IJECA-ISSN: 2543-3717. June 2021 Page 18 

 

 

International Journal of Energetica (IJECA) 

https://www.ijeca.info 

ISSN: 2543-3717 Volume 6. Issue 1. 2021 Page 18-24 

 

Influence of the geographical parameters on the performance of 

hybrid solar gas turbine 

 
Omar Behar

1,2
, Basim Belgasim

3
,
4
 Daniel Sbarbaro

1,2
, Luis Moran

1,2
 

 
1
Solar Energy Research Center (SERC-Chile), Santiago de Chile, CHILE 

2
Department of electrical engineering, University of Concepcion, Concepcion, CHILE 

3
Center for Solar Energy Research and Studies, Tripoli, LIBYIA 

4
Mechanical Engineering Department, University of Benghazi, Benghazi, LIBYIA 

 

 

Email* : beharomar@gmail.com 

 
 

Abs tract – This study aims to investigate the influence of the geographical and climate 

parameters on the performance of the hybrid solar gas turbine with a pressurized air receiver. A 

number of sites located in South America (Chile, Bolivia, and Peru) and North Africa (Algeria and 

Libya) are considered. The geometric design parameters of the solar receiver and the tower are 

calculated using an in-house code. The layout and the optical performance of the heliostat field 

are carried out using SolarPILOT software. The si mulation of the complete hybrid solar gas 

turbine is carried out using TRNSYS software. A  50 M We hybrid solar gas turbine is chosen in this 

study. Results show that a hybrid solar gas turbine installed in North Africa performs better than 

that installed in South America. This is mainly due to the optical performance of the heliostat field, 

which are better in North Africa are than in South America. The highest annual optical efficiency 

of a solar field is observed at Bechar (Algeria) 56.8% while the lowest annual efficiency is 

observed at Antofagasta (Chile) 48.1%.The solar-to-electric efficiency at Atacama Desert  is lower 

than in the Sahara Desert. Indeed, in Atacama region the solar -to-electric efficiency varies from 

17% at Antofagasta to about 18% in Arequipa while it is above 19% at Sabha and Bechar. 

 
Keywords: Solar energy, hybrid solar gas turbine, solar thermal power plants, concentrating 

solar power, solarPILOT, TRNSYS. 

 

 
Received: 30/04/2021 – Accepted: 15/06/2021 

 

 
I.  Introduction 

Concentrating solar power has attracted a lot of interest 

due to its potential for integration with the conventional 

power conversion cycles including Rankine cycles and 

Brayton cycles [1]. The integration of the central rece iver 

system with the Brayton cycles  and combined cycles 

offers several advantages including high solar to electric 

conversion efficiency and scalability [2]. The concept 

that integrates  the central receiver system with the 

 
Brayton cycle is known  as Hybrid  Sola r Gas Turbine 

(HSGT ). In a  typical HSGT, concentrated solar heat is 

used to preheat the compressed air prior to combustion. 

Three research pro jects  name ly SOLGAT E [3–5], 

SOLHYCO [6], and SOLUGAS [7, 8] have 

demonstrated the HSGT technology. 

In sma ll scale systems, the HSGT  technology has been 

studied intensively by many researchers. Researchers 

have investigated the performance of mic ro HSGT 

systems  under different operation conditions  [9]. 

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Omar Behar et al 

IJECA-ISSN: 2543-3717. 

 

 

𝑦 

√𝜃r𝑒𝑐
.𝜋2.𝐻𝖶𝑅r𝑒 𝑐 

Page 19 

 
 

 

the performance of the GT based on a parabolic 

concentrator has been analysed for solar only and hybrid 
𝑃𝑛𝑜𝑚_𝑟𝑒𝑐 = 

𝑆𝑀.𝑃𝑛𝑜𝑚_𝑝𝑏 

𝑦𝑛𝑜𝑚_𝑝𝑏 

 

(1) 

operation [10]. Technica l, economic and environ mental 

evaluation including therma l design were  presented by an 

in-depth study [11]. Thermo-economic  modelling and 

simu lation were  also provided [12]. The effect of in let 

temperature on the performance of sma ll scale  HSGT  

systems were presented [13]. A thermodynamic  and CFD  

modelling were presented for a small scale HSGT power 

Where SM is the solar mult iple, P re fers to power, and  

η refe rs  to the efficiency. Subscripts  “nom” and “pb” 

refer to nominal and power block respectively. 

