Concentrating Solar Power: The Emerging Solar Energy Technology

1. Concentrating Solar Power: The Emerging Solar Energy Technology Presentation to Electric Power 2010 Session 4B: Solar Power and Photovoltaic Dr. Allan R. Hoffman U.S. Department of Energy 19 May 2010

2. Outline of Presentation • Why the renewed interest? • The four “flavors” of concentrating solar power (CSP) • CSP history • Advantages and disadvantages • Thermal storage • Current status • Concluding remarks

3. Why the Renewed Interest in CSP? • traditional CSP (trough, tower, dish) is not new – long history dating back to 1980’s • key advantage: close resemblance to existing plants • use many of the same technologies and equipment • substitutes concentrated high-temperature solar heat for combustion of fossil fuels or heat from nuclear reactors • Increasing utility interest in deployment of CSP plants to meet requirements of state renewable portfolio standards • huge solar resource in Southwest U.S. • federal government encouraging development of CSP plants through 30% investment tax credit • good through FY 2016 • alternative 30% Treasury grant good through FY 2010

5. State Renewable Portfolio Standards • States with RPS • States with RPS goal http://www.epa.gov/chp/state-policy/renewable_fs.html

6. Four CSP technologies • CSP technology systems use reflective surfaces to gather and concentrate unscattered solar radiation to create heat • The requirement for unscattered (“direct normal”) radiation limits CSP plants to certain locations, primarily desert regions with limited cloud cover • Three of the four CSP technologies use the collected heat to power conventional Rankine steam cycles, similar to those used for coal and nuclear plants • parabolic trough, linear Fresnel, power tower • Dish-engine systems use the concentrated sunlight to power a small heat engine at the dish’s focal point

7. Parabolic Trough Kramer Junction, CA

8. Power Tower Barstow, CA

9. Dish-Engine

10. Compact Linear Fresnel

11. CSP History - Luz and SEGS • nine trough systems, SEGS I-IX, built by Luz International between 1984 and 1990 (354 MWe total) • SEGS I: 13.8MWe • SEGS II-VII: 30MWe each • SEGS VIII, IX: 80 MWe each • regulatory and policy obstacles forced Luz bankruptcy in 1991 • plans to construct SEGS X, XI and XII canceled (240 MWe) • nine original SEGS plants still operating, feeding power into Southern CA Edison power grid (but under new ownership) • largest solar power station complex in operation • original Luz owner now head of Bright Source Energy Inc. • Luz II technology uses distributed power towers (DPT)

12. Advantages • resemble traditional power plants • generation based on steam and is large scale • use standard equipment for power generation • can be built in small sizes and added to as needed • can achieve high steam operating temperatures, allowing more efficient power generation • capable of combined heat and power generation • steam for absorption chillers, industrial process heat, desalination • Non-carbon emitting power generation • incorporates storage • storage not major part of generation cost • size of steam power plant that lacks storage does not have to be increased when storage added • added storage cost effective if energy sold at peak hours • allows generation to match utility load profile • can be hybridized with intermittent renewables

13. Disadvantages • high upfront capital costs for concentrators and storage • require unscattered “direct normal” solar radiation, thus limiting where CSP plants can be located • desert areas are best (but also arid) • require cooling, as with any steam power plant, creating a requirement for water or air cooling • water limitations may necessitate air cooling in many locations, with penalty in capital cost, generating efficiency and energy cost • require large surface areas for placement of concentrators

14. Thermal Storage • SEGS-I storage method used an organic heat transfer fluid (HTF) • organic HTFs can only be used below 800F • troughs can operate at just over 1000F, thus use of HTF limits plant efficiency by >12% • power towers can reach very high temperatures (>2000F) but have only been used to date with molten salt storage • Salt melts at 430F (must be kept heated) • maximum storage temperature: 950F • Modern trough plants: • either use no storage • more profitable under current U.S. incentives to build without storage, or • use HTF and molten salt storage

