In 1986 solar panels were literally ripped from the White House roof. But political will and financial incentives have reignited the search for efficient, affordable ways to harness the sun’s energy. Two new solar thermal technologies—which focus sunlight to create heat rather than convert it directly to electricity, as photovoltaics do—promise to make solar power practical at vastly different scales.
The SunCatcher solar thermal system, developed by Tessera Solar and built by Stirling Energy Systems at the Sandia National Laboratories’ National Solar Thermal Test Facility, captures solar energy at 31.25 percent efficiency, the highest ever achieved by this technology. Each of SunCatcher’s 38-foot-wide dishes collects enough heat energy to run a Stirling engine that can then generate 25 kilowatts of electric power. The system will fulfill two of the world’s largest solar contracts, providing a planned 1,600 megawatts to Southern California by 2014. It improved on its predecessor with a new design that makes each dish substantially lighter and cheaper to manufacture.
Meanwhile, a group of recent and current MIT engineering students is working to bring solar thermal to Africa with an off-grid system that operates on a much smaller scale. The team has developed a microgenerator capable of producing 3 kilowatts of electric power plus hundreds of gallons of hot water each day using relatively inexpensive, readily available components such as auto parts. Engineer and cofounder Amy Mueller says that the MIT group’s nonprofit, called STG International, has already set up microgenerators at two locations in Lesotho. A third Lesotho installation is under construction at a medical clinic, where it will provide power for lighting and communications equipment as well as hot water.