The inc ident receiver power on the receiver fro m the  

heliostat field is a function of the receiver nominal 

efficiency: 

generation unit [14]. A sma ll scale solar tower integrated 

with gas turbine system has been presented [15]. Behar 

investigated an innovative design for the the preheating 

𝑃𝑛𝑜𝑚_𝑟𝑒𝑐_ i𝑛𝑐 = 
𝑃𝑛𝑜𝑚_ r𝑒𝑐

 

𝑛𝑜𝑚_r𝑒𝑐 
(2) 

system of the HSGT  p lants [16]. Also, a  therma l analysis 

of HSGT system integrated with parabolic d ish collector 

was presented by a group of researchers [17]. A  study 

investigated the domestic applications  of the small scale 

Subscripts  “rec” and “inc” refer to the receiver and 

incident power respectively. The average allowable flux 

is calculated as: 

HSGT systems  based on axial turbine system [18]. 

Investigation predicted the simulation procedure of the 
𝐹𝑎𝑣g = 

𝐹𝑝𝑒𝑎𝑘 

𝐹𝑅 
(3) 

performance of the HSGT systems  [19]. Regarding to 

large scale HSGT  systems, there is a c lear shortage in the 

studies  and research based on the previous  literature. 

Recently study suggested a design methodology for the 

Where Favg is the average heat flux, Fpeak is the peak 

heat flux, and FR is the peak-to-average heat flux ratio. 

The receiver area is calculated as: 

 
𝑃𝑛𝑜𝑚_ i𝑛𝑐 

solar field of the large scale HSGT systems  [20]. The 

study included modelling and simulation validated by 

𝐴𝑟𝑒𝑐 = 
𝐹𝑎𝑣𝑔 

(4) 

real data from a case study. 
The radius  of the receiver is given as: 

This  paper aims  to investigate the influence of the    

geographical and climate parameters  on the performance 

of commercial HSGTs  integrated with heliostat solar 
𝑅𝑟𝑒𝑐 = 

  𝐴r𝑒𝑐  

𝜋 

(5) 

filed and central pressurized  air receiver.  A nu mber of 

sites  located in South America and North Africa a re 

selected. A simp lified  methodology is adopted to design 

the solar filed of each site and the optical performance is  

predicted using SolaPILOT simu lation tool. The whole 

system is modelled using the well-known energy 

simulation tool TRNSYS 18 using the input data from 

Where: θrec is the opening angle of the cavity. 

HWRrec is the height to width ratio of the receiver. 

The height of the receiver is: 

𝐻𝑟𝑒𝑐 = 2. 𝑅𝑟𝑒𝑐. 𝐻W𝑅𝑟𝑒𝑐 (6) 

The width of the aperture of the receiver is 

the design process  and optical analysis  for each of the 

proposed locations  of the study. 
W𝑎𝑝 = 2. 

𝑅𝑟𝑒𝑐 
. cos (𝜋−𝜃r𝑒𝑐) . AWR (7) 

2 

 
II.  Methods and tools 

 
II. 1 .  A practical technique to design the solar receiver 

and the tower 

The central receiver system includes  the heliostat 

fie ld, the solar receiver, and the tower. A pract ical 

technique is used to design the solar receiver and the  

tower. A cavity-type receiver is considered in this study. 

The nominal powe r of the receiver can  be ca lculated 

using the following expression: 

Where: AWR is the aperture width to total width ratio. 

