Arizona Utility Tries Storing Solar Energy for Use in the Dark Oct 18 2013

When it snowed in Flagstaff, Ariz., recently, thousands of people woke up and turned up their electric heating, and Arizona Public Service saw electricity demand reach a morning peak. To meet the demand, the company used the previous afternoon’s sunshine.

In a closely watched new solar project called Solana, the energy is gathered in a three-square-mile patch of desert bulldozed flat near Gila Bend, about 50 miles southwest of Phoenix. A sprawling network of parabolic mirrors focuses the sun’s energy on black-painted pipes, which carry the heat to huge tanks of molten salt. When the sun has set, the plant can draw heat back out of the molten salt to continue making steam and electricity.

The emerging technology is one way that the utility industry is trying to make electricity from the sun available even when it is not shining, overcoming one of the major shortcomings of solar power. . . .