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Technical and economic assessment of the integrated solar combined cycle power plants in Iran
Renewable Energy 30 (2005) 1541–1555 www.elsevier.com/locate/renene
Technical and economic assessment of the integrated solar combined cycle power plants in Iran R. Hosseinia,*, M. Soltanib,1, G. Valizadehb,1 a
Mechanical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., P.O. Box 15875-4413, Tehran, Iran b Mechanical Systems Department, Niroo Research Institute (NRI), End of Pounak Bakhtari Blvd., P.O. Box 14665-517, Shahrak Gharb, Tehran, Iran Received 13 June 2004; accepted 7 November 2004 Available online 24 December 2004
Abstract Thermal efficiency, capacity factor, environmental considerations, investment, fuel and O&M2 costs are the main parameters for technical and economic assessment of solar power plants. This analysis has shown that the Integrated Solar Combined Cycle System with 67 MW e solar field (ISCCS-67) is the most suitable plan for the first solar power plant in Iran. The Levelized Energy Costs (LEC) of combined cycle and ISCCS-67 power plants would be equal if 49 million $ of ISCCS-67 capital cost supplied by the international environmental organizations such as Global Environmental Facilities (GEF) and World Bank. This study shows that an ISCCS-67 saves 59 million $ in fuel consumption and reduces about 2.4 million ton in CO2 emission during 30 years operating period. Increasing of steam turbine capacity by 50%, and 4% improvement in overall efficiency are other advantages of ISCCS-67 power plant. The LEC of ISCCS-67 is 10 and 33% lower than the combined cycle and gas turbine, respectively, at the same capacity factor with consideration of environmental costs. q 2004 Elsevier Ltd. All rights reserved. Keywords: Solar thermal; Parabolic trough; Power plant; Assessment
* Corresponding author. Tel.: C98 21 6405844; fax: C98 21 6419736. E-mail addresses: [email protected] (R. Hosseini), [email protected] (M. Soltani), [email protected] (G. Valizadeh). 1 Tel.: C98 21 8079393; fax: C98 21 8590171. 2 Operation and maintenance. 0960-1481/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2004.11.005
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Nomenclature AC C Cg Cs Csol Cf CRF Eout Fb gf Ha1 Ha2 Hsol kg ks ksol LEC LHV N Ng Ns O&M PVF r Wg Wgn Wsn Wsr h hg hs
Annual investment cost, $ Total investment cost, $ Initial investment cost in gas unit, $ Initial investment cost in steam unit, $ Initial investment cost in solar unit, $ Basic fuel price, ¢/m3 Cost Recovery Factor Total amount of gross generated energy, kW h Annual fuel cost without consideration of discount rate, $ Annual fuel cost discount rate, % Annual working hours of power plant (peak mode) Annual working hours of gas units (peak mode) Annual working hours of solar unit O&M factor for gas unit O&M factor for steam unit O&M factor for solar unit Levelized energy cost, ¢/kW h Fuel lower heating value, kJ/m3 Power plant life expectancy, year Number of gas units Number of steam units Operation and maintenance cost, $ Annual fuel cost, $ Dollar discount rate, % Net power of gas unit, MW Nominal power of gas units, MW Nominal power of steam units, MW Net power of steam unit, MW Thermal efficiency, % Annual net efficiency of gas unit, % Net efficiency of SEGS power plant in fossil mode, %
1. Introduction Iran is situated in 378N and has large areas that receive solar energy. It has a considerable potential for solar power plants. About 25% of Iran is consisted of deserts which receive daily solar irradiation about 5 kW h/m2. If 1% of these areas can be covered
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by solar collectors,3 energy obtained will be five times more than annual gross electricity production in Iran4 [1]. Suitable areas for constructing solar thermal power plant in Iran are in center and south of Iran. Studies show that the most suitable place is in Yazd5 [2]. Nowadays, the highest capacity of solar power plants belongs to solar troughs. This kind of solar power plant is more economical than the others. Pressure drop in solar field limits the capacity of solar trough to 100 MW. Pressure drop is a direct function of solar field dimensions. The solar field is comprised of parallel rows of Solar Collector Assemblies (SCA). SCAs supply thermal energy to produce steam to drive a steam turbine/generator in Rankine cycle or ordinary combined cycle. The collectors are singleaxis tracking and aligned on a north–south line, thus tracking the sun from east to west. Low-iron glass parabolic mirrors reflect the solar radiation to the absorber, which is situated in focus axis of mirrors. The concentration factor of solar radiation on absorber is about 20–100%. This value is about 80% in LS-3 collectors [3]. The maximum temperature in absorber is about 400 8C. Thermal storage system is rarely used because of high prices, however, it can be used in small solar power plants6. This technology can be used for nations in regions with high direct normal solar radiation (such as Africa, China, Middle East, the Mediterranean and Central and South America) to develop a rational approach the deployment of solar thermal electric systems within their country. Egypt, Jordan and Brazil are considered for building Integrated Solar Combined Cycle System (ISCCS). Financial analysis in Jordan has shown that solar thermal electricity generation is possible at 4.5 ¢/kW h [4]. The cost of electricity from line—concentrator solar parabolic trough plants decreased by 83% in less than a decade, due both to technological improvements and economies of scale in production [4]. The World Bank has made 200 million USD in financial assistance available for new combined-cycle gas and solar thermal power plants in developing countries. In Spain, a law increasing compensation for electricity produced from solar thermal energy with a premium of 12 ¢/kW h above the market price of 4 ¢/kW h is expected shortly [5]. A feasibility study was carried out for the World Bank/GEF and the Commission Federal de Electricidad on a net 285.1 MW e power plant consisting of a solar steam system integrated with a natural gas fired combined cycle system located at Cerro Prieto near Mexicali, Baja California Norte. The Levelized Electricity Cost is about 9 ¢/kW h [6]. Solar trough is among the most cost effective renewable power technologies with nearterm power generation costs in the range of 12–20 ¢/kW h and of 5–10 ¢/kW h for long term considerations. And it is the lowest cost solar electricity in the world, promising cost competitiveness with fossil-fuel plants in future. The Intergovernmental Panel for Climate Change (IPCC) demands drastic reductions of the greenhouse gas emissions in order to avoid a collapse of the world climate by committed itself to a 6%, US to 7% and 3
Assume the efficiency of solar energy conversion to electricity 10%. Total gross electricity production in 2001 is 127,138 MW h. 5 It is situated in center of Iran. 6 Lower than 15 MW. 4
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the European Union to 8% CO2 reduction of the 1990 levels until 2012 [7]. Also some of the main sponsors of energy investments in the developing world, i.e. the Worldbank Group, the Kreditanstals fur Wiederaufbau (KfW) and the European Investment Bank (EIB) have recently been convinced of the environmental promises and the economic prospectives of Solar Thermal Power technologies: only in spring 2000, the broad of the GEF approved grants for first solar thermal projects in Egypt, India, Mexico, and Morocco of app. US$ 200 million in total [7]. In 1998, Pilkington predicted 877 $/kW capital cost and lower than 8 ¢/kW h Energy price for an ISCCS plant in Morocco [8]. The main parameters, which considered and compared in these plants, are power plant net efficiency, capacity factor, fuel consumption and solar field capacity. The Levelized Energy Cost method (LEC) is a suitable way for economical assessment of different cases. LEC is the summation of investment, operation and maintenance cost as well as fuel cost, and it is expressed as ¢/kW h. In this study, six cases are considered for Yazd power plant (1) Gas Turbine power plant (GT): 2!123.4 MW gas turbine; (2) Combined Cycle power plant (CC): 2!123.4 MW gas turbine C123.4 MW steam turbine; (3) Integrated Solar Combined Cycle System with 33 MW e solar field (ISCC-33): 2! 123.4 MW gas turbine C156 MW steam turbine C33 MW solar field; (4) Integrated Solar Combined Cycle System with 67 MW e solar field (ISCC-67): 2! 123.4 MW gas turbine C198 MW steam turbine C67 MW solar field; (5) Integrated Solar Combined Cycle System with 67 MW e solar field and Auxiliary Firing system (ISCC67-AF): 2!123.4 MW gas turbine C198 MW steam turbine C 67 MW solar field C67 MW Auxiliary Firing; (6) Solar Electric Generating System (SEGS): 67 MW steam turbine C67 MW solar field.
