Harvesting Power from the Ocean

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So far, this prototype produces only about five watts of power--enough for a small light bulb. But because the rubber is thin--about 0.1 millimeters thick--it's possible to roll up much more of it and still fit it into the same buoy. A bundle of rubber about a meter long and half a meter thick, with optimized electronics and an improved buoy design, could generate a kilowatt of electricity, Kornbluh says. A string of buoys or larger floating structures could then generate appreciable amounts of electricity. (A thousand buoys could power about 750 houses.) An alternative design could involve submerged sheets of rubber that generate power as the force of currents or tides makes them flap back and forth. Such a system might prove more resilient than the turbines recently used in the East River in New York: their mechanical parts proved unable to withstand tidal forces.

The SRI system produces high voltages, in the range of a kilovolt. That was a problem for the shoe generator, which required a transformer to decrease the voltage enough that it wouldn't fry cell phones and other devices but still had to fit in a shoe. But for the buoy application, high voltage is an advantage, since it makes it more efficient to transmit electricity back to shore along underwater cables. The main challenge moving forward, the researchers say, is to develop a reliable manufacturing process. Their recent tests of the system also underscored the importance of designing new buoys that respond to waves in the best way for generating power. And they'll need to design electronics that, by varying the voltage across the polymer, can modify the stiffness of the system to adapt to different weather conditions.

The system's first commercial applications will likely be in systems for powering navigation, communications, and sensor buoys, and these could come within two years, Kornbluh estimates. But it could be five to ten years before the system can be ramped up for large-scale electricity generation.

"It's very exciting," says Ray Baughman, a professor of chemistry at the University of Texas at Dallas. "It's a promising direction for harvesting energy, not only for remote devices in the ocean but also perhaps for larger-scale energy harvesting."