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See Inside Scientific American Volume 309, Issue 1

Patent Granted for a Buoy That Generates Power




COURTESY OF U.S. PATENT AND TRADEMARK OFFICE

Apparatus for underwater environmental energy transfer with a long lead zirconate titanate transducer: Buoys bobbing in the ocean do more than just mark navigational hazards. They help researchers track water and wind conditions, aid weather forecasters, listen for whale song and help the military detect underwater vehicles. Most buoys use batteries for power, but engineers have long tried to harness the crashing, roiling power of waves. Waves, however, do not move turbines fast enough to generate consistent current.

Instead build the buoy out of power-generating material, says Derke R. Hughes, a senior research engineer at the U.S. Navy's Naval Undersea Warfare Center. So-called piezoelectric compounds develop voltage when compressed. The compounds have a crystal-lattice structure with positive and negative poles. Under pressure, enough of the crystals align to produce a flow of charged particles or electricity.

Patent no. 8,274,167 describes a buoy that generates its own power. The floating section of the buoy is connected to a long cable anchored to the ocean floor or a weight. The cable has a core made of piezoelectric lead zirconate titanate, a chemical compound first synthesized at the Tokyo Institute of Technology. As currents flow around the cable, microeddies move it like the “strumming of a guitar string,” Hughes says. The power generated depends on the cable's length and tension, but it theoretically could be enough to power a sonar array. Could a farm of buoys generate the megawatts needed for power back on land? “You could envision running enough of them together in a series,” Hughes says. “It's just a matter of doing it right.” The buoy has yet to be prototyped, so for now the idea is just on paper.

This article was originally published with the title "Patent Watch."

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