Scientists have known for decades that muddy coastal sediments absorb the power of waves as they roll toward beaches. The result is a free service courtesy of soft ocean bottoms that diminishes the sea's energy before it reaches the communities living beyond them.
Now an engineering team is working to expand the muddy seafloor's portfolio of services to include power generation. They are building a "carpet" system meant to be installed underwater on coastlines that would harvest power from waves.
"Mud basically moves up and down under the action of the waves and small-scale motions called turbulence occurs within the mud layer and that converts the wave energy into heat," says Reza Alam, a University of California, Berkeley assistant mechanical engineering professor who is leading the effort. "Our idea was to design a carpet that sits on the seafloor and acts like a mud layer to extract energy from ocean waves and convert it into useful energy."
Their prototype consists of a rubber sheet topping a grid of hydraulic actuators, cylinders and tubes. Waves cause the sheet to pump the cylinders up and down, which transfer hydraulic pressure ashore that is then converted into electricity, says Marcus Lehmann, a doctoral student on Alam's team working on the project as part of his degree.
So far, they've built a working prototype in their university wave tank and now they'retrying to crowdsource nearly $10,000 of funding to develop a pilot generator for launch in 2016. If they produce a working plant, they expect to put it in shallow coastal waters about 60 feet deep. Alam's calculations estimate that almost 11 square feet of the carpet could power two U.S. homes.
They say an analysis from the nonprofit Carbon Trust estimates that coastal wave energy conversion has the potential to generate 2,000 terawatt-hours of electricity annually, or 10 percent of global demand. Their creation would join a growing number of wave energy capture systems cropping up around the world.
"There is a vast amount of untapped energy in the oceans, and with increasing worldwide demand for power, the need to find cleaner alternatives to fossil fuels is critical," Alam said in a university release. "We are also seeing greater population growth along coastal cities, so the ocean-based system we are developing would produce electricity in a carbon-neutral way right where it is needed."