2. Integrated solar combined cycle system In an ISCC, gas turbine is the same as conventional combined cycle, and the required energy for producing steam can be supplied by both gas turbine exhaust and solar field (Fig. 1). Preheating the feed water and superheating the steam will be performed by gas turbine exhaust. In ISCC power plant, higher pressure and temperature steam can be produced because of extra solar energy compared with combined cycle. Steam produced in ISCC power plant is 500 8C with 100 bar pressure. These values are higher than steam properties in SEGS and conventional combined cycle, thus the efficiency in ISCC is more than SEGS and CC. Steam turbine capacity in conventional combined cycle, is 50% of gas turbine capacity, but in ISCC, the solar field increases steam turbine capacity about 50% compared with CC. Electricity production drop in summer does not occur in ISCC because as ambient
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Fig. 1. Schematic of an integrated solar combined cycle system.
temperature increases, solar field absorbs more energy. Thus, it has a stable energy production through the year. The ISCC can work in following modes (1) Integrated solar combined cycle mode at solar hours; (2) Conventional combined cycle mode at non-solar hours; (3) Gas turbine mode when the steam turbine is not functioning. This study considers three ISCC power plant. ISCC-33 is a combination of two gas turbine (each one has 123 MW e), a steam turbine (161 MW e) and solar field (33 MW e), ISCC-67 is the same, but the steam turbine capacity is 198 MW e and solar field (67 MW e), ISCC67-AF is the same as ISCC-67, but it has auxiliary firing system for nonsolar hours. The capacity of auxiliary firing system is 67 MW e. At non-solar hours, steam turbine of ISCC-67 will work in 63% of its capacity. Therefore, an auxiliary firing system can be performed to use the idle capacity of steam turbine. Auxiliary firing devices, can be installed at the inlet of flue gas passage. When flue gas passes through this system, its temperature will raise and more steam in heat recovery steam generator can be produced. The efficiency of fuel energy conversion to electricity in auxiliary burners is about 36.9%.7 This amount is lower than the gas turbine efficiency in ISO conditions [9]. Therefore, it is recommended to use auxiliary firing system just at peak hours. For example, if we use it 4 h a day (1200 h a year), the annual electricity production will be 85.8 GW h and fuel consumption through this period will be 22!106 m3 [9,10]. 7
Ambient temperature is assumed 20 8C.
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Fig. 2. Net efficiency of different cases in maximum capacity factor.
For ISCC-33, steam turbine will work in 78% of its full capacity at non-solar hours. So it is not essential to use the auxiliary firing system. Other advantages of ISCC power plants are Increasing the steam turbine capacity of conventional combined cycle; Better performance of combined cycle power plants in warm days.
3. Technical assessment of the cases One of the main factors in technical evaluation of different power plants, is the net efficiency. Annual net efficiency of six cases are shown in Fig. 2. These values are related to maximum capacity factor. Low quality of generated steam in SEGS decreases its efficiency to the lowest level. Extra solar energy in ISCC-33, ISCC-67 and ISCC67-AF, raises the quality of generated steam and thus their efficiencies are higher than the conventional combined cycle hISCC67 O hISCC67AF O hISCC33 O hCC O hSEGS O hGT Energy production is influenced by local conditions of power plant. Table 1 shows the produced energy of the cases in different seasons. Produced energy in different seasons by ISCC-67 are shown in Fig. 3. It can be seen that the energy production by solar part is maximum in summer. As mentioned before, power generation in summer decreases in ordinary power plants, but in Table 1 Energy production in different seasons Total energy production (MW h)
Spring
Summer
Autumn
Winter
Annual
CC ISCC-33 Solar field of ISCC-33 ISCC-67 Solar field of ISCC-67
749,868 767,298 17,430
708,059 732,090 24,031
737,931 756,494 18,563
780,890 794,084 13,194
2,976,748 3,049,966 73,218
785,257 35,389
756,850 48,791
775,619 37,688
807,678 26,788
3,125,403 148,655
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Fig. 3. Variation of energy production of ISCC-67 through seasons.
solar power plants the power generation drop in summer is compensated by the solar energy. So solar power plants have more stable power generation. Fig. 4 is a comparison of power generation between CC, ISCC-33 and ISCC-67 in a summer day. It expresses that when power generation in combined cycle is minimum, the others have maximum power generation. To specify the capacity of solar field, some points should be considered. At non-solar hours, the steam turbine must work at least in its 50% capacity. So the maximum capacity of solar field will be 100 MW. On the other hand, for SEGS and ISCCS, the solar field capacity cannot be more than 100 MW, because the pressure drop through the solar field rises considerably and the main part of absorbed energy should be used to overcome the pressure drop. Therefore, in this study two capacity, that is 33 and 67 MW e are considered for solar field. These are 22 and 37% of steam turbine capacity, respectively. So at nonsolar hours the steam turbine will work in a capacity factor which is higher than 0.7. The proposed thermal capacity in conceptual design is 185 MWth (equal to 67 MW e) [9]. Although, the lower field capacity like 33 MW e makes the power plant performance better, but decreases solar energy share in power generation about 50%. This reduces
Fig. 4. Net power variation of ISCC plans and CC in a summer day.
