Or they would, if engineers could figure out how to capture that power. Most prototypes for wave-energy converters have been massive and costly, or else they're torn apart during violent storms at sea. But a Swedish company called CorPower Ocean may finally have a solution. Tests show its new buoy can produce three times as much electricity as the best rival tech, with a far more practical design.

For starters, it's relatively small: Whereas other devices can stretch hundreds of feet across and weigh well over a thousand tons, CorPower's bobbing red machine is a mere 26 feet in diameter. Yet a single buoy stationed offshore can generate about 250 kilowatts of power—enough to cover the electricity needs of 200 homes. Wave-power farms could contain hundreds or even thousands of them.