1. ABENGOA SOLAR Solar Power for a Sustainable World Past, Present, and Future of Solar Thermal Generation Bruce Kelly Abengoa Solar, Incorporated Berkeley, California June 2008

2. Solar Power for a Sustainable World ABENGOA 2 Topics –Solar resource –Solar thermal technologies –Early projects –Current projects –Future plans

3. Solar Power for a Sustainable World ABENGOA 3 Solar Resource Southwest US, filtered for environmental areas, urban areas, water, and slope < 3% 9,800 TWhe potential 3,800 TWhe US energy consumption

4. Solar Power for a Sustainable World ABENGOA 4 Parabolic Trough Type: Glass mirror; single axis tracking; line focus Nominal concentration: 80:1 Heat collection fluid: Synthetic oil Peak temperature: 393 C

5. Solar Power for a Sustainable World ABENGOA 5 Central Receiver Photo by Mike Taylor, SEPA Type: Glass mirror, two axis tracking, point focus Nominal concentrations: 600 to 1,200:1 Heat collection fluids: Steam, air, or nitrate salt Peak temperatures: 400 to 850 C

6. Solar Power for a Sustainable World ABENGOA 6 Linear Fresnel Photos taken by Mike Taylor, SEPA Type: Glass mirror, single axis tracking, line focus Nominal concentration: ~100:1 Heat collection fluid: Saturated steam Peak temperature: ~260 C

7. Solar Power for a Sustainable World ABENGOA 7 Parabolic Trough

8. Solar Power for a Sustainable World ABENGOA 8 Parabolic Trough Early projects –Solar Electric Generating Stations (SEGS) –SEGS I and II: 14 and 30 MWe; Daggett –SEGS III through VII: 30 MWe; Kramer Junction –SEGS VIII and IX: 80 MWe; Harper Lake Financed through very favorable combination of investment tax credits, Standard Offers, and PURPA requirements All are still in operation

9. Solar Power for a Sustainable World ABENGOA 9 Parabolic Trough Current projects –Acciona: 64 MWe Nevada Solar One –Solar Millennium: 50 MWe AndaSol 1 Nevada Solar One financed through investment tax credit and renewable portfolio standard AndaSol 1 financed through Spanish feed-in tariff at ~$0.40/kWhe Parabolic trough technology investment to date ~$3,000 million

10. Solar Power for a Sustainable World ABENGOA 10 Parabolic Trough Future plans –Spain: 50 MWe; limited by tariff structure –US: 125 to 250 MWe; economies of scale Advanced collector coolants –Direct steam generation, and inorganic nitrate salt mixtures –450 to 500 C collector field temperatures –More efficient Rankine cycles –Why not yet? Direct steam generation has complex controls, and salt freezes

11. Solar Power for a Sustainable World ABENGOA 11 Central Receiver

12. Solar Power for a Sustainable World ABENGOA 12 Central Receiver Early projects –France, Spain, Italy, Japan, and United States –1 to 10 MWe –Receiver coolants: Sodium; nitrate salt; compressed air; and water/steam Design point efficiencies were close to, but annual energy efficiencies were well below, predictions Most suffered from lack of operating funds

13. Solar Power for a Sustainable World ABENGOA 13 Central Receiver Current projects –Abengoa: PS10 and PS20 –US DOE: Solar Two (1999) PS10 and PS20: Saturated steam receivers; high reliability, but below-commercial efficiency Solar Two: Nitrate salt receiver, thermal storage, and steam generator; high efficiency, but poor reliability Technology investment to date ~$1,000 million

14. Solar Power for a Sustainable World ABENGOA 14 Central Receiver Future plans –Abengoa: Superheated steam; compressed air; and nitrate salt –SolarReserve: Nitrate salt in South Africa and US –eSolar: 13 distributed superheated steam receivers; very small heliostats; central 30 MWe Rankine cycle –BrightSource: 4 towers; small heliostats; central 100 MWe reheat Rankine cycle

15. Solar Power for a Sustainable World ABENGOA 15 Central Receiver Why not yet? –Superheated steam: Moderate annual efficiencies; thermal storage may be impractical –Compressed air: Complex receiver; small plant sizes; thermal storage may be impractical –Nitrate salt: Less than perfect operating experience; equipment development must occur at commercial scale, with ~$750 million project investment

16. Solar Power for a Sustainable World ABENGOA 16 Performance and Cost Annual efficiencies, capital costs, operation and maintenance costs, and levelized energy costs Parabolic trough Nitrate salt central receiver

17. Solar Power for a Sustainable World ABENGOA 17 Parabolic Trough Annual solar-to-electric efficiencies 14 to 16 percent gross 12 to 14 percent net Capital cost ~$4/We without thermal storage; includes project financing, interest during construction, and owners costs ~$5 to $8/We with thermal storage

18. Solar Power for a Sustainable World ABENGOA 18 Parabolic Trough Operation and maintenance cost $0.02 to $0.04/kWhe Levelized energy costs $0.14 to $18/kWhe with Southwest US direct normal radiation and 30 percent investment tax credit $0.35 to $0.40/kWhe with southern Spain direct normal radiation and no financial incentives

19. Solar Power for a Sustainable World ABENGOA 19 Salt Central Receiver Annual solar-to-electric efficiencies 17 to 19 percent gross 15 to 17 percent net Capital cost ~$4/We with minimum thermal storage; includes project financing, interest during construction, and owners costs ~$7/We with thermal storage at 70 percent annual capacity factor

20. Solar Power for a Sustainable World ABENGOA 20 Salt Central Receiver Operation and maintenance cost $0.02 to $0.03/kWhe Levelized energy cost For a commercially mature design (which does not yet exist), a nominal 20 percent below that of a parabolic trough project

21. Solar Power for a Sustainable World ABENGOA 21 Future Markets Capital investment essentially dictated by commodity prices Energy price parity with natural gas combined cycle plant is unlikely Solar thermal energy is Much better matched to utility peak demand than wind Immune to rapid changes in plant output common with photovoltaic projects

22. Solar Power for a Sustainable World ABENGOA 22 Future Markets With 30 percent investment tax credit and property tax exemption, solar energy prices are within $0.02 to $0.03/kWhe of market price referant Renewable portfolio standards, plus a modest carbon tax, should provide a commercial, multi-GWe market for solar thermal projects