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Table 2 Gross energy production in different cases Type of power plant
Annual energy production (GW h)
Capacity factor (%)
Annual work hours (full load)
GT CC ISCC-33 ISCC-67 ISCC67-AF SEGS
1732 2730 2799 2870 2958 140
80.1 82.8 79.3 73.7 76 23.9
7017 7343 6950 6453 6658 2092
the chance to gain loans from World Bank and Global Environmental Facilities (GEF) [11, 12]. Also economical aspects are main characters in specifying the solar field capacity. One of the main variables for technical evaluation of a power plant is the capacity factor, which is defined as the ratio of annual produced energy to maximum annual energy that can be produced. To determine capacity factor, we should know the annual energy production. By considering 1 month for power plant overhauls, total annual energy production and the capacity factor of GT, CC, ISCC-33, ISCC-67, ISCC67-AF and SEGS are calculated and shown in Table 2. The capacity factor of combined cycle is about 5–10% more than ISCC plans. The reason is that the solar hours are eliminated through the year.
4. Economical assessment of the cases Levelized Energy Cost method (LEC), is used to compare different cases. The lowest LEC determines the best choice. So, the investor should calculate the LEC of power plant at first. The lowest LEC does not mean the best efficiency. LEC is a relationship between the efficiency and cost and LEC calculation can lead us to the economical choice. LEC can be expressed as: LEC Z
ðACÞ C ðO&MÞ C ðPVFÞ Eout
(1)
This part describes the method of calculating the LEC. Cost Recovery Factor (CRF) cross to total investment cost (C) gives annual investment cost AC Z ðCRFÞ !C Eq. (3) determines the cost recovery factor: r ðCRFÞ Z 1 K ð1 C rÞKN
(2)
(3)
Gas turbine life expectancy is about 20 years and the steam power plant and ISCC plans life are 30 years. Eq. (4) calculates the total investment cost (C) C Z Cg C Cs C Csol
(4)
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The operation and maintenance cost is a percentage of total investment cost. It is 5, 2 and 1.5% of investment cost in gas unit, steam unit and solar unit, respectively ðO&MÞ Z kg Cg C ks Cs C ksol Csol
(5)
To find fuel cost, it is required to determine the net power and net efficiency of gas unit.8 For SEGS power plant, the net power of steam unit, its efficiency and working hours should be specified 1 C gf 1 C gf N PVF Z Fb 1K (6) r K gf 1 Kr Fb can be caculated as follows: Fb1 Z
Cf !Wsr !ðHa1 K Hsol Þ ðfor SEGSÞ hs !LHV
(7)
Fb2 Z
Cf !Wgr !Ha2 ðfor other casesÞ hg !LHV
(8)
Ha1 Z Cf !8760
(9)
Total amount of gross generated power is: Eout Z ðNg !Wgn C Ns !Wsn Þ !Cf !8760
(10)
Substituting these values in Eq. (1), will give us the LEC. Because of complicated calculations and many parameters involved, a computer program was prepared. 5. Results Fig. 5 shows the fuel consumption in six cases. In order to compare the fuel consumption of each power plant, it is expressed as m3/MW h. The fuel consumption in conventional combined cycle is more than the others. The ISCC-67 has lower fuel consumption about 16% than combined cycle. The decrease in fuel consumption in ISCC33 and SEGS are 8 and 13% respect to combined cycle. The ISCC-67 and SEGS have the same solar field capacity, but the better efficiency of ISCC-67 makes its fuel consumption lower. Studies show that by using solar field, fuel cost of conventional combined cycle decreases considerably. If we assume the fuel price (natural gas) 4.5 ¢/m3, ISCC-67 and SEGS save about 1.3!109 m3 (58.8 million $) through 30 years. This amount for ISCC-33 is about 29 million $. Greenhouse effects lead us to consider the environmental effects of different cases. CO2 is the main part of pollution in atmosphere, which increases greenhouse effects. Fig. 6 shows the CO2 production by different cases in capacity factor of 0.74. CO2 production in gas unit is maximum and it decreases in SEGS, conventional combined cycle, ISCC-33, ISCC-67, respectively. ISCC-33 and ISCC-67 produce 16 and 8% lower CO2 than 8
Only gas unit consumes fuel.
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Fig. 5. Natural gas consumption per unit of produced energy for different cases in capacity factor 0.74.
combined cycle. Pollutant emission not only has the environmental effects, but also results to economical problem. This economical problem returns to extra cost for equipments that can remove the CO2 from flue gas. If we consider the CO2 removal cost about 25 $/ton [13], the difference in specific cost between combined cycle, ISCC-33 and ISCC-67 will be decreased about 74–168 $/kW. LEC is the main economical parameter for evaluating the proposed cases. The economical assumptions for calculating LEC are presented in Table 3. Fig. 7 shows the LEC amount based on Table 3 values and the maximum capacity factor. It has broken the LEC to three parts as investment cost, O&M cost and fuel cost. Fig. 8 shows the amount of LEC at conditions like Fig. 7, but it considers the environmental costs. The interesting point of Fig. 7 is the effect of environmental cost. As mentioned before, the pollutant emission damages the environment and increases the cost. If we ignore the environmental cost, the combined cycle has the lowest LEC (Fig. 7). In this case, the LEC of ISCC-33, 14%, ISCC-67, 24% and gas unit 21% are higher than combined cycle. In Fig. 8, where the environmental effects are considered, LEC of ISCC-67 will be lower than combined cycle. In this case the LEC of ISCC-33, 8%, combined cycle 11%
Fig. 6. CO2 emission per unit of produced energy for different cases in capacity factor 0.74.
