BrightSource Adding Molten-Salt Solar Storage

Promising the hottest and highest pressure steam generated by solar heating – and, most significantly, the capability of storing energy – an Oakland company is targeting utilities with a new solar thermal plant system. BrightSource Energy, which earlier this year announced plans to go public, said its SolarPlus technology could cut solar electricity generation costs by coaxing more heat and pressure from each power plant.

The new BrightSource system uses a mixture of molten sodium nitrate and potassium nitrate as “solar salts” as a storage medium that allows solar plants to produce electricity later in the day and after the sun sets. That addition of storage capacity means utilities can reduce the cost of energy generation, BrightSource said, something that could make solar thermal plants more attractive than wind-powered plants or solar plants that generate electricity via photovoltaic cells.

brightsource solar

Image via BrightSource Energy

In a system similar to a Spanish solar thermal plant described by EarthTechling in July, BrightSource’s technology arranges special mirrors around a tower topped with a water boiler. Computers control the mirrors to direct solar energy to the boiler to produce steam that turns a turbine to generate electricity. That steam — which can reach temperatures of 540 degrees Celsius and pressures of 140 bars — then goes through a heat exchanger that heats the specialized salts. The heat in those salts is used to generate more steam when additional power is needed.

BrightSource also announced Aug. 8 that it applied for permits to build two solar thermal power plants at a site in California’s Inyo County. Those plants would each be capable of producing up to 250 megawatts of electricity.

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