Forget Elon's Batteries—Fix the Grid With a Rock-Filled Train on a Hill WIRED

THE ARES IS pretty simple, as cutting-edge energy storage technology goes. A lot of rocks. A few railcars that, if they weren’t traveling up and down the same 5.5-mile track on a Nevada hillside, would probably be hauling ore around a mining operation. Throw in an electric generator, and you’ve got the future of the American energy grid.

Well, one possible future. Energy storage is a hot topic, because federal and state guidelines are fast pushing utility companies to ramp up their use of renewable energy sources. (California’s supply, for example, has to be 50 percent renewable by 2030.)

The problem is, today’s coal and natural gas guzzling grid doesn’t hold onto the electricity it generates. Utilities immediately deliver whatever they produce, and produce exactly what’s needed, from moment to moment.

Renewables, though, don’t work that way. The wind doesn’t always blow, the sun doesn’t always shine. So utilities are in search of ways to store surplus energy when they’ve got it, so they can distribute it later, when it’s needed.

Full article on wired.com