and more sustainable future. the article reviewed the development system of production and investment support for renewable energy sources in kazakhstan. several key findings and recommendations were made that underscore the pivotal role of renewable energy sources. investment support programs for res development have significantly boosted the growth of solar and wind energy projects. these efforts not only reduce co₂ emissions but also stimulate economic growth, create jobs, and enhance the country’s energy security. regulatory challenges, technological limitations, and financial barriers must be addressed through coordinated efforts involving government agencies, businesses, and research institutions. government bodies play a central role in shaping the future of renewable energy. clear and consistent policies, streamlined regulatory processes, and incentives for research and innovation are imperative. government authorities should also focus on raising public awareness, promoting environmental responsibility, and cultivating a culture of energy efficiency. companies can contribute to investments and growth in the res sector. investing in research and development is especially important. collaborating with international partners and participating in public-private partnerships can accelerate the adoption of advanced renewable energy solutions. moreover, companies should actively engage with the public, informing communities about the benefits of res and sustainable practices. involving communities in dialogue, addressing concerns, and highlighting the tangible benefits of res projects fosters a sense of ownership and pride. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] lim n., zhanadilova z., chadiarova j., begenova s., kim m., (2021). renewable energy market in kazakhstan: potential, challenges and prospects, 1st ed. 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[34] sinha a., ghosh v., hussain n., nguyen d. k., das n., (2023). green financing of renewable energy generation: capturing the role of exogenous moderation for ensuring sustainable development, energy economics, 126, 107021, https://doi.org/10.1016/j.eneco.2023.107021. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 22 article assessment of occupational radiation exposure in academic office environments: a systematic study of the faculty of science, university of maiduguri, nigeria dennis solomon balami1*, musa muhammad gadaka1, chigozie ivor nwobi2, flavious bobuin nkubli2, mathew garba abubakar2, yakubu h. ngadda1 1department of physics, university of maiduguri, borno state, nigeria 2department of medical radiography, university of maiduguri, borno state, nigeria a r t i c l e i n f o article history: received 19 july 2025 received in revised form 25 august 2025 accepted 16 september 2025 keywords: occupational radiation exposure, radiation safety, dose assessment, gamma radiation, academic institutions *corresponding author email address: dennisolomon59@gmail.com doi: 10.55670/fpll.fusus.4.1.3 a b s t r a c t assessing occupational radiation exposure in academic institutions is crucial for ensuring compliance with international safety standards and mitigating risks associated with natural background radiation. to evaluate radiation dose rates across office spaces in the faculty of science, university of maiduguri, nigeria, and verify compliance with the international commission on radiological protection (icrp) public dose limit. a cross-sectional survey measured gamma radiation at 21 office locations using the radeye g-10 gamma survey meter. a three-zone protocol recorded dose rates (μsv/hr) one meter outside doors, at thresholds, and one meter inside offices. geographic coordinates were logged via gps, and statistical analyses (anova, correlations, k-means clustering) assessed dose variations and spatial patterns. annual doses were calculated using 2000 working hours/year. the mean dose rate was 0.19 ± 0.05 μsv/hr. annual doses ranged from 0.24–0.52 msv (external), 0.24– 0.68 msv (threshold), and 0.24–0.68 msv (internal), with location a15 reaching 0.68 msv/year (68% of icrp limit) in threshold/internal zones. all doses were below the icrp 1 msv/year public limit. the radiation exposure index (rei) and k-means clustering identified three elevated-risk locations (a12, a15, a21; 0.50–0.70 msv/year). radiation levels comply with icrp standards, but three locations warrant quarterly monitoring and material investigations (e.g., granite content). the three-zone protocol and rei provide a replicable framework for radiation safety assessments in academic settings, particularly in developing nations. 1. introduction occupational radiation exposure assessment is a fundamental component of radiation safety programs in academic institutions, where scientific research and educational activities involving radioactive materials are conducted [1]. the systematic evaluation of radiation levels in these environments ensures compliance with international radiation protection standards while safeguarding the health and well-being of faculty, students, and visitors [2]. natural background radiation constitutes approximately 85% of total human radiation exposure, originating from primordial, cosmogenic, and anthropogenic sources. primordial radionuclides, present in the earth's crust since its formation, include the decay series of uranium-238 (²³⁸𝑈) and thorium232 (²³²th), along with the single-member decay chain of potassium-40 (⁴⁰𝐾) [3]. these naturally occurring radioactive materials contribute significantly to ambient radiation levels in both outdoor and indoor environments [4]. the human body experiences continuous exposure to external and internal radiation sources. external sources encompass natural components such as cosmic and terrestrial radiation, as well as artificial sources, including radiation generators [5]. internal exposure occurs primarily through the presence of 𝐾40 in body tissues and potential contamination from radionuclides such as radon and its decay products. the geological and geographical characteristics of a region significantly influence natural radioactivity levels in soil and surrounding environments, ultimately affecting future sustainability open access journal https://doi.org/10.55670/fpll.fusus.4.1.3 february 2026| volume 04 | issue 01 | pages 22-36 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:dennisolomon59@gmail.com https://doi.org/10.55670/fpll.fusus.4.1.3 https://fupubco.com/fusus ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 23 external gamma radiation exposure [6]. recent epidemiological studies supporting the linear-no-threshold hypothesis have identified potential adverse effects from both background natural radiation and low-level doses typically associated with diagnostic medical exposures [7]. however, ongoing scholarly debate exists regarding the health impacts of low-dose radiation exposure, with some researchers suggesting possible hormetic effects at low dose levels [8]. academic settings, particularly within science faculties conducting diverse research activities, require a comprehensive assessment of occupational radiation exposure. the systematic monitoring of workplace radiation levels ensures adequate protection for personnel who may spend extended periods in these environments [1]. modern radiation detection instruments, such as the thermo scientific radeye g-10 gamma survey meter equipped with energy-compensated geiger-müller tube detectors, provide reliable measurement capabilities for dose rates ranging from 0.5 𝜇𝑆𝑣/ℎ to 100 𝑚𝑆𝑣/ℎ, making them particularly suitable for workplace radiation monitoring applications [9]. the university of maiduguri's faculty of science, located at latitude 11°52' n and longitude 13°14' e, houses multiple departments conducting various scientific activities. the faculty's architectural layout and operational characteristics necessitate a comprehensive radiation level assessment to ensure compliance with safety standards and protect occupants from potential radiation hazards. this research addresses the critical need for systematic radiation exposure evaluation in academic environments, particularly within developing nation contexts where such assessments remain underrepresented in the literature. the primary objective of this study is to evaluate radiation exposure levels across selected office spaces within the faculty of science using systematic measurement protocols and statistical analysis. the research aims to document radiation dose rates, compare findings against established international safety benchmarks, and develop appropriate risk mitigation strategies to enhance workplace safety. these findings will contribute to the broader understanding of occupational radiation exposure in academic institutions while providing valuable reference data for similar assessments in educational and research facilities. 2. literature review and theoretical framework 2.1 radiation protection principles the fundamental principles of radiation protection, as established by the international commission on radiological protection (icrp), form the theoretical foundation for occupational exposure assessment. these principles include justification, optimization, and dose limitation, collectively ensuring that radiation exposure remains as low as reasonably achievable while maintaining operational effectiveness (international commission on radiological protection, 2007). the linear no-threshold model continues to serve as the basis for radiation protection standards, despite ongoing scientific debate regarding its validity at low doses. this model assumes that any radiation exposure, regardless of magnitude, carries some risk of adverse health effects, with risk increasing proportionally with dose [10]. table 1 summarizes the regulatory annual radiation dose limits recommended by the icrp (2007) for occupational and public exposure, as well as equivalent dose limits for specific anatomical sites. these limits provide the framework for assessing the occupational radiation exposure measured in this study, which are compared against the public limit of 1 msv/year. table 1. regulatory annual radiation dose limits for different categories of exposure and anatomical sites 2.2 natural background radiation natural background radiation exposure varies significantly based on geographical location, geological characteristics, and altitude [11]. terrestrial gamma radiation, primarily from uranium and thorium decay series along with potassium-40, constitutes a major component of natural background exposure. the relationship between geological formations and radiation levels has been extensively studied, with granite-rich regions typically exhibiting higher natural radiation levels compared to sedimentary areas (united nations scientific committee on the effects of atomic radiation, 2000). 2.3 regulatory framework and international standards this study adheres to radiation protection principles established by the international commission on radiological protection publication 103 (2007), the international atomic energy agency safety standards series no. gsr part 3 (2014), and world health organization recommendations for occupational exposure. national regulatory requirements, as specified by the nigerian nuclear regulatory authority, provide the legal framework for radiation protection in academic institutions [12]. dose limits applied in this assessment follow icrp recommendations: public exposure limited to 1 msv annually, occupational exposure limited to 20 msv annually averaged over five consecutive years, and apprentice exposure limited to 6 msv annually for individuals between 16 and 18 years of age [1, 10]. 3. materials and methods 3.1 study design and area a cross-sectional survey design was implemented to assess occupational radiation hazards in selected offices within the faculty of science at the university of maiduguri, borno state, nigeria. category/anatomical site annual dose limit (msv/year) notes occupational (effective dose) 20 averaged over 5 years, with a maximum of 50 msv in any single year public (effective dose) 1 applies to the general population, including non-workers lens of the eye (equivalent dose) 20 occupational; also a benchmark for public exposure where relevant skin (equivalent dose) 500 occupational; averaged over 1 cm² of the most exposed area extremities (equivalent dose) 500 occupational; applies to hands, feet, forearms, and ankles ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 24 the study area is situated between latitude 11°52' n and longitude 13°14' e, with the university campus bordered by mairi, 202 housing estate, 303 housing estate, and dalori communities. the faculty of science comprises seven departments: mathematical sciences (mathematics, computer science, and statistics), physics, chemistry (chemistry, industrial chemistry, and petroleum chemistry), biological sciences (environmental biology, zoology, and botany), geology, biochemistry, and microbiology. figure 1 presents the geographical location of the faculty of science within the university of maiduguri campus. 3.2 instrumentation the primary instrument used for radiation measurements was the radeye g-10 gamma survey meter, specifically designed for gamma radiation surveys ranging from background levels to personal safety thresholds. table 2 presents the comprehensive technical specifications for this instrument as provided by the manufacturer [9]. the instrument features energy compensation across its operational range, ensuring accurate measurements for various gamma radiation energies. table 2. technical specifications of radeye g-10 gamma survey meter [9] parameter specification measuring range 0.5 μsv/h 100 msv/h energy range 45 kev 3 mev (according to iec 60846-1) detector type energy-compensated geiger-mueller tube sensitivity approximately 1.7 s⁻¹/μsv/hr for photon radiation 660 kev (¹³⁷cs) alarm indications audible, visual, and vibrating alarms dimensions 9.6 × 3.1 × 6.1 cm weight 160 g the detector system utilizes a geiger-müller tube with energy compensation to provide a consistent response across the specified energy range of 45 kev to 3 mev, in accordance with iec 60846-1 standards. figure 2a displays the back view of the radeye g-10 gamma survey meter, showing the instrument's compact design and control interface. figure 2b presents the front view of the device during operation, illustrating the clear graphic display and alarm indicators. the instrument incorporates audible, visual, and vibrating alarm systems, making it suitable for workplace monitoring and radiation protection applications. (a) (b) figure 2. radeye g-10 gamma survey meter (a) back view (b) front view during operation the radeye g-10 gamma survey meter underwent comprehensive calibration using certified ¹³⁷cs reference sources traceable to national standards. calibration verification was performed at multiple energy levels to ensure accurate response across the instrument's operational range. background measurements were recorded at the beginning and end of each measurement session to account for temporal variations. the instrument's response linearity was verified using sources of varying activities, demonstrating linear response within ±5% across the measurement range [14, 15]. figure 1. map of the university of maiduguri, showing the location of the faculty of science location [13] ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 25 3.3 sampling strategy and measurement protocol twenty-one different locations throughout the faculty of science were selected for radiation measurements. the sampling points were chosen to represent various office types and functional areas within the faculty, including administrative offices, departmental head offices, and general faculty offices. the measurement methodology implemented a systematic three-zone approach to ensure comprehensive data collection. the protocol began with external measurements, where three distinct readings were taken at a distance of one meter from each office door. this initial measurement zone provided baseline data for radiation levels in corridor areas and helped identify potential radiation spread beyond office confines. threshold measurements were conducted directly at office doors, with three separate readings at each position serving as critical transition point data. these measurements established whether radiation levels changed significantly as one approached office spaces and provided valuable information regarding containment effectiveness and potential exposure risks for individuals passing by offices. internal measurements focused on the office environment, with three readings taken at a distance of one meter inside each office space. these internal measurements determined actual exposure levels that office occupants experience during regular work activities. the three measurement zones provided complete radiation distribution profiles and helped identify potential gradient patterns between interior and exterior spaces. all measurements were performed during daylight hours to ensure consistent environmental conditions. the mean value of three readings at each point was calculated and recorded as the measured background dose for that specific location. standard deviation and confidence intervals were calculated for each measurement set to assess measurement precision. 3.4 geographical coordinates the precise location of each measurement point was recorded using gps navigation to determine exact latitude and longitude coordinates. this geographical data was essential for mapping radiation distribution across faculty premises and enabling future comparative studies. table 3 presents the complete geographical coordinates for all 21 measurement locations. 3.5 mathematical framework and dose calculations the effective dose calculations were performed using the fundamental equation: 𝐸 = ∑ 𝑊𝑇𝐻𝑇𝑇 (1) where 𝐻𝑇 represents the equivalent dose in tissue 𝑇 and 𝑊𝑇 is the tissue weighting factor. the tissue equivalent dose is defined as: 𝐻𝑇 = ∑ 𝑊𝑅𝐷𝑇,𝑅𝑅 (2) with 𝑊𝑅 being the radiation weighting factor and 𝐷𝑇,𝑅 representing the average absorbed dose in organ or tissue t from radiation type r. the mean effective dose is calculated as: 𝐸𝑚 = ∑ 𝑊𝑇𝐻𝑇 𝑁 (3) where 𝑁 represents the number of measurement cycles in a year. table 3. geographic coordinates of office locations for occupational exposure assessment, annual dose rates were calculated using: 𝐷𝑎𝑛𝑛𝑢𝑎𝑙 = �̇� × 𝑇𝑤𝑜𝑟𝑘 × 𝐹𝑜𝑐𝑐 × 𝐹𝑢𝑠𝑒 (4) where: �̇�: measured dose rate (μsv/hr) 𝑇𝑤𝑜𝑟𝑘: annual working hours 𝐹𝑜𝑐𝑐: occupancy factor 𝐹𝑢𝑠𝑒 : facility use factor standard deviation was calculated using: 𝜎 = √ ∑ (𝑥𝑖−�̅�)2𝑛 𝑖=1 𝑛−1 (5) confidence intervals were determined using: 𝐶𝐼 = �̅� ± 𝑡𝛼 2 ⋅ 𝜎 √𝑛 (6) where 𝑡𝛼 2 represents the critical t-value for the desired confidence level. 3.6 data recording and management a comprehensive data documentation system was implemented to ensure accurate, accessible, and traceable measurement records, adhering to quality assurance protocols. all radiation readings were recorded in standardized formats capturing key parameters: unique office identification codes, location details, precise geographical coordinates (latitude and longitude), environmental conditions (temperature, humidity, and time of measurement), and calibration information. measurements were conducted between 8 am and 4 pm, with background readings repeated every 4 hours to capture diurnal fluctuations (±8% variation, primarily due to radon levels). for each of the 21 measurement locations, three distinct dose rate readings were documented at each of the three zones location latitude (°𝑵) longitude (°𝑬) a1 11.8312 13.1512 a2 11.8310 13.1514 a3 11.8308 13.1516 a4 11.8306 13.1518 a5 11.8304 13.1520 a6 11.8314 13.1510 a7 11.8316 13.1508 a8 11.8318 13.1506 a9 11.8320 13.1504 a10 11.8322 13.1502 a11 11.8313 13.1513 a12 11.8311 13.1515 a13 11.8309 13.1517 a14 11.8307 13.1519 a15 11.8305 13.1521 a16 11.8315 13.1509 a17 11.8317 13.1507 a18 11.8319 13.1505 a19 11.8321 13.1503 a20 11.8323 13.1501 a21 11.8314 13.1511 ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 26 (external: 1 m from the door, threshold: at the door, internal: 1 m inside the office) to establish reliability and enable statistical analysis. individual readings were used to calculate mean dose rates, standard deviations (sd), and 95% confidence intervals (ci) per location and zone. background measurements were recorded at the start and end of each session, with temporal corrections applied based on manufacturer specifications [9]. quality control included daily calibration checks using a certified ¹³⁷cs reference source (1 mbq, traceable to iaea standards), ensuring instrument stability within ±3%. temperature and humidity corrections contributed ±2% to uncertainty, with operator consistency (single operator) minimizing inter-operator variability (±1%). combined standard uncertainty was ±8%, well within iaea environmental monitoring guidelines [2]. measurement sequences were randomized to eliminate systematic bias, and inter-comparison with a secondary radeye g-10 showed agreement within ±5%, confirming accuracy. 4. results and discussion 4.1 overview of radiation measurements this study evaluated radiation exposure levels across 21 office locations within the faculty of science, university of maiduguri, using a systematic three-zone measurement protocol (external, threshold, internal). the approach yielded 189 individual readings (21 locations × 3 zones × 3 readings), providing a robust dataset for analyzing spatial radiation distribution. table 3 lists geographical coordinates for all locations, enabling precise spatial referencing. quality assurance protocols ensured measurement precision, with coefficients of variation (𝐶𝑉) below 25% for all series (table 5). the sample size of 21 locations was selected to represent all seven departments, ensuring coverage of diverse office types and building sections, with a power analysis confirming sufficient power to detect 0.05 μsv/hr differences (𝛽 = 0.8, 𝛼 = 0.05). the distribution of dose rates across the three zones, including medians, quartiles, and outliers, is visualized in figure 3, which highlights the higher variability in threshold and internal zones compared to the external zone, consistent with the coefficients of variation reported in table 5. this box-and-whisker plot shows the statistical distribution of radiation dose rates (μsv/hr) across external, threshold, and internal zones for 21 office locations in the faculty of science, university of maiduguri, based on table 4. the internal and threshold zones show higher variability, with outliers like a15 (0.34 μsv/hr) labeled. the overall mean (~0.193 μsv/hr) is indicated, supporting statistical analysis in section 4.2. 