Salty Solar Storage

A couple of solar articles from the US describing plants about to be built using molten salt heat storage to extend or shift the generating ability of the solar thermal plant.

Solar Plant to Generate Power After Sundown
Rebecca Smith, WSJ, 31st Dec 2010

Abengoa's $2 billion Solana plant is expected to be the first major stored-heat plant in the U.S. when it enters service in 2013. Some already exist in Spain and a few more are on the drawing board for Nevada and California.

On Dec. 21, Abengoa, a unit of Spanish utility company Abengoa SA, cleared a major hurdle when it announced it received a $1.45 billion U.S. loan guarantee for the 250-megawatt Arizona project, planned for a site 70 miles southwest of Phoenix near Gila Bend.

The Solana plant will be able to meet winter heating and lighting needs by putting electricity on the grid early in the morning—before the sun is shining—and help satisfy summer cooling demand by producing power after sundown. The plant, which can power up to 70,000 houses, has signed a 30-year agreement to sell electricity to utility company Arizona Public Service.

Such utility-scale solar plants use mirrors to focus the sun's rays on a liquid, contained in tubes, which can be heated to very hot temperatures. The liquid is used to boil water and create steam. By using a conventional steam-turbine generator, electricity is produced.