Fixing solar’s intermittency: Do SolarReserve and PG&E have the answer?
By Tom Slater in Greanbeat, December 23 2009
Pacific Gas & Electric has signed a contract with SolarReserve to buy power from its 150-megawatt plant. Power purchase agreements like this are pretty commonplace at this point — so what makes this one special? SolarReserve claims its technology can supply solar-generated power even when the sun’s not shining — revolutionizing the way we look at solar.
SolarReserve relies on solar thermal systems to make this possible. Using a field of reflective mirrors, it concentrates sunlight on a central receiving tower. The intense heat, topping 1,000 degrees Fahrenheit, is stored in molten salt in this tower. This salt solution is then funneled into a storage tank where it can sit there, glowing hot, for hours, before being used to generate steam to turn a turbine. The salt can retain useful amounts of energy for up to a week after it was last exposed to the sun — essentially taking care of solar’s intermittency problem.