Aerospace engineers are working to make ocean wave energy the nation’s newest source of green power by applying the physics of wind turbines to the sea.
Former U.S. Air Force Academy scientists took over Texas A&M University’s wave tank recently to test the idea that if air can produce affordable electricity, so can ocean water.
For decades, researchers have sought ways to turn the energy in ocean waves into electricity – economically and with minimal impact to marine environments. But as other forms of renewable energy have flourished, commercial power from ocean waves hasn’t made it onto U.S. grids.
“Ocean wave energy is decades behind wind. But with all the resource in the ocean, it’s much more attractive,” said Stefan Siegel, who led the testing at Texas A&M.
“The wind doesn’t always blow. The sun doesn’t always shine. But ocean waves, they are always there.”
Siegel’s Colorado-based startup, Atargis Energy Corp., developed a device using components similar to airplane wings or wind turbine blades. Incoming waves rotate the two wings around a central axis. The movement activates generators connected to the device, transforming the mechanical energy into electricity.
The prototype, about one-tenth the size of a full-scale device, produced 370 watts during testing at Texas A&M, Siegel said. He hopes that with design improvements, a full-scale version will churn out 5 megawatts in the ocean, enough to power 3,000 to 4,000 U.S. homes.
However, the wave tank testing revealed design weaknesses that Atargis must address to make its device ocean-ready, Siegel said.
Texas A&M’s wave tank, one of the world’s oldest and largest, typically tests offshore oil and gas platforms. The 19-foot-deep tank is about half the size of a football field and simulates various ocean conditions, producing waves as high as 3 feet.
It opened in 1991, but didn’t get its first renewable ocean energy trial until 2003, director Richard Mercier said.
He said the devices he sees there struggle to extract the maximum energy from waves while minimizing construction and installation costs.
“If it’s ever going to become reality, it has to get much more sophisticated in design,” Mercier said of ocean wave energy.
Existing technologies often use buoys or cylindrical floaters that bob or bend with the water’s motion. Their movements typically operate hydraulic pumps connected to generators.
Siegel believes Atargis addresses some of the challenges. The rotating blades capture about 95 percent of a wave’s energy, he said. And the device operates just below the water’s surface, partially shielding it from violent storms.
But other challenges face ocean wave energy, said Belinda Batten, director of the Northwest National Marine Renewable Energy Center based at Oregon State University.
Unlike wave tanks, the ocean is home to animals and produces waves that are difficult to predict. The harsh environment can drive up the cost of a device and the electricity it produces, Batten said.
“You can have the most amazing device in the world. If it has negative environmental effects, you are not going to go in the ocean,” she said.
Batten was a program manager at the Air Force Academy and oversaw funding for the work that generated Siegel’s idea for the Atargis wave energy device a decade ago.
Since then, Atargis has received $285,000 from the National Science Foundation and $400,000 from the U.S. Department of Energy.
With the results of the Texas A&M testing, the Atargis team plans to make design improvements in a larger model, including blades that better conform to various wave patterns. By 2014, Atargis hopes to test in the open ocean.
Siegel acknowledged that ocean wave technology development has a long way to go.
“The engineering issues are huge,” he said. “It’s much more difficult than getting an airplane in the air.”