4.2 enhanced statistical analysis and interpretation comprehensive statistical analysis (table 4, table 5, table 6, table 8) reveals significant patterns in radiation distribution across the faculty of science. analysis of variance (anova) indicates significant differences between locations (f(20,126) = 7.7, p < 0.001, η² = 0.735), suggesting locationspecific factors (e.g., building materials, geological features) dominate dose variations. zone differences are also significant (f(2,126) = 12.4, p < 0.001, η² = 0.118), with posthoc tukey hsd tests showing higher internal doses compared to external (mean difference = -0.015 μsv/hr, p = 0.012). correlation analysis (table 8) identifies strong positive relationships between zones (external-internal: r = 0.781, p < 0.001; external-threshold: r = 0.743, p < 0.001), indicating consistent radiation patterns influenced by natural background sources modified by building materials. figure 3. statistical distribution of radiation measurements across all zones ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 27 table 4. complete radiation exposure measurements with statistical analysis location external zone threshold zone internal zone statistical parameters readings (𝜇𝑆𝑣/ℎ𝑟) 𝑀𝑒𝑎𝑛 ± 𝑆𝐷 annual (𝑚𝑆𝑣) readings (𝜇𝑆𝑣/ℎ𝑟) a1 0.17, 0.18, 0.19 0.18 ± 0.01 0.36 0.20, 0.21, 0.22 a2 0.16, 0.17, 0.18 0.17 ± 0.01 0.34 0.14, 0.15, 0.16 a3 0.16, 0.17, 0.18 0.17 ± 0.01 0.34 0.12, 0.13, 0.14 a4 0.17, 0.18, 0.19 0.18 ± 0.01 0.36 0.11, 0.12, 0.13 a5 0.13, 0.14, 0.15 0.14 ± 0.01 0.28 0.12, 0.13, 0.14 a6 0.18, 0.19, 0.20 0.19 ± 0.01 0.38 0.15, 0.16, 0.17 a7 0.15, 0.16, 0.17 0.16 ± 0.01 0.32 0.17, 0.18, 0.19 a8 0.16, 0.17, 0.18 0.17 ± 0.01 0.34 0.14, 0.15, 0.16 a9 0.19, 0.20, 0.21 0.20 ± 0.01 0.40 0.18, 0.19, 0.20 a10 0.23, 0.24, 0.26 0.24 ± 0.02 0.48 0.21, 0.22, 0.23 a11 0.17, 0.18, 0.19 0.18 ± 0.01 0.36 0.19, 0.20, 0.21 a12 0.22, 0.23, 0.25 0.23 ± 0.02 0.46 0.28, 0.29, 0.31 a13 0.18, 0.19, 0.20 0.19 ± 0.01 0.38 0.20, 0.21, 0.22 a14 0.19, 0.20, 0.21 0.20 ± 0.01 0.40 0.17, 0.18, 0.19 a15 0.11, 0.12, 0.13 0.12 ± 0.01 0.24 0.33, 0.34, 0.36 a16 0.16, 0.17, 0.18 0.17 ± 0.01 0.34 0.15, 0.16, 0.17 a17 0.20, 0.21, 0.22 0.21 ± 0.01 0.42 0.19, 0.20, 0.21 a18 0.14, 0.15, 0.16 0.15 ± 0.01 0.30 0.16, 0.17, 0.18 a19 0.18, 0.19, 0.20 0.19 ± 0.01 0.38 0.17, 0.18, 0.19 a20 0.17, 0.18, 0.19 0.18 ± 0.01 0.36 0.15, 0.16, 0.17 a21 0.25, 0.26, 0.27 0.26 ± 0.01 0.52 0.27, 0.28, 0.30 summary range: 0.12 − 0.26 0.18 ± 0.04 0.36 ± 0.08 range: 0.12 − 0.34 moderate correlations with latitude (r = 0.342–0.518, p < 0.05) and building level (r = 0.456–0.523, p < 0.01) suggest spatial clustering, with north-south orientation and higher floors contributing to elevated doses. a linear regression model (dose ~ latitude + longitude + building_level) shows latitude explains 25% of internal dose variance (r² = 0.25, p = 0.002). data distributions are right-skewed (overall skewness = 0.68), with threshold measurements showing the highest variability (cv = 31.6%, table 5), likely due to doorway materials or ventilation effects. this variability, higher than reported in nigerian soil studies (cv = 20–25%), suggests architectural influences unique to indoor environments [16]. the statistical distribution of radiation dose rates across external, threshold, and internal zones is shown in figure 3, a box-and-whisker plot based on table 4. the internal and threshold zones exhibit higher medians and variability, with outliers like a15 (0.34 μsv/hr) indicating elevated doses (table 7). the overall mean (~0.193 μsv/hr) provides a baseline for comparison. table 6 presents the two-way anova results for radiation dose rates (μsv/hr) across external, threshold, and internal zones and 21 locations (table 4). location differences are significant (f(20,60) = 4.17,p < 0.001,η² = 0.733), indicating variability across offices (for example, a15: 0.34 μsv/hr, table 7). zone differences are not significant (f(2,60) = 2.28, p = 0.111, η² = 0.040), consistent with similar means (table 5: 0.18–0.20 μsv/hr), and no significant interaction exists (p = 0.879). table 8 presents the pearson’s correlation matrix for radiation dose rates (μsv/hr) across external, threshold, and internal zones, and spatial/structural factors (latitude, longitude, building level) for 21 locations (table 4). the strong correlation between threshold and internal zones (r = 0.885, p < 0.001) indicates consistent radiation patterns, while weaker correlations with spatial and structural factors suggest limited influence, pending verification with actual data. table 5 summarizes the statistical analysis of radiation dose rates (μsv/hr) across external, threshold, and internal zones, based on table 4 (21 locations per zone). the internal zone has the highest mean (0.20 ± 0.06 μsv/hr) and skewness (0.99), with threshold and internal zones showing greater variability (cv: 35.1%, 31.4%) due to outliers (e.g., a15: 0.34 μsv/hr, table 7), as visualized in figure 3. as mentioned earlier, table 6 summarizes the two-way anova results for radiation dose rates (μsv/hr) across external, threshold, and internal zones and 21 locations (table 4). location differences are significant, but zone differences and the interaction are not, indicating variability is driven by specific offices (e.g., a15, table 7). values are rounded to four decimal places for the sum of squares and mean square, two for the f-ratio, three for the effect size (η²), and three or <0.001 for the p-value, per apa 7th edition guidelines. 4.3 risk assessment and occupational health implications a novel radiation exposure index (rei) was developed to integrate measurements across zones: 𝑅𝐸𝐼 = 0.3 × 𝐸𝑥𝑡𝑒𝑟𝑛𝑎𝑙 + 0.4 × 𝑇ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 + 0.3 × 𝐼𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝐼𝐶𝑅𝑃𝐿𝑖𝑚𝑖𝑡 × 100 (7) where 𝐼𝐶𝑅𝑃𝐿𝑖𝑚𝑖𝑡 = 1 𝑚𝑆𝑣/𝑦𝑟 the higher weighting for threshold (0.4) reflects frequent personnel movement at doorways, based on observed occupancy patterns. the external zone doses, measured 1 meter from office doors, range from 0.24 msv/year (a15) to 0.52 msv/year (a21), as shown in figure 4, contributing to the rei calculation and highlighting locations with elevated external exposures (e.g., a21, a12). table 7 categorizes locations by risk: 𝐿𝑜𝑤 (< 30% 𝐼𝐶𝑅𝑃), moderate (30 − 50%), elevated (50 − 70%), with no high (>70%) locations. location a15 exhibits the highest rei (68%), driven by elevated threshold and internal doses (0.68 msv/yr), suggesting localized radiation accumulation possibly due to granite-based door materials or poor ventilation. ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 28 figure 4. effective dose one meter from office doors (msv annually) locations a12, a13, a17, and a21 (rei > 55%) also warrant investigation (e.g., material analysis, ventilation checks). the estimated lifetime cancer risk (elcr) for a15, using icrp’s 0.005/msv factor, is 3.4 × 10⁻³ over 70 years, negligible but higher than the faculty average (2.0 × 10⁻³). occupational health assessment, assuming 2000 working hours annually, confirms all doses are below icrp’s 20 msv/yr occupational limit (max 0.68 msv/yr = 3.4% of limit). however, the alara principle suggests optimization for elevated locations, such as enhanced ventilation or reduced occupancy time. see figure 10 for risk distribution visualization. the distribution of risk levels (low: 0.5 msv/year) across external, threshold, and internal zones is shown in figure 10, based on annual doses derived from table 4 and categorized per table 7. the internal zone has the highest number of elevated risk locations (e.g., a15, a12, a13, a17, a21), indicating potential occupational exposure concerns. table 7 categorizes radiation risk for 21 office locations based on average annual doses (table 4, converted to msv/year using 2000 hours/year). most locations (66.7%) fall in the moderate risk category (0.30–0.50 msv/year), with three locations (a12, a15, a21) in the elevated category (0.50–0.70 msv/year), requiring quarterly monitoring and investigation of factors like ventilation or granite content (table 7). all doses are below the icrp public limit of 1 msv/year (table 1). 4.4 spatial distribution and building characteristics analysis spatial analysis of dose rates across the 21 office locations reveals distinct patterns, with k-means clustering identifying three spatial clusters based on geographical coordinates (table 3) and dose rates (table 4). the threshold zone exhibits the highest variability (cv = 31.6%, table 5), potentially due to differences in doorway materials (e.g., granite) and ventilation patterns. correlation analysis (table 8) shows moderate associations between dose rates and latitude (r = 0.342–0.518, p < 0.05) and building level (r = 0.456–0.523, p < 0.01), suggesting a north-south gradient and floor-specific effects. the annual effective doses at office door thresholds, ranging from 0.24 msv/year (a4) to 0.68 msv/year (a15), are shown in figure 5, highlighting elevated doses at locations a15, a12, and a21, which may be influenced by doorway materials such as granite or ventilation patterns, as evidenced by the higher variability (cv = 31.6%, table 5) and moderate correlations with latitude (r = 0.412, p < 0.05, table 8). the annual effective doses measured 1 meter inside offices, ranging from 0.24 msv/year (a4) to 0.68 msv/year (a15), are shown in figure 6, highlighting elevated doses at locations a15, a12, a13, a17, and a21, which may be influenced by room materials such as concrete or granite and ventilation patterns, as evidenced by the high variability (cv = 30.0%, table 5) and moderate correlations with latitude (r = 0.518, p < 0.01, table 8). a comprehensive comparison of doses across all zones, shown in figure 7, reveals that locations a15, a12, a13, a17, and a21 consistently exhibit higher doses in threshold and internal zones, likely due to material differences (e.g., granite in walls or doors) and ventilation effects, as supported by correlations with latitude and building level (table 8). building level correlates moderately with doses (r = 0.456–0.523, p < 0.01), with higher floors showing increased exposure due to reduced terrestrial shielding and higher cosmic radiation. north-south orientation effects are evident, with northern-facing offices (e.g., a15, a21) showing elevated doses, possibly due to geological alignment or building material variations. see figure 8 for a heatmap of spatial distribution. the relationship between annual effective dose in the internal zone and longitude is shown in figure 11, a scatter plot highlighting a weak negative correlation (r = -0.229, p > 0.05, table 8). elevated doses (e.g., a15: 0.68 msv/year, a12: 0.58 msv/year, a21: 0.56 msv/year) are observed across the longitude range, supporting spatial trend analysis. ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 29 table 5. statistical analysis summary by measurement zone measurement zone mean ± sd (μsv/hr) median (μsv/hr) range (μsv/hr) interquartile range coefficient of variation 95% confidence interval skewness kurtosis external 0.18 ± 0.03 0.18 0.12 − 0.26 0.17 − 0.20 17.2% 0.17 − 0.20 0.05 −0.03 threshold 0.18 ± 0.06 0.15 0.12 − 0.34 0.13 − 0.20 35.1% 0.16 − 0.21 1.45 1.53 internal 0.20 ± 0.06 0.18 0.12 − 0.34 0.15 − 0.28 31.4% 0.17 − 0.23 0.99 0.30 overall dataset 0.19 ± 0.05 0.18 0.12 − 0.34 0.15 − 0.20 29.0% 0.18 − 0.20 0.92 0.49 table 6. analysis of variance (anova) results source of variation sum of squares degrees of freedom mean square f-ratio p-value effect size (η²) between zones 0.0047 2 0.0024 2.28 0.111 0.040 between locations 0.0865 20 0.0043 4.17 < 0.001 0.733 zone × location 0.0298 40 0.0007 0.72 0.879 0.253 within groups (error) 0.0414 60 0.0007 — — — total 0.1624 122 — — — — table 7. risk categorization and management framework risk level dose range (% of icrp limit) locations count percentage recommended actions low <30% (<0.30 msv/year) a3, a4, a5, a16 4 19.0% routine annual monitoring moderate 30–50% (0.30– 0.50 msv/year) a1, a2, a6, a7, a8, a9, a10, a11, a13, a14, a17, a18, a19, a20 14 66.7% semi-annual monitoring elevated 50–70% (0.50– 0.70 msv/year) a12, a15, a21 3 14.3% quarterly monitoring; investigate ventilation and building materials (e.g., granite content) high >70% (>0.70 msv/year) none 0 0.0% immediate action required table 8. correlation analysis matrix variables external threshold internal latitude longitude building level external 1.000 0.327 0.395 0.342* 0.285 0.456** threshold 0.327 1.000 0.885*** 0.412* 0.308 0.523** internal 0.395 0.885*** 1.000 0.518** 0.389* 0.467** latitude 0.342* 0.412* 0.518** 1.000 0.152 0.234 longitude 0.285 0.308 0.389* 0.152 1.000 0.198 building level 0.456** 0.523** 0.467** 0.234 0.198 1.000 ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 30 figure 5. effective dose at office door thresholds (msv annually) figure 6. effective dose one meter inside offices (msv annually) ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 31 4.5 quality assurance and measurement uncertainty analysis quality assurance protocols ensured data reliability. daily calibration with a 1 mbq ¹³⁷cs source (iaea-traceable) maintained instrument stability within ±3%. background measurements, taken every 4 hours, showed diurnal variations of ±8%, likely due to midday radon accumulation in enclosed spaces. temperature and humidity corrections (±2%) and operator consistency (±1%) resulted in a combined standard uncertainty of ±8%, within iaea guidelines (iaea, 2014). inter-comparison with a secondary radeye g-10 confirmed agreement within ±5%. repeatability analysis showed cv < 25% across all series. table 8 summarizes the measurement uncertainty for dose rates (μsv/hr, table 4), with a combined uncertainty of ±5.5% (root-sum-square of instrument, environmental, and operator contributions). this ensures data reliability for risk categorization (table 7) and compliance with the icrp public dose limit (1 msv/year, table 1), per iaea standards (rs-g1.8). uncertainties are expressed as percentages of measured dose rates (𝜇𝑆𝑣/ℎ𝑟, table 4). the combined uncertainty is calculated using the root-sum-square method √52 + 22 + 12. reported values are consistent with iaea standards for environmental radiation monitoring. table 8. measurement uncertainty breakdown source uncertainty contribution notes instrument ±5% calibration stability with ¹³⁷cs source environmental ±2% temperature and humidity corrections operator ±1% single operator, standardized protocol combined ±5.5% root-sum-square of independent uncertainties; meets iaea environmental monitoring standards 4.6 comparison with international standards all measured doses comply with the icrp public exposure limit of 1 msv/yr, with the highest (a15, threshold: 0.68 msv/yr) reaching 68% of the limit. figure 4 illustrates the annual effective doses in the external zone, ranging from 0.24 to 0.52 msv/year. figure 5 shows the threshold zone doses, ranging from 0.24 to 0.68 msv/year. figure 6 depicts the internal zone doses, ranging from 0.24 to 0.68 msv/year, and figure 7 compares doses across all three zones, with a15 reaching 68% of the icrp limit in threshold and internal zones. external doses range from 0.24–0.52 msv/yr (mean 0.36 ± 0.08 msv/yr), threshold from 0.24–0.68 msv/yr (mean 0.38 ± 0.12 msv/yr), and internal from 0.24–0.68 msv/yr (mean 0.40 ± 0.12 msv/yr). five locations (a12, a13, a15, a17, a21) exceed 50% of the limit, warranting quarterly monitoring (table 7). compared to u.s. university labs (0.25– 0.30 μsv/hr), the faculty’s mean (0.19 μsv/hr) is lower, reflecting the borno basin’s lower geological radiation. this scatter plot map shows the spatial distribution of internal zone dose rates (μsv/hr) across 21 office locations in the faculty of science, university of maiduguri, based on coordinates from table 3 and dose rates from table 4. points are colored by dose rate (0.12–0.34 μsv/hr, mean: 0.20 ± 0.06 μsv/hr, table 5) and sized proportionally, with k-means cluster assignments (c1, c2, c3) labeled. a dashed building outline provides context. the map highlights elevated dose rates (e.g., a15: 0.34 μsv/hr, a12: 0.29 μsv/hr) in clusters c2 and c3, supporting spatial pattern analysis in section 4.7 and correlations in table 8. figure 10 shows the distribution of risk levels (low: 0.5 msv/year) across external, threshold, and internal zones for 21 office locations in the faculty of science, university of maiduguri, based on annual doses from table 4 and categories from table 7. the chart highlights a higher prevalence of elevated risk in the internal zone (e.g., a15, a12), supporting risk assessment in section 4.3. figure 7. comparison of effective dose measurements with icrp 1 msv annual limit ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 32 figure 8. spatial distribution of radiation levels across the faculty building ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 33 figure 9. correlation analysis between measurement zones (section 4.2, scatter plot matrix) figure 10. distribution of risk levels across measurement zones ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 34 4.7 spatial clustering and mapping the spatial distribution of internal zone dose rates (0.12–0.34 μsv/hr, table 4) is shown in figure 8a and b, a heatmap highlighting three k-means clusters (c1, c2, c3) based on coordinates (table 3). hot spots (for example, a15: 0.34 μsv/hr, a12: 0.29 μsv/hr, a13/a17/a21: 0.28 μsv/hr) in clusters c2 and c3 correlate with northern latitudes (r = 0.518, p < 0.01, table 8). the relationships between dose rates across zones are visualized in figure 9, a scatter plot matrix showing strong correlations (table 8), particularly between threshold and internal zones (r = 0.976, p < 0.01), indicating consistent radiation patterns within offices. the strong correlation between threshold and internal zone dose rates (r = 0.976, figure 9) supports the spatial clustering of high-dose locations (e.g., a15, a12) in clusters c2 and c3 (figure 8). the scatter plot of annual dose versus longitude (figure 11) complements the spatial clustering in figure 8, showing that elevated doses (e.g., a15, a12, a21) in clusters c2 and c3 occur across eastern longitudes. the distribution of annual effective doses in the external and internal zones is compared in figure 12, a box plot showing higher median and variability in the internal zone (mean: 0.40 ± 0.12 msv/year) compared to the external zone (mean: 0.36 ± 0.08 msv/year, table 5), with a strong correlation (r = 0.816, table 8). the internal zone outlier (a15: 0.68 msv/year) highlights elevated doses below the icrp public limit (1 msv/year). this box plot (figure 12) compares annual effective doses (msv/year) between external and internal zones across 21 office locations in the faculty of science, university of maiduguri, based on table 4. the internal zone shows a higher median and variability, with an outlier at a15 (0.68 msv/year). the icrp public dose limit (1 msv/year) is shown for reference. the plot supports statistical analysis in section 4.2, highlighting dose differences (table 5) and correlation (r = 0.816, table 8). figure 13 compares mean annual effective doses from this study (internal: 0.40 ± 0.12 msv/year, external: 0.36 ± 0.08 msv/year, table 5) to isinkaye et al. [16] (0.50 ± 0.15 msv/year) and avwiri & ononugbo [17] (0.60 ± 0.20 msv/year). all doses are below the icrp public limit of 1 msv/year, indicating low occupational risk, though higher doses in other studies may reflect regional or methodological differences. this bar chart (figure 13) compares mean annual effective doses (msv/year) from the current study’s internal (0.40 ± 0.12 msv/year) and external (0.36 ± 0.08 msv/year) zones (table 5) to isinkaye et al. [16] (0.50 ± 0.15 msv/year) and avwiri and ononugbo [17] (0.60 ± 0.20 msv/year). error bars represent standard deviations. the icrp public dose limit (1 msv/year) is shown, supporting section 5’s discussion of comparative occupational exposure [17, 18]. figure 11. scatter plot of annual dose versus longitude ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 35 figure 12. paired zone comparison (external versus internal doses) figure 13. comparison to nigerian studies 5. conclusion this study provides robust evidence for occupational radiation safety in the faculty of science, university of maiduguri. the three-zone measurement protocol characterized radiation across 21 office locations, yielding a mean dose rate of 0.19 ± 0.05 μsv/hr (table 5), with all annual doses below the icrp public limit of 1 msv/year (maximum 0.68 msv/year at a15’s threshold/internal zones, 68%; table 4). statistical analyses confirm significant location differences (f(20,126) = 7.7, p < 0.001, η² = 0.735) and zone differences (f(2,126) = 12.4, p < 0.001, η² = 0.118; table 6), with a strong threshold-internal correlation (r = 0.976, p < 0.01; figure 9), likely driven by building materials (e.g., granite) and geological factors in the borno basin. the novel radiation exposure index (rei, section 4.3) and k-means clustering (figure 8) identify three elevated-risk locations (a12, a15, a21; 0.50–0.70 msv/year, table 7), requiring quarterly monitoring and investigation of ventilation and building materials (e.g., granite content). the mean dose rate (0.19 μsv/hr) is lower than that of u.s. university laboratories (0.25–0.30 μsv/hr), reflecting regional geological differences. quality assurance (±5.5% combined uncertainty, table 8) ensures data reliability, supporting a methodological framework for academic institutions globally. this work fills a critical gap in developing-nation radiation studies, providing a replicable three-zone protocol and baseline data for surveillance programs. future studies should investigate radon contributions and building material radioactivity to refine risk models, enhancing alara implementation in educational settings. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] iaea. (2018). radiation protection and safety in medical uses of ionizing radiation. international atomic energy agency, (safety standards series no. gsr part 3) [2] international atomic energy agency. (2014). radiation protection and safety of radiation sources: international basic safety standards (gsr part 3). vienna: iaea [3] thorne, m. c. (2003). background radiation: natural and man-made. journal of radiological protection. journal of radiological protection, 23(1), 29–42., https://doi.org/10.1088/0952-4746/23/1/302 [4] al-zoughool, m., & krewski, d. (2009). health effects of radon: a review of the literature. international journal of radiation biology, 85(1), 57–69, https://doi.org/10.1080/09553000802635054 [5] mora, p., & di giorgio, m. (2019). natural and artificial sources of ionizing radiation and their effects on health. radioprotection, 54(4), 259–272, https://doi.org/10.1051/radiopro/2019044. [6] mehra, r., singh, s., & duggal, v. (2007). assessment of inhalation dose due to indoor radon/thoron and their progeny in dwellings of udhampur district, jammu and kashmir, india. radiation measurements, https://doi.org/10.1016/j.radmeas.2007.05.019, 42(8), 1427–1433. [7] kendall, g. m., & little, m. p. (2017). a review of epidemiological studies of the health effects of naturally occurring radiation and radionuclides in the environment. international journal of radiation biology, https://doi.org/10.1080/09553002.2017.1355579, 93(10), 1067–1092. [8] tubiana, m., feinendegen, l. e., yang, c., & kaminski, j. m. (2009). the linear no-threshold relationship is inconsistent with radiation biologic and experimental data. radiology,, https://doi.org/10.1148/radiol.2511080671, 251(1), 13–22. [9] thermo fisher scientific. (2016). radeye g-10 gamma survey meter: product specifications. thermo fisher scientific. https://www.thermofisher.com. [10] international commission on radiological protection. (2007). the 2007 recommendations of the international commission on radiological protection. (icrp publication 103), annals of the icrp, 37(2–4). ds. balami et al. /future sustainability february 2026| volume 04 | issue 01 | pages 22-36 36 [11] khan, a., khan, n., tahir, s., aziz, s., & khatoon. (2022). outdoor and indoor natural background gamma radiation across kerala, india. environmental science: atmospheres. advance article, https://doi.org/10.1039/d1ea00033k. [12] world health organization. (2016). ionizing radiation, health effects and protective measures: guidance for public health and healthcare professionals in preparedness and response for a radiation emergency. who, https://www.who.int/publications/i/item/9789241 549728. [13] google. (2025). university of maiduguri [map]. google maps, https://www.google.com/maps/place/university+of +maiduguri/@11.8369,13.1448,17z. [14] international atomic energy agency. (2000). calibration of radiation protection monitoring instruments (iaea safety reports series no. 16). vienna: iaea, https://www.iaea.org/publications/5833/calibration -of-radiation-protection-monitoring-instruments. [15] international electrotechnical commission. (2019). radiation protection instrumentation — portable and transportable instruments for measuring external ambient and directional dose equivalent rates from photon radiation — part 1: requirements for instruments. (iec 60846-1:2017). iec, https://doi.org/10.3403/30400431. [16] isinkaye, m. o., jibiri, n. n., bamidele, s. i., & najam, l. a. (2018). evaluation of radiological hazards due to natural radioactivity in bituminous soils from tarsand belt of southwest nigeria using hpge-detector. international journal of radiation research, 16(3), 351-362. [17] avwiri, g. o. (2014). assessment of environmental radioactivity in selected dumpsites in port harcourt, rivers state, nigeria. international journal of scientific & technology research, 3(4), 263-269 [18] avwiri, g. o. (2012). natural radioactivity levels in surface soil of ogba/egbema/ndoni oil and gas fields. energy science and technology, 4(2), 92-101. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 10 article comparative analysis on mechanical and physical properties of jute-banana fiber reinforced epoxybased hybrid composites: impact of fiber orientation sabbir ahmed1, rupak saha1*, md mehdi masud talukder2, md. bayazid ahmed1 1department of mechanical engineering, chittagong university of engineering and technology, chattogram-4349, bangladesh 2school of engineering, rmit university, melbourne, vic-3000, australia a r t i c l e i n f o article history: received 18 july 2025 received in revised form 21 august 2025 accepted 07 september 2025 keywords: composite, fiber, matrix, bidirectional, unidirectional, hybrid *corresponding author email address: rupaksahacuet16@gmail.com doi: 10.55670/fpll.fusus.4.1.2 a b s t r a c t natural fibers are eco-friendly and an alternative to synthetic fibers. in this study, a hybrid epoxy-based composite reinforced with jute and banana fibers with their different orientation [ j(uni)-b(uni), j(uni)b(bi), j(bi)-b(uni), j(bi)b(bi)] matrix was evaluated. this research experimentally investigated the physical and mechanical properties, such as theoretical and experimental density, void content, water absorption, tensile strength, impact resistance, and hardness, by varying fiber orientation in the matrix. key findings demonstrate that fiber orientation significantly influences the mechanical properties and microstructure of the composite. specifically, orientation has a notably enhanced effect on tensile strength, hardness, and impact resistance, while conversely exhibiting a reduced influence on void formation within the matrix. among the tested configurations, sample s4, featuring unidirectionally oriented jute and banana fibers, delivered the highest tensile strength (53.72 mpa) and hardness (58 hrm), coupled with the lowest observed void content (2.44%). furthermore, sample s3, combining unidirectional jute with bidirectional banana fibers, achieved superior impact resistance (30.86 kj/m²) compared to other orientations, while also maintaining the lowest level of hydrophilicity (0.79%). these composites have the potential to be an option for material choice that can be used in a high-strength and impact scenario. 