The aperture height is 

 
𝐻𝑎𝑝 = 2. 𝐻𝑟𝑒𝑐. 𝐴𝐻𝑅 (8) 

 
Where: AHR is the aperture he ight to total height 

ratio. The tower height is estimated using the following  

expression: 

 

𝐻𝑡𝑜w𝑒𝑟 = 0.6806. 𝑃𝑛𝑜𝑚_𝑟𝑒𝑐 + 106.60 (9) 

Pnom_rec is in MW is the above equation. 



Omar Behar et al 

IJECA-ISSN: 2543-3717. 

 

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II. 2 .  The tool used to design the heliostat field 

SolarPILOT is  used to design the heliostat field. 

SolarPILOT software is dedicated to design and estimate  

the performance of the central rece iver systems. It was  

developed as  an extension to DELSOL3 with several 

improve ments  in the he liostat field  layout, 

characterizat ion, para metric  simu lation, plotting, and 

optimization of the centra l receiver system. It uses the 

analytical flu x image He rmite series approximat ion and 

applies  the analytical model to individual he liostat 

images. In addit ion, it  uses a Monte-Carlo ray-t racing 

technique for the optical modeling of the solar receiver. 

 
II. 3 .  The tool used to design the simulate the complete 

system 

TRNSYS is used to simu late the performance of the  

HSGT. T RNSYS is a simu lation tool of time -dependent 

energy systems. It has a solar library, wh ich includes 

some solar concentrating collectors such as the parabolic  

trough concentrator and central rece iver system. The 

lib rary na med Sola r Therma l Electricity Co mponents 

(ST EC) is useful to model and simulate the HSGT. It  

includes  Rankin  and Bryton cycles  in addit ion to the 

central rece iver system. The HSGT mode l is illustrated in  

Figure 1. It consists  from three weather data file, 

heliostat solar field, centra l pressurized air receiver and  

Briton cycle components. 

 
 

 
 

Figure 1. T RNSYS model of HSGT  syst em. 

 

 
 

III.  Results and discussions 

The locations proposed to be considered in this study 

are de monstrated in Tab le 1 including the country, 

latitude, longitude and time zone. 

 

T able 1. Select ed locat ions for t he st udy 
 

C ou ntry Ti me  

z on e 

C h i le  

Ant ofagasta ( 23°39'3.34"S 70°23'51.01"W) ele 16m GMT -4 

Pe ru   

Arequipa-Characa ( 16°30'26.19"S 71°31'15.30"W) 
ele 2782m 

GMT -5 

Bol ivi a  

Oruro-Juan-Mendoza ( 17°57'48.24"S 67° 4'23.77"W) 
ele 3709m 

GMT -4 

Al ge ria  

Bechar ( 31°37'25.72"N 2°12'58.48"W) ele 791m GMT +1 

Li bya  

Sebha ( 27° 2'11.55"N 14°25'44.49"E) ele 426m GMT +2 

 

III. 1 .  Results of heliostat field and receiver design 

To calculate  the geo metric  design para meters of the  

tower and the receiver, the nominal e ffic iency of the GT  

is taken as 37%. The no mina l efficiency of the receiver is  

80% . The rece iver is supposed to be built with Incoloy  

800H. The allowab le peak flu x is 1000 kW/m
2
. A pea k to 

average flu x ratio of 1.78 is considered. The opening 

angle of the rece iver is 180°. The  aspect ratio of the 

receiver (height to diameter ratio) is  1.27. 

 
The ratio of the height of the aperture to the height of 

the receiver is 0.9. The rat io of the width of the aperture 

to the total width of the rece iver is 0.9. The solar mu ltip le 

SM=1. Table  2 illustrates the design para meters of the  

central rece iver system for a  hybrid solar gas turbine of 

50 MWe. The nominal power o f the receiver is 135.14 

MWth, its absorptive surface is 300.68 m
2
. The aperture 

of the rece iver is a rectangle of 11.20 m in height and 8.8 

m in width. The height of the tower is 198.57 m. The  

reflective surface of the heliostat field is  248776.02 m
2
. 

