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DOE announced on September 19 that it will invest up to $35 million over the next 4 years in 15 concentrating solar power (CSP) projects which, combined with the project cost-sharing from the project participants, will result in up to $67.6 million being invested in these projects. CSP technologies concentrate the sun's heat for conversion into electricity, and the ability to store that thermal energy and draw on it after sunset will greatly increase the economic feasibility of CSP power plants. Of the 15 projects, 11 will involve the research and development (R&D) of thermal energy storage technologies, 1 involves R&D for advanced heat transfer fluids, and 3 will be geared toward near-term demonstrations of thermal storage technologies. The projects are expected to further DOE's goal of reducing the cost of CSP electricity from today's 13-16 cents per kilowatt-hour (kWh) with no thermal storage to 8-11 cents per kWh with 6 hours of thermal storage by 2015, and to less than 7 cents per kWh with 12-17 hours of thermal storage by 2020. Seven companies and six universities were selected for this award.
The 11 projects that were awarded funding for thermal energy storage R&D will investigate a variety of methods to store extremely high-temperature thermal energy for CSP applications. Many of these projects are testing the feasibility of yet-untested techniques, such as General Atomics' use of thermochemical cycles to store solar heat. Infinia Corporation will add thermal storage to dish-shaped solar concentrators, demonstrating its use of phase-change materials on 40-50 dish-engine systems at DOE's Sandia National Laboratories. Phase-change materials will also be investigated by Lehigh University, Terrafore, and the University of Connecticut, with the latter embedding passive heat exchangers in the materials. Abengoa, Acciona, the City University of New York (CUNY), and the University of Arkansas will investigate the use of solid materials for heat storage, with Abengoa and CUNY using ceramics and the University of Arkansas exploring the use of high-performance concrete. And both the University of Alabama and Texas Engineering Experiment Station (TEES) will investigate the use of molten salts, with TEES creating a suspension of carbon nanotubes in a molten salt material to improve its thermal stability at 500°-600°C.
Under the only project to receive funding for R&D of advanced heat transfer fluids, Symyx will study salt mixtures to identify heat transfer fluids that can function across the wide temperature range of 80°-500°C. Finally, three projects relate to near-term demonstrations of thermal energy storage technologies. Abengoa will analyze several new energy storage concepts to see if any can cut costs by at least 20%; Acciona will design, validate, and demonstrate a prototype for storing 800 megawatts of thermal energy for four hours; and U.S. Solar Holdings will explore two or more utility-scale energy storage technologies, which will be integrated with the 1-megawatt Arizona Public Service CSP plant, located in Red Rock, Arizona.