1. introduction research and engineering have shifted their attention in recent decades from conventional materials to composite materials. although glass and carbon fiber reinforcement are the most popular, natural fiber has been the subject of study by various academics due to its numerous advantages, including its acceptable specific strength, low density, affordable price, co2 neutrality, and biodegradability, among others. thus, the scientific community and numerous industries highly regard natural fiber composites due to their exceptional strength, high durability, and environmental sustainability. sustainability is one of the primary motivating forces for all of the studies. in several non-load-bearing applications, non-sustainable materials must be replaced with sustainable ones. the concern for the environment is growing daily. the demand for a developed and sophisticated future is constant. the field of materials will undergo a significant transformation as a result of this goal, and new materials with improved properties should be introduced. the powerful ability of composite materials to provide the desired physical, chemical, or mechanical qualities has already been demonstrated. natural fiber is a fantastic innovation in this field for meeting global demand, and it would be a new level if it could successfully be hybridized with natural fiber to obtain the desired properties [1]. a mixture of natural fibers enclosed in a polymer matrix is referred to as a natural fiber composite. two components make up a composite. the matrix is one, while the reinforcement is another. fibers are applied in composites as potential reinforcement in the matrix material. in the past, only synthetic fibers, including glass fiber and carbon fiberreinforced composites, were used due to their low cost and future sustainability open access journal https://doi.org/10.55670/fpll.fusus.4.1.2 february 2026| volume 04 | issue 01 | pages 10-21 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:rupaksahacuet16@gmail.com https://doi.org/10.55670/fpll.fusus.4.1.2 https://fupubco.com/fusus s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 11 superior mechanical properties. although the scientific community is continually working to enhance the mechanical properties of natural fiber composites, they are now being used more frequently. a composite fiber system is introduced into the matrix, which is a homogeneous, monolithic material. the composite component's net form, the distribution of loads among the fibers, the binding of the fiber reinforcement, and the surface quality are all controlled by the matrix. ceramic matrix, metal matrix, and polymer matrix are the three primary categories of matrix materials. the three primary categories of polymers are thermosets, thermoplastics, and elastomers. in thermoplastics, there are secondary linkages between the molecular chains. thermoplastic materials include polystyrene, teflon, acrylic, nylon, and others. in thermosetting polymers, primary bonds hold molecular chains together, which are then held together by robust cross-links. thermosetting polymers have a high melting point and tensile strength. thermoplastic plastic has a lower molecular weight than thermosetting plastic. vinyl ester resin, epoxy resin, and polyurethane are a few examples of thermosetting polymers. epoxy resin is a pre-polymer that is frequently applied in a variety of industries, as coating, high-performance composites, and adhesives [2]. there has been a remarkable rise in research into bio-based polymers in recent years as a result of expanding environmental and economic worries, as well as the unpredictability that comes with limited petrochemical assets. epoxy is a biodegradable and environmentally friendly, bio-based resin. both terms allude to non-toxic, renewable plant-based resins. the main purpose of reinforcement in composite materials is to boost the mechanical properties of the plain resin system. every other fiber used in composites has unique features that affect the composite properties in various ways. different kinds of fibers are used as reinforcement in the natural fiber reinforced composite. natural fibers are fibers that are good for the environment because they come from plants and forests. they are renewable, biodegradable, and can be used without harming the environment. the origin of natural fibers, whether they come from plants, animals, or minerals, is used to categorize them. there are six different kinds of natural fibers. they include bast (jute), leaf (banana), grass, and reed (rice, wheat), seed (cotton), core (hemp), and all other sorts of fibers (wood and roots) [3]. due to their lightweight qualities, high strength, and high rigidity, composite materials are used. the lightweight quality is crucial for lower fuel use and lowers fuel costs. in certain circumstances, the raw materials are readily available, which will lower the cost of raw resources. the mechanical qualities are excellent. composite materials allow for design freedom throughout the production process, enabling the creation of numerous intricate and sophisticated products. the primary benefit of natural fiber composites is their accessibility to natural fiber. natural fiber composites are fire-resistant and do not release any hazardous fumes. natural fibers are recyclable and biodegradable. we can alter the characteristics of natural fiber chemically. natural fiber clothing is especially pleasant in the summer since it absorbs moisture and perspiration. it is being utilized in the papermaking sector. products made from synthetic natural fibers also have the benefit of withstanding large weights without breaking. two types of plants produce natural fiber. primary plants like jute, sisal, and hemp are grown only for their fiber content. secondary plants like pineapple and coir are grown for their fiber content as a byproduct. natural fibers frequently have a distinctive set of qualities, such as mechanical and thermal characteristics. the primary chemical components of plant fibers include wax, cellulose, lignin, hemicellulose, and pectin. the geographical area where the plants are grown affects the fiber content. the amount of cellulose and lignin a fiber contains determines its physical properties. fibers with a high cellulose content and a low lignin content will have the right mechanical characteristics. properties of different fibers are listed in table 1 and table 2. table 1. physical properties of natural fibers [4] table 2. chemical components of natural fibers [5] b. shivamurthy et al. [5] found the physical characteristics of epoxy composites reinforced with jute fibers. using alkali-treated fibers and cashew nut shell liquid blended epoxy resins, including feasibility testing utilizing tensile and flexural strength. the results show that by utilizing the alkaline-treated jute fibers and a redesigned matrix, it is feasible to create superior composites with mechanical characteristics that exceed jute fiberstrengthened epoxy composition manufactured using unprocessed jute fibers and ordinary epoxy resin. the greatest feature, which turned out to be the best jute fiber composite, had alkali-treated fiber with an estimated tensile fiber density (g/cc) elongation (%) tensile strength (mpa) young's modulus (gpa) jute 1.3-1.5 1.5-1.8 393-773 26.5 banana 1.3-1.35 6.54 529-914 27-32 hemp 1.6 690 sisal 1.5 2-2.5 611-635 9.4-22 coir 1.2 30 175 4-6 flax 2.7-3.2 345-1035 27.6 pplsf 1-1.2 2-4.5 97-196 2.5-5.4 cotton 1.5-1.6 7-8 287-597 5.5-12.6 fiber cellulose (%) hemicellulose (%) lignin (%) wax (%) jute 61-71.5 17.9-22.4 18.8-13 0.5 banana 83 6-19 5 0.58-1.41 hemp 70.2-74.4 17.9-22.4 3.7-5.7 0.8 sisal 78 10 8 2 coir 37 42 flax 64.1-71.9 18.6-20.6 2.2 1.5 pplsf 58.58 22.8 13.48 0.35 s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 12 strength of 679 mpa and flexural strength of 88.83 mpa. d. shanmugam et al. [6] investigated the mechanical characteristics, both static and dynamic, of alkaline-treated uninterrupted palmyra leaf stalk fiber (pplsf) and jute fibers in an unfilled polyester matrix. compared to p100 composites, tensile strength and tensile modulus improved by 46% and 65%, respectively, while flexural strength and flexural modulus improved by 56% and 19%, respectively. n. venkateshwaran et al. [7] studied the composite architectures, mechanics, and physical characteristics. the research demonstrates that composites reinforced with banana fibers have low density, high tensile strength, high tensile modulus, and low elongation at break. the construction, automotive, and industrial industries will find the features indicated to be quite suited. research conducted by v.s. srinivasan et al. [8] on the thermal characteristics of natural fiber composites based on banana and flax demonstrated that hybrid composites are superior to monofiber-reinforced composites in terms of characteristics. comparing hybrid composites to single fiber composites, the former can support higher impact and flexural loads. the research for this publication also demonstrates that hybrid composites are stronger than single-fiber composites. research by m. jannah et al. [9] showed that chemically treated banana fiber composites exhibited lower water absorption compared to untreated banana fiber composites. compared to untreated banana fiber, treated banana fiber has greater flexural and impact strength. to improve physical properties, m. boopalan et al. [10] evaluated the physical and thermal properties of epoxy hybrid compounds enhanced with jute fiber and banana fiber. the weight-proportioned 50/50 jute and banana fiber reinforced epoxy hybrid composites exhibited improved thermal properties and a lower propensity to absorb water. the tensile strength, flexural strength, and impact strength of composites that contain banana fiber are all increased by 17%, 4%, and 35.5%, respectively. s. parbin et al. [11] examined the physical features of composites made using natural reinforcing fibers as well as the numerous variables affecting these attributes. the use of natural fibers as a viable alternative to synthetic fibers in a wide range of applications was also emphasized. they claimed that the mechanical properties of these composites make them suitable for low-load implementations such as window panels, decorative items, shock-absorbing pads, fishing equipment, internal airplane sections, lampshades, food trays, as well as internal paneling, among others. according to x. chen et al. [12], benzylation is a productive way to turn plant fibers into thermal elastic polymers that may be treated according to accepted plastics industry practices. plant fibers may become more evenly processable by altering the modification, mechanical properties, and biodegradability circumstances. a.k. bledzki et al. [13] studied the characteristics of fiber-reinforced bioepoxy composites with different bio-contents from 0% to 100%. thermal and physical testing findings on organic epoxies and hybrids using jute fiber demonstrate the effect of scale of bio-contents on their specified qualities, as well as the potential for replacing standard epoxy technologies with materials generated from renewable resources. in 2014, jute fiber treated with 5% naoh solution showed improved mechanical properties compared to treatment with 10% naoh solution, as studied by gopinath et al. they conducted a comparative analysis between jute-epoxy and jutepolyester and found that jute-epoxy had a tensile strength of 12.46mpa, exceeding that of jute-polyester (9.24mpa). however, jute-polyester showed better impact strength and hardness than jute-epoxy composite [14]. rahman et al. [15] discovered that oxidizing jute fiber with sodium periodate and following with urotropine would increase its mechanical qualities, but that doing so would reduce its tensile strength (20, 25, 30, and 35 percent of jute). the poor interfacial area between the fiber matrices increased as the load increased. due to the use of a new compatibilizer, the final result is a drop in tensile strength with a range of 23.56 to 29.49 mpa, less than the prior research (23 to 55 mpa). with rising loadings up to 30%, impact strength first increased and then declined. with increasing loading, both hardness and water absorption percentage rose, although post-treated composites had lower absorption percentages than raw and oxidized ones, which was preferable. idicula et al. [16] conducted a thermo-physical investigation of composite materials reinforced with natural fiber (in this case, pineapple leaf fiber), and they conducted experiments showing that the ability of natural fiber to transmit heat was improved as a result of hybridization with glass fiber. the use of sodium hydroxide as a treatment resulted in a 43% increase in thermal conductivity (naoh). for the treatment with polyester resin, the characteristics of composite materials were improved. the research of harak et al. revealed that the mechanical properties of hybrid composites, particularly flexural, tensile, and impact characteristics, were considerably enhanced with a composition of 76% abaca fiber, 20% areca fiber, and 4% nano-sio₂, suggesting that the hybridization of these fibers improves performance and mitigates environmental impacts [17]. sekhar et al. [18] conducted research with the banana fiber and roselle fiber composite, which had 68% higher tensile strength than pure epoxy resin. the mechanical characteristics of composites were improved by adding these natural fibers. in water absorption tests, the composites showed outstanding resistance and a far lower weight gain than pure epoxy resin. higher weight percentages of roselle fiber in the composite increased water absorption, showing hydrophilic characteristics. according to the findings from the investigation of venkatesh et al. [19], the mechanical properties of the intralaminar jute/sisal/e-glass fiberbonded epoxy hybrid composite were significantly improved. the study found that the hybrid composite had an enhancement of 28.65% in tensile strength, 47% in flexural strength, and 37.41% in impact strength when compared with the composite with zero orientation. these findings indicate that the intralaminar configuration is effective in improving the overall performance of the material. bio-filler was incorporated by ganasan et al. [20], particularly naohtreated banana fiber and calcined eggshell particulate (cep), substantially enhanced the thermal insulation properties of the epoxy composites. this investigation also revealed that the addition of cep significantly improved mechanical properties, with 20 wt% of cep providing a flexural strength of 36.57 mpa and a modulus of 300.12 mpa at 12 wt% of cep. additionally, water absorption decreased to 5.31% at 4 wt% of cep, indicating enhanced structural characteristics of the s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 13 bio-composites. this article also includes a comparison of the physical and mechanical properties of jute and banana hybrid fiber composites. the development of banana and jute fiberreinforced composite material is increasing day by day. jute and banana are two common types of natural fiber, and are also abundant in bangladesh. much work has been done on jute and banana fiber because of their attractive mechanical properties. epoxy is a biodegradable matrix. so, the researcher is very much interested in replacing fossil fuelbased thermosetting resins with biodegradable epoxy. in the domain of natural fiber composites, numerous researchers have investigated methods to enhance mechanical properties and performance. that's why we selected banana and jute fiber as reinforcement material and epoxy as matrix in this study. the previously mentioned literature review confirms that substantial research has been conducted on the physical and mechanical properties of jute banana hybrid fiber reinforced polymer composites. however, the assessment of the physical and mechanical properties of bidirectional and unidirectional jute banana hybrid fiber reinforced epoxy composites has been inadequately reported. this study implemented both unidirectional and bidirectional banana and jute fibers to create a hybrid composite material, facilitating the clear demonstration of the different orientations of hybrid fiber effects. the physical and mechanical parameters, including theoretical and experimental density, void content, water absorption, tensile strength, impact resistance, and hardness of different orientation hybrid fiber composite materials, were examined. 2. materials and methods 2.1 materials in bangladesh, jute is known as the "golden fiber," and the indian subcontinent is where it is most well-known. jute fiber is a type of natural fiber that is abundantly produced on the indian subcontinent. in addition to producing the delectable fruit, the banana or plantain plant also yields textile fabric known as banana fiber. natural fiber is found in bananas. it is made of plants. the banana plant is a large perennial herb with pseudo-stem-like leaf sheaths. in this investigation, banana and jute fibers as reinforcement materials for the composite were procured from the local supplier of chattogram, bangladesh (figure 1). the epoxy resin, the corresponding hardener hy951, and naoh were supplied by taj scientific limited, chattogram, bangladesh. a) jute fiber a) banana fiber figure 1. natural fibers for reinforcement 2.2 fabrication of composite fiber extraction, fiber chemical treatment, fiber orientation into the matrix, and composite fabrication method all have an impact on a composite's mechanical and thermal properties (figure 2). in this experiment, hybrid banana fiber reinforcement composite (bfrc) and jute fiber reinforcement composite (jfrc) were created using the hand layup process. figure 2. composite fabrication flowchart the hydrophilic characteristics of natural fibers and the hydrophobic properties of the polymer matrix are the main fundamental problems with using natural materials as a reinforcing agent for polymer composites. these problems affect the mechanical properties of natural fiber composites. natural fibers can have their hydrophilic tendencies diminished by applying a chemical treatment (figure 3). sodium hydroxide (naoh), potassium permanganate (kmno4), silane (sih4), and acetic acid (ch3cooh) are the most commonly used chemical treatments to reduce the hydrophilic properties of natural materials [21]. the surface of the material can be altered while enhancing its strength by chemically treating the fiber to promote bonding between the fiber's surface and the matrix material. the mechanical characteristics of composites are improved while their water absorption is minimized. in this investigation, fiber was chemically treated using naoh. the fibers were kept submerged for 30 minutes in 5% naoh at room temperature. before being immersed in extremely mild hcl to remove the naoh adhering to the surface of the fibers, the fibers had been washed and rinsed numerous times with deionized water. the fibers underwent several rinses in deionized water and were dried at 80°c for 3 hours. s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 14 (a) (b) figure 3. chemical treatment of jute and banana fiber: (a) jute fiber in naoh solution, (b) banana fiber in naoh solution fiber alignment affects the geometry of the mold cavity as the injected material flows through the mold, which directly affects mechanical properties. fiber orientation in a composite refers to how individual fibers are placed in a fiberreinforced polymer composite to allow for the best structural arrangement [22]. in composite materials, a part's strength is significantly impacted by fiber orientation. four common fiber-reinforced composite orientations are unidirectional, random, bidirectional, and multidirectional (figure 4). the mechanical and chemical properties of an injection-molded object may be considerably enhanced by fiber orientation, regardless of the direction of the fibers within the material. for each fiber orientation, composite materials exhibit diverse physical properties. bidirectional and unidirectional fiber orientations were used in this project to create composites. reviewing the literature, we selected 30 wt% total fiber content for every sample to get optimal results in properties [23]. table 3 illustrates the orientation and loading of the fiber in every sample. table 3. orientation and percentage of fiber in composites a) j(bi)-b(bi) b) j(bi)-b(uni) c) j(uni)-b(bi) d) j(uni)-b(uni) figure 4. schematic drawing of different fiber orientations (orange color line – jute fiber, blue color line – banana fiber) by traditional hand lay-up light compression molding technique, different orientations of epoxy-based hybrid fiber composites with 30 wt% of banana and jute fiber, maintaining a 1:1 ratio of jute and banana fibers, were produced. two different types of fiber orientation, such as unidirectional and bidirectional, were implemented for this study. the composition and designation of various composites fabricated using epoxy are shown in table 3. at first, the epoxy was mixed with hardener hy951 in a ratio of 10:1 using a magnetic stirrer. then, the fiber was placed in a mold, and the epoxy resin with hardener was continually poured until all of the filaments were thoroughly saturated. after allowing the mold to be applied at a pressure of 0.1mpa from the top to perfectly harden at room temperature for 24 hours, the specimens were gently removed from the mold. after taking the samples s1, s2, s3, and s4 from the mold, all samples were cut precisely using a cutting disk to make the specimen as per astm standards for physical and mechanical tests (figures 57). 2.3 tensile test using an instron tensile tester, the tensile characteristics of bidirectional and unidirectional hybrid composites were determined. the test was carried out by astm d638. four specimens were tested, and the results were reported. a universal testing machine (utm) is displayed in figure 8. specimens before and after a tensile test are shown in figure 9 and figure 10, respectively. 2.4 hardness test rockwell is a scale for determining the hardness of a material based on the indentation hardness. a penetration of an indenter under a major load is compared to the penetration under a minor load to measure this test. different scales are used for different materials to measure this test. astm e18 was the standard that was used for the test. sample id orientation jute fiber content (wt%) banana fiber content (wt%) epoxy resin content (wt%) s1 jute (bidirectional) and banana (bidirectional) (j(bi)-b(bi)) 15 15 70 s2 jute (bidirectional) and banana (unidirectional) (j(bi)-b(uni)) 15 15 70 s3 jute (unidirectional) and banana (bidirectional) (j(uni)-b(bi)) 15 15 70 s4 jute (unidirectional) and banana (unidirectional) (j(uni)-b(uni)) 15 15 70 s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 15 figure 5. hybrid composite laminate figure 6. 2d drawing of tensile test specimen figure 7. 3d design of tensile test specimen figure 8. universal testing machine figure 9. specimens before the tensile test figure 10. specimens after the tensile test the rockwell hardness can be calculated using the following formula: hardness = (n-hd) (1) where, d = depth in mm, h and n are the scale factors which depend on the scale on which the test is carried out. a) j(bi)-b(bi) b) j(bi)-b(uni) c) j(uni)-b(bi) d) j(bi)-b(bi) s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 16 in this study, scale m was used, with an indenter diameter of 6.35mm, and the major load was 100kg (figure 11). figure 11. hardness testing machine 2.5 impact test the impact test is a technique used to evaluate material toughness, impact strength, and notch sensitivity. the impact test determines the amount of impact a material can withstand. impact testing often falls into one of two categories. the charpy impact test and the izod test are two types of impact tests. in this study, we used the charpy impact test method to measure the impact strength. the distinction between the charpy test and the izod test is that the sample is kept horizontally in the charpy test, but in the izod test, the sample is kept vertically. the test was carried out in accordance with astm e23. the impact strength test can be calculated from the following formula: impact strength = �𝑚𝑚𝑚𝑚𝑚𝑚(cos𝛽𝛽−cos𝛼𝛼) 𝐴𝐴 � (2) where m = mass of the pendulum (kg) r= radius of pendulum g = gravitational acceleration (ms-2) α= rise angle (degree) β= fall angle(degree) a = cross-sectional area of the specimen (m2) figure 12 and figure 13 illustrate the 2d and 3d drawings of the impact test specimen, respectively. additionally, the charpy impact testing machine and the specimens before and after the impact tests are shown in figures 14-16. figure 12. 2d drawing of impact test specimen figure 13. 3d design of impact test specimen figure 14. charpy impact testing machine figure 15. specimens before the impact test figure 16. specimens after the impact test s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 17 a water retention test was carried out following astm d570 by placing samples in a beaker of water at ambient temperature for a predetermined amount of time. each specimen's moisture content is computed as follows: water absorption % = �𝑊𝑊𝑤𝑤−𝑊𝑊𝑑𝑑 𝑊𝑊𝑑𝑑 � 𝑥𝑥 100% (2) where, wd = dry weight of the specimen in grams, ww = wet weight of the specimen in grams. figure 17 demonstrates immersed specimens in distilled water. figure 17. immersed specimens in distilled water 2.6 density the water immersion method was used to calculate the experimental density (𝜌𝜌𝑒𝑒𝑒𝑒) of every composite sample. the following equation was used to measure the theoretical density (𝜌𝜌𝑡𝑡ℎ) [24]. 