 
T able 2. Design parameters of a heliostat field system for 50MWe solar 

gas t urbine. 

Parameter u n i t Val u e 

Nominal power of the receiver MW 135,14 

P ower int ercept on t he receiver MW 168,92 

Receiver absorbt ive surface m
2  

300,68 

Receiver height M 12,44 

Radius of t he receiver M 4,90 

Widt h of the aperture M 8,80 

Height  of t he aperture M 11,20 

Apert ure area m2 98.71 

Height  of t he tower M 198,57 

Reflect ive surface of t he solar field m2 248776,02 



Omar Behar et al 

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The layout and the optical perfo rmance of the heliostat 

fie ld are  carried out using Sola rPILOT  software. This  

software requires  main ly the data of the location, the 

dimensions  of a single heliostat, the geometric  

dimensions of the receiver and the tower, and the optical 

proprieties  of the heliostat and the receiver. Figure 2 

shows the layout and the annual optical efficiency of the  

heliostat field  installed at the selected sites. The layout 

method is radia l stagger and the sun location at the 

design point is the summer solstice. 

 

 

Figure 2a. Layout  and average annual optical efficiency of the solar 

field inst alled at  Bechar, Algeria. 

 

Figure 2b. Layout  and average annual optical efficiency of the solar 

field inst alled at  Oruro, Bolivia. 

 

Figure 2c. Layout  and average annual optical efficiency of the solar 

field inst alled at  Antofagasta, Chile. 

 

 
Figure 2d. Layout  and average annual optical efficiency of t he solar  

field inst alled at  Sebha, Libya. 

 

Figure 2e. Layout and average annual optical efficiency of the solar  

field inst alled at  Arequipa, P eru. 

 
Table 3 illustrates  the nominal and annual optical 

efficiencies of the heliostat field at each site. There is a 

slight diffe rence between the nominal effic iencies of the 

heliostat fie ld at the selected locations. It varies fro m 

59.5%  at  Sebha (Libya) to 62.1 at  Arequipa (Peru). 

However, there is a significant difference between the 

annual optical effic iencies. The annual optical e ffic iency 

of a heliostat field installed in No rth Africa is so much 

higher than the annual optical efficiency of a heliostat 

fie ld installed in South A merica. The highest annual 

optical effic iency of a solar fie ld is observed at Bechar 

(Algeria) 56.8% fo llo wed by Sebha (Libya) 56.2 %. The  

lowest annual effic iency is  observed at Antofagasta 

(Chile) 48.1%. 

 
T able 3. T he nominal and annual optical efficiency of the heliostat field 

at  different  locat ions. 

Locat ion Count ry Nominal 

opt ical 

efficiency (%) 

Annual opt ical 

efficiency (%) 

Bechar Algeria 60.9 56.8 

Oruro Bolivia 61.5 49.9 

Ant ofagasta Chile 59.1 48.1 

Sebha Libya 59.5 56.2 

Arequipa P eru 62.1 50.3 



Omar Behar et al 

IJECA-ISSN: 2543-3717. 

 

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Figure 3 shows  the heat flu x distribution at the 

receiver aperture, on March 21
st

 at noon, for the five 

selected sites. The direct norma l irrad iance is 1 kW/ m
2
. 

The average heat flux at the receiver’s aperture varies 

fro m 1147.6 to 1421.9 kW/m
2
. This corresponds to an 

average heat flu x on the receiver’s absorptive surface of 

376.26-463.28 kW/m
2
. 

