 Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Piglets Comfort with Hot Water by Biogas Combustion under Controllable Ventilation Cheng-Chang Lien 1,* , Ching-Hua Ting 2 , Jun-Han Mei 3 1 Department of Biomechatronic Engineering, National Chiayi University, Chiayi, Taiwan, ROC. 2 Department of Mechanical and Energy Engineering , National Chiayi University, Chiayi, Taiwan, ROC. 3 Graduate student, Department of Bioelectromechanical Engineering, National Chiayi University , Chiayi, Taiwan, ROC. Received 05 June 2017; received in revised form 23 August 2017; accept ed 13 Sept ember 2017 Abstract The purpose of this study is to develop a hot -water heating system for pig fa rms which use biogas as the energy source while the air quality is regulated using an inverter-controlled fan. The biogas is a by-product from the 3-stage wastewater treat ment process in regula r p ig farms. The b iogas is burned for hot water which is c irculated to wa rm piglet compart ments with regulated, forced ventilation. The hot water is connected to a heat exchanger and hot air is hence blown into the pigsty. To maintain the pigsty at a comfort at mosphere, ventilation is regulated using an inverter-controlled fan. The mechanica l ventilation is to be optimized as a compromise between indoor air quality and ventilation rate. The te mperature uniformity and a ir quality in the p igsty is to be secured for comfortability. Expe rimental results show that hot water circu lating at 0.043 m 3 / min and 60°C could keep the pigsty at 28°C for a stocking density of 1.77 pig/ m 2 . Forced ventilat ion of 1.7 A CH (air change rate per hour) at 28°C could keep the pigsty comfort in terms of indoor temperature, relative humidity, and carbon -dioxide concentration. Keywor ds : biogas, piglets, hot-water heating s ystem, force ventilation 1. Introduction Biogas is the combustible gas generated through the mic roorganism fe rmentation of organic waste under the anaerobic environment. It is one of the renewable energy to replace the requirement of future energy resource, the generated volume will be affected along with the factors of solid ingredients, fermented temperature, humidity, pH value, microbia l strains and fermentation time of fe rmented organic matter so that the compositions are not e xactly the sa me. The ma in constituent of biogas is methane (CH4) which is around 55-70%, carbon dio xide (CO2) appro ximately 30-40%, 0.2-05% of hydrogen sulfide (H2S), and very small a mounts of carbon monoxide, n itrogen and ammonia etc. Direct e mission of methane in the atmosphere will cause the global greenhouse effect growing in intensity, and the capability of causing the greenhouse effect per unit of methane is 23 times of carbon d io xide, its harm to the earth environ ment for direct e mission of biogas cannot be ignored indeed [1-4]. The process of 3-stage wastewater treatment facility promoted in the pig farms of Ta iwan includes the three stages of solid-liquid separation of e xcreta, anaerobic treat ment and aerob ic treat ment, and large a mount of biogas is generated during the anaerobic proces s, however most of p ig husbandry in Ta iwan does not utilize the b iogas but emits to the at mosphere directly. As pointed out from the research, the methane content as generated from p ig sewage is higher than what is generated fro m the waste of crop farm, each hog sewage with the we ight of 60 kg is able to generate appro ximately 0.23 m 3 biogas per * Corresponding author. E-mail lanjc@mail.ncyu.edu.tw Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 87 day. Biogas has high heating value and the fuel characteristics as well, it has been considered as the energy resource worth to promote and utilize, after biogas is burned, methan e becomes the carbon dioxide wh ich is able to lo wer the greenhouse effect, if the heat energy generated from the burned biogas is able to utilize, it may save significant energy, therefore, through th e utilization of biogas energy, the requirement of energy saving and carbon reduction can be achieved synchronously [5]. Pig let will be weaned about four weeks after birth, the piglet just off from the weaning is very sensitive to the temperature in pigsty, if the daily te mperature in p igsty drop is over 2°C, it will introduce the group diarrhea and respiratory diseases , and significantly affect the growth performance for p iglet. There fore, the te mperature control in pigsty is one of the key factors for enhancing the production performance an d economic benefit of p ig fa rms [6]. The ventilat ion of p igsty can be categorized as the natural ventilation and forced ventilation (mechanica l ventilation). The main purpose of ventilation is to supply the oxygen required