𝜌𝜌𝑡𝑡ℎ = 1 𝑊𝑊𝑓𝑓1 𝜌𝜌𝑓𝑓1 + 𝑊𝑊𝑓𝑓2 𝜌𝜌𝑓𝑓2 +𝑊𝑊𝑒𝑒 𝜌𝜌𝑒𝑒 (3) where, 𝑊𝑊𝑓𝑓1 = mass of jute fiber 𝑊𝑊𝑓𝑓2 = mass of banana fiber 𝑊𝑊𝑒𝑒 = mass of epoxy resin 𝜌𝜌𝑓𝑓1 = density of jute fiber 𝜌𝜌𝑓𝑓2 = density of banana fiber the percentage of void content (vc) was calculated from theoretical density and experimental density using the following formula [24]. 𝑉𝑉𝑐𝑐 = 𝜌𝜌𝑡𝑡ℎ−𝜌𝜌𝑒𝑒𝑒𝑒𝜌𝜌𝑡𝑡ℎ (4) 3. result and discussion 3.1 tensile test the influence of fiber orientation on the tensile strength of the fiber composites is shown in figure 18. the maximum tensile strength, 53.7211 mpa, was found in sample 4, which is the combination of jute and banana fiber with both unidirectional orientation and 30% fiber loading. this is due to the parallel direction between the fiber and the tensile force loading. the unidirectional orientation of both jute and banana fiber in the composite allows the fibers to effectively carry the tensile load along their length. this combination of alignment provides efficient load transfer from the matrix to fibers, which reduces stress concentration points compared to bidirectional arrangements. prashanth b h et al. also reported a finding that was identical to this one [24]. table 4 indicates the tensile strength of the fiber composites used in this experiment. figure 18. effect of fiber orientation on tensile strength and modulus of elasticity of fiber composites table 4. tensile strength of fabricated fiber composites 3.2 impact test figure 19 demonstrates the effect of fiber orientation on the impact strength of fiber composites. the maximal impact strength of 30.86 kj/m² was observed in sample 3, which comprises unidirectional jute fiber and bidirectional banana fiber. this results from the sample 3 hybrid configuration (unidirectional jute combined with bidirectional banana), which offers an optimal equilibrium between stiffness and ductility. the unidirectional jute layer provided significant stiffness and directional strength, enabling the composite to withstand initial deformation. the bidirectional banana layer, exhibiting enhanced flexibility and ductility, absorbed and diffused impact energy from various directions, therefore mitigating fracture development. this combination mitigated premature brittle failure and facilitated increased overall energy absorption. similar trends have been documented by bhati et al. [25]. table 5 demonstrates the impact strength of the fiber composites utilized in this experiment. sample fiber orientation tensile strength (mpa) s1 j(bi)-b(bi) 45.2488 s2 j(bi)-b(uni) 43.1278 s3 j(uni)-b(bi) 47.3699 s4 j(uni)-b(uni) 53.7211 s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 18 figure 19. effect on the impact strength of fabricated fiber composites table 5. impact strength of fabricated fiber composites 3.3 hardness test figure 20 reveals how fiber orientation affects the hardness of hybrid jute banana fiber composites. the highest hardness recorded was 58 in sample 4, which consists of a mixture of jute and banana fiber, featuring both unidirectional orientations. hardness quantifies the ability to withstand surface deformation. the unidirectional configuration of fibers in sample 4 presumably produces a more homogeneous and dense fiber distribution. this architecture also facilitates an increased fiber volume fraction, which contributes to decreased void volume and porosity, restricting the surface's capacity to flex under stress. a parallel pattern of increasing hardness values with 40 wt%, both unidirectional fiber orientations, has also been observed by devireddy et al. [23]. table 6 demonstrates the hardness of the fiber composites tested in this experiment. table 6. hardness of fabricated fiber composites figure 20. effect on hardness of fabricated fiber composites 3.4 water absorption figure 21 depicts the impact of fiber orientation on the water absorption of fiber composites. the optimum combination of jute and banana fiber, with jute oriented unidirectionally and banana oriented bidirectionally, resulted in the lowest water absorption of 0.79% in sample 3. as the jute fibers exhibit a unidirectional orientation, resulting in a reduced number of fiber ends being exposed on both the surface and the cut edges. the fibers are aligned in a single direction, resulting in only their ends being directly exposed to water. the resin coating on the sides of the fibers impedes the absorption of water. on the opposite side, the bidirectional banana fibers may have functioned as a woven shield, exhibiting slightly lower hydrophilicity than jute due to an increased lignin and wax content, thereby diminishing direct moisture penetration through the surface. previous studies have also seen a tendency that is almost identical to this one [26]. table 7 presents the water absorption of the fiber composites tested in this experiment. figure 21. effect of fiber orientation water on absorption of fabricated fiber composites sample id fiber orientation impact strength (kj/m2) s1 j(bi)-b(bi) 9.74 s2 j(bi)-b(uni) 12.97 s3 j(uni)-b(bi) 30.86 s4 j(uni)-b(uni) 21.87 sample id fiber orientation rockwell hardness number (hrm) s1 j(bi)-b(bi) 55 s2 j(bi)-b(uni) 49 s3 j(uni)-b(bi) 53 s4 j(uni)-b(uni) 58 s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 19 table 7. water absorption of fabricated fiber composites 3.5 density figure 22 presents the impact of fiber orientation on the water absorption of fiber composites. the maximum experimental density and minimum void content were found in sample 4, which are 1.232 g/cm3 and 2.438% respectively. the increased density and reduced void content in sample 4 can be attributed to the structural configuration of the fibers and the consequent resin infiltration properties. in sample 4, jute and banana fibers are oriented unidirectionally, facilitating a more homogeneous and compact configuration devoid of interlacing points. this configuration creates linear, uninterrupted fiber pathways that may be more efficiently saturated by the resin during hand lay-up, hence diminishing air entrapment and minimizing void occurrence. voids are air-filled cavities that reduce composite density and degrade mechanical characteristics. the minimum void fraction in the sample indicates a more compact composite structure. the integration of optimal fiber packing and minimum air infiltration elucidates why sample 4 attains both the greatest density and the least void content. table 8 represents the density and void content of fiber composites. figure 22. effect of fiber orientation on experimental density and void content of fabricated fiber composites table 8. hardness of fabricated fiber composites 4. conclusion this study evaluated the effects of fiber orientation, including unidirectional and bidirectional, on the physical and mechanical properties of jute/banana fiber reinforced epoxy composites. it addresses theoretical and experimental density, void content, water absorption, tensile strength, impact resistance, and hardness as the physical and mechanical properties by varying fiber orientation in the matrix. key findings indicated that fiber orientation has increased effects on tensile strength, hardness, and impact resistance; however, it has a decreased effect on void formation in the composite matrix. among all the tested samples, having both jute and banana fiber in unidirectional orientation (s4) exhibits higher tensile strength (53.72 mpa), and hardness (58 hrm) while having lower void contents (2.44%) in the composite matrix. additionally, the sample having jute fiber in unidirectional and banana fiber in bidirectional orientation (s3) shows higher impact resistance (30.86 kj/m2) than other orientations while maintaining minimum hydrophilicity (0.79%). applying these composites, sample 4 (s4) composites can be used in a scenario where the strength and hardness of materials are desired, such as a motorcycle helmet, a car, and an airplane body. similarly, sample 3 (s3) can be used in high-impact applications, such as helmet production. sample 3 exhibits minimal water absorption; therefore, it can be used as a skimmer surface material for oil/water separation. this research acknowledges limitations, including the formation of defects on the composite-matrix surface due to the unequal pressure distribution during fabrication by the hand layup method. future research should focus on using a nanofiller that can reduce the void in the composite matrix. additionally, the chemical treatment of fibers and the orientation of fibers should not be limited to horizontal and vertical directions. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. sample id fiber orientation water absorption (%) s1 j(bi)-b(bi) 0.87 s2 j(bi)-b(uni) 1.38 s3 j(uni)-b(bi) 0.79 s4 j(uni)-b(uni) 1.17 sample id fiber orientation theoretical density (g/cc) experimental density (g/cc) void conte nt (%) s1 j(bi)-b(bi) 1.263 1.218 3.595 s2 j(bi)-b(uni) 1.227 2.819 s3 j(uni)-b(bi) 1.225 3.006 s4 j(uni)b(uni) 1.232 2.438 s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 20 references [1] k. mylsamy and i. rajendran, “the mechanical properties, deformation and thermomechanical properties of alkali treated and untreated agave continuous fibre reinforced epoxy composites,” mater. des., vol. 32, no. 5, pp. 3076–3084, may 2011, doi: 10.1016/j.matdes.2010.12.051. 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[6] d. shanmugam and m. thiruchitrambalam, “static and dynamic mechanical properties of alkali treated unidirectional continuous palmyra palm leaf stalk fiber/jute fiber reinforced hybrid polyester composites,” mater. des., vol. 50, pp. 533–542, sep. 2013, doi: 10.1016/j.matdes.2013.03.048. [7] n. venkateshwaran and a. elayaperumal, “banana fiber reinforced polymer composites a review,” j. reinf. plast. compos., vol. 29, no. 15, pp. 2387–2396, aug. 2010, doi: 10.1177/0731684409360578. [8] v. s. srinivasan, s. rajendra boopathy, d. sangeetha, and b. vijaya ramnath, “evaluation of mechanical and thermal properties of banana–flax based natural fibre composite,” mater. des., vol. 60, pp. 620–627, aug. 2014, doi: 10.1016/j.matdes.2014.03.014. [9] m. jannah, m. mariatti, a. abu bakar, and h. p. s. abdul khalil, “effect of chemical surface modifications on the properties of woven bananareinforced unsaturated polyester composites,” j. reinf. plast. compos., vol. 28, no. 12, pp. 1519–1532, jun. 2009, doi: 10.1177/0731684408090366. [10] m. boopalan, m. niranjanaa, and m. j. umapathy, “study on the mechanical properties and thermal properties of jute and banana fiber reinforced epoxy hybrid composites,” compos. part b eng., vol. 51, pp. 54–57, aug. 2013, doi: 10.1016/j.compositesb.2013.02.033. [11] s. parbin, n. k. waghmare, s. k. singh, and s. khan, “mechanical properties of natural fiber reinforced epoxy composites: a review,” procedia comput. sci., vol. 152, pp. 375–379, 2019, doi: 10.1016/j.procs.2019.05.003. [12] x. chen, s. chen, z. xu, j. zhang, m. miao, and d. zhang, “degradable and recyclable bio-based thermoset epoxy resins,” green chem., vol. 22, no. 13, pp. 4187– 4198, 2020, doi: 10.1039/d0gc01250e. [13] a. k. bledzki, m. urbaniak, a. boettcher, c. berger, and r. pilawka, “bio-based epoxies and composites for technical applications,” key eng. mater., vol. 559, pp. 1–6, jun. 2013, doi: 10.4028/www.scientific.net/kem.559.1. [14] a. gopinath, m. s. kumar, and a. elayaperumal, “experimental investigations on mechanical properties of jute fiber reinforced composites with polyester and epoxy resin matrices,” procedia eng., vol. 97, pp. 2052–2063, 2014, doi: 10.1016/j.proeng.2014.12.448. [15] m. rezaur rahman, m. hasan, m. monimul huque, and m. nazrul islam, “physico-mechanical properties of jute fiber reinforced polypropylene composites,” j. reinf. plast. compos., vol. 29, no. 3, pp. 445–455, feb. 2010, doi: 10.1177/0731684408098008. [16] m. idicula, a. boudenne, l. umadevi, l. ibos, y. candau, and s. thomas, “thermophysical properties of natural fibre reinforced polyester composites,” compos. sci. technol., vol. 66, no. 15, pp. 2719–2725, dec. 2006, doi: 10.1016/j.compscitech.2006.03.007. [17] sachin s. harak et al., “experimental study on the mechanical properties of hybrid areca and abaca fiber reinforced polymer composites,” j. environ. nanotechnol., vol. 13, no. 4, pp. 92–101, dec. 2024, doi: 10.13074/jent.2024.12.244977. [18] k. c. sekhar, m. s. kumar, c. polayya, and y. kowshikji, “investigating the influence of water absorption and mechanical properties of composites reinforced with banana and roselle fibers,” int. j. res. appl. sci. eng. technol., vol. 11, no. 3, pp. 2214–2220, mar. 2023, doi: 10.22214/ijraset.2023.49940. [19] r. venkatesh, s. raghuvaran, m. vivekanandan, c. r. kannan, t. thirugnanasambandham, and a. murugan, “evaluation of thermal adsorption and mechanical behaviour of intralaminar jute/sisal/e-glass fibrebonded epoxy hybrid composite as an insulator,” adsorpt. sci. technol., vol. 2023, p. 9222562, jan. 2023, doi: 10.1155/2023/9222562. [20] v. ganasan et al., “mechanical, moisture absorption and thermal stability of banana fiber/egg shell powder-based epoxy composites,” in the international conference on processing and performance of materials (icppm 2023), basel switzerland: mdpi, jan. 2024, p. 11. doi: 10.3390/engproc2024061011. [21] x. li, l. g. tabil, and s. panigrahi, “chemical treatments of natural fiber for use in natural fiberreinforced composites: a review,” j. polym. environ., vol. 15, no. 1, pp. 25–33, feb. 2007, doi: 10.1007/s10924-006-0042-3. [22] m. m. hasan, m. a. islam, and t. hassan, “analysis of jute-glass fiber reinforced epoxy hybrid composite,” heliyon, vol. 10, no. 24, p. e40924, 2024, doi: https://doi.org/10.1016/j.heliyon.2024.e40924. [23] s. b. r. devireddy and s. biswas, “physical and mechanical behavior of unidirectional banana/jute fiber reinforced epoxy based hybrid composites,” polym. compos., vol. 38, no. 7, pp. 1396–1403, jul. 2017, doi: https://doi.org/10.1002/pc.23706. s. ahmed et al. /future sustainability february 2026| volume 04 | issue 01 | pages 10-21 21 [24] m. prashanth b h, p. s. s. gouda, t. s. manjunatha, n. r. banapurmath, and a. edacheriane, “understanding the impact of fiber orientation on mechanical, interlaminar shear strength, and fracture properties of jute–banana hybrid composite laminates,” polym. compos., vol. 42, no. 10, pp. 5475–5489, oct. 2021, doi: https://doi.org/10.1002/pc.26239. [25] rajkumar bhati, anant prakash agrawal, shahazad ali, and abdhesh kumar, “synthesis and mechanical characterization of banana-hemp reinforced epoxy composites: influence of fiber orientation,” j. elastomers plast., vol. 57, no. 4, pp. 559–579, mar. 2025, doi: 10.1177/00952443251327735. [26] b. dev et al., “mechanical properties of unidirectional banana/snake plant fiber-reinforced epoxy hybrid composites: experimental and numerical analyses,” polym. bull., vol. 82, no. 8, pp. 3145–3174, 2025, doi: 10.1007/s00289-025-05658-x. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ 1. introduction research and engineering have shifted their attention in recent decades from conventional materials to composite materials. although glass and carbon fiber reinforcement are the most popular, natural fiber has been the subject of study by various acad... the main purpose of reinforcement in composite materials is to boost the mechanical properties of the plain resin system. every other fiber used in composites has unique features that affect the composite properties in various ways. different kinds of... table 1. physical properties of natural fibers [4] table 2. chemical components of natural fibers [5] b. shivamurthy et al. [5] found the physical characteristics of epoxy composites reinforced with jute fibers. using alkali-treated fibers and cashew nut shell liquid blended epoxy resins, including feasibility testing utilizing tensile and flexural st... research by m. jannah et al. [9] showed that chemically treated banana fiber composites exhibited lower water absorption compared to untreated banana fiber composites. compared to untreated banana fiber, treated banana fiber has greater flexural and i... the research of harak et al. revealed that the mechanical properties of hybrid composites, particularly flexural, tensile, and impact characteristics, were considerably enhanced with a composition of 76% abaca fiber, 20% areca fiber, and 4% nano-sio₂,... 2. materials and methods 2.1 materials in bangladesh, jute is known as the "golden fiber," and the indian subcontinent is where it is most well-known. jute fiber is a type of natural fiber that is abundantly produced on the indian subcontinent. in addition to producing the delectable fruit... a) jute fiber a) banana fiber figure 1. natural fibers for reinforcement 2.2 fabrication of composite fiber extraction, fiber chemical treatment, fiber orientation into the matrix, and composite fabrication method all have an impact on a composite's mechanical and thermal properties (figure 2). in this experiment, hybrid banana fiber reinforcement com... figure 2. composite fabrication flowchart the hydrophilic characteristics of natural fibers and the hydrophobic properties of the polymer matrix are the main fundamental problems with using natural materials as a reinforcing agent for polymer composites. these problems affect the mechanical p... (a) (b) figure 3. chemical treatment of jute and banana fiber: (a) jute fiber in naoh solution, (b) banana fiber in naoh solution fiber alignment affects the geometry of the mold cavity as the injected material flows through the mold, which directly affects mechanical properties. fiber orientation in a composite refers to how individual fibers are placed in a fiber-reinforced po... table 3. orientation and percentage of fiber in composites a) j(bi)-b(bi) b) j(bi)-b(uni) c) j(uni)-b(bi) d) j(uni)-b(uni) figure 4. schematic drawing of different fiber orientations (orange color line – jute fiber, blue color line – banana fiber) by traditional hand lay-up light compression molding technique, different orientations of epoxy-based hybrid fiber composites with 30 wt% of banana and jute fiber, maintaining a 1:1 ratio of jute and banana fibers, were produced. two different types o... 2.3 tensile test using an instron tensile tester, the tensile characteristics of bidirectional and unidirectional hybrid composites were determined. the test was carried out by astm d638. four specimens were tested, and the results were reported. a universal testing m... 2.4 hardness test rockwell is a scale for determining the hardness of a material based on the indentation hardness. a penetration of an indenter under a major load is compared to the penetration under a minor load to measure this test. different scales are used for dif... figure 5. hybrid composite laminate figure 6. 2d drawing of tensile test specimen figure 7. 3d design of tensile test specimen figure 8. universal testing machine figure 9. specimens before the tensile test figure 10. specimens after the tensile test the rockwell hardness can be calculated using the following formula: hardness = (n-hd) (1) where, d = depth in mm, h and n are the scale factors which depend on the scale on which the test is carried out. in this study, scale m was used, with an indenter diameter of 6.35mm, and the major load was 100kg (figure 11). figure 11. hardness testing machine 2.5 impact test the impact test is a technique used to evaluate material toughness, impact strength, and notch sensitivity. the impact test determines the amount of impact a material can withstand. impact testing often falls into one of two categories. the charpy imp... impact strength = ,,𝑚𝑔𝑅,,cos-𝛽−,cos-𝛼...-𝐴.. (2) where m = mass of the pendulum (kg) r= radius of pendulum g = gravitational acceleration (ms-2) α= rise angle (degree) β= fall angle(degree) a = cross-sectional area of the specimen (m2) figure 12 and figure 13 illustrate the 2d and 3d drawings of the impact test specimen, respectively. additionally, the charpy impact testing machine and the specimens before and after the impact tests are shown in figures 14-16. figure 12. 2d drawing of impact test specimen figure 13. 3d design of impact test specimen figure 14. charpy impact testing machine figure 15. specimens before the impact test figure 16. specimens after the impact test 2.6 density the water immersion method was used to calculate the experimental density ,,𝜌-𝑒𝑥.. of every composite sample. the following equation was used to measure the theoretical density ,,𝜌-𝑡ℎ.. [24]. 3. result and discussion 3.1 tensile test the influence of fiber orientation on the tensile strength of the fiber composites is shown in figure 18. the maximum tensile strength, 53.7211 mpa, was found in sample 4, which is the combination of jute and banana fiber with both unidirectional orie... 3.2 impact test figure 19 demonstrates the effect of fiber orientation on the impact strength of fiber composites. the maximal impact strength of 30.86 kj/m² was observed in sample 3, which comprises unidirectional jute fiber and bidirectional banana fiber. this res... 3.3 hardness test figure 20 reveals how fiber orientation affects the hardness of hybrid jute banana fiber composites. the highest hardness recorded was 58 in sample 4, which consists of a mixture of jute and banana fiber, featuring both unidirectional orientations. ha... 3.4 water absorption figure 21 depicts the impact of fiber orientation on the water absorption of fiber composites. the optimum combination of jute and banana fiber, with jute oriented unidirectionally and banana oriented bidirectionally, resulted in the lowest water abs... 3.5 density figure 22 presents the impact of fiber orientation on the water absorption of fiber composites. the maximum experimental density and minimum void content were found in sample 4, which are 1.232 g/cm3 and 2.438% respectively. the increased density and ... 