10 Green Structural Engineering Marvels

Autonomous PowerBuoy
A PB150 PowerBuoy wave energy device waits on the dockside in Invergordon, Cromarty Firth Scotland. © Ashley Cooper/Corbis

Educated guesses of recoverable oceanic wave energy can reach into the tens to hundreds of terawatts (trillions of watts) per year, but figuring out an environmentally friendly way to tap those tasty waves has historically left engineers feeling sunk. Lately, however, the field has experienced a sea change, thanks to folks like Ocean Power Technologies.

The Autonomous PowerBuoy's appeal derives from both its small footprint and its straightforward principle: A 5-foot (1.50-meter) tall buoy bobs on the waves, pulling on an anchoring spar linked to a rotary motor on the seafloor. The up-and-down wave motion cranks the motor, which generates electricity. If that sounds simple, it's not: To handle variances in pulling power caused by different-sized waves, the float needs an onboard computer to adjust the spar's resistance 10 times per second [sources: Fecht; OPT].

A number of PowerBuoys currently operate in the waters around Hawaii, each generating 0.04 megawatts of power, but buoys planned for Scottish waters might bump that number to as much as 0.15 megawatts. According to manufacturer Ocean Power Technologies, once set up in grids, the bobbing contraptions might scale up to hundreds of megawatts [sources: Fecht; OPT].

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