Research on metal hydrides revived for next-generation solutions to renewable energy storage
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Energy Sector Analysis
These energy-dense materials could help reduce costs of storing thermal energy at concentrating solar thermal power plants.
Research on metal hydrides revived for next-generation solutions to renewable energy storage By Melissae Fellet Feature Editors Craig E. Buckley, Mark Paskevicius, and Drew A. Sheppard
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ome renewable energy power plants store solar energy as heat, which is used to generate electricity after sunset. But as with many clean energy technologies, economics influences how far energy storage can spread through the emerging market for commercial-scale solar power. A class of materials called metal hydrides could be the next generation of heat storage materials to help reduce the cost of thermal energy storage at solar power plants, and thus further the development of renewable energy worldwide. The most efficient use of sunlight to generate enough power for base-load consumption is called concentrating solar power (CSP). At CSP plants, mirrors focus sunlight onto a fluid, like oil or molten salts. The hot fluid then flows through a heat exchanger, producing steam to drive a turbine that generates electricity. There are 80 operational CSP plants around the world, mainly in Spain and the United States, with 1.9 GW of total capacity as of March 2012. Another 23 are under construction in India, China, Australia, and South Africa, among other places. Currently 40% of the commercial CSP plants store thermal energy to generate from 30 minutes to 15 hours of electricity on demand. One CSP plant with thermal storage is a state-of-the-art 110 MW plant in Nevada called the Crescent Dunes Solar Energy Plant, with construction to be finished by the end of 2013. At this plant, energy storage is integrated into the plant’s power generation system, and electricity production can occur without intermittency. “Depending on what a utility company needs, we can develop this plant to run 24 hours a day, seven days a week,” said Mary Grikas, Vice President of Communications at SolarReserve, the company developing the Crescent Dunes plant. “That makes this plant more like a coal or natural gas plant, as far as a utility company is concerned.” At this plant, solar energy is collected and stored in a material called molten salt, a mixture of sodium nitrate and potassium nitrate, both ingredients commonly found in fertilizer. During the day, mirrors shine sunlight onto a receiver atop a central tower. Molten salt flows through the tower, where it is warmed to 565°C as it flows through the receiver. The hot salt is then pumped into an insulated storage tank. When electricity is needed during the day or night, the hot salt is moved from the tank through a Craig E. Buckley, Mark Paskevicius, and Drew A. Sheppard, Curtin University, Australia Melissae Fellet, [email protected]
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MRS BULLETIN
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VOLUME 38 • DECEMBER 2013
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www.mrs.org/bulletin • Energy Quarterly
heat exchanger, where it cools to about 290°C as the stored heat generates steam to power a standard turbine. The cooled sal
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