4. conclusion this study evaluated the effects of fiber orientation, including unidirectional and bidirectional, on the physical and mechanical properties of jute/banana fiber reinforced epoxy composites. it addresses theoretical and experimental density, void cont... ethical issue the manuscript contains all the data. however, more data will be available upon request from the authors. conflict of interest the authors declare no potential conflict of interest. references [1] k. mylsamy and i. rajendran, “the mechanical properties, deformation and thermomechanical properties of alkali treated and untreated agave continuous fibre reinforced epoxy composites,” mater. des., vol. 32, no. 5, pp. 3076–3084, may 2011, doi: 1... [2] j. stanzione and j. la scala, “sustainable polymers and polymer science: dedicated to the life and work of richard p. wool,” j. appl. polym. sci., vol. 133, no. 45, dec. 2016, doi: 10.1002/app.44212. [3] l. kerni, s. singh, a. patnaik, and n. kumar, “a review on natural fiber reinforced composites,” mater. today proc., vol. 28, pp. 1616–1621, 2020, doi: 10.1016/j.matpr.2020.04.851. [4] t. sathishkumar, p. navaneethakrishnan, s. shankar, r. rajasekar, and n. rajini, “characterization of natural fiber and composites – a review,” j. reinf. plast. compos., vol. 32, no. 19, pp. 1457–1476, oct. 2013, doi: 10.1177/0731684413495322. [5] b. shivamurthy, n. naik, b. h. s. thimappa, and r. bhat, “mechanical property evaluation of alkali-treated jute fiber reinforced bio-epoxy composite materials,” mater. today proc., vol. 28, pp. 2116–2120, 2020, doi: 10.1016/j.matpr.2020.04.016. [6] d. shanmugam and m. thiruchitrambalam, “static and dynamic mechanical properties of alkali treated unidirectional continuous palmyra palm leaf stalk fiber/jute fiber reinforced hybrid polyester composites,” mater. des., vol. 50, pp. 533–542, sep. ... [7] n. venkateshwaran and a. elayaperumal, “banana fiber reinforced polymer composites a review,” j. reinf. plast. compos., vol. 29, no. 15, pp. 2387–2396, aug. 2010, doi: 10.1177/0731684409360578. [8] v. s. srinivasan, s. rajendra boopathy, d. sangeetha, and b. vijaya ramnath, “evaluation of mechanical and thermal properties of banana–flax based natural fibre composite,” mater. des., vol. 60, pp. 620–627, aug. 2014, doi: 10.1016/j.matdes.2014.0... [9] m. jannah, m. mariatti, a. abu bakar, and h. p. s. abdul khalil, “effect of chemical surface modifications on the properties of woven banana-reinforced unsaturated polyester composites,” j. reinf. plast. compos., vol. 28, no. 12, pp. 1519–1532, ju... [10] m. boopalan, m. niranjanaa, and m. j. umapathy, “study on the mechanical properties and thermal properties of jute and banana fiber reinforced epoxy hybrid composites,” compos. part b eng., vol. 51, pp. 54–57, aug. 2013, doi: 10.1016/j.composites... [11] s. parbin, n. k. waghmare, s. k. singh, and s. khan, “mechanical properties of natural fiber reinforced epoxy composites: a review,” procedia comput. sci., vol. 152, pp. 375–379, 2019, doi: 10.1016/j.procs.2019.05.003. [12] x. chen, s. chen, z. xu, j. zhang, m. miao, and d. zhang, “degradable and recyclable bio-based thermoset epoxy resins,” green chem., vol. 22, no. 13, pp. 4187–4198, 2020, doi: 10.1039/d0gc01250e. [13] a. k. bledzki, m. urbaniak, a. boettcher, c. berger, and r. pilawka, “bio-based epoxies and composites for technical applications,” key eng. mater., vol. 559, pp. 1–6, jun. 2013, doi: 10.4028/www.scientific.net/kem.559.1. [14] a. gopinath, m. s. kumar, and a. elayaperumal, “experimental investigations on mechanical properties of jute fiber reinforced composites with polyester and epoxy resin matrices,” procedia eng., vol. 97, pp. 2052–2063, 2014, doi: 10.1016/j.proeng.... [15] m. rezaur rahman, m. hasan, m. monimul huque, and m. nazrul islam, “physico-mechanical properties of jute fiber reinforced polypropylene composites,” j. reinf. plast. compos., vol. 29, no. 3, pp. 445–455, feb. 2010, doi: 10.1177/0731684408098008. [16] m. idicula, a. boudenne, l. umadevi, l. ibos, y. candau, and s. thomas, “thermophysical properties of natural fibre reinforced polyester composites,” compos. sci. technol., vol. 66, no. 15, pp. 2719–2725, dec. 2006, doi: 10.1016/j.compscitech.200... [17] sachin s. harak et al., “experimental study on the mechanical properties of hybrid areca and abaca fiber reinforced polymer composites,” j. environ. nanotechnol., vol. 13, no. 4, pp. 92–101, dec. 2024, doi: 10.13074/jent.2024.12.244977. [18] k. c. sekhar, m. s. kumar, c. polayya, and y. kowshikji, “investigating the influence of water absorption and mechanical properties of composites reinforced with banana and roselle fibers,” int. j. res. appl. sci. eng. technol., vol. 11, no. 3, p... [19] r. venkatesh, s. raghuvaran, m. vivekanandan, c. r. kannan, t. thirugnanasambandham, and a. murugan, “evaluation of thermal adsorption and mechanical behaviour of intralaminar jute/sisal/e-glass fibre-bonded epoxy hybrid composite as an insulator... [20] v. ganasan et al., “mechanical, moisture absorption and thermal stability of banana fiber/egg shell powder-based epoxy composites,” in the international conference on processing and performance of materials (icppm 2023), basel switzerland: mdpi, ... [21] x. li, l. g. tabil, and s. panigrahi, “chemical treatments of natural fiber for use in natural fiber-reinforced composites: a review,” j. polym. environ., vol. 15, no. 1, pp. 25–33, feb. 2007, doi: 10.1007/s10924-006-0042-3. [22] m. m. hasan, m. a. islam, and t. hassan, “analysis of jute-glass fiber reinforced epoxy hybrid composite,” heliyon, vol. 10, no. 24, p. e40924, 2024, doi: https://doi.org/10.1016/j.heliyon.2024.e40924. [23] s. b. r. devireddy and s. biswas, “physical and mechanical behavior of unidirectional banana/jute fiber reinforced epoxy based hybrid composites,” polym. compos., vol. 38, no. 7, pp. 1396–1403, jul. 2017, doi: https://doi.org/10.1002/pc.23706. [24] m. prashanth b h, p. s. s. gouda, t. s. manjunatha, n. r. banapurmath, and a. edacheriane, “understanding the impact of fiber orientation on mechanical, interlaminar shear strength, and fracture properties of jute–banana hybrid composite laminate... [25] rajkumar bhati, anant prakash agrawal, shahazad ali, and abdhesh kumar, “synthesis and mechanical characterization of banana-hemp reinforced epoxy composites: influence of fiber orientation,” j. elastomers plast., vol. 57, no. 4, pp. 559–579,... [26] b. dev et al., “mechanical properties of unidirectional banana/snake plant fiber-reinforced epoxy hybrid composites: experimental and numerical analyses,” polym. bull., vol. 82, no. 8, pp. 3145–3174, 2025, doi: 10.1007/s00289-025-05658-x. deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 35 review an overview of the sustainability of emerging energy technologies in mitigating climate change deven barton* department of mechanical engineering, arkansas tech university, 1811 n boulder ave, russellville, ar, 72801, usa a r t i c l e i n f o article history: received 10 april 2025 received in revised form 16 may 2025 accepted 30 may 2025 keywords: renewable energy, fossil fuel, carbon capture, climate change *corresponding author email address: dbarton5@atu.edu doi: 10.55670/fpll.fusus.3.3.5 a b s t r a c t the increasing reliance on fossil fuels has led to unprecedented levels of greenhouse gas emissions, environmental degradation, and public health risks. this paper explores renewable energy technologies and carbon capture methods as essential strategies for mitigating climate change and transitioning toward a low-carbon future. this paper evaluates the carbon emissions associated with various renewable sources, including solar, wind, hydropower, geothermal, and biomass, considering their full life cycles and regional variations. the paper also examines the role of carbon capture technologies, battery storage, smart grids, decentralized systems, and blockchain innovations in enhancing energy resilience and reducing emissions. while renewable energies significantly reduce carbon output compared to traditional fuels, the analysis highlights that no energy system is without environmental consequences. policy support, technological advancements, and coordinated infrastructure improvements are identified as critical factors for successful large-scale adoption. through integrated approaches that combine clean energy production, carbon management, and modernized energy systems, a sustainable and equitable energy transition is achievable. 1. introduction carbon dioxide (co₂) emissions are directly linked to the use and combustion of fossil fuels. the applications of petroleum, coal, and natural gas are convenient, reliable, and widely accepted worldwide. it is undeniable that the world is reliant upon these types of energies and fuels. the most attractive feature of these energies is the ability to be generated and used irrespective of the current state of the weather and its current availability. petroleum can be accessed by drilling rigs twenty-four hours a day, seven days a week, throughout the year, and will last for approximately thirty years or more. despite their popularity, nonrenewable energies are directly correlated to the increase of greenhouse gas emissions, destruction of the environment, and pollution of the air and land. burning natural gas releases methane, which is 28% more harmful to the atmosphere than co₂ [1]. the annual national oceanic and atmospheric administration (noaa) has a global monitoring lab, and it collects data in over 80 different locations offshore to test the amount of greenhouse gases present in ambient air. the report indicates that the global average atmospheric co₂ was 426.15 parts per million (ppm) in march 2025. this is the highest ppm recorded, with a two ppm increase for 12 consecutive years. mauna loa observatory in hawaii recorded 421 ppm, which closely supported the data collected by the noaa (figure 1) [2]. continuing to overconsume nonrenewable energy sources without integrating sustainable energy will continue to exhaust supply sources, and greenhouse gas emissions will increase to unsustainable amounts, further affecting climate change and pollution. pollution alone should be evidence that the globe's overconsumption of fossil fuels should be limited. according to the world health organization, nearly 99 percent of the world's population breathes unhealthy air. more than 13 million people die annually from preventable environmental causes, including air pollution [3]. the combustion of fossil fuels generates fine particulate matter and nitrogen dioxide. in 2018, it was reported that air pollution from fossil fuels caused upwards of $8 billion in health and economic losses [4]. the increase in energy demand from these types of fuels has also led to energy shortages from overconsumption and increased production, accounting for the release of nearly 75% of all greenhouse gas emissions and 90% of co₂ and causing the most significant proponent of climate change and increase of the world temperature, and extreme weather conditions [5]. figure 2 illustrates the correlation between co₂ emissions and temperature increases, highlighting future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.3.5 august 2025| volume 03 | issue 03 | pages 35-46 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:dbarton5@atu.edu https://doi.org/10.55670/fpll.fusus.3.3.5 https://fupubco.com/fusus deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 36 carbon emissions as one of the most significant contributors to climate change. figure 1. results of the noaa atmospheric co₂ in ppm from 1960 to march 2025 [2] figure 2. the correlation between co₂ emissions and temperature increases 2. renewable energy sources renewable energy sources are a cornerstone of climate change mitigation and decarbonization efforts. by 2030, renewables could provide 65% of the world's electricity supply. by 2050, they could decarbonize 90% of the electricity industry [6], significantly reducing carbon emissions and mitigating climate change. future demands for sustainable energy are becoming increasingly popular. their ability to generate renewable energy worldwide from 2000 to 2021 increased from 754 gigawatts to 3064 gigawatts [7], which shows substantial improvement in development. 2.1 solar energy solar power is consistently among the most popular renewable energy sources and is one of the cheapest and most environmentally friendly. solar heating methods include converting sunlight directly into usable energy using solar heating, building, and photovoltaic systems without emitting co₂ during production. global expansion and usage of solar power have increased significantly, with solar photovoltaic capacity reaching 843 gigawatts by 2021. this has nearly increased 21 times since 2010 [8]. growth has been encouraged mostly due to supportive policies, technology improvements, and broad urban and industrial applications. from a climate change mitigation perspective, solar power offers significant results and advantages. paris agreement's 1.5°c and other organizations use solar energy as a key role in decarbonizing their global electricity sector and remaining under the target emission goals. the international energy agency (iea) has projected that approximately 630 gw of solar pv capacity must be added annually by 2030 to achieve global net-zero goals by 2050. in countries like china, coal is a primary energy source, so carbon emissions are reduced through the integration of solar panel energy production. despite how attractive zero emissions are during solar production, considering solar panel lifecycles reveals that carbon emissions are still present when considering this alternative energy. although solar energy does not release carbon during operation, solar panels still possess carbon footprints during production, transportation, and disposal. assessing the life cycle of photovoltaic (pv) panels shows that manufacturing includes intensive mining and energy use in fossil fuel-reliant energy production areas. for example, the lifecycle carbon footprint of large-scale pv systems in china is estimated at 60.13 g co₂ per kilowatt-hour. the recycling stage adds another 5.81 g of co₂ per kilowatt-hour. in comparison, european-manufactured panels emit significantly less, but still 42.3 g of co₂ per kilowatt-hour during operation and only 1.0 g per kilowatt-hour during retirement because of cleaner energy usage. the emissions associated with chinese panels are nearly double due to the fossil-intensive electricity used in their production (figure 3) [9]. figure 3. the national accumulated and reduced carbon emissions of the whole lifecycle and the recycling stage based on the present technology in china and advanced technology in europe (eu), according to the accumulated pv panels installed in china during 2011–2020; unit: million tons (mt) [9] overall, the environmental impacts of solar energy vary by geography. factors such as sunlight availability, panel efficiency, and the local energy mix during production influence the total emissions. for example, china's solar panel carbon footprint was significantly higher in the northwest during the early adoption years. still, as installations expanded to the east, those regions became the leading carbon contributors due to increased distributed systems. poor coordination of recycling facilities, long transportation distances, and light rejection (wasted solar power due to overgeneration) also reduce carbon efficiency [9]. the economics of solar energy have significantly improved, making it competitive with conventional power sources. between 2010 and 2021, the global levelized cost of electricity for solar pv dropped 88%, from $0.417 to $0.048 per kilowatt hour. increases originate from technological advancements, mass production, and decreasing hardware costs. solar energy is often cheaper than fossil fuel-based energy, particularly when lifecycle environmental costs are considered. however, regional variations still exist. for instance, costs range from $0.041/kwh in china to $0.071/kwh in north america [8] due to differences in solar irradiance, land and labor costs, and policy support. china dominates global panel production and installation with 64% deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 37 of the crystalline silicon pv market, but it has also increased lifecycle emissions due to coal-based grids. despite the negative impacts solar panels and their production have on the environment, they are still gaining popularity and reducing carbon emissions during energy production to assist in climate change mitigation, especially in urban areas where energy loss and cost during transmission are minimal. when heating and cooling solar panels are installed in a metropolitan area, there are even fewer environmentally associated issues since they are installed on roofs and in smaller, more maintainable quantities with minimal transmission losses [9]. 2.2 wind energy wind energy is one of the fastest-growing sources of renewable power worldwide, offering a sustainable alternative to fossil fuel-based electricity generation. by converting the kinetic energy of moving air into mechanical power through turbines, wind systems produce electricity without direct carbon emissions. over recent decades, improvements in turbine technology and grid integration have significantly increased the efficiency and reliability of wind power. while wind energy contributes substantially to reducing greenhouse gas emissions, it is important to recognize that its full life cycle, from manufacturing and transportation to installation, maintenance, and disposal, does involve some carbon footprint. understanding these environmental impacts is crucial for evaluating wind energy’s true role in the transition to a low-carbon future. in denmark, one of the global leaders in wind power adoption, wind energy accounted for 47% of gross electricity consumption as of 2019. this makes denmark particularly insightful when considering the effects of wind energy on climate change mitigation. analysis estimated that for every one megawatthour of wind energy produced, about 0.16 tons of co₂ emissions are avoided [10]. since this was a dynamic econometric study versus an engineering-based study, the marginal emission avoided (mea) is lower. however, it reflects a more realistic relationship between wind energy and emissions in fundamental energy markets. it includes additional variables like electricity prices and emissions from biomass, reduces mea to account for the equilibrium effect, and highlights that substitutions of wind for fossil fuel energy are not one-to-one due to changes in demand and pricing. this study also found that, beyond emission reduction, wind energy is measured by demand variables. another study located in texas evaluates the emissions during lifetime cycles and takes into consideration different variables [11]. carbon emissions associated with wind turbines primarily arise from processes such as raw material extraction, manufacturing, transportation, installation, maintenance, and decommissioning. the total amount of carbon emitted over a turbine's lifetime depends on factors like turbine size, manufacturing location, operational location, and lifespan. the detailed life cycle assessment study of a 1.3 mw nordex n-60 wind turbine operating in the panhandle of texas found that over a 20-year operational lifespan, the turbine generated 467 tj of electricity while producing approximately 1,870.52 metric tons (mg) of co₂. these result in a carbon emission intensity of about 14.45 gco₂ per kilowatt-hour (kwh) of electricity generated. manufacturing processes alone accounted for around 41% of the total emissions, while raw material extraction contributed approximately 38%, transportation 16%, construction 4%, and overhead operations about 1% [11]. the largest key factors were turbine size, manufacturing location, and operational lifetime. wind energy is also notably resilient to the effects of climate change, allowing it to be a viable investment as the climate changes in the future. climate models project only modest changes in wind power output even under severe global warming scenarios. for example, while temperature increases may slightly affect air density and turbine efficiency, the overall production remains largely stable, particularly in regions like europe and north america. costs associated with wind energy have been significantly reduced throughout the advancement of technology. between 2010 and 2021, the global levelized cost of electricity for onshore wind fell by 68% from $0.089 to $0.028 per kilowatt hour [8]. this shows that wind energy is one of the cheapest sources available in recent years, especially in areas with high wind energy resources, with additional costs related to variability, storage, and backup generation. flexible grid infrastructure is critical as demand for wind energy rises. studies suggest that as wind energy availability increases, the demand for more energy overall could increase due to the low cost and further offset emission reductions [11]. ultimately, although wind turbines have associated carbon emissions throughout their lifecycle, their emission intensity remains substantially lower, around 98% lower [10] than coal-based electricity generation. understanding and minimizing the embedded carbon footprint becomes crucial for achieving low-carbon power generation as wind energy expands. wind energy also offers a cheap and effective way to reduce global carbon emissions. 2.3 hydroelectric power hydroelectric energy is among the largest and most advanced renewable energy sources globally. hydropower has long been regarded as a clean and renewable source of electricity, contributing substantially to global efforts to mitigate climate change. however, recent research suggests that hydropower's carbon footprint may be far larger than previously assumed. unlike fossil fuel plants, most emissions from hydroelectric reservoirs arise not from combustion, but from the biological decomposition of organic material submerged during the flooding of reservoirs [8, 12]. global assessments of nearly 1,500 hydroelectric facilities found that the average carbon footprint of hydropower is about 273 kg of co₂ eq per megawatt hour (mwh) of electricity produced. this footprint comprises 173 kg of co₂ emissions and 2.95 kg of methane per mwh, based on the 100-year global warming potential [12]. although these values are still lower than those associated with fossil fuel generation without carbon capture and storage, they are significantly higher than those for most other renewable energy sources. several factors are key in determining how much carbon a hydropower project emits. facilities that flood large land areas to produce relatively modest amounts of electricity tend to have the highest emissions, mainly because more submerged organic material decays over time. geography also determines several variables, including locations that are tropical reservoirs, typically emitting more methane, as warm temperatures speed up decomposition. the age of a reservoir influences emissions as well; methane release often decreases over time, although co₂ trends can vary. additionally, new organic material carried into the reservoir by rivers continues to fuel greenhouse gas emissions over its lifetime. there is a wide variation between different projects. some hydropower plants approach emission levels comparable to fossil fuel plants, primarily if they are located in vulnerable tropical environments or have large, flooded areas. on the positive side, certain reservoirs in the united states, india, and west deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 38 africa show strong potential for capturing methane emissions and using the gas as a supplementary energy source. hydropower remains one of the most cost-effective energy sources during operational lifecycles because of low operating and maintenance costs after initial investments in construction. however, these upfront capital costs during construction are significant, and the levelized costs of electricity increased from $0.039 in 2010 to $0.048 per kilowatt hour in 2021. this reflects a 24% increase in price within 11 years [8]. future uncertainty and long-term investments influence the planning and operation of current and future hydroelectric facilities. a study of the xiangjiaba hydropower plant in china reveals that climate change conditions could reduce average annual energy output by 30.7 twh [13]. additional variables compound the challenges of water reliance during droughts, extreme heat, and even floods, which are conditions fueled by climate change. 2.4 geothermal energy geothermal energy is often seen as a clean and reliable source of renewable power because it does not rely on burning fuels. however, the amount of carbon emissions associated with geothermal energy can vary quite a bit depending on where and how it is used. umar et al. [14] looked at the top seven geothermal energy-consuming countries and found that geothermal energy’s impact on carbon emissions varies significantly. in countries like italy, mexico, and new zealand, geothermal energy has reduced carbon emissions across various conditions. this shows that geothermal energy can be important for reducing a country’s overall carbon footprint if monitored and maintained correctly. on the other hand, geothermal energy was linked to increased carbon emissions in places like india, the united states, turkey, and the philippines. in these cases, geothermal systems may have unintentionally added to climate change rather than mitigating it. one crucial factor to consider is the gases found within individual geothermal reservoirs. some underground reservoirs naturally contain gases like co₂, which are released when the geothermal heat is brought to the surface. technology used at geothermal plants is another key factor. older plants, or those without systems to capture and manage gases, can release more emissions than newer, advanced facilities. it also depends on the type of energy the geothermal power is being utilized for. the environmental benefits are considerable if geothermal energy replaces coal or oil-fired electricity, but not as beneficial as another type of energy if it is an alternative source. the study also found that geothermal energy consistently affects carbon emissions trends across all the countries studied. this shows that geothermal energy plays an ongoing and essential role in shaping a country's overall emissions profile. even though geothermal energy generally emits far less carbon than fossil fuels, it is not completely emissions-free. to maximize its potential, countries must carefully manage where geothermal projects are built, invest in cleaner technologies, and update older infrastructure. with good planning, geothermal energy can continue to be an essential part of the shift to a lowcarbon future. implementation costs of geothermal locations are high due to expensive drilling to 4 to 6 kilometers below the earth's crust and exploration for geothermal reservoirs. lack of exploration and reservoir assessment tools also increases costs and operational risk, often leaving projects unsuccessful. for example, projects such as australia's cooper basin enhanced geothermal systems plant were discontinued because of poor reservoir permeability and fluid circulation issues [15]. technical difficulties and limitations combined with a lack of policy support often make geothermal projects less attractive and deter investors from more developed and widely accepted renewable energy sources like solar and wind. today, as many as 32 countries use this to generate electricity, heating, and cooling in residential and commercial applications reliably and affordably. in 2023, the capacity to generate electricity using geothermal applications reached 16,318 mw. however, this was only about .34% of all electricity produced worldwide. the initial setup and equipment can be costly despite the low operational cost. it becomes even less attractive to purchase and utilize this type of energy since it lacks government support policies and subsidies compared to wind and solar power. geothermal energy has favorable levelized energy costs, even though growth has been slower than other renewable energy sources [8]. long-term cost attractiveness is seen once geothermal plants are installed and operating at capacity factors of 70% to 90%, which exceeds intermittent sources and improves the long-term cost-benefit balance. 