Malta taps into the laws of thermodynamics to store renewable and fossil energy as heat in molten salt and cold in low-temperature anti-freeze until it's needed -- you probably still need electricity at night, when the sun isn't shining on your local solar farm. The company is working on a pilot plant, backed by $26 million from its first funding round, which was led by a fund Jeff Bezos, Bill Gates and Michael Bloomberg are involved with.

Power storage is often a cumbersome, expensive problem, particularly for the likes of wind and solar farms. Providing them with a reliable, inexpensive way to keep electricity in reserve could cut down on waste, while helping renewable energy companies find the bandwidth to generate more power.