...AND CHEAPER...:

Here's how the $1-billion project in California's Kern County will work: The developer, Hydrostor, will drill three shafts thousands of feet below ground, and send down miners to dig out a series of rows and columns. When the project is ready to go in 2028, the underground caverns will have a collective volume equivalent to two football fields about 100 yards high.

During times of day when electricity is cheap -- such as sunny afternoons when California has more solar power than it needs -- Hydrostor will use that low-cost energy to push air down into the caverns. Think of it like storing sunlight in a bottle.

When Hydrostor's customer, Central Coast Community Energy, needs to draw on the stored power -- on a cloudy January day, for instance -- the company will open a valve and funnel the high-pressure air through a turbine, generating electricity.

It's not the only long-duration storage technology on the market. But Hydrostor President Jon Norman says it's ready to go.

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