Bldg blog:

A new electricity distribution system being described as the “‘Hoover Dam’ of the 21st century” will bring wind energy from Wyoming to customers in California—and it will get there by way of a $1.5 billion artificial cave built specifically for storing air inside a salt dome in Utah.
 The particular geologic site chosen for this underground storage facility is “a five-mile long, two-mile deep salt deposit,” the Casper Star Tribune reports. “Electricity there would be used to compress air into four underground caverns hallowed [sic] out of the salt deposit. During times of high-demand, air would be released, turning a turbine to create electricity.”
 It’s a kind of clockwork weather system buried inside the earth, like something out of the Aeneid.
 Dresser Rand, the firm behind the new storage facility, describes a related complex they worked on in Alabama. In a PDF available on their website, they write that their technology allows them to “store air in a salt dome at pressures up to 1100 psig.” To create that facility, the Alabama plant manager explains, “we solution mined it for 629 days. That created 19 million cubic feet of cavern storage.” That’s roughly half an Empire State Building of empty space.

Via Desi.