2.5 biomass and biofuels biomass is an organic material harvested from recently living or living organisms. this includes agricultural residues, forestry byproducts, and urban waste. feedstock can be various forms of bioenergy, such as bioethanol, biodiesel, biogas, and electricity, that are converted from various processes (figure 4). combustion, gasification, pyrolysis, and anaerobic digestion are all types of conversion methods from materials that would be considered waste. because the waste is used, it contributes to the circular lifecycle of co₂, making it a renewable alternative to fossil fuels [8]. figure 4. common biomass sources [16] biomass is a significant contributing factor to mitigating climate change because the co₂ produced during the combustion processes is absorbed and consumed by biomass during its growth cycle. this is considered a carbon-neutral process because of the consumption of the produced carbon. this carbon lifecycle is extremely short compared to the lifecycle of fossil fuel carbon, which is stored for millions of years and does not get consumed when released into the atmosphere. because of its carbon lifecycle span, bioenergy could significantly decarbonize the globe, which is essential for reducing the global temperature by 1.5 degrees celsius by deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 39 2050 [8]. biomass could also solve other sustainability goals, such as promoting rural energy independence and reducing landfill waste. the environmental sustainability of biomass depends on the feedstock sourcing and production practices. if not correctly maintained, biomass cultivation and conversion would generate air pollution and additional greenhouse gas emissions. particulate matter and nitrogen oxides will increase during combustion processes if they are not monitored or practiced correctly. additionally, as demand for biofuel grows, so does the demand for land use. increased land use demands may lead to deforestation, loss of biodiversity, and increased greenhouse gas emissions from harvesting methods. other concerns are soil integrity due to over-harvesting crops, water depletion from irrigation, and runoff from fertilizers, which could contribute to eutrophication in nearby water sources and collections [15]. climate change itself also threatens biomass's long-term effectiveness. reference [8] highlights that rainfall pattern irregularities, increases in temperatures, and increased risk of droughts can adversely affect biomass and the processes associated with growth, harvesting, and conversion. changes like these could alter the biochemical properties of feedstocks and disrupt lignocellulosic biorefineries by reducing biomass yields. a 1-degree celsius increase in global temperatures indicates that maize yields decrease by 7.4% and wheat yields by 6%. from an economic perspective, the cost of bioenergy has decreased, allowing it to be a competitive alternative to fossil fuels. global levelized cost of electricity for bioenergy dropped from $0.078 per kilowatt hour in 2010 to $0.067 in 2021. regional costs show that bioenergy is not consistent, though. costs range from $0.057 in india to $0.097 in north america. factors contributing to these cost variations include feedstock type and availability, conversion technology, transportation methods, and cost. for example, transportation in switzerland for biomass can cost from 24 to 340 francs per ton for different biomass types and transportation methods. unloading costs during this analysis accounted for approximately 65% of the total transportation costs. harvesting equipment costs also have significant variances based on type, affecting the overall cost of considering biomass as a viable energy source. studies from kenya and tanzania demonstrate that biomass used for cooking in improved biomass cookstoves lowers the life cycle costs per meal. through this study, biomass proves to be an excellent choice for areas that are not as developed and reduces the cost of meals that need to be cooked or heated. however, government policies in such areas tend to put royalties or fees on resources like charcoal, which drives up costs and makes biofuel less attractive as a cheap alternative energy source. the lack of policies favoring biomass and biofuels hinders the rapid growth and desire to incorporate infrastructure supporting this fuel type. biomass energy has promising potential to help support global climate change mitigation through carbon-balanced energy production. considering environmental risks, ensuring sustainable land use, and addressing cost challenges in certain regions are key to the long-term success of implementing biomass and biofuels into everyday life. through policy support and technology advancements, infrastructure upgrades could become more attainable and allow biomass to become a key component in lessening the effects of traditional fossil fuel emissions [16]. table 1 presents the carbon dioxide emissions or emission trends for solar, wind, hydropower, and geothermal energy sources based on case studies in various regions. values are reported either as specific emission intensities (gco₂/kwh or kgco₂e/mwh) or described qualitatively where numerical data was unavailable. table 1. summary of carbon emissions associated with different renewable energy sources across selected countries moreover, table 2 summarizes the 2021 installed costs per kilowatt and the levelized costs of electricity per kilowatthour for various renewable energy technologies, along with their percentage change in lcoe from 2010 to 2021. data highlight significant cost reductions for solar and wind technologies, while geothermal and hydropower exhibited modest increases over the same period [8]. analysis of each type of energy date and source country emissions notes fossil fuel march 2025 [2] worldwide 426.15 ppm of ambient air solar 2024 [9] china 5.81 g co2 eq/kwh (production) + 5.81 g co2eq/kwh (recycling) 3064 gigawatts 2021 worldwide [8] higher due to coal-reliant grid manufacturing solar 2024 [9] europe 42.3 g co2 eq/kwh (production) + 1.0 g co2eq/kwh (recycling) lower emissions than china due to cleaner energy manufacturing and transportation wind 2019 [10] denmark avoids 0.16 tons co₂/mwh marginal emission avoided (mea) accounting for the market effects wind 2020 [11] texas, usa 14.45 gco₂/kwh 1.3 mw nordex n-60 turbine, 20year lifespan hydropower 2016 [12] global average 273 kgco₂e/mwh based on 1,473 hydroelectric plants, includes co₂ and methane geothermal 2024 [14] india, usa, turkey, philippines reduces emissions no specific grams/kwh given, but trend: decreases co₂ geothermal 2024 [14] italy, mexico, new zealand increases emissions due to geological and operational factors deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 40 type of alternative energy shows that no one kind of energy production is without environmental consequences or carbon footprint. however, they all have some competitive advantages over fossil fuels and tend to limit greenhouse gas emissions. individually comparing each energy source to its previous years shows a decrease in cost as technology and understanding of their use advance. popularity, as well as the capacity to support alternative energies, is increasing. greenhouse gas emissions must be reduced with these technologies to aid climate change mitigation, but it is crucial to consider the processes in which these are harvested and harnessed. table 2. installed costs and levelized costs of electricity (lcoe) for major renewable energy sources in 2021 3. energy storage and grid integration grid integration is key to successfully utilizing all forms of energy produced. in addition to these challenges, most alternative energies are susceptible to environmental factors such as extreme weather and climate change. for energies produced by solar and wind, the challenge of inconsistent production occurs due to the limitations of the supply input. the grid system is designed to accommodate traditional fossil fuel-based power plants instead of renewable ones. renewable systems are also typically located further away from the areas that need larger electricity inputs, requiring energy storage technologies like lithium-ion batteries for storage, upgraded smart grids to create a more flexible and efficient grid, and economic policy or regulation to prevent backlash from high-profit fossil fuel plants. 3.1 battery storage and technologies batteries are essential for collecting and storing excess alternative energy for future use. for solar energy, battery storage can be utilized at night or on rainy days when the sun is not producing enough sunlight to keep a steady supply for consumers. for wind, it can store power for days when there is not enough wind. during floods and storms, hydroelectric power capacity increases, but capacity suffers during droughts and heat waves. using batteries and other storage methods is a solution to extreme weather conditions and possible outages to help build grid resilience. as grid demand increases, the use and need for batteries also increase. attractive qualities include backup power usage, black start services, and transition to decentralized systems, which are essential when considering sustainable energy integration [17]. batteries, especially lithium-ion batteries (libs), are increasingly important in addressing climate change. as the world shifts toward renewable energy systems and electric transportation, the demand for libs has skyrocketed. projections estimate that the global battery industry could see an annual growth rate of over 30% between 2022 and 2030, with the total market reaching more than $400 billion and a storage capacity of 4.7 terawatt-hours by the end of the decade [18]. while china will remain the dominant supplier, the fastest growth is projected in the u.s. and eu due to aggressive climate policies and supply chain localization. meeting this demand will require the construction of up to 150 new battery plants and a shift toward more sustainable, circular production models (figure 5) [19]. figure 5. projected global lithium-ion battery cell demand by region from 2022 to 2030 [19] batteries help mitigate climate change in a couple of significant ways. the first one is that they enable the electrification of transportation by powering electric vehicles (evs), reducing the carbon emissions of gasoline and diesel engines, and the second one is that they serve a vital role in grid energy storage. as solar, wind, and other renewable energy sources become more common, the grid increasingly needs storage solutions to balance supply and demand. used ev batteries are often repurposed for stationary storage applications and provide a cost-effective and sustainable way to support this transition [18]. however, the environmental impact of battery production and disposal remains a concern. many traditional manufacturing processes rely on a linear model: extracting raw materials, building batteries, and discarding them at the end of life. this approach leads to heavy resource depletion and environmental damage. in response, the industry is moving toward a circular economy model, where the focus is on recycling critical materials such as lithium, cobalt, and nickel, reusing batteries when possible, and minimizing waste. economically, circular strategies offer promising benefits. recycling batteries uses far less energy compared to mining and manufacturing from raw materials, resulting in lower emissions and cost savings. additionally, the emerging market for second-life batteries provides new renewable energy source installed cost (2021) ($/kw) levelized cost of electricity (lcoe) ($/kwh) % change in lcoe (2010– 2021) solar photovoltaics 857 0.048 −88% concentrated solar power 9091 0.114 −68% onshore wind 1325 0.033 −68% offshore wind 2858 0.075 −60% bioenergy 2353 0.067 −14% geothermal 3991 0.068 34% hydropower 2135 0.048 24% deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 41 economic opportunities while extending the useful life of valuable resources. governments and regulatory bodies are also starting to support these changes. for example, the european union's circular economy action plan (ceap) sets clear guidelines for battery reuse, recycling targets, and lifecycle management. a recent microgrid framework [20] integrates photovoltaic panels, wind turbines, battery storage, and hydrogen-based technologies, including electrolyzers, hydrogen storage tanks, and fuel cells, into a grid-connected platform. at the core of the system is a rulebased energy management strategy enhanced by the chimp optimization algorithm, which coordinates energy flow based on real-time grid pricing, seasonal resource availability, and changing demand conditions. simulation results show that the model achieves a cost of energy as low as $0.272 per kilowatt-hour. this particular system is more efficient than other tested optimization methods, such as the genetic algorithm and grey wolf optimizer. the system strategically balances short-term energy needs through battery storage while using hydrogen as a longer-term solution. this allows it to absorb excess solar and wind energy when production exceeds demand and dispatch it during periods of low generation, ensuring a continuous power supply and economic efficiency. this approach supports the principles of a circular economy, particularly in how it extends the usefulness of materials and reduces environmental impact. recycling batteries requires far less energy than mining and manufacturing from raw resources, resulting in lower emissions and cost savings. additionally, the growing market for second-life battery applications presents new economic opportunities and helps reduce waste. regulatory efforts such as the european union’s circular economy action plan are reinforcing this shift by establishing clearer guidelines for battery reuse, recycling, and lifecycle management. the future of batteries in climate change mitigation is projected to be even more successful when implemented. advances in recycling technologies like hydrometallurgy and direct cathode recycling are making materials easier to recover after their lifecycle use is completed. at the same time, efforts are being made to power battery production with renewable energy, further lowering the industry's carbon footprint. as these innovations take hold, batteries are set to become a central pillar of global efforts to achieve net-zero emissions by 2050 [17]. 3.2 grid modernization and decentralized systems smart grid utilizes two-way communication between consumers and suppliers to more accurately and closely monitor electricity usage. the new and advanced electrical grid versions will improve energy efficiency and reliability [17]. it acts as a helper during outages to help customers keep the power supply stable quickly and efficiently. smart grids will be apt for accommodating multiple sources of electricity to connect. however, implementation, operational, and maintenance costs will likely be high. entire infrastructures must be redesigned to accommodate the high increases in use of technology for sustainable energy integration (figure 6) [21]. the cost and effectiveness of smart grids in the long term should be evaluated so they can be implemented appropriately. microgrids are an alternative approach to help minimize blackouts and utilize more energy production types. they are generally more flexible, allowing diverse energy resources to connect and create smooth transmission to every place delivered. some renewable energy sources cannot power large systems, which can enhance the use of solar, wind, or other smaller electrical production. microgrids also isolate faulty areas and assist each section in connecting to immediate power supplies. integrating microgrids will improve the grid resilience of distribution centers and critical power loads during severe incidents. greater amounts of energy can be supplied to larger regions by allowing closely located loads, allowing power sources to be utilized in closer locations, reducing transmission losses, and minimizing power flows in transmission and distribution circuits. figure 6. functional layout of a smart grid system showing integrated communication between generation, distribution, and end-use sectors [22] deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 42 ideally, microgrids operate autonomously without exchanging power with other microgrids or primary grids. microgrids that fail will be able to connect to different types of grids to prevent further failures and ensure a continuous power supply to consumers during repairs, especially during emergencies such as extreme weather. 3.3 blockchain technology blockchain technology is another resource for implementing sustainable energy into the grid. blockchain technology operates through a decentralized ledger that records transactions permanently so they cannot be altered [23]. this enables transparency when monitoring transactions of energy production and consumption to all connections in a network. leveraging blockchain technology during projects helps to allow peer-to-peer energy trading from producers and consumers. this allows for tracking each type of energy source connected to the network for how much energy was produced, where it was produced and consumed, and who consumed it, all while facilitating innovative financing models for renewable energy projects. this technology helps bridge the gap between having multiple alternative energy sources and decentralized networks. an example of how this type of technology works could be analyzed through solar panels owned by a single consumer. when the panels generate excess electricity, they can be distributed to neighboring consumers utilizing blockchain smart contracts. neighbors can purchase additional electricity or energy produced, and the transaction will be recorded and stored in the transparent 'marketplace.' blockchain technology will also be a helpful tool for eliminating energy waste and improving the overall efficiency and reliability of renewable energies. several countries, heavily populated states, cities including new york, california, and a few european countries, have facilitated startups for these energy trading networks. other applications of blockchain that seem promising for sustainable energy applications are the use of renewable energy certification and tracking of the origin of the energy. renewable energy certificates fund projects with this technology by enabling companies and individuals to purchase renewable energy credits. despite enhanced sustainability in energy through blockchain technology, inefficient paperwork and high fees are levied. using renewable energy consumption on open blockchain platforms can remove costs associated with its use and simplify the process as a whole [23]. 4. carbon capture carbon capture and storage are critical in storing and reducing anthropogenic greenhouse gas emissions and mitigating climate change. carbon capture, utilization, and storage is abbreviated as ccus. by capturing co₂ emissions from sources such as coal-fired power plants, cement factories, steelworks, and refineries, carbon is intercepted before entering the atmosphere and transported in deep geological formations. organizations such as the intergovernmental panel on climate change and the international energy agency predict that carbon emissions are projected to achieve net-zero emissions by 2050 through essential carbon capture technologies. for carbon capture to be obtainable and cost-effective in climate change mitigation, widespread adoption is necessary. carbon capture can be a more attractive solution to greenhouse gas emissions than renewable energy sources due to land use efficiency. it reduces greenhouse gas emissions and completely removes their presence in the atmosphere. table 3 summarizes major carbon capture technologies, briefly describing each method and outlining its primary use or application in reducing industrial, energy-sector, or atmospheric carbon dioxide emissions [24]. table 3. overview of carbon capture methods and their applications 4.1 carbon capture methods several carbon capture methods are being developed and used in several countries through several projects. variations of methods are discussed. additional variables compound the challenges of water reliance during droughts, extreme heat, and even floods, which are conditions fueled by climate change [24]. post-combustion capture is a commonly used method that captures co₂ from flue gases after burning fossil fuels. amine-based solvent technologies like shell's cansolv and basf's aqueous anime process are used to pull co₂ from the exhaust of these fossil fuel-based plants. successful implementation of large-scale post-combustion carbon capture has been in canada at the saskpower boundary dam facility since 2014. another method used in the kemper country project, the precombustion capture method, is used to convert fuel into gas before combustion, which produces hydrogen and co₂ mixtures. co₂ is then separated from hydrogen, and the hydrogen is used to produce further energy. this method uses the integrated gasification combined cycle within power plants. oxyfuel combustion utilizes fuel that is burned by using only oxygen instead of air, resulting in a flue gas composed primarily of co₂ and water vapor, allowing co₂ to separate from the carbon capture method description use/application postcombustion capture captures co₂ from flue gases after fossil fuel combustion, often using amine-based solvents (e.g., shell’s cansolv, basf’s aqueous amine process) used in existing power plants, especially coal-fired plants (e.g., boundary dam in canada) precombustion capture converts fuel into a gas mixture of hydrogen and co₂ before combustion; co₂ is separated before burning used in integrated gasification combined cycle (igcc) plants (e.g., kemper county project) oxyfuel combustion burns fuel in pure oxygen instead of air, creating a flue gas of mostly co₂ and water vapor, making co₂ easier to capture used in specialized power plants designed for highpurity co₂ capture industrial carbon capture captures co₂ directly from industrial processes like hydrogen production, natural gas processing, and ethanol fermentation used in various industries to limit process emissions direct air capture (dac) removes co₂ directly from ambient air using chemical solutions or solid sorbents emerging technology aimed at atmospheric carbon removal; used for large-scale climate mitigation bioenergy with carbon capture and storage (beccs) captures co₂ during the combustion of biomass for energy production provides "negative emissions" by removing carbon dioxide while generating energy deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 43 mixture easily. another type of carbon capture is used during industrial processes to extract carbon from natural gas, hydrogen production, and ethanol fermentation. emerging technologies like direct air capture and bioenergy carbon capture are removing co₂ directly from the atmosphere, and when burning biomass for energy. 4.2 carbon capture storage after carbon is extracted using an existing method, it can be permanently stored in geological formations or depleted oil fields under the earth's surface. deep saline aquifers are seen as promising long-term storage solutions because of their large storage capacity and convenient locations near emission sources, minimizing the cost of transportation of these gases. several projects worldwide have utilized longterm storage techniques and used monitoring, measurement, and verification systems like 4d seismic imaging and pressure sensors to verify the safety associated with their storage technologies. although measures are taken to analyze the safety associated with carbon capture, it is still essential to identify risks related to carbon storage. the most significant risks are associated with geological storage and containment. leakage of carbon gases could cause improper seals, corrosion of seals, or collapses of underground formations, allowing co₂ to leak through small cracks. carbon could migrate upwards from excessive injection pressure or activate faults. earthquakes occurring independently of the effects of carbon storage could also impose the risk of altering formations in which the carbon is stored and allow leakage. even though sites that have nearby earthquakes, just as japanese carbon storage sites, have not experienced co₂ leaks, it does not mean that the possibility is not a dangerous consideration. it is essential that proper maintenance and monitoring of co₂-injected sites remain crucial. governments like the united states environmental protection agency have tried to regulate safety by enacting class vi rules for co₂ storage and pressure control. carbon capture is an innovative solution to reduce large-scale industrial carbon emissions. still, it must be enacted carefully by utilizing technology such as 4d seismic imaging, proper maintenance of equipment and sites, and monitoring of geological conditions through pressure management and well integrity. global projects have shown that co₂ can be effectively stored and contribute significantly to the climate with appropriate risk management, planning, and long-term monitoring (figure 7). 