A Californian company, SolarReserve, is developing a solar power system that can store seven hours’ worth of solar energy by focusing mirrors onto millions of gallons of molten salt, allowing the plant to provide electricity 24 hours a day.
The company has applied to regulators in California for permission to build the 150-megawatt Rice Solar Energy Project solar farm near the abandoned town of Rice in San Bernadino County, California.
The solar energy is stored using a massive circular array of up to 17,500 mirrors (heliostats), each measuring 24 by 28 feet and attached to a 12-foot pedestal. The heliostat field encircles a concrete Solar Power Tower 538 feet high, with a 100-foot high receiver on top, which holds 4.4 million gallons of molten salt. When the heliostats focus the sunlight onto the receiver the salt is heated to over 1,000 degrees Fahrenheit.
When it is needed, such as at night or at peak times, the heat is released by passing the molten salt through a steam generator that drives a turbine to produce electricity. The cooled salt is then recirculated to the receiver for re-heating. The project brings the dream of a solar system that generates electricity in the dark to a reality, and avoids the need to use fossil fuel plants for backup electricity generation.