 

 

Figure 3a. Heat  flux dist ribution at t he aperture of t he solar receiver for 

t he case of Bechar (Algeria) 

 

 

Figure 3b. Heat  flux dist ribut ion at the aperture of the solar receiver for 

t he case of Oruro (Bolivia) 

 

 

Figure 3c. Heat  flux dist ribution at t he aperture of t he solar 

receiver for t he case of Antofagasta (Chile) 

 

 
Figure 3d. Heat  flux dist ribut ion at  the aperture of the solar 

receiver for t he case of Sebha (Lybia) 

 

Figure 3e. Heat  flux dist ribution at t he aperture of t he solar 

receiver for t he case of Arequipa (P eru) 

 

 
 
 

III. 2 .  Results of the complete HSGT system 

The Siemens  SGT-800 gas  turbine system of capacity 

50 MWe is used as a case study in this  work. The 

Brayton cycle design and operation parameters of this 

type of gas  turbine is  shown in Table 4. 

 
T able 4. Gas t urbine t echnical dat a. 

 

Parameter Val u e  

Out put  power ISO 50.5 MWe 

Elect rical efficiency 38.3% 

Heat  rat e 9,407 kJ/kWh 

Compressor pressure ratio 21.1:1 

Exhaust  gas flow 134.2 kg/s 

T urbine inlet temperature 1237.6 °C 

Exhaust  t emperature 553 °C 

 

The HSGT  system is simulated based on the results of 

the solar fie ld and centra l rece iver obtained in  the 

previous section. These results are integrated  with the 

design and operation parameters of SGT -800 gas turbine 

in the T RNSYS model. The gas turbine cycle e ffic iency 

of the all locations is presented in Figure 4. It can be 

noticed that the gas turbine effic iency at Atacama Desert 

(Che li, Pe rue and Bo liv ia) is higher than Sahara region  

(Algeria and Libya) in which it is 40% and 39% 

respectively. This  result is due to the fact that the annual 



Omar Behar et al 

IJECA-ISSN: 2543-3717. 

 

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average ambient temperature at Atacama locations  is 

lower than at Sahara Desert as can be seen in Table 5. 

 
 

Figure 4. Gas t urbine efficiency for the all locations 

 

 
T able 5. Average annual ambient  t emperat ure. 

 

Locat ion Average t emperature 

Oruro-Bolivia 5.8 °C 

Ant ofagasta-Chile 16.8 °C 

Arequipa-P eru 14.7 °C 

Bechar-Algeria 22.4 °C 

Sebha-Libya 23 °C 

 

Figure 5 de monstrates the solar-to-electric efficiency 

of the HSGT system fo r the all locations. It can be 

noticed that the solar-to-electric  effic iency at Atacama 

Desert is lowe r than in the Sahara  Desert. In more details, 

in Atacama region the solar-to-electric e fficiency varies 

fro m 17% at Antofagasta to about 18% in Arequipa. On  

the other hand, the efficiency of Sabha and Bechar is  

above 19.5%. The reason behind this is e xpla ined in the  

previous section in which the optical effic iency of the 

heliostat field in Sahara Desert is higher than in the 

Atacama region. 

 
 

Figure 5. Solar-t o-elect ric efficiency of HSGT  

IV .  Conclusion 

 
This paper investigated the influence of the location 

on the performance of the hybrid solar gas turbine. An  in-

house code and   two co mmerc ia l software were used  to 

provide a co mprehensive study. Results showed that  the 

location has a strong influence on the layout and the 

annual optical efficiency of the heliostat field. 

The annual optical efficiency of a heliostat field in North  

Africa is higher than that in South America. The highest 

annual optical effic iency of a  solar fie ld is observed at 

Bechar (56.8% ) while lowest is observed at Antofagasta 

(48.1%). However, because of the lo w a mbient 

temperature at Atacama, the gas turbine effic iency at in 

Chlie, Perue and Boliv ia is higher than Sahara (Algeria  

and Libya). Overa ll, the solar-to-e lectric e ffic iency at 

Atacama is lower than in the Sahara Desert. In Ataca ma  

the solar-to-electric e ffic iency varies fro m 17% to 18% 

while in Sahara it is above 19%. 

 
Acknowledgements 

This work was supported by La Agencia Nacional de  

Investigación y Desarrollo (ANID), project nu mber 

ANID/FONDAP/ 15110019 “ Solar Ene rgy Research 

Center” SERC-Chile. 

 
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