for the an ima l breathing, re move the e xcess heat and moisture, p lus reduce the dust and limit the generation of harmful gases, such as ammonia and carbon dio xide etc. As pointed fro m the research, the staffs of livestock farm shall not e xpose to the environmental with the concentration of carbon dioxide (CO2) over 1500 pp m and concentration of ammonia (NH3) over 7 ppm, the effective ventilat ion system shall be able to provide the best mic roclimate condition for the working area o f p ig farme rs and anima l living a rea [7-8]. The design of heat preservation fac ility for piglets in Netherlands is to use the hot air fro m underground tunnels exchanged heat through the hot -water pipes to heat and preserve the heat for the piglet living area [9]. The purpose of this research is to develop a set of hot-water heating system using biogas as the fuel, and take the advantage of biogas energy generated fro m the 3 -stage wastewater treatment process and apply it to pig farms for the heat preservation of piglets. Ut ilize the burning of biogas and heating the water, delivered to the pigsty via pipeline, the hot-water flow blowe rs to blow the hot air through the air heater and exchanges heat in the pigsty to proceed the heating preservation for piglets, the pigsty collocates with the inverter fan to proceed the mechanica l ventilation test with different forced ventilation temperature and regular ventilation percentage, and explore against the temperature uniformity and air quality in the pigsty. 2. Material & Method 2.1. Experimental equipment The biogas generated from the pen manure of pig fa rms through the anaerobic fermentation process treatment, use the pipeline de livered/centralized to store in the red mud rubber bags, since the biogas contains the hydrogen sulfide which is corrosive to the metal equip ment, use the blower to dra w the biogas with the averagely negative pressure of 0.2 MPa through the biogas purification device to re move the hydrogen sulfide in the biogas, and then deliver to the biogas burning furnace a s the source of burning energy. The schematic image of biogas burning hot-water piglet heat preservation system is shown in the Fig. 1. The imp le mentation of biogas burning hot-water heat preservation system can be categorized as the biogas hot -water heating device, enclosed pigsty heat preservation system and inverter fan control system. The biogas hot-water heating device includes the biogas -burning furnace, electrical au xiliary heating device and hot -water storage tank. Inside the ma in body of biogas -burning furnace is able to store appro ximately 0.7 m 3 water, and 52 pcs of stainless steel pipes are installed as the passage for hot air, when the biogas furnace is burned/heated fro m the bottom, the heated area will be able to increase via t he hot air passed through the hot air passage, so that the heating efficiency is enhanced and the tempe rature of hot-water increases rapidly, wh ile an electrical au xilia ry heating device is added to deal with the situation of insufficient b iogas volume, and the temperature sensor of hot-water is installed to measure the hot-water temperature (Tw), so that the heating device is able to operate year-round. Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 88 When the thermocouple temperature o f a ir (Tc) in the enclosed pigsty is lower than the default temperature (Tset), the piglet heat preservation system starts the external c ircu lation, de liver the hot -water through the inverter motor and enter into the circulation-type blower in the pigsty to proceed the heat exchange, heat up the air inside the pigsty by blowing the hot air in order to achieve the effect of temperature control and heat preservation in the pigsty. Since the pigsty is an enclosed space, the ventilation system is required to ventilate and change air in orde r to avoid the high concentration of noxious gas in the pig sty, this research uses the inverter fan control system to perform the ventilat ion and air change of p igsty, the inverter fan system consists of 2 inverter fans with the ventilation efficiency of 0.64 m 3 /s (SLF-730, Autofan, Korea) collocating with the inverter control system (ECS-3M , Va rifan, USA), plus integrates the default temperature (Tw) and the defaulted setting of air temperature in the pigsty (Tset) together with the low limit air temperature setting function. Fig. 1 Schematic image of biogas burning hot-water piglet heat preservation system 2.2. Experimental methods PLEASE LOCATE FIG. 2. UNDER THE TEXT This research uses temperature/humid ity sensing recorder (U10-003, HOBO-Onset, USA) and carbon dio xide sensing recorder (attach with te mperature/humidity sensing , Telaire 7001, Te laire, USA) to