— Each stretch of an artificial muscle attached to a buoy can generate 20 watts of power (Image: SRI)
Artificial muscles are being used to turn the ocean's waves into electrical power in a novel pilot project off the coast of Florida, US.
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."
In the last year, nearly 40 applications were filed with the US Federal Energy Regulation Commission for installing the ocean energy systems along the US coastline. It is a crowded field, but Kornbluh believes the simplicity and low cost of his design could give it advantages over competitors.
No adverse affects
"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."
The US energy market could welcome ocean energy technology with open arms. A recent report issued by the Electric Power Research Institute suggested that ocean energy could expand to meet 10% of the total electricity demands of the US without any measurable adverse effects on the environment.
"Either way it's encouraging that someone is working with artificial muscles and moving in a direction that is really our problem now energy," says Yoseph Bar-Cohen of Jet Propulsion Laboratory in Pasadena, California.