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Table 3 Economic assumptions for calculating the LEC in different cases Parameter
Symbol
Unit
Value
Life expectancy of steam unit Life expectancy of gas unit Life expectancy of solar field Annual discount rate Specific cost of steam unit of CC Specific cost of gas unit Specific cost of solar field 33 MW Specific cost of solar field 67 MW O&M cost factor of steam unit of CC O&M cost factor of gas unit O&M cost factor of solar field LHV of natural gas Natural gas price Solar hours (full load) Net efficiency of SEGS Efficiency of supplementary heater of SEGS Annual net efficiency of gas turbine Efficiency of auxiliary firing unit Internal consumption of SEGS Internal consumption of gas unit Internal consumption of CC Internal consumption of ISCC-33 Internal consumption of ISCC-67
Ns Ng Nsol R Cs Cg Csol33 Csol67 ks kg ksol LHV Cf Hsol hSEGS hH hg hAF ASEGS AG ACC AISCC-33 AISCC-67
year year year year $/kW $/kW $/kW $/kW % % % kcal/m3 ¢/m3 h % % % % % % % % %
30 15 30 10 635 235 1400 1000 2 5 1.5 8590 4.5 2092 33.4 83 32.2 36.9 8 1.5 3 3.5 3.9
and gas turbine 33% are higher than ISCC-67. The environmental cost in combined cycle and gas turbine increases their LEC about 38 and 36%, respectively. Figs. 9 and 10 show the LEC of cases as a function of capacity factor. As it can be seen, the LEC decreases by increasing the capacity factor. Fig. 11 explains the variation of ISCC-67 LEC, when solar field specific cost, changes.
Fig. 7. LEC of different cases in maximum capacity factor without considering environmental cost (natural gas price, 4.5 ¢/m3).
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Fig. 8. LEC of different cases in maximum capacity factor with considering environmental cost (natural gas price, 4.5 ¢/m3).
If the solar field specific cost decreases to 300 $/kW, the LEC without considering environmental effects, is equal to conventional combined cycle. So it is required to invest 49 million $ extra to economize the ISCC-67 case. The other main parameter in economical assessment is the specific cost. The specific cost of each part of power plant is in certain range (Table 4), but for power plant it should be calculated.
Fig. 9. LEC variation of different cases without considering the environmental costs (natural gas price, 4.5 ¢/m3).
Fig. 10. LEC variation of different cases with considering the environmental costs (natural gas price, 4.5 ¢/m3).
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Fig. 11. LEC variation of ISCC-67 in different solar field specific cost.
The computer program, calculates this parameter. The results are presented in Fig. 12. It expresses that the specific costs of ISCC plans are about 37–52% more than conventional combined cycle. Thus, these projects need to be supported by international organizations like GEF. GEF statistics shows that four projects in India, Morraco, Egypt and Mexico have used this loan [14]. Table 4 Overall technical and economic specifications of different cases for Yazd solar power plant Parameter
Unit
GT
CC
ISCC-33
ISCC-67
ISCC67AF
Nominal capacity of power plant Annual net efficiency Maximum capacity factor Investment cost Specific cost Saving fuel in 30 yearsa CO2 emission reduction in 30 yearsa LECb LECc
MW e
246
371
407
444
444
a
SEGS 67
%
32.2
49.3
50.9
51.6
50.9
35.4
%
80.1
83.8
79.3
73.7
76
74
255 573 59
110 1635 59
Million $ $/kW Million $
58 235 –
137 370 –
Million ton
–
–
¢/kW h ¢/kW h
1.986 2.716
1.639 2.263
206 506 29
251 564 59
1.2
2.4
2.4
2.4
1.878 2.195
2.035 2.035
2.087 2.29
4.116 4.116
Fuel saving and reduction in CO2 emission return to solar energy usage. Without considering of environmental costs (pollutant removal cost), natural gas price 4.5 ¢/m3 and in maximum capacity factor. c With considering of environmental costs (pollutant removal cost), natural gas price 4.5 ¢/m3 and in maximum capacity factor. b
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Fig. 12. Specific cost of different cases.
6. Conclusions The technical and economic assessment of different cases for Yazd solar power plant shows that the INTEGRATED SOLAR COMBINED CYCLE SYSTEM (ISCC-67) is the most suitable project for construction of first solar power plant in Iran. Its construction can be performed modular, which is consisted of solar field and combined cycle. The results of technical and economical assessment are summarized in Table 4. It shows that, LEC of combined cycle without considering the environmental effects is the lowest. If we consider the environmental effects, the ISCC-67 will have the lowest LEC, which is about 10 and 33% lower than combined cycle and gas turbine, respectively. Also if 49 million $ of investment cost is supplied by international organizations, the LEC of ISCC67 will be equal to combined cycle. If we assume the natural gas price 4.5 ¢/m3, we will save 59 million $.9 This amount will change to 118 million $ if we consider the natural gas price 8.5 ¢/m3. On the other hand, using solar field decreases the CO2 emission about 2.4 million ton. Using auxiliary burners in ISCC67-AF will increase LEC about 2.5% more than ISCC-67 case, but will enable us to use the idle steam turbine capacity in non-solar hours especially at peak hours. Auxiliary firing system increases 3% the power plant capacity factor.
References [1] Tavanir Organization. Detail statistics of Iran power industry. Tehran, Iran: Statistics Department; 2002. [2] Mechanical Engineering Department. Assignment of suitable areas for installation of first solar power plant in Iran. Tehran, Iran: Electric Power Reasearch Center; 1997. [3] Benemann J. Status report on solar thermal power plants. Munich: Pilkington Solar International GmbH; 1996. [4] Terrado E. Economics and financing of solar thermal power. The WorldBank. www.SolarPACES.org/ solutions/economics.html [5] Quaschning V, Muriel MB. Photovoltaics or solar thermal power plants. Brussels: VGB Congress Power Plants; 2001.
9
If we use 67 MW e solar field.