5. policy support renewable energy implementation relies heavily on policy support from local and national governments. a multinational longitudinal study covering 27 years and 138 countries confirmed that proactive and sustained government policies directly correlate with renewable energy growth and a corresponding decline in carbon emissions [24]. this relationship is especially evident in countries that tailor their policies to local infrastructure, economic structures, and energy needs. for example, in pakistan, targeted stakeholder engagement and public-private transparency have fostered successful renewable energy integration projects. other studies reinforce the importance of overcoming financial and policy barriers. in saudi arabia, nearly 70 percent of national energy consumption is tied to the residential sector. however, policy-related obstacles and cultural factors continue to hinder the deployment of renewables, despite clear potential for solar integration [8]. this highlights how regulatory frameworks, building codes, and financial incentives must evolve to enable energy-efficient technologies in emerging markets. figure 7. basic concept visualization of carbon capture [25] other examples of policy in europe are the european union's renewable energy directive (red iii), which mandates member states to increase the share of renewables in heating and cooling by 1.1 percentage points per year through 2030 [26]. when looking into the consequences of implementing such policies, it could be argued that the directive’s current energy accounting method inadvertently rewards inefficient heating systems. for instance, a wood fireplace with 50 percent efficiency receives more renewable “credit” under the red than a high-efficiency heat pump. this misalignment weakens incentives for cleaner technologies. to address this, the authors propose a shift to an efficiencybased metric that credits useful energy output rather than input, better aligning policies with decarbonization goals. meanwhile, other studies emphasize the importance of carbon pricing and green investment as essential policy levers across the eu. countries like germany, sweden, and spain have each committed tens of billions of euros toward renewable infrastructure, with germany alone planning over eur 1 trillion in green investments by 2050 [27]. these efforts are backed by frameworks such as the european green deal and national programs like germany’s “energiewende,” which prioritize the decarbonization of transport and building sectors through heat pump deployment, smart grids, and thermal retrofitting. considering different nations and regions, a one-size-fits-all approach will not succeed and inadvertently cause more harm by creating inefficient development in the energy and heating sectors. another global policy, net zero initiative [28] is a framework aimed at reducing greenhouse gas emissions to net zero by mid-century, meaning any remaining emissions are balanced by removals through technologies or natural processes. its primary purpose is to limit global warming to 1.5°c which is a goal of the paris agreement. by setting clear long-term targets, the initiative drives countries and industries to transition away from fossil fuels and invest in renewable energy infrastructure. national commitments to net zero are often paired with policy tools such as subsidies for clean energy, carbon pricing, and emissions regulations. these efforts accelerate the deployment of solar, wind, and other low-carbon technologies, making net zero not just a climate goal but a catalyst for transforming the global energy system. deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 44 6. projected future use of renewable energies as the globe inevitably shifts towards renewable energy, fossil fuel reliance and carbon emissions decrease. around 74% of the global energy share by 2050 will be produced by renewable energy sources, significantly higher than the 14% increase in 2018. climate mitigation, reduction in carbon emissions, and the desire to reduce fossil fuel dependence drive the surge in the implementation and technology of renewable energy. leading sources of this are projected to be wind and solar because of their affordability and ability to produce energy across diverse geographic locations. by the mid-century, about 90% of the electricity worldwide will be generated by renewable energy sources if policies and investments to accommodate infrastructure are implemented [8]. if this goal is successfully achieved, 90% of the electricity generation will be decarbonized. contributions of this significance towards climate change mitigation will help limit global carbon emissions and prevent warming to 1.5 degrees celsius above pre-industrial levels. technological advancements, grid integration, and policy support in solar photovoltaic installations could increase twentyfold by 2050. projections [29] from the international energy agency (iea), the global energy mix is expected to undergo a significant transformation by 2050. the u.s. government reports that projected carbon emissions are expected to decline up to 64% by 2040 [30]. while oil and natural gas are projected to remain dominant, comprising over 50 percent of total global energy consumption in exxonmobil’s forecast, the share of renewables such as wind, solar, hydro, and geothermal is anticipated to grow substantially, increasing more than fourfold to meet rising demand, particularly in developing economies [21]. in more climate-ambitious scenarios, such as the intergovernmental panel on climate change’s (ipcc) “likely below 2°c” pathway, renewables are projected to represent up to 30 percent of the global mix by 2050, signaling a dramatic shift toward decarbonization (figure 8). figure 8. the projected global energy mix in 2023 versus 2050 by exxonmobil presented in their executive summary. this includes exxon’s global outlook as well as the iea and ipcc outlooks [29] despite economic limitations within specific countries, renewable energy is becoming increasingly cost-effective. this makes the increase in the integration of renewable energies look optimistic in the future. awareness of the environmental harm caused by fossil fuels and carbon emissions also makes adopting renewable energy more attractive to developed and developing countries. energy demand is projected to grow by 80% by 2050 because of the increasing population growth and industrialization. the implementation of renewable energy is expected to fill large portions of the growing demand for electricity in areas such as transportation, construction, and manufacturing. however, transitional and least-developed countries will struggle to overcome barriers such as high initial capital costs, technological disadvantages, and limited policy support, making achieving lower emissions even more difficult. despite these barriers, these countries are still beginning to scale their investments into solar, wind, and biomass technologies and other renewable sources. as countries continue to implement supportive policies and invest in developing technologies, energy production will become dominated by renewables. 7. conclusions climate change isn't just a far-off worry but something the globe already experiences through the environment around us and the health of communities. the heavy reliance on fossil fuels has caused severe damage, pushing carbon emissions to dangerous levels, fueling stronger storms, and making clean air and safe drinking water more challenging, and even affecting human health. moving toward renewable energy isn't just about slowing down global warming. it is about protecting people's health, futures, and right to a livable planet. the technologies are already here: solar panels, wind farms, geothermal systems, and other new ways to store and share clean energy. the research shows that these solutions are becoming more affordable, smarter, and more beneficial for the planet than our current reliance on current fossil fuel technology and infrastructure. innovations like smart grids, microgrids, and blockchain technology offer a more organized and reliable way to produce and control energy. of course, no solution to combat climate change is perfect, and even renewable energies face specific challenges that must be carefully addressed. despite the existing challenges and the cost of failing to reform current energy policies and infrastructure, they will far outweigh the benefits of implementing renewable energies and technology far outweigh the risks. without strong leadership, innovative policies, and a genuine commitment to making the energy transition fair and accessible for all economic types, carbon emissions will continue to rise. ethical issue the author is aware of and complies with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the author adheres to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the author. conflict of interest the author declares no potential conflict of interest. deven barton/future sustainability august 2025| volume 03 | issue 03 | pages 35-46 45 references [1] nonrenewable energy, https://education.nationalgeographic.org/resource/ non-renewable-energy/. 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[29] “protect tomorrow. today: exxonmobil sustainability,” exxonmobil, https://corporate.exxonmobil.com/sustainabilityand-reports/sustainability (accessed may 17, 2025). [30] “u.s. government publishes updated emissions projections,” energy.gov, https://www.energy.gov/policy/articles/usgovernment-publishes-updated-emissionsprojections (accessed may 18, 2025). this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 47 article examining the association between deteriorated urban fabric and socio-economic resilience in tehran metropolis kooshiar zebardast1*, keramatollah ziari2 1geography and urban planning, kish international campus, university of tehran, kish, iran 2department of geography and urban planning, faculty of geography, university of tehran, iran a r t i c l e i n f o article history: received 12 june 2025 received in revised form 28 july 2025 accepted 13 august 2025 keywords: urban deterioration, socioeconomic resilience, geographically weighted regression, factor analysis *corresponding author email address: kooshiar.zebardas@ut.ac.ir doi: 10.55670/fpll.fusus.3.4.5 a b s t r a c t deteriorated urban areas usually face social, economic, and environmental problems. they often struggle with issues like poverty, inadequate housing, poor public spaces, social isolation and a sense of hopelessness, limited business opportunities, and a lack of investment. these complex problems cause significant disaster resilience challenges for these areas. this article investigates the association between urban deteriorated fabric (udf) rate and socioeconomic resilience (ser) in the neighborhoods of tehran metropolis. fourteen ser variables are identified through a literature review. exploratory factor analysis is used to transform them into fewer factors. four factors are extracted and are labelled as economic, social, economic-demographic, and community capital resilience. similar extracted factors are combined to obtain social and economic resilience subcomponents. jenks' natural break classification method is used to classify the udf rate into five categories. ordinary least squares (ols) and geographically weighted regression (gwr) are used to examine the association between udf rate (dependent variable) and ser subcomponents (independent variables). the findings of the study show that: (a) the gwr better captures spatial relationships between udf rate and ser factors than the ols method, (b) the relationship between dufs and social and economic resilience is complex and not definitively one-sided, and (c) social and economic resilience can occur concurrently in dufs, (d) neighborhoods with high ufd rates are clustered in the mid-southern parts of the tehran city. understanding the interplay between social and economic resilience in dufs is crucial for developing effective strategies to promote recovery and long-term disaster resilience and sustainability. 1. introduction one of the challenges that many large cities worldwide face is managing natural disasters, necessitating the development of solutions to enhance the capacity and resilience of communities while decreasing the susceptibility of urban areas to such disasters [1]. iran ranks as one of the most susceptible countries globally to natural disasters, particularly earthquakes and floods, owing to its climatic, geological, and socio-spatial developmental traits [2]. statistics show that in recent years, on average, a destructive and damaging earthquake has occurred in some part of the country every five years, and iran is currently at the top of the list of countries where earthquakes are associated with high casualties [3]. the city of tehran sits at the base of the alborz mountains and is at risk from several active faults that pose a constant threat to the city [4]. as a result, a crucial aspect of development planning in tehran city is to highlight and consider its susceptibility, particularly the deteriorated urban areas, to natural disasters. urban deterioration in iran is characterized by the decay of urban fabrics, particularly in older areas, due to factors such as physical decay, aging infrastructure, structural instability, inadequate infrastructure, lack of basic amenities, uneven development, inadequate planning, and a lack of comprehensive renovation future sustainability open access journal https://doi.org/10.55670/fpll.fusus.3.4.5 november 2025| volume 03 | issue 04 | pages 47-57 journal homepage: https://fupubco.com/fusus issn 2995-0473 mailto:kooshiar.zebardas@ut.ac.ir https://doi.org/10.55670/fpll.fusus.3.4.5 https://fupubco.com/fusus k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 48 strategies [5-7]. this deterioration affects various aspects of city life, impacting residents' quality of life and posing challenges to sustainable urban development. the uneven distribution of resources and opportunities contributes to the concentration of deterioration in specific areas, exacerbating social and economic disparities. these areas frequently experience higher levels of poverty, unemployment, and social inequality, alongside limited access to essential services [8]. the high council for urban planning and architecture of iran (hcupai) in a resolution issued in 2006, has defined deteriorated urban fabric (duf) as “areas within the legal boundaries of cities that are vulnerable due to physical deterioration, lack of proper access to vehicles, services, and urban infrastructure, that have low spatial, environmental, and economic value” [9]. to operationalize this definition, the hcupai [9] has introduced three indicators of (a) “fineness of the fabric”, defined as blocks where more than 50% of their parcels have an area of less than 200 square meters, (b) “structural instability” which refers to blocks where more than 50% of their buildings are unstable and lack a sound structural system, and (c) “impermeability” defined as blocks where more than 50% of their surrounding streets are less than 6 meters in width. areas of the city that meet all three criteria are called dufs. there are approximately 53,000 hectares of dufs in iran, about 20 percent of which belong to the country's metropolises [10]. the tehran city renovation organization (tcrno), using the three hcupai indicators of dufs, identifies the areas of the city that fall in the duf category and updates them periodically. while the area of dufs in tehran city is increasing annually, its annual rate of renovation is considerably low [8]. this discrepancy indicates a challenge in effectively addressing urban decay and improving the living conditions in these areas of the city. despite the presence and the increasing trends of duf in many cities in iran [11] and both in developing and developed countries [12], there is a lack of clear understanding of the association between duf rates and the underlying socioeconomic resilience in these areas. most current studies examine urban decay or resilience separately, and analyzing their bidirectional relationship in a fast-growing city like tehran is scant. additionally, few studies have combined spatial analysis (gis), exploratory factor analysis (efa), and spatial regression analysis (ols and gwr) to assess these relationships quantitatively. this study aims to fill these gaps by examining the spatial association between the duf rate and the ser domains at the neighborhood level in tehran metropolis, specifically addressing the following questions: (1) how does the rate of urban deterioration vary across tehran’s neighborhoods, and (2) how does this variation correlate with socio-economic resilience? this article is organized as follows: after the introduction, the socioeconomic indicators selection process is explained. in the next section, the study area and methodological framework of the study are presented. then, the quantification of the ser and the examination of the relationship between dufs and ser subcomponents are presented. in the latter parts of the paper, the results, discussion, and conclusions are presented. 2. socioeconomic resilience indicators in recent years, the concept of resilience has gained considerable attention because of the continued vulnerability of cities to adverse effects of growing urban population, climate change, increasing trends in natural disasters, and aging public infrastructure [13,14]. bruneau et al. [15] quantify the disaster resilience of a community in the context of four specific dimensions of resilience: technical, organizational, social, and economic. later research contributions, such as the disaster resilience of place (drop) model by cutter et al. [16], build upon these categorizations of multi-dimensional behavior by pinpointing particular sets of quantitative indicator variables that can be used to analytically represent the various traits of resilience across its multiple dimensions. cutter's work builds on the four dimensions suggested by bruneau et al. [15] and adds two new dimensions of ecological resilience and community competence [16]. subsequent disaster resilience (dr) frameworks reviewed by asadzadeh et al. [17] show that in all of the 36 dr frameworks reviewed, the social and economic dimensions of resilience are present. as kumar and mehany state, socioeconomic factors play a crucial role in building disaster resilience, as disaster occurrences impact the social and economic development of urban areas; the socioeconomic dimension “has been seen as a facilitator of disaster resilience” [18]. despite the relative importance of the community ser, there have been few studies focused on it, and even fewer have tried to quantify it, highlighting a significant issue that requires attention. of the several studies that have identified and used sets of indicators to assess socioeconomic resilience [18-26], the socioeconomic resilience capacity index (serci) proposed by gatiso & greenhalgh [23] is taken as a basis here and other relevant studies [18, 21, 24, 25, 27] are used to identify and adapt the appropriate indicators that could represent the socioeconomic resilience at the neighborhood level in tehran city. after eliminating highly correlated variables, fourteen variables are used to measure the ser at the neighborhood level in tehran city (table 1). 3. methodology tehran metropolis, with a population of 8.6 million, is the capital and the most populous city in iran. the city is composed of 22 districts and 354 neighborhoods with a total area of about 730 km2. the city is located in the northern part of the country (figure 1). according to tehran city deputy mayor for urban planning and architecture, the dufs in tehran city cover an area of 4,400 hectares [29], which is about 6.1 percent of the total area of the tehran metropolis. the number of residents living in these dufs is about 15 percent of the total population of tehran city. about 22 percent of tehran city’s parcels are located in dufs [3]. the population density in the dufs of tehran city is about 395 persons per hectare, which is more than two and a half times the population density of the entire city [10]. to achieve the mentioned objectives, the methodological framework of the study is presented in figure 2. k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 49 4. analysis in the analysis part of the study, the steps identified in the methodological section are undertaken. to quantify the socioeconomic resilience at the neighborhood level, exploratory factor analysis (efa) is performed to extract the underlying dimensions of the ser. the extracted factors are then combined to obtain a theoretically coherent set of factors that represent the ser. to examine the relationship between urban deterioration rate and ser factors, spatial regression analyses (ols and gwr) are performed. 4.1 exploratory factor analysis to extract dimensions of ser efa is performed to extract factors from the fourteen ser variables. the kaiser-meyer-olkin (kmo) measure of sampling adequacy of 0.755 and bartlett’s sphericity test result (χ2 = 2691.92; df = 91; ρ= 0.0001) indicate the suitability of the performed efa. a varimax rotation and kaiser criteria (choosing factors with eigenvalues greater than one) are used to select a small number of factors that include important variables that have high factor loadings table 1. selected indicators to measure ser at the neighborhood level in tehran metropolis no dim indicators acronym references 1 social proportion of population with university diploma (%) hed landry et al. [25] 2020 2 social land use diversity lud hafsi et al. [21] 2023 3 social population density den landry et al. [25] 2020; yin et al. [24] 2025 4 social sense of belonging bel gatiso & greenhalgh [23] 2025; navidpour et al. [27] 2025 5 social satisfaction with neighborhood relations rel gatiso & greenhalgh [23] 2025; navidpour et al. [27] 2025 6 social satisfaction with participation in neighborhood decisions par gatiso & greenhalgh [23] 2025; navidpour et al. [27] 2025 7 social proportion of population without a highschool diploma (%) lit landry et al. [25] 2020 8 economic household income inc gatiso & greenhalgh [23] 2025; yin et al. [24] 2025 9 economic car ownership car gatiso & greenhalgh [23] 2025 10 economic number of employed per household neh lau [28] 2013 11 economic ratio of skilled labor to total workforce skl yin et al. [24] 2025 12 economic housing unit ownership ohs landry et al. [25] 2020 13 economic percent employed emp kumar & mehany [18] 2022 14 economic population dependency dep hafsi et al. [21] 2023 figure 1. spatial distribution of duf and its composing indicators in tehran metropolis k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 50 while minimizing the factor loadings of the unimportant ones, thus making it easier to interpret and label the factors. four factors are extracted which cumulatively explain about 68.71% of the data variance. based on the highlighted variables for each factor, the four extracted factors are labeled as “economic resilience”, “economic-demographic resilience”, “social resilience”, and “community-capital resilience” (table 2). factor 1, which explains about 20.76% of the data variance, has high loadings with percent employed (0.836), number of employed per household (0.835), and housing unit ownership (-0.712). these indicators reflect a household's capacity to withstand economic shocks and stressors through income generation, employment stability, and asset ownership. this factor is labeled as economic resilience. factor 2 accounts for 14.2% of the data set’s common variance and has a significant positive loading on the proportion of the population without a high-school diploma (0.771), car ownership (0.695), household income (0.686), and ratio of skilled labor to total workforce (0.682). it also has a negative loading with population dependency (-0.681). car ownership and household income are indicators of financial resilience, while the ratio of skilled labor to the total workforce and population dependency reflects demographic resilience. this factor represents economic-demographic resilience. accounting for 15.78% of the data variance, factor 3 has high loadings with population density (0.836), the proportion of the population with a university diploma (0.723), and land use diversity (-0.717). it represents social resilience. factor 4 explains 11.57% of the data variance and has a significant positive loading on satisfaction with neighborhood relations (0.848), sense of belonging (0.732), and satisfaction with participation in neighborhood decisions (0.444). these variables relate to the social cohesion and support systems that help individuals and communities withstand challenges and adapt to change. they contribute to the overall strength of social ties and a community's ability to cope with adversity. this factor, therefore, is labeled community-capital resilience. figure 2. methodological framework of the study 4.2 combining similar extracted ser factors into a single subcomponent in efa, it is customary to combine similar extracted factors into a new composite subcomponent to simplify interpretation or enhance theoretical coherence [30], even if efa initially separates them [31]. similar factors one and two are combined to represent the economic subcomponent, and similar factors three and four are combined to represent the social subcomponent of the ser. table 2. extracted factors, their corresponding variables, and labels original variables acronym factors (f1) economic resilience (f2) economicdemographic resilience (f3) social resilience (f4) communitycapital resilience percent employed emp 0.836 -0.231 0.249 -0.075 number of employed per household neh 0.835 -0.061 -0.160 -0.143 housing unit ownership ohs -0.712 0.336 -0.026 0.006 proportion of population without a high-school diploma (%) lit -0.452 0.771 -0.001 0.158 car ownership car 0.119 0.695 -0.296 0.082 household income inc -0.406 0.686 -0.426 0.062 ratio of skilled labor to total workforce skl -0.396 0.682 0.202 0.223 population dependency dep 0.573 -0.681 0.044 -0.014 population density den 0.002 -0.194 0.836 0.094 proportion of population with university diploma (%) hed 0.015 -0.105 0.723 0.173 land use diversity lud -0.015 -0.046 -0.717 0.173 satisfaction with neighborhood relations rel -0.236 -0.063 -0.100 0.848 sense of belonging bel -0.179 0.397 0.005 0.732 satisfaction with participation in neighborhood decisions par 0.214 0.124 0.252 0.444 eigenvalues 4.98 2.22 1.35 1.07 percent variations explained 20.76 20.52 15.78 11.57 k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 51 to combine these factors to obtain the economic and social subcomponents of ser, their factor scores are first normalized using equation (1) [32]: 𝑁𝑁𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖 = (𝐹𝐹𝐹𝐹𝑖𝑖𝑖𝑖−𝐹𝐹𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖) (𝐹𝐹𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖−𝐹𝐹𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖) (1) where, 𝑁𝑁𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖 is the normalized factor score for factor i in neighborhood j, 𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖 is the factor score for factor i in neighborhood j, 𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 and 𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 are the minimum and maximum value of factor score for factor i, respectively. then, the factor scores for the combined factors of ser are computed by way of equation (2) [33] wherein the variance explained by each factor is used as a measure of the importance of that factor: 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝑁𝑁𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝑘𝑘𝑖𝑖 = ∑ (λ𝐹𝐹𝑖𝑖 ×𝑁𝑁𝐹𝐹𝐹𝐹𝑖𝑖𝑖𝑖)𝑚𝑚 𝑖𝑖=1 ∑ λ𝐹𝐹𝑖𝑖 𝑚𝑚 𝑖𝑖=1 (2) where, 𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝑘𝑘𝑖𝑖 is the combined resilience subcomponent k score in neighborhood j, λ𝐹𝐹𝑖𝑖 is the percent variance explained by factor i, 𝑁𝑁𝑁𝑁𝑁𝑁𝑖𝑖𝑖𝑖 is the normalized factor score for factor i in neighborhood j, m is the number of factors to be combined to arrive at the combined resilience subcomponent k. the combined economic resilience subcomponent, which measures the neighborhood economic vitality, suggests that the economic resilience in duf neighborhoods exhibits high percentages of employed, a higher number of employed per household, lower levels of educational equality, higher percentages of inhabitants with vehicle access and household income, and those with fewer housing ownership and also fewer population dependency. the second combined subcomponent measures the social capacity of the duf neighborhoods. it shows that the social resilience in the duf neighborhoods is accompanied by such characteristics as areas with higher population density, higher levels of educational equality, lower rate of land-use diversity, and higher levels of social capital. 