measure the air te mperature, hu mid ity and concentration of carbon dioxide in the pigsty. Their planned locations are shown in the Fig. 2. Te mpe rature/humid ity sensing recorders are located left front (LF), left rea r (LR), right front (RF) and right rear (RR) separately, their he ight fro m the raising bedding is 80 c m, the height fro m the ra ising bedding is 25 c m for rear front down (RFD) and right rear down (RRD), the carbon dio xide sensing recorder is erected at the central location of p igsty, the height fro m the raising bedding is 90 c m, it is able to measure the central air te mperature (TM), central re lative humid ity (RHM) and concentration of carbon dioxide (CO2) of central location in the pigsty simu ltaneously, both temperature/humidity sensing recorders and carbon dio xide sensing recorde r are configured to record the data once every 30 seconds. Fig. 2 Schematic image of temperature/humidity s ensing recorders and carbon dioxide sensor location in enclosed pigsty Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 89 The stocking density of piglets in the pigsty is 1.77 pig/ m 2 , it is assumed that the pigsty is fully enclosed and the air amount flowed into the pigsty (Qin) is equal to the air amount flowed out fro m the pigsty (Qout), while define the air change rate per hour (ACH) in the enclosed pigsty is the times that the outside air a mount of pigsty to replace the equivalent amount of volume space in the pigsty, its calculation formula is shown as eq. (1). ACH = Qv / V (1) In which, ACH: air change rate in p igsty (time/hr), Qv: a ir a mount flowed into pigsty from outside of pigsty per hour (m 3 /hr), V: total volu me of enclosed pigsty is 287.28 m 3 , when perform the ventilation and air change at the regular ventilation percentage of 10%, 20% and 30%, a fter conversion, its ventilation and air change rate is 1.7 ACH, 3.4 A CH and 5.1 A CH separately. The hot-water temperature (Tw) configured at e xperiment is 60°C, hot-water flo w rate is 0.043 m 3 /min and the default temperature in the pigsty (Tset) is 28°C, and collocate with the inverter fan control system to perform the ventilation and air change to maintain the a ir quality. As to the setting part of forced ventilation te mperature, when the inside air te mperature of pigsty is higher than the forced ventilation temperature, then start the inverter fan, continue to operate with the bleed air rate of 1.27 m 3 /s until the thermocouple temperature in the pigsty (Tc) consistent with the forced ventilation temperature, and the stop. As to the setting part of regula r ventilation percentage, the ventilation and a ir change cycle is once per 10 minutes, if the configured ventilation percentage is 10%, the inverter fan operates 1 minute and then stops for 9 minutes, if the configured ventilation percentage is 30%, the inverter fan operates 3 minutes and then stops for 7 minutes. The calculation method of temperature uniformity (Tu) is to take the air te mperature of different measuring location to subtract the air temperature of centra l location (TM) separately, then select the average value of two ma ximu m a ir te mperature difference, this average value is the temperature uniformity, shown as eq. (2). Tu = (TD1+TD2)/2 (2) In which, T D1: largest air te mperature difference between different measuring location and central location (°C), T D2: second largest air temperature difference between different measuring location and central location (°C). This research performs the ventilation and air change of enclosed pigsty by using the biogas burning hot -water heat preservation system collocated with the inverter fan, and performs the e xperiment in the pigsty with stocking density of 1.77 pig/m 2 , measures the air te mperature, hu mid ity and concentration of carbon dio xide at d ifferent location in the pigsty, the forced ventilation te mpe rature configured by the inverter fan is 28°C, and changes the air change rate of ventilat ion to 1.7 A CH, 3.4 ACH and 5.1 A CH separately, fro m the calculated temperature uniformity, e xp lore if the air te mperature distribution in the pigsty is uniform or not, and illustrates if the air quality is suitable or not by the concentration of carbon dio xide in the pigsty. 