Wednesday, November 04, 2009 at 12:49:46 PM - by Nate Lew

Rice Solar Energy, part of a spin-off from United Technologies, is planning a solar energy installation in an uninhabited part of eastern Riverside County, California.

The system relies on melted salt - 4.4 million gallons' worth - in a 538-foot tower. Mirrors around the tower reflect sunlight onto it, heating the salt to such great temperatures that it retains a useful amount of heat seven hours after sundown.

The technology underpinning Rice Solar Energy's project, called concentrating solar power (CSP), involves 18,000 mirrors - called heliostats - aiming light at the tower. The salt inside looks like water when melted, says the California Energy Commission in its review of the project.

Melted salt is stored in tanks and used to heat water into steam. The steam - as in most power-generating technologies - spins a turbine that creates electricity.

"Water consumption is an issue with concentrating solar power plants," said the Department of Energy in a report to Congress, "because they are most cost-effective in locations where the sun is most intense, which in turn often corresponds to places … where there is little water."

Nevertheless, the DOE adds, "[solar energy] is so widespread that CSP projects covering 1.4 percent of Southwestern land could potentially generate as much power as used in the entire U.S."