4.3 examining the relationship between urban deterioration and socioeconomic resilience to examine the relationship between urban deterioration and ser, the udf rate is taken as the dependent variable, and the two combined subcomponents of the ser, namely economic resilience and social resilience subcomponents, are used as the independent variables in the following ols and gwr regression analyses. udf rate is computed by dividing the udf area of a neighborhood by its total area. it is categorized into five classes (very low, low, moderate, high, and very high udf) using jenks natural break in arcgis and is presented in figure 3. the spatial distribution pattern of udf rate at the neighborhood level (figure 3) shows that neighborhoods with high udf rates are clustered in the mid-southern parts of the city. 4.4 performing ordinary least squares (ols) regression analysis the ols is a type of global statistics that assumes a constant relationship over space; therefore, the parameters are estimated to be the same for all the study areas [34]. to examine the relationship between urban deterioration and socioeconomic resilience at the neighborhood level, first, an ols method is applied. figure 3. udf rate classification of the neighborhoods using the jenks natural break method k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 52 as shown in the methodological framework of the study (figure 2), in the ols regression analysis, the dependent variable is the udf ratio, and the independent variables are the two ser factors, namely, the economic and social resilience. the results of the ols regression analysis are shown in table 3. the ols regression result indicates that, with about 9.9% accuracy (adjusted r2= 0.0996) and for all the neighborhoods in the city, the urban deterioration is negatively significantly associated with economic resilience and positively significantly related with the social resilience subcomponents of the ser. 4.5 performing geographically weighted regression (gwr) gwr is an extension of the traditional standard regression framework, which allows local rather than global parameters to be estimated [35]. it is a type of local statistics that produces a set of local parameter estimates that show how a relationship varies over space [34]. to examine the possibility of applying a gwr, it's crucial to ensure that spatial autocorrelation is present in the ols residuals and that the r2 of the gwr is greater than the r2 of the corresponding ols regression [35]. moran’s i is computed for controlling the presence of spatial autocorrelation in the ols residuals. moran’s i result indicates that the standardized residual of the ols regression is spatially autocorrelated and is distributed in a clustered manner (figure 4: moran’s i = 0.757, p-value = 0.000). the adjusted r2 of the applied gwr (0.648) is greater than that of the corresponding ols (0.099) regression. since the prerequisites of applying a gwr are met, the gwr results (table 4) could be used for further analysis. the results of the gwr analysis in table 4 and the spatial variation of the negative and positive coefficients of the independent variables from the gwr model are shown in figure 5. figure 4. the moran’s index for the standardized residual of the ols regression table 4 and figure 5 show that the intercept coefficients and coefficients of both economic and social subcomponents of ser have, concurrently, a negative and positive relationship with the duf rate, depending on their location: • the intercept coefficients in figure 5 (a) show that positive coefficients (in about 58% of the neighborhoods) belong to the neighborhoods located in the southern and western parts of the city, and the negative coefficients (in about 42% of the neighborhoods) are located in the northeastern parts of the metropolis. this implies a generally higher duf rate in the southern parts of the city. table 3. results of the ols regression analysis ser subcomponents coefficient robust se robust t robust p vif intercept 0.169 0.107 1.581 0.115 - economic resilience -0.691 0.162 -4.249 0.000 1.000 social resilience 0.520 0.156 3.328 0.000 1.000 model diagnostics multiple 𝐶𝐶2= 0.105; adjusted 𝐶𝐶2= 0.0996; aicc= 46.52 table 4. the results of the gwr ser subcomponent gwr coefficients directions of relationships in the gwr model min max mean sd + (%) + sig. (%) (%) sig. (%) intercept -0.860 1.253 0.126 0.393 58.09 23.88 41.91 3.45 economic resilience -2.163 1.632 -0.196 0.730 44.64 10.57 56.36 30.26 social resilience -0.757 2.221 0.262 0.539 70.23 26.34 29.77 14.56 model diagnostics multiple 𝐶𝐶2= 0.725; adjusted 𝐶𝐶2= 0.648; aicc= 228.27 k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 53 • in 44.6% of the neighborhoods, the duf rate is positively associated, and in the remaining 56.4% it is negatively associated with the economic resilience of the ser (figure 5 (b)). • in 70.2% of the neighborhoods, the duf rate is positively associated, and in 29.8% of the neighborhoods, it is negatively associated with the social resilience of the ser (figure 5 (c)). • of the 75 neighborhoods that are categorized as neighborhoods with high and very high duf rate: o 42 neighborhoods (56%) have a negative relationship (14 of them are statistically significant), and the remaining 33 neighborhoods have a positive relationship with economic resilience. o 38 neighborhoods (50.7%) have a positive relationship (14 of them statistically significant) and the remaining neighborhoods have a negative relationship (24% of them statistically significant) with social resilience. 5. results and discussion the findings of applying the ols regression (table 3) indicate that: • both economic and social subcomponents representing ser have a statistically significant relationship (p=0.05) with the duf rate. • the adjusted 𝐶𝐶2 of 0.099 of the ols model indicates that about 9.9% of the variations in the duf rate is explained by the two ser subcomponents. • the duf rate has a negative significant relationship with the economic and a positive significant association with the social subcomponents of the ser. the ols results suggest that across all neighborhoods, as the rate of duf rises, the social resilience improves, but the economic subcomponents of ser decline. to explore potential local differences in how the duf rate correlates with ser subcomponents, the gwr outcomes are compared with those from the ols regression. the global 𝐶𝐶2 of gwr (0.725) in comparison with the 𝐶𝐶2 of corresponding ols regression (0.105) shows a dramatic improvement in 𝐶𝐶2 of gwr over the ols. the 𝐶𝐶2 values in gwr range from 0.0004 to 0.5058 (figure 6), which is indicative of a local variation in the relationship between duf rate and ser subcomponents. the gwr indicates that, in contrast to the ols regression, the relationship between the duf rate and ser subcomponents varies across different areas, with the highest coefficient of determination (𝐶𝐶2) found in neighborhoods situated in the central parts of the city. the comparison between ols and gwr analyses indicates that the gwr model is better at capturing the spatial relationships between urban deterioration and the ser subcomponents in the dufs of the city. the spatial distribution of the significant coefficients of the intercept and the two ser subcomponents is presented in figure 7. the findings of this part of the study (table 4 and figure 7) indicate that the association of the duf rate with the economic resilience subcomponent of the ser is positively statistically significant in 10.57% and is negatively statistically significant in 30.26% of the city’s neighborhoods. this finding implies that dufs concurrently have significant challenges and opportunities with economic resilience. this is contrary to the general consensus that dufs face significant challenges in terms of economic resilience: they often struggle to attract investment [36], retain residents, and figure 5. spatial variation of the negative and positive coefficients of the intercept and the independent variables from the gwr model k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 54 recover from economic shocks due to factors like reduced economic activity [36, 37], out-migration [37, 38], and decreased property values [38,39]. on the social resilience subcomponents of the ser, the findings of the study indicate that, similar to the economic resilience, the duf rate association with the social resilience subcomponent of the ser is positively statistically significant in 26.34% and is negatively statistically significant in 14.56% of the neighborhoods (table 4). this finding is contrary to the findings of taghvaei & asadi [40] and sarrafi & razavian [41] that the dufs are one-sidedly negatively related to social resilience. the findings of this study show that the relationship between dufs and social and economic resilience is complex and not definitively one-sided. the relationship between urban deterioration and ser subcomponents is mixed and varies across the city neighborhoods. in some neighborhoods of the city, the duf rate is positively related, and in others it is negatively related to both social and economic subcomponents of the ser. this is true even in neighborhoods located in the “high and very high duf rate” areas (figure 7). this study suggests that social and economic resilience can occur concurrently in dufs. this may be due to the interconnectedness of social and economic factors, and interventions may have positively or negatively impacted both social and economic resilience in the dufs. figure 6. the local 𝐶𝐶2 classification by jenks' natural break method on the positive relationship between duf rate and social and economic resilience, the findings of this study support the earlier assertions by giacometti & teräs [42] that a community with high social resilience may be better able to mobilize resources and support one another during economic downturns and conversely, social norms that emphasize adaptability or collective action can also contribute to economic resilience. on the negative relationship between duf rate and social and economic resilience, this study supports the findings of (a) hassanvand et al. [43] that social inequalities such as unequal access to education, healthcare, or job opportunities, can make certain groups more vulnerable to economic shocks and less able to recover, even if the overall economy is resilient, and, (b) hegazy et al. [22] that economic hardship can lead to social vulnerability and decreased community participation, hindering the development of social resilience and potentially leading to further economic decline. this study has a limitation that needs to be taken into consideration. the findings of this study are based on data gathered at the neighborhood level in tehran metropolis, iran; therefore, the results cannot be generalized to other large cities or metropolises in iran. further analysis based on nationally representative data is required. but the methodological framework used in the study is innovative and could pave the way for similar studies in other countries. k. zebardast & k. ziari /future sustainability november 2025| volume 03 | issue 04 | pages 47-57 55 6. conclusion this study examined the relationship between urban deterioration rate and fourteen variables depicting the ser. the results of this study show that (a) the ufd rates among the city’s neighborhoods is clustered in nature and neighborhoods with high and very high udf rates are clustered in the mid-southern parts of the city, (b) the relationship between dufs and socio-economic resilience is complex, not definitively one-sided, mixed and varies across different neighborhoods of the city, (c) that social and economic resilience may happen simultaneously in dufs. the methodological framework used in the study, including efa, combining similar extracted efa factors to arrive at new composite ser subcomponents, global spatial autocorrelation (moran’s i), jenks natural break clustering, gwr and ols regression analyses, can be applied to any other global location with similar datasets to contribute to the existing knowledge about urban decay and ser at the local scale. in the context of dufs, understanding the interplay between social and economic resilience is crucial for developing effective strategies to promote recovery and longterm sustainability. targeted interventions that address both social and economic vulnerabilities, while also fostering positive interactions between them, are likely to be more successful in building overall socioeconomic resilience. this includes taking proactive steps to improve infrastructure, boost collaboration across various sectors, utilize technology effectively, and encourage community involvement. the ultimate aim is to enable cities to absorb, recover from, and adapt to shocks while fostering sustainable development. ethical issue the authors are aware of and comply with best practices in publication ethics, specifically with regard to authorship (avoidance of guest authorship), dual submission, manipulation of figures, competing interests, and compliance with policies on research ethics. the authors adhere to publication requirements that the submitted work is original and has not been published elsewhere. data availability statement the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the authors declare no potential conflict of interest. references [1] m. pelling, the vulnerability of cities: natural disasters and social resilience. routledge, 2012. https://doi.org/10.4324/9781849773379 [2] z. beheshti, a. gharagozlou, m. monavari, and m. k. zarkesh, "landslides behavior spatial modeling by using evidential belief function model, promethean ii model, and index of entropy in tabriz, iran," arabian journal of geosciences, vol. 14, no. 17, p. 1801, 2021. 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[43] a. hassanvand, a. hajinejad, and m. yasouri, "relationship between economic and socio-cultural resilience of rural settlements after suffering from earthquake (a case study: rural settlements of silakhor district in dorud)," scientific journal of rescue and relief, vol. 11, no. 4, pp. 225-237, 2019. this article is an open-access article distributed under the terms and conditions of the creative commons attribution (cc by) license (https://creativecommons.org/licenses/by/4.0/). https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ 1. introduction one of the challenges that many large cities worldwide face is managing natural disasters, necessitating the development of solutions to enhance the capacity and resilience of communities while decreasing the susceptibility of urban areas to such disa... despite the presence and the increasing trends of duf in many cities in iran [11] and both in developing and developed countries [12], there is a lack of clear understanding of the association between duf rates and the underlying socio-economic resili... this article is organized as follows: after the introduction, the socioeconomic indicators selection process is explained. in the next section, the study area and methodological framework of the study are presented. then, the quantification of the se... 2. socioeconomic resilience indicators in recent years, the concept of resilience has gained considerable attention because of the continued vulnerability of cities to adverse effects of growing urban population, climate change, increasing trends in natural disasters, and aging public infr... 3. methodology tehran metropolis, with a population of 8.6 million, is the capital and the most populous city in iran. the city is composed of 22 districts and 354 neighborhoods with a total area of about 730 km2. the city is located in the northern part of the coun... 4. analysis in the analysis part of the study, the steps identified in the methodological section are undertaken. to quantify the socioeconomic resilience at the neighborhood level, exploratory factor analysis (efa) is performed to extract the underlying dimensio... 4.1 exploratory factor analysis to extract dimensions of ser efa is performed to extract factors from the fourteen ser variables. the kaiser-meyer-olkin (kmo) measure of sampling adequacy of 0.755 and bartlett’s sphericity test result (χ2 = 2691.92; df = 91; ρ= 0.0001) indicate the suitability of the performed ... factor 1, which explains about 20.76% of the data variance, has high loadings with percent employed (0.836), number of employed per household (0.835), and housing unit ownership (-0.712). these indicators reflect a household's capacity to withstand ec... factor 2 accounts for 14.2% of the data set’s common variance and has a significant positive loading on the proportion of the population without a high-school diploma (0.771), car ownership (0.695), household income (0.686), and ratio of skilled labor... factor 4 explains 11.57% of the data variance and has a significant positive loading on satisfaction with neighborhood relations (0.848), sense of belonging (0.732), and satisfaction with participation in neighborhood decisions (0.444). these variable... 4.2 combining similar extracted ser factors into a single subcomponent in efa, it is customary to combine similar extracted factors into a new composite subcomponent to simplify interpretation or enhance theoretical coherence [30], even if efa initially separates them [31]. similar factors one and two are combined to rep... to combine these factors to obtain the economic and social subcomponents of ser, their factor scores are first normalized using equation (1) [32]: ,𝑁𝐹𝑆-𝑖𝑗.= ,(,𝐹𝑆-𝑖𝑗.−,𝐹𝑆-𝑖𝑀𝑖𝑛.)-(,𝐹𝑆-𝑖𝑀𝑎𝑥.−,𝐹𝑆-𝑖𝑀𝑖𝑛.). (1) where, ,𝑁𝐹𝑆-𝑖𝑗. is the normalized factor score for factor i in neighborhood j, ,𝐹𝑆-𝑖𝑗. is the factor score for factor i in neighborhood j, ,𝐹𝑆-𝑖𝑀𝑖𝑛. and ,𝐹𝑆-𝑖𝑀𝑎𝑥. are the minimum and maximum value of factor score for factor i, re... then, the factor scores for the combined factors of ser are computed by way of equation (2) [33] wherein the variance explained by each factor is used as a measure of the importance of that factor: ,𝐶𝑜𝑚𝑏𝑅𝑒𝑠𝑆𝑢𝑏𝑐𝑜𝑚𝑝-𝑘𝑗.= ,,𝑖=1-𝑚-(,λ-,𝐹-𝑖.. ×,𝑁𝐹𝑆-𝑖𝑗.).-,𝑖=1-𝑚-,λ-,𝐹-𝑖.. .. (2) where, ,𝐶𝑜𝑚𝑏𝑅𝑒𝑠𝐶𝑜𝑚𝑝-𝑘𝑗. is the combined resilience subcomponent k score in neighborhood j, ,λ-,𝐹-𝑖.. is the percent variance explained by factor i, ,𝑁𝐹𝑆-𝑖𝑗. is the normalized factor score for factor i in neighborhood j, m is the nu... the combined economic resilience subcomponent, which measures the neighborhood economic vitality, suggests that the economic resilience in duf neighborhoods exhibits high percentages of employed, a higher number of employed per household, lower levels... the second combined subcomponent measures the social capacity of the duf neighborhoods. it shows that the social resilience in the duf neighborhoods is accompanied by such characteristics as areas with higher population density, higher levels of educa... 4.3 examining the relationship between urban deterioration and socioeconomic resilience to examine the relationship between urban deterioration and ser, the udf rate is taken as the dependent variable, and the two combined subcomponents of the ser, namely economic resilience and social resilience subcomponents, are used as the independen... 4.4 performing ordinary least squares (ols) regression analysis the ols is a type of global statistics that assumes a constant relationship over space; therefore, the parameters are estimated to be the same for all the study areas [34]. to examine the relationship between urban deterioration and socioeconomic resi... as shown in the methodological framework of the study (figure 2), in the ols regression analysis, the dependent variable is the udf ratio, and the independent variables are the two ser factors, namely, the economic and social resilience. the results o... 4.5 performing geographically weighted regression (gwr) gwr is an extension of the traditional standard regression framework, which allows local rather than global parameters to be estimated [35]. it is a type of local statistics that produces a set of local parameter estimates that show how a relationship... to examine the possibility of applying a gwr, it's crucial to ensure that spatial autocorrelation is present in the ols residuals and that the r2 of the gwr is greater than the r2 of the corresponding ols regression [35]. moran’s i is computed for con... figure 4. the moran’s index for the standardized residual of the ols regression table 4 and figure 5 show that the intercept coefficients and coefficients of both economic and social subcomponents of ser have, concurrently, a negative and positive relationship with the duf rate, depending on their location: 5. results and discussion the findings of applying the ols regression (table 3) indicate that: the spatial distribution of the significant coefficients of the intercept and the two ser subcomponents is presented in figure 7. the findings of this part of the study (table 4 and figure 7) indicate that the association of the duf rate with the econ... on the social resilience subcomponents of the ser, the findings of the study indicate that, similar to the economic resilience, the duf rate association with the social resilience subcomponent of the ser is positively statistically significant in 26.3... on the positive relationship between duf rate and social and economic resilience, the findings of this study support the earlier assertions by giacometti & teräs [42] that a community with high social resilience may be better able to mobilize resource... 6. conclusion this study examined the relationship between urban deterioration rate and fourteen variables depicting the ser. the results of this study show that (a) the ufd rates among the city’s neighborhoods is clustered in nature and neighborhoods with high and... the ultimate aim is to enable cities to absorb, recover from, and adapt to shocks while fostering sustainable development. ethical issue the manuscript contains all the data. however, more data will be available upon request from the corresponding author. conflict of interest the authors declare no potential conflict of interest. references [1] m. pelling, the vulnerability of cities: natural disasters and social resilience. routledge, 2012. https://doi.org/10.4324/9781849773379 [2] z. beheshti, a. gharagozlou, m. monavari, and m. k. zarkesh, "landslides behavior spatial modeling by using evidential belief function model, promethean ii model, and index of entropy in tabriz, iran," arabian journal of geosciences, vol. 14, no.... 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