The pioneer: Dr. Donald Sadoway, Professor of Materials Chemistry, Massachusetts Institute of Technology

The concept: Batteries made of liquid metals. Picture a container of oil and vinegar — these liquids don’t mix, they stratify into two layers. The liquid metals in MIT’s battery stratify too — into three distinct layers (cathode, anode and electrolyte) that interact with each other and conduct electrical current. Conventional batteries made of solid metals are expensive and hard to build big. But liquid batteries could be enormous in size — large enough to store power from wind, solar, and other intermittent sources of energy, and discharge it on demand. They could also be sited at or near the buildings they’re powering, eliminating the need for new transmission lines to urban centers. Don’t expect to see liquid car batteries, though — all that sloshing would disrupt the current.

The payout: $6,949,624.00

The goal: In the next 18 months Sadoway and his team plan to scale up their prototype “from the size of a shot glass to the size of a deep-dish pizza box,” which could provide enough power for a home office. (By 2015, he plans to have a trash barrel-sized liquid battery that would power a small home.) For continuous wind and solar power on the grid, however, the batteries might have to be as big as an eighteen-wheeler, or bigger. It’s too early to put a timeframe on that super-sizing.

The hurdles: Cost, scale, and the laws of physics. A lithium-ion battery — commonly used in small-scale applications like cell phones and laptops — that was big enough to power a house or a neighborhood, would cost more than 1000 times what we now pay for energy from the grid. We need a new approach. The question is whether the laws of physics will cooperate. Energy doesn’t like to be stored; it likes to move. Capturing and containing energy cheaply and on a grand scale “is a seemingly impossible challenge,” said Sadoway, “but that’s what makes it so exciting.”

The promise: “All these people working to improve solar-cell efficiency and wind-turbine performance — that’s great. But it won’t make a difference if you can’t store and discharge that power on demand. Liquid batteries could give us electricity from the sun even when the sun isn’t shining, and from the wind when it isn’t blowing. Storage is everything. It’s a world-changer.”