BrightSource Energy announced yesterday the launch of SolarPLUS, a combination of its solar tower technology and a way to store the power it generates using molten salts. Storage of solar energy has long been a sticking point, given that a solar plant can't generate power when the sun isn't shining.

Molten salt storage has been proven in other countries in recent years, as described by our own Peter Fairley in a story on the Andasol 1 plant in Spain. Like the Spanish facility, BrightSource will use a combination of sodium nitrate and potassium nitrate in its system. Basically, the salts are heated during the day when the sun is shining using a heat exchanger, and the process is reversed at night when power is needed but no sun is available.

BrightSource's solar technology involves the solar tower concept, in which a huge array of thousands of mirrors -- known as heliostats, because they track the sun across the sky -- concentrates the sun's rays on to a centralized tower. Inside the tower, steam is generated from the heat, and the steam is used to run a turbine just as in a standard power plant. The molten salt storage will allow the turbines to turn after dark. Though possible to keep them turning all night, the company says a two- to six-hour window is optimal. BrightSource is currently building the Ivanpah Solar plant in the Mojave Desert, a 392-megawatt project that has generated controversy for its use of public lands and the potential environmental harm involved.

(Image via BrightSource Energy)