|Two farms being planned by SolarReserve of Santa Monica, Calif., would store the sun’s energy in molten salt, releasing the heat at night when it could be used to drive a turbine and generate electricity. An artist's rendering of such a solar plant is shown here.|
Solar farms that would serve two Western utilities are planning to use technology that will generate electricity after the sun goes down, a move that could be a potential game-changer for the industry.
The two farms being planned by SolarReserve of Santa Monica, Calif., would store the sun's energy in molten salt, releasing the heat at night when it could be used to drive a turbine and generate electricity. Two utilities, NV Energy in Nevada and Pacific Gas and Electric, Northern California's biggest utility, would buy the power.
The sun's intermittent nature has made large-scale solar farms most useful as so-called peaker plants that supply electricity when demand spikes, typically in the late afternoon on hot days. But the ability of SolarReserve to store the sun's energy for use at night would be a step forward in technology.
"The energy storage characteristics were a key factor in our selection of the Tonopah solar energy project," NV Energy's chief executive, Michael Yackira, said in a statement. The utility will be able to draw electricity from the solar farm more or less on demand, which makes it easier to balance the load on the power grid.
NV Energy would buy power from the 100-megawatt Crescent Dunes Solar Energy Project being planned on federal land near Tonopah, Nev., about 215 miles northwest of Las Vegas.
"We're expecting to put in 12 hours of storage, which allows us to move power within the day to meet peak requirements as well as to operate at full load," SolarReserve's chief executive, Kevin Smith, said of the Tonopah plant.
But the technology comes with its own set of problems.
The site of the Nevada project has been moved several times because of concerns from the Air Force that the project would interfere with advanced radar systems. The solar farm features a 538-foot-tall concrete tower topped by a 100-foot receiver that contains millions of gallons of molten salt. The Rocketdyne division of United Technologies developed the molten salt technology and has licensed it to SolarReserve.
Huge fields of mirrors called heliostats focus the sun on the receiver, which heats the salt to 1,050 degrees. The liquefied salt flows through a steam-generating system to drive the turbine and is returned to the receiver to be heated again.
SolarReserve's other farm, the 150-megawatt Rice Solar Energy Project for P.G.and E. in California, is expected to have seven hours of energy storage. The solar farm, to be built on private land near the desert ghost town of Rice, will provide electricity to the utility under a 25-year contract.
SolarReserve, which is also building a solar power plant in Spain, expects the California and Nevada projects to create 900 construction jobs.