3. Results & Discussion When the forced ventilation te mperature is 28°C and air change rate of regular ventilat ion is 3.4 ACH, the typical diagra m of time variation of the right front (RF), right rear (RR) and right front down (RFD), right rear down (RRD) te mperature in t he pigsty versus the outside temperature of pigsty (T0) for 4 consecutive days is shown as Fig. 3, it can be seen fro m Fig. 3a , the outside temperature fluctuation of T0 is more obvious in the day and night. The temperature of right front is slightly greater than temperature of right rear in the night which indicates that the pigsty has greater impact by the hot air blo wn fro m the a ir heater. However, on the whole, the te mperature change of RF and RR is not much , it indicates that the overall te mperature Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 90 change in the pigsty is quite stable. The te mperature change of RFD and RRD can be considered as the temperature change of activity range for p iglets, therefore, it can be seen fro m Fig. 3b, the temperature variat ion curves of RFD and RRD nearly overlap which indicates that the temperature change of activity range for the piglets in the overall pigsty is quite consistent. (a) RF, RR and outside temperature (To) (b) RFD, RRD and outside temperature (T o) Fig. 3. Typical d iagra m of RF, RR, RFD and RRD versus outside temperature of pigsty (T0) for 4 consecutive days under 28°C for forced ventilation temperature and 3.4 ACH for Regular Ventilation Under the condition of 28°C for the forced ventilation te mperature and 3.4 A CH for the air change rate of regula r ventilation, the typical diagra m of time variation of the right front (RF), right rear (RR), left front (LF) and left rear (LR) temperature in the pigsty for 4 consecutive days is shown as Fig. 4, it can be seen fro m the figure, the te mperature ch ange of right front (RF) and left front (LF), right rear (RR) and left rear (LR) nearly overlap wh ich indicates that the temperature change of left and right sides on the pigsty is quite consistent. Fig. 4 Typica l d iagra m o f RF, RR, RR and LR versus outside temperature of p igsty (T0) for 4 consecutive days under 28° C for forced ventilation temperature and 3.4 ACH for regular ventilation. Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 91 Under the condition of 28°C fo r the forced ventilation te mperature, the statistic table of te mperature and re lative hu midity for the right front (RF), right rear (RR), le ft front (LF), le ft rear (LR), right front down (RFD) and right rear down (RRD) to the diffe rent air change rate of regula r ventilat ion is shown as Table 1. It can be seen that the temperature of each location in the pigsty is quite close to the defaulted temperature of 28°C in the p igsty which indicates that the temperature change in the overall pigsty is quite uniform and stable, however, the te mperature of RFD and RRD is slightly lo wer than 28°C, its temperature difference is only 0.29°C ~1.39°C appro ximately. It can also be seen that since the location of RR and LR are more c lose to the inverter fan, RR and LR has higher relat ive hu midity as relat ive to RF and LF, however, the relat ive hu midity of piglet growth area (RFD, RRD) does not change along with the air change rate of regular ventilation i.e . ma intains between 80%-89%. Table 1 Under 28°C for the forced ventilation te mperature, at the d iffe rent air change rate o f regular ventilation, the statistic table of temperature and re lative hu mid ity for its right front (RF), right rear (RR), le ft front (LF), le ft rear (LR), right front down (RFD) and right rear down (RRD) Temperature (°C) Air change rate per hour (ACH) Relative humility (%) Air change rate per hour (ACH) 1.7 ACH 3.4 ACH 5.1 ACH 1.7 ACH 3.4 ACH 5.1 ACH RF 30.17±0.86 *1 29.57±0.84 30.09±0.74 RF 66.76±9.69 75.71±9.21 65.37±7.37 RR 28.29±0.39 28.71±0.40 28.24±0.28 RR 77.05±6.30 81.67±6.02 77.23±4.57 LF 29.93±0.73 29.44±0.71 - *2 LF 69.26±9.05 77.91±8.74 - *2 LR 28.32±0.44 28.82±0.43 28.02±0.30 LR 84.96±8.92 86.37±2.77 83.40±2.05 RFD 27.03±0.52 27.71±0.53 27.12±0.43 RFD 87.41±3.74 89.29±4.57 84.91±2.79 RRD 26.61±0.73 27.59±0.62 26.89±0.50 RRD 81.83±4.72 83.79±4.28 80.02±3.42 *1 : mean ± std *2 : Lost data due to bit off by the piglets. Under the condition of 28°C for the forced ventilation temperature and 3.4 ACH for the regular ventilat ion, the typical diagra m of central te mperature (TM), concentration of carbon dioxide in the pigsty and outside temperature of pigsty (To) is shown as Fig. 5. It can be seen fro m the figure , the central te mperature (TM) does not have the great fluctuation along with the outside temperature change of pigsty, its te mperature va lue stably maintains around 28°C. The concentration of ca rbon dio xide changes along with the t ime and has the significant fluc tuation, it shall be relat ive to the lifestyle of p iglets. As shown in the figure, the sudden drop of carbon dioxide (a rrow 1) is caused due to the owner entered into the pigsty to observe the night life situation of piglets ; the sudden drop of rear section (arrow 2) is caused due to the owner entered into the pigsty for cleaning. Fig. 5 Typica l diagra m o f