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[6] Spencer Management Associates. Mexico feasibility study for an integrated solar combined cycle system (ISCCS). WorldBank; 2000. [7] Geyer M, Quaschning V. Solar thermal power. Renewable Energy World, July–Aug 2000 p. 184–91. [8] Morse HF. The commercial path forward for concentrating solar power technologies. Washington, DC: Morse Associates, Inc.; 2000. [9] Mechanical Engineering Department. Technical and economic assessment of Yazd solar power plant. PMESB01/T1. Tehran, Iran: Niroo Reasearch Institute; 2000. [10] Renewable Energies Department. Feasibility study of the first solar power plant in Iran. Tehran, Iran: Niroo Reasearch Institute; 2000. [11] Enermodal Engineering Ltd, Marbek Resource Consultants Ltd. Cost reduction study for solar thermal power plants. Washington, DC: WorldBank; 1999. [12] Brakmann G. Integrated technical, economic and ecological consideration of large scale solar thermal power plants for developing countries. World Clean Energy Conference UNCED, Geneva; 1991. [13] Tavanir Organization. Plan power generation. Economic comparison of solar thermal power plants. Tehran, Iran; 2000. [14] Sunlab. Quarterly news and information about parabolic trough technology. www.eren.gov/troughnet/ documents/jan_2000.html
Technical and economic assessment of the integrated solar combined cycle power plants in Iran R. Hosseinia,*, M. Soltanib,1, G. Valizadehb,1 a
Mechanical Engineering Department, Amirkabir University of Technology, 424 Hafez Ave., P.O. Box 15875-4413, Tehran, Iran b Mechanical Systems Department, Niroo Research Institute (NRI), End of Pounak Bakhtari Blvd., P.O. Box 14665-517, Shahrak Gharb, Tehran, Iran Received 13 June 2004; accepted 7 November 2004 Available online 24 December 2004
Abstract Thermal efficiency, capacity factor, environmental considerations, investment, fuel and O&M2 costs are the main parameters for technical and economic assessment of solar power plants. This analysis has shown that the Integrated Solar Combined Cycle System with 67 MW e solar field (ISCCS-67) is the most suitable plan for the first solar power plant in Iran. The Levelized Energy Costs (LEC) of combined cycle and ISCCS-67 power plants would be equal if 49 million $ of ISCCS-67 capital cost supplied by the international environmental organizations such as Global Environmental Facilities (GEF) and World Bank. This study shows that an ISCCS-67 saves 59 million $ in fuel consumption and reduces about 2.4 million ton in CO2 emission during 30 years operating period. Increasing of steam turbine capacity by 50%, and 4% improvement in overall efficiency are other advantages of ISCCS-67 power plant. The LEC of ISCCS-67 is 10 and 33% lower than the combined cycle and gas turbine, respectively, at the same capacity factor with consideration of environmental costs. q 2004 Elsevier Ltd. All rights reserved. Keywords: Solar thermal; Parabolic trough; Power plant; Assessment
* Corresponding author. Tel.: C98 21 6405844; fax: C98 21 6419736. E-mail addresses: [email protected] (R. Hosseini), [email protected] (M. Soltani), [email protected] (G. Valizadeh). 1 Tel.: C98 21 8079393; fax: C98 21 8590171. 2 Operation and maintenance. 0960-1481/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.renene.2004.11.005
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Nomenclature AC C Cg Cs Csol Cf CRF Eout Fb gf Ha1 Ha2 Hsol kg ks ksol LEC LHV N Ng Ns O&M PVF r Wg Wgn Wsn Wsr h hg hs
Annual investment cost, $ Total investment cost, $ Initial investment cost in gas unit, $ Initial investment cost in steam unit, $ Initial investment cost in solar unit, $ Basic fuel price, ¢/m3 Cost Recovery Factor Total amount of gross generated energy, kW h Annual fuel cost without consideration of discount rate, $ Annual fuel cost discount rate, % Annual working hours of power plant (peak mode) Annual working hours of gas units (peak mode) Annual working hours of solar unit O&M factor for gas unit O&M factor for steam unit O&M factor for solar unit Levelized energy cost, ¢/kW h Fuel lower heating value, kJ/m3 Power plant life expectancy, year Number of gas units Number of steam units Operation and maintenance cost, $ Annual fuel cost, $ Dollar discount rate, % Net power of gas unit, MW Nominal power of gas units, MW Nominal power of steam units, MW Net power of steam unit, MW Thermal efficiency, % Annual net efficiency of gas unit, % Net efficiency of SEGS power plant in fossil mode, %
1. Introduction Iran is situated in 378N and has large areas that receive solar energy. It has a considerable potential for solar power plants. About 25% of Iran is consisted of deserts which receive daily solar irradiation about 5 kW h/m2. If 1% of these areas can be covered
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by solar collectors,3 energy obtained will be five times more than annual gross electricity production in Iran4 [1]. Suitable areas for constructing solar thermal power plant in Iran are in center and south of Iran. Studies show that the most suitable place is in Yazd5 [2]. Nowadays, the highest capacity of solar power plants belongs to solar troughs. This kind of solar power plant is more economical than the others. Pressure drop in solar field limits the capacity of solar trough to 100 MW. Pressure drop is a direct function of solar field dimensions. The solar field is comprised of parallel rows of Solar Collector Assemblies (SCA). SCAs supply thermal energy to produce steam to drive a steam turbine/generator in Rankine cycle or ordinary combined cycle. The collectors are singleaxis tracking and aligned on a north–south line, thus tracking the sun from east to west. Low-iron glass parabolic mirrors reflect the solar radiation to the absorber, which is situated in focus axis of mirrors. The concentration factor of solar radiation on absorber is about 20–100%. This value is about 80% in LS-3 collectors [3]. The maximum temperature in absorber is about 400 8C. Thermal storage system is rarely used because of high prices, however, it can be used in small solar power plants6. This technology can be used for nations in regions with high direct normal solar radiation (such as Africa, China, Middle East, the Mediterranean and Central and South America) to develop a rational approach the deployment of solar thermal electric systems within their country. Egypt, Jordan and Brazil are considered for building Integrated Solar Combined Cycle System (ISCCS). Financial analysis in Jordan has shown that solar thermal electricity generation is possible at 4.5 ¢/kW h [4]. The cost of electricity from line—concentrator solar parabolic trough plants decreased by 83% in less than a decade, due both to technological improvements and economies of scale in production [4]. The World Bank has made 200 million USD in financial assistance available for new combined-cycle gas and solar thermal power plants in developing countries. In Spain, a law increasing compensation for electricity produced from solar thermal energy with a premium of 12 ¢/kW h above the market price of 4 ¢/kW h is expected shortly [5]. A feasibility study was carried out for the World Bank/GEF and the Commission Federal de Electricidad on a net 285.1 MW e power plant consisting of a solar steam system integrated with a natural gas fired combined cycle system located at Cerro Prieto near Mexicali, Baja California Norte. The Levelized Electricity Cost is about 9 ¢/kW h [6]. Solar trough is among the most cost effective renewable power technologies with nearterm power generation costs in the range of 12–20 ¢/kW h and of 5–10 ¢/kW h for long term considerations. And it is the lowest cost solar electricity in the world, promising cost competitiveness with fossil-fuel plants in future. The Intergovernmental Panel for Climate Change (IPCC) demands drastic reductions of the greenhouse gas emissions in order to avoid a collapse of the world climate by committed itself to a 6%, US to 7% and 3
Assume the efficiency of solar energy conversion to electricity 10%. Total gross electricity production in 2001 is 127,138 MW h. 5 It is situated in center of Iran. 6 Lower than 15 MW. 4
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the European Union to 8% CO2 reduction of the 1990 levels until 2012 [7]. Also some of the main sponsors of energy investments in the developing world, i.e. the Worldbank Group, the Kreditanstals fur Wiederaufbau (KfW) and the European Investment Bank (EIB) have recently been convinced of the environmental promises and the economic prospectives of Solar Thermal Power technologies: only in spring 2000, the broad of the GEF approved grants for first solar thermal projects in Egypt, India, Mexico, and Morocco of app. US$ 200 million in total [7]. In 1998, Pilkington predicted 877 $/kW capital cost and lower than 8 ¢/kW h Energy price for an ISCCS plant in Morocco [8]. The main parameters, which considered and compared in these plants, are power plant net efficiency, capacity factor, fuel consumption and solar field capacity. The Levelized Energy Cost method (LEC) is a suitable way for economical assessment of different cases. LEC is the summation of investment, operation and maintenance cost as well as fuel cost, and it is expressed as ¢/kW h. In this study, six cases are considered for Yazd power plant (1) Gas Turbine power plant (GT): 2!123.4 MW gas turbine; (2) Combined Cycle power plant (CC): 2!123.4 MW gas turbine C123.4 MW steam turbine; (3) Integrated Solar Combined Cycle System with 33 MW e solar field (ISCC-33): 2! 123.4 MW gas turbine C156 MW steam turbine C33 MW solar field; (4) Integrated Solar Combined Cycle System with 67 MW e solar field (ISCC-67): 2! 123.4 MW gas turbine C198 MW steam turbine C67 MW solar field; (5) Integrated Solar Combined Cycle System with 67 MW e solar field and Auxiliary Firing system (ISCC67-AF): 2!123.4 MW gas turbine C198 MW steam turbine C 67 MW solar field C67 MW Auxiliary Firing; (6) Solar Electric Generating System (SEGS): 67 MW steam turbine C67 MW solar field.
