As any renewable energy buff (or casual bystander) knows, solar panels are rendered useless when the sun sets. The Rice Solar Energy Project doesn't change that, but it gets pretty close—the proposed project in California's Sonoran Desert stores up to 7 hours worth of solar power in molten salt. Heat from the salt can be released whenever power is needed, no matter if that's in the middle of the night or during a storm.
The 150 megawatt heliostat solar plant, proposed recently by SolarReserve, works with a 100-foot receiver filled with a salt mixture of sodium and potassium nitrates. The mixture is heated to 1,050 degrees Fahrenheit by 18,000 heliostats (sun-tracking mirrors). When power is needed, the hot salt is routed to a heat exchanger. The exchanger spins a turbine, generates electricity, and sends the salt back to the receiver to start the cycle all over again.
The technology for the Rice Solar Energy Project isn't new—rocket engine company RocketDyne developed it years ago, and the solar salt concept was proven to be viable at the 10 MW Solar Two project near Barstow, California in the 1990s.
SolarReserve's project is expected to go online in 2013, but it could run into some delays. Conservationists might complain that the solar tower destroys desert vistas—a problem that impeded a SolarReserve plant in Nevada. But in this case, the benefits outweigh any aesthetic consequences. If solar salt is proven to work efficiently on a large scale, utilities will be able to more confidently pursue solar power as a reliable form of on-the-grid energy.