central Te mperature (TM), concentration of carbon dioxide and outside temperature of pigsty (T0) for 4 consecutive days under 28°C for forced ventilation temperature and 3.4 ACH for regular ventilation At the condition of 28°C for the forced ventilat ion te mperature, the statistic of central te mperature (TM), te mperature error rate, central re lative humid ity (RHM) and concentration of carbon dio xide (CO2) in the pigsty under the different a ir change rate of regular ventilation is shown as Table 2. It can be seen from the table, under the different setting of air change rate for regular ventilation, central te mperature (TM ) is stable between 28°C-29°C and the standard deviation is very small, it is indicated that the temperature change in the pigsty is quite s table, and the temperature e rror rate is around 1.93% -3.88% , this a lso indicates Advances in Technology Innovation, vol. 3, no. 2, 2018, pp. 86 - 93 Copyright © TAETI 92 that the temperature control of this heat preservation system is quite stable. The central re lative humid ity (RHM) is stable between 73.11%-82.21% at diffe rent air change rate of regular ventilat ion, and the concentration of carbon dioxide is ma intained under 1000 ppm. When the air change rate of regular ventilation is 5.1 A CH, the concentration of carbon dio xide in the pigsty is very close to the outdoor concentration of carbo n dioxide, the air quality in the pigsty is good. Table 2 Statistic of centra l te mperature (TM), te mperature error rate, centra l relat ive humid ity (RHM) and concentration of carbon dioxide (CO2) in pigsty at 28°C for forced ventilation te mperature under different a ir change rate of regular ventilation Air change rate per hour (ACH) 1.7 ACH 3.4 ACH 5.1 ACH TM(°C) 28.49±0.52 29.09±0.46 28.79±0.31 E. R. * (%) 1.93%±1.68% 3.88%±1.65% 2.83%±1.12% RHM(%) 73.11±12.94 77.19±15.99 82.21±8.54 CO2(ppm) 896.26±145.08 598.57±294.02 406.80±108.18 * E. R. : Error rate (%) =[(Tset-TM) /Tset]*100% , Tset =28°C Take the measured temperature of RF, RR, LF, LR, RFD & RRD and the central te mperature (TM) to perform the calculation of te mperature uniformity, the results are shown as Table 3, it can be seen fro m the table, at the defaulted temperature 28°C in the pigsty, the temperature uniformity of enclosed pigsty under different air change rate of regular ventilation is between 0.99°C -1.78°C, under the condition of 3.4 ACH for the a ir change rate of regular ventilat ion and 28° C for the forced ventilation temperature have better temperature uniformity inside the pigsty. Table 3 Te mperature Un iformity in enclosed pigsty under the diffe rent air change rate of regular ventilation at 28°C for forced ventilation temperature Air change rate per hour (ACH) 1.7 ACH 3.4 ACH 5.1 ACH Temperature uniformity (°C) 1.78 0.99 1.6 4. Conclusions The stoking density of piglets in the enclosed pigsty is 1.77 pig/ m 2 , under the setting of 28°C for both defaulted air temperature and forced ventilation te mperature in the pigsty, collocate with different a ir change rate of regular ventilation, i.e. 1.7 A CH, 3.4 ACH and 5.1 A CH to perfo rm the e xperiment. The concentration of ca rbon dio xide at diffe rent air change rate of regular ventilation are lower than 900 pp m, it is able to stably ma intain the temperature, re lative humidity and concentration of carbon dioxide in the nursery, and achieve the effective heat preservation effect, and maintain the good air quality in the pigsty. When the air change rate of regular ventilation is configured as 5.1 ACH, the concentration of carbon dio xide in the pigsty is quite close to the 400 pp m concentration of carbon dioxide outside the nursery, it is indicated that the air quality in the pigsty is very good. As known fro m the e xpe rimental results, this biogas burn ing hot-water system co llocating with inverter fan to perfo rm the ventilation in enclosed the pigsty, the temperature change in the pigsty is quite un iform, apply to the heat preservation for the enclosed pigsty is feasible and efficient. References [1] P. V. Rao, S. B. Saroj, R. Dey, and S. Mutnuri “Biogas generation potential by anaerobic digestion for sustainable energy development in india,” Renewable and Sustainable Energy Reviews , vol. 14, no. 7, pp. 2086-2094, September 2010. [2] M. Van Haren and R. Fleming, “Electricity and heat production using biogas from the anaerobic digestion of livestock manure-literature review,” University of Guelph, Ridgetown College, 2005. [3] J. B. Holm-Nielsen, T. A. Seadi, and P. Oleskowicz-Popiel, “The future of anaerobic digestion and biogas utilization,” Bioresource Technology, vol. 100, no. 22, pp. 5478-5484, November 2009. 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