15. Can We Do Better? • Modern high efficiency power plants can be designed to use steam at 1300-1400F • ideal storage temperature: 1500-1700F • desired top temperature for gas turbines is > 1700F • a heat transfer fluid and storage method that operate at temperatures above those of HTFs and molten salt would lead to significant energy cost reductions (>30%) • Such a heat transfer and storage system has been invented by Dr. Reuel Shinnar (City University of New York) (patent # 20090178409/Apparatus and Method for Storing Heat Energy, 16 July 2009)

16. The Shinnar Thermal Storage System • combines two proven concepts with a special adaptation • uses pressurized CO2as the heat transfer fluid flowing in a closed loop through the solar collectors and either through the power plant or the heat storage system • compressed CO2 is one of the most effective gaseous high temperature heat transfer fluids used in industry • The heat storage system uses commercially available vessels (cylindrical metal pipe) filled with a ceramic solid filler • can be designed to operate at temperatures up to 3000F • special feature: uses a cyclic counter-current pebble bed • pebble-bed heat exhanger based on theory developed in 1920s • has been used reliably for many industrial processes • heat propagates as a sharp front: one end of storage remains cold, the other end hot at constant temperature • allows recovery of heat at same top temperature it was stored

17. Current Status • after a long hiatus, deployed CSP capacity has expanded from 354 MWe to more than 820 MWe today • many new projects are in the pipeline in many countries • when those under construction are completed, capacity will approach 3,000 MWe • an even greater number of projects are in development • > 10,000MWe in the U.S. alone • CSP plants deployed or under development in • USA • Spain • Italy • Morocco • Algeria • Egypt • Jordan • Tunisia

18. SolarPACES (Solar Power And Chemical Energy Systems) • collaborative RD&D program (Implementing Agreement) under umbrella of International Energy Agency that focuses on development and marketing of CSP systems • Currently has 16 member countries • Australia, Austria, Algeria, Egypt, EC, France, Germany, Israel, Italy, Mexico, S. Korea, S. Africa, Spain, Switzerland, UAE, USA • membership open to all countries • compiles data on CSP projects around the world that have plants that are operational, under construction, or under development • can browse project files by country, project name, technology and status • http://www.solarpaces.org/News/Projects/projects.htm

19. CSP Projects in the U.S. • California • Abengoa Mojave Solar Project • Alpine Sun Tower • Blythe Solar Power Project • Calico-Solar one • Genesis Solar Energy Project • Imperial Valley-Solar Two • Ivanpah Solar Electric Generating Station • Kimberlina Solar Electric Generating Station • Palen Solar Power Project • Rice Solar Energy Project • Ridgecrest Solar Power Project • Sierra SunTower • SEGS I-IX

20. CSP Projects in the U.S. (continued) • Nevada • Crescent Dunes Solar Electric Project (Tonopah) • Nevada Solar One (NSO) • Arizona • Maricopa Solar Project • Saquaro Power Plant • Solana • Florida • Martin Next Generation Solar Energy Center MNGSEC) • New Mexico • New Mexico SunTower

21. DESERTEC • Derives from the TREC concept which has been around for many years: • generate CSP electricity in N. Africa, ship electricity to Europe, use revenues to stimulate African development • DESERTEC Foundation created in 2008 to advance DESERTEC Concept worldwide • DESERTEC Industrial Initiative (DII) established in 2009 under German law to create the conditions for accelerated implementation of the DESERTEC Concept in EUMENA (Europe, Middle East, North Africa) • HVDC transmission to southern Europe (loss 3% per 103 km) • less seasonal variation in solar insolation MENA vs. S. Europe

22. Concluding Remarks • CSP has the potential to supply a significant share of U.S. and global electricity demand • ability to load follow, firm up intermittent generation, incorporate storage, and provide heat and electricity are major advantages • cooling requirements present a water and cost challenge (as do requirements of other steam power plants) • costs still high but should come down significantly as more and more systems are manufactured and deployed

23. Thank You Contact information: E-mail: allan.hoffman@ee.doe.gov Telephone: 202-586-8302

24. Additional Material on Shinnar TS System “I now believe that CSP technology which follows the guidelines outlined in our report could be designed at approximately half the cost of CSP plants today despite the fact that storage and air cooling have been added.” (letter from Dr. Shinnar to Thomas Rueckert, CSP program manager, U.S. DOE, 21 April 2010)