The storage of renewable energy is a challenge as the sun doesn’t always shine and the wind doesn’t always blow. The cutting-edge technology solution comes from ever more clever batteries. But what about a 19th century solution for a 21st century problem, with help from the abundant natural resource that is gravity? When the local utility’s got surplus electricity, it powers up the electric motors that drag 9,600 tons of rock- and concrete-filled railcars up a 2,000-foot hill. When it’s got a deficit, 9,600 tons of railcar rumble down, and those motors generate electricity via regenerative braking—the same way your Prius does. Effectively, all the energy used to move the train up the hill is stored, and recouped when it comes back down.
Renewable energy storage: A train filled with rocks on a hill
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