2. Integrated solar combined cycle system In an ISCC, gas turbine is the same as conventional combined cycle, and the required energy for producing steam can be supplied by both gas turbine exhaust and solar field (Fig. 1). Preheating the feed water and superheating the steam will be performed by gas turbine exhaust. In ISCC power plant, higher pressure and temperature steam can be produced because of extra solar energy compared with combined cycle. Steam produced in ISCC power plant is 500 8C with 100 bar pressure. These values are higher than steam properties in SEGS and conventional combined cycle, thus the efficiency in ISCC is more than SEGS and CC. Steam turbine capacity in conventional combined cycle, is 50% of gas turbine capacity, but in ISCC, the solar field increases steam turbine capacity about 50% compared with CC. Electricity production drop in summer does not occur in ISCC because as ambient
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Fig. 1. Schematic of an integrated solar combined cycle system.
temperature increases, solar field absorbs more energy. Thus, it has a stable energy production through the year. The ISCC can work in following modes (1) Integrated solar combined cycle mode at solar hours; (2) Conventional combined cycle mode at non-solar hours; (3) Gas turbine mode when the steam turbine is not functioning. This study considers three ISCC power plant. ISCC-33 is a combination of two gas turbine (each one has 123 MW e), a steam turbine (161 MW e) and solar field (33 MW e), ISCC-67 is the same, but the steam turbine capacity is 198 MW e and solar field (67 MW e), ISCC67-AF is the same as ISCC-67, but it has auxiliary firing system for nonsolar hours. The capacity of auxiliary firing system is 67 MW e. At non-solar hours, steam turbine of ISCC-67 will work in 63% of its capacity. Therefore, an auxiliary firing system can be performed to use the idle capacity of steam turbine. Auxiliary firing devices, can be installed at the inlet of flue gas passage. When flue gas passes through this system, its temperature will raise and more steam in heat recovery steam generator can be produced. The efficiency of fuel energy conversion to electricity in auxiliary burners is about 36.9%.7 This amount is lower than the gas turbine efficiency in ISO conditions [9]. Therefore, it is recommended to use auxiliary firing system just at peak hours. For example, if we use it 4 h a day (1200 h a year), the annual electricity production will be 85.8 GW h and fuel consumption through this period will be 22!106 m3 [9,10]. 7
Ambient temperature is assumed 20 8C.
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Fig. 2. Net efficiency of different cases in maximum capacity factor.
For ISCC-33, steam turbine will work in 78% of its full capacity at non-solar hours. So it is not essential to use the auxiliary firing system. Other advantages of ISCC power plants are Increasing the steam turbine capacity of conventional combined cycle; Better performance of combined cycle power plants in warm days.
3. Technical assessment of the cases One of the main factors in technical evaluation of different power plants, is the net efficiency. Annual net efficiency of six cases are shown in Fig. 2. These values are related to maximum capacity factor. Low quality of generated steam in SEGS decreases its efficiency to the lowest level. Extra solar energy in ISCC-33, ISCC-67 and ISCC67-AF, raises the quality of generated steam and thus their efficiencies are higher than the conventional combined cycle hISCC67 O hISCC67AF O hISCC33 O hCC O hSEGS O hGT Energy production is influenced by local conditions of power plant. Table 1 shows the produced energy of the cases in different seasons. Produced energy in different seasons by ISCC-67 are shown in Fig. 3. It can be seen that the energy production by solar part is maximum in summer. As mentioned before, power generation in summer decreases in ordinary power plants, but in Table 1 Energy production in different seasons Total energy production (MW h)
Spring
Summer
Autumn
Winter
Annual
CC ISCC-33 Solar field of ISCC-33 ISCC-67 Solar field of ISCC-67
749,868 767,298 17,430
708,059 732,090 24,031
737,931 756,494 18,563
780,890 794,084 13,194
2,976,748 3,049,966 73,218
785,257 35,389
756,850 48,791
775,619 37,688
807,678 26,788
3,125,403 148,655
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Fig. 3. Variation of energy production of ISCC-67 through seasons.
solar power plants the power generation drop in summer is compensated by the solar energy. So solar power plants have more stable power generation. Fig. 4 is a comparison of power generation between CC, ISCC-33 and ISCC-67 in a summer day. It expresses that when power generation in combined cycle is minimum, the others have maximum power generation. To specify the capacity of solar field, some points should be considered. At non-solar hours, the steam turbine must work at least in its 50% capacity. So the maximum capacity of solar field will be 100 MW. On the other hand, for SEGS and ISCCS, the solar field capacity cannot be more than 100 MW, because the pressure drop through the solar field rises considerably and the main part of absorbed energy should be used to overcome the pressure drop. Therefore, in this study two capacity, that is 33 and 67 MW e are considered for solar field. These are 22 and 37% of steam turbine capacity, respectively. So at nonsolar hours the steam turbine will work in a capacity factor which is higher than 0.7. The proposed thermal capacity in conceptual design is 185 MWth (equal to 67 MW e) [9]. Although, the lower field capacity like 33 MW e makes the power plant performance better, but decreases solar energy share in power generation about 50%. This reduces
Fig. 4. Net power variation of ISCC plans and CC in a summer day.
