SUN STORED IN MOLTEN SALTS

Molten salt is "secret sauce" of new solar energy technology
Peter Pae, June 8, 2009 (LA Times via Seattle Times)

"…[A] storied rocket maker and a renewable-energy company are hoping to take what [was] learned [a] the long-closed desert facility to build a much larger plant that could power 100,000 homes — all from a mix of sun, salt and rocket science once believed too futuristic to succeed…

"… SolarReserve has licensed the technology, developed by engineers at Rocketdyne…[Its] molten salt technology is considered one of the more unusual and — to some energy analysts — one of the more promising [concepts] in the latest rush to build clean electricity generation…[SolarReserve] is financing and marketing the project…is working on agreements with several utilities to buy [its] electricity…[and] hopes to have announcements in a few months that could help jump-start construction…likely on private land in the Southwest…"

click to enlarge

"The company last fall secured $140 million in venture capital…The plant could begin operating by 2012 or early 2013. It would use an array of 15,000 heliostats, or large tilting mirrors about 25 feet wide, to direct sunlight to a solar collector atop a 600-foot-tall tower — somewhat like a lighthouse in reverse.

"The mirrors would heat up molten salt flowing through the receiver to more than 1,000 degrees Fahrenheit, hot enough to turn water into powerful steam in a device called a heat exchanger. The steam…would drive a turbine to create electricity…The molten salt, once cooled, would be pumped back through the solar collector to restart the process…"

A solar power tower. (click to enlarge)

"…[S]ome environmentalists have criticized solar-thermal plants for requiring vast tracts of land…[and] precious water for generating steam and for cooling the turbines…[T]he SolarReserve plant would take up about two square miles. Transmission lines also would be needed to transport the power…With dozens of solar, wind and geothermal projects planned for California's deserts, some fear this unique habitat will be destroyed…SolarReserve officials said its plant would use one-tenth the amount of water required by a conventional plant and that mirrors will be "benign" to the environment…

"…The technology, with the exception of using salt, is similar to those that Rocketdyne engineers developed for the nation's more notable space programs…[E]ngineers who came up with the SolarReserve technology also developed the power system for the international space station, the rocket engine for the space shuttle and the propulsion system for the Apollo lunar module…United Technologies bought the Rocketdyne unit from Boeing…It didn't know about the solar project until after the acquisition…The solar-thermal technology actually was proved workable more than a decade ago…[but abandoned] when the cost of natural gas fell to one-tenth of what it is today."