Wednesday, August 8, 2007

Oh Buoy!

Buoys flex artificial muscles for renewable energy
Each stretch of an artificial muscle attached to a buoy can generate 20 watts of power The "muscles" produce electricity as they bob up and down attached to buoys. Although they only generate enough power to light a small light bulb currently, the scientists involved see it as a first step to implementing a new, cheap technology for harvesting renewable energy from the ocean.
The artificial muscles are made from electroactive polymers, a material that can be physically activated with a jolt of electricity.
Electroactive polymer artificial muscles (EPAMs) are heralded as a key technology for powering future robots and other machinery. The design is remarkably simple – essentially several sheets of specialised rubber sandwiched between two elastic, oppositely-charged electrodes. When an electric charge is applied the electrodes squeeze the rubber. When the charge is dropped, the rubber relaxes.
Roy Kornbluh of SRI International in California, US, and colleagues simply reversed the process. They rolled a sheet of EPAM into a cylindrical shape, and attached a weight to one end. They then fixed it to a weather and navigation buoy inside a watertight capsule.As the buoy floats on the ocean surface, the force generated by the wave action stretches and relaxes the rubber, oscillating the distance between electrodes and generating electricity (see image, right, and a video animation showing the system in action).With an average 0.8-meter wave, each stretch of the muscle can generate as much as 20 watts of power. Since waves tend to come about every 4 seconds, though, the sustained energy output is closer to 5 watts.
"Right now we're just powering lighting systems on a buoy," Kornbluh admits, "but we want to scale up by orders of magnitude, and you can imagine hundreds or thousands of these thing scattered in the ocean."
"Most wave systems are more complicated, they use flowing hydraulic fluid to turn a transmission, which then spins a turbine," Kornbluh says. "We're just stretching our generator. It's hard to imagine anything more simple."...more>>

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