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Table 2 Gross energy production in different cases Type of power plant
Annual energy production (GW h)
Capacity factor (%)
Annual work hours (full load)
GT CC ISCC-33 ISCC-67 ISCC67-AF SEGS
1732 2730 2799 2870 2958 140
80.1 82.8 79.3 73.7 76 23.9
7017 7343 6950 6453 6658 2092
the chance to gain loans from World Bank and Global Environmental Facilities (GEF) [11, 12]. Also economical aspects are main characters in specifying the solar field capacity. One of the main variables for technical evaluation of a power plant is the capacity factor, which is defined as the ratio of annual produced energy to maximum annual energy that can be produced. To determine capacity factor, we should know the annual energy production. By considering 1 month for power plant overhauls, total annual energy production and the capacity factor of GT, CC, ISCC-33, ISCC-67, ISCC67-AF and SEGS are calculated and shown in Table 2. The capacity factor of combined cycle is about 5–10% more than ISCC plans. The reason is that the solar hours are eliminated through the year.
4. Economical assessment of the cases Levelized Energy Cost method (LEC), is used to compare different cases. The lowest LEC determines the best choice. So, the investor should calculate the LEC of power plant at first. The lowest LEC does not mean the best efficiency. LEC is a relationship between the efficiency and cost and LEC calculation can lead us to the economical choice. LEC can be expressed as: LEC Z
ðACÞ C ðO&MÞ C ðPVFÞ Eout
(1)
This part describes the method of calculating the LEC. Cost Recovery Factor (CRF) cross to total investment cost (C) gives annual investment cost AC Z ðCRFÞ !C Eq. (3) determines the cost recovery factor: r ðCRFÞ Z 1 K ð1 C rÞKN
(2)
(3)
Gas turbine life expectancy is about 20 years and the steam power plant and ISCC plans life are 30 years. Eq. (4) calculates the total investment cost (C) C Z Cg C Cs C Csol
(4)
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The operation and maintenance cost is a percentage of total investment cost. It is 5, 2 and 1.5% of investment cost in gas unit, steam unit and solar unit, respectively ðO&MÞ Z kg Cg C ks Cs C ksol Csol
(5)
To find fuel cost, it is required to determine the net power and net efficiency of gas unit.8 For SEGS power plant, the net power of steam unit, its efficiency and working hours should be specified 1 C gf 1 C gf N PVF Z Fb 1K (6) r K gf 1 Kr Fb can be caculated as follows: Fb1 Z
Cf !Wsr !ðHa1 K Hsol Þ ðfor SEGSÞ hs !LHV
(7)
Fb2 Z
Cf !Wgr !Ha2 ðfor other casesÞ hg !LHV
(8)
Ha1 Z Cf !8760
(9)
Total amount of gross generated power is: Eout Z ðNg !Wgn C Ns !Wsn Þ !Cf !8760
(10)
Substituting these values in Eq. (1), will give us the LEC. Because of complicated calculations and many parameters involved, a computer program was prepared. 5. Results Fig. 5 shows the fuel consumption in six cases. In order to compare the fuel consumption of each power plant, it is expressed as m3/MW h. The fuel consumption in conventional combined cycle is more than the others. The ISCC-67 has lower fuel consumption about 16% than combined cycle. The decrease in fuel consumption in ISCC33 and SEGS are 8 and 13% respect to combined cycle. The ISCC-67 and SEGS have the same solar field capacity, but the better efficiency of ISCC-67 makes its fuel consumption lower. Studies show that by using solar field, fuel cost of conventional combined cycle decreases considerably. If we assume the fuel price (natural gas) 4.5 ¢/m3, ISCC-67 and SEGS save about 1.3!109 m3 (58.8 million $) through 30 years. This amount for ISCC-33 is about 29 million $. Greenhouse effects lead us to consider the environmental effects of different cases. CO2 is the main part of pollution in atmosphere, which increases greenhouse effects. Fig. 6 shows the CO2 production by different cases in capacity factor of 0.74. CO2 production in gas unit is maximum and it decreases in SEGS, conventional combined cycle, ISCC-33, ISCC-67, respectively. ISCC-33 and ISCC-67 produce 16 and 8% lower CO2 than 8
Only gas unit consumes fuel.
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Fig. 5. Natural gas consumption per unit of produced energy for different cases in capacity factor 0.74.
combined cycle. Pollutant emission not only has the environmental effects, but also results to economical problem. This economical problem returns to extra cost for equipments that can remove the CO2 from flue gas. If we consider the CO2 removal cost about 25 $/ton [13], the difference in specific cost between combined cycle, ISCC-33 and ISCC-67 will be decreased about 74–168 $/kW. LEC is the main economical parameter for evaluating the proposed cases. The economical assumptions for calculating LEC are presented in Table 3. Fig. 7 shows the LEC amount based on Table 3 values and the maximum capacity factor. It has broken the LEC to three parts as investment cost, O&M cost and fuel cost. Fig. 8 shows the amount of LEC at conditions like Fig. 7, but it considers the environmental costs. The interesting point of Fig. 7 is the effect of environmental cost. As mentioned before, the pollutant emission damages the environment and increases the cost. If we ignore the environmental cost, the combined cycle has the lowest LEC (Fig. 7). In this case, the LEC of ISCC-33, 14%, ISCC-67, 24% and gas unit 21% are higher than combined cycle. In Fig. 8, where the environmental effects are considered, LEC of ISCC-67 will be lower than combined cycle. In this case the LEC of ISCC-33, 8%, combined cycle 11%
Fig. 6. CO2 emission per unit of produced energy for different cases in capacity factor 0.74.
