Earth Equity News

Companies Seek Ways to Store Sun's Heat By Matthew L. Wald, NYTimes, April 15, 2008. "Solar thermal systems are built to gather heat from the sun, boil water into steam, spin a turbine and make power, as existing solar thermal power plants do -- but not immediately. The heat would be stored for hours or even days, like water behind a dam. A plant that could store its output could pick the time to sell the production based on expected price, as wheat farmers and cattle ranchers do. Ausra, of Palo Alto, Calif., is making components for plants to which thermal storage could be added... A competitor a step behind... plans a slightly different technique in which adding storage seems almost trivial. It is a 'power tower,' a little bit like a water tank on stilts surrounded by hundreds of mirrors that tilt on two axes, one to follow the sun across the sky in the course of the day and the other in the course of the year. In the tower and in a tank below are tens of thousands of gallons of molten salt that can be heated to very high temperatures and not reach high pressure. 'You take the energy the sun is putting into the earth that day, store it and capture it, put it into the reservoir, and use it on demand,' said Terry Murphy... of SolarReserve."