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Table 3 Economic assumptions for calculating the LEC in different cases Parameter
Symbol
Unit
Value
Life expectancy of steam unit Life expectancy of gas unit Life expectancy of solar field Annual discount rate Specific cost of steam unit of CC Specific cost of gas unit Specific cost of solar field 33 MW Specific cost of solar field 67 MW O&M cost factor of steam unit of CC O&M cost factor of gas unit O&M cost factor of solar field LHV of natural gas Natural gas price Solar hours (full load) Net efficiency of SEGS Efficiency of supplementary heater of SEGS Annual net efficiency of gas turbine Efficiency of auxiliary firing unit Internal consumption of SEGS Internal consumption of gas unit Internal consumption of CC Internal consumption of ISCC-33 Internal consumption of ISCC-67
Ns Ng Nsol R Cs Cg Csol33 Csol67 ks kg ksol LHV Cf Hsol hSEGS hH hg hAF ASEGS AG ACC AISCC-33 AISCC-67
year year year year $/kW $/kW $/kW $/kW % % % kcal/m3 ¢/m3 h % % % % % % % % %
30 15 30 10 635 235 1400 1000 2 5 1.5 8590 4.5 2092 33.4 83 32.2 36.9 8 1.5 3 3.5 3.9
and gas turbine 33% are higher than ISCC-67. The environmental cost in combined cycle and gas turbine increases their LEC about 38 and 36%, respectively. Figs. 9 and 10 show the LEC of cases as a function of capacity factor. As it can be seen, the LEC decreases by increasing the capacity factor. Fig. 11 explains the variation of ISCC-67 LEC, when solar field specific cost, changes.
Fig. 7. LEC of different cases in maximum capacity factor without considering environmental cost (natural gas price, 4.5 ¢/m3).
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Fig. 8. LEC of different cases in maximum capacity factor with considering environmental cost (natural gas price, 4.5 ¢/m3).
If the solar field specific cost decreases to 300 $/kW, the LEC without considering environmental effects, is equal to conventional combined cycle. So it is required to invest 49 million $ extra to economize the ISCC-67 case. The other main parameter in economical assessment is the specific cost. The specific cost of each part of power plant is in certain range (Table 4), but for power plant it should be calculated.
Fig. 9. LEC variation of different cases without considering the environmental costs (natural gas price, 4.5 ¢/m3).
Fig. 10. LEC variation of different cases with considering the environmental costs (natural gas price, 4.5 ¢/m3).
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Fig. 11. LEC variation of ISCC-67 in different solar field specific cost.
The computer program, calculates this parameter. The results are presented in Fig. 12. It expresses that the specific costs of ISCC plans are about 37–52% more than conventional combined cycle. Thus, these projects need to be supported by international organizations like GEF. GEF statistics shows that four projects in India, Morraco, Egypt and Mexico have used this loan [14]. Table 4 Overall technical and economic specifications of different cases for Yazd solar power plant Parameter
Unit
GT
CC
ISCC-33
ISCC-67
ISCC67AF
Nominal capacity of power plant Annual net efficiency Maximum capacity factor Investment cost Specific cost Saving fuel in 30 yearsa CO2 emission reduction in 30 yearsa LECb LECc
MW e
246
371
407
444
444
a
SEGS 67
%
32.2
49.3
50.9
51.6
50.9
35.4
%
80.1
83.8
79.3
73.7
76
74
255 573 59
110 1635 59
Million $ $/kW Million $
58 235 –
137 370 –
Million ton
–
–
¢/kW h ¢/kW h
1.986 2.716
1.639 2.263
206 506 29
251 564 59
1.2
2.4
2.4
2.4
1.878 2.195
2.035 2.035
2.087 2.29
4.116 4.116
Fuel saving and reduction in CO2 emission return to solar energy usage. Without considering of environmental costs (pollutant removal cost), natural gas price 4.5 ¢/m3 and in maximum capacity factor. c With considering of environmental costs (pollutant removal cost), natural gas price 4.5 ¢/m3 and in maximum capacity factor. b
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Fig. 12. Specific cost of different cases.
6. Conclusions The technical and economic assessment of different cases for Yazd solar power plant shows that the INTEGRATED SOLAR COMBINED CYCLE SYSTEM (ISCC-67) is the most suitable project for construction of first solar power plant in Iran. Its construction can be performed modular, which is consisted of solar field and combined cycle. The results of technical and economical assessment are summarized in Table 4. It shows that, LEC of combined cycle without considering the environmental effects is the lowest. If we consider the environmental effects, the ISCC-67 will have the lowest LEC, which is about 10 and 33% lower than combined cycle and gas turbine, respectively. Also if 49 million $ of investment cost is supplied by international organizations, the LEC of ISCC67 will be equal to combined cycle. If we assume the natural gas price 4.5 ¢/m3, we will save 59 million $.9 This amount will change to 118 million $ if we consider the natural gas price 8.5 ¢/m3. On the other hand, using solar field decreases the CO2 emission about 2.4 million ton. Using auxiliary burners in ISCC67-AF will increase LEC about 2.5% more than ISCC-67 case, but will enable us to use the idle steam turbine capacity in non-solar hours especially at peak hours. Auxiliary firing system increases 3% the power plant capacity factor.
References [1] Tavanir Organization. Detail statistics of Iran power industry. Tehran, Iran: Statistics Department; 2002. [2] Mechanical Engineering Department. Assignment of suitable areas for installation of first solar power plant in Iran. Tehran, Iran: Electric Power Reasearch Center; 1997. [3] Benemann J. Status report on solar thermal power plants. Munich: Pilkington Solar International GmbH; 1996. [4] Terrado E. Economics and financing of solar thermal power. The WorldBank. www.SolarPACES.org/ solutions/economics.html [5] Quaschning V, Muriel MB. Photovoltaics or solar thermal power plants. Brussels: VGB Congress Power Plants; 2001.
9
If we use 67 MW e solar field.
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[6] Spencer Management Associates. Mexico feasibility study for an integrated solar combined cycle system (ISCCS). WorldBank; 2000. [7] Geyer M, Quaschning V. Solar thermal power. Renewable Energy World, July–Aug 2000 p. 184–91. [8] Morse HF. The commercial path forward for concentrating solar power technologies. Washington, DC: Morse Associates, Inc.; 2000. [9] Mechanical Engineering Department. Technical and economic assessment of Yazd solar power plant. PMESB01/T1. Tehran, Iran: Niroo Reasearch Institute; 2000. [10] Renewable Energies Department. Feasibility study of the first solar power plant in Iran. Tehran, Iran: Niroo Reasearch Institute; 2000. [11] Enermodal Engineering Ltd, Marbek Resource Consultants Ltd. Cost reduction study for solar thermal power plants. Washington, DC: WorldBank; 1999. [12] Brakmann G. Integrated technical, economic and ecological consideration of large scale solar thermal power plants for developing countries. World Clean Energy Conference UNCED, Geneva; 1991. [13] Tavanir Organization. Plan power generation. Economic comparison of solar thermal power plants. Tehran, Iran; 2000. [14] Sunlab. Quarterly news and information about parabolic trough technology. www.eren.gov/troughnet/ documents/jan_2000.html