Air Force fully harnesses wave power

U.S. Air Force / Rachel Boettcher

A wave energy converter generates power in a tank at the Air Force Academy. The converter was designed by Department of Astronautics researchers Stefan Siegel and Jurgen Seidel. It converts 99 percent of the energy in a simulated ocean wave.



By John Roach

Air Force engineers have used their skills in keeping airplanes aloft to harness more than 99 percent of the energy in a simulated deep ocean wave. A scaled up version of the technology should be as efficient, they report.

The free-floating, fully-submerged wave energy converter effectively cancels incoming waves, capturing their energy while flattening them out. This differs from other wave energy technologies that are tethered to the seafloor and tend to be battered by storms.

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Researchers at the U.S. Air Force Academy who have expertise in feedback flow control and fluid dynamics for various military aircraft and NASA spacecraft began working on the project in 2008.

Feedback flow control research involves the use of sensors and adjustable parts to control how fluids flow around airfoils like wings. The researchers decided to apply this knowledge to wave energy after reading about the field in a magazine and realizing the similarities.

The team presented their design and computer simulation results at the annual meeting of the American Physical Society’s Division of Fluid Dynamics in November 2009. The latest tests are experimental confirmation of the computer simulations.

“Nobody believes simulations other than the guy who did it,” Stefan Siegal, who is leading the wave energy effort, said in a news release announcing the result. “So we set up a very small, about 1:300 scale version of the deep ocean wave in a lab.”

When they put in a scale model of the wave energy converter, they were able to capture about 95 percent of the wave’s energy. “That is in a sense confirming the results that we got out of the simulations,” Siegal said.

The remaining five percent was lost to harmonic waves. The team tweaked the feedback flow control and increased the efficiency to 99 percent in subsequent tests.

Siegel expressed confidence in the press release that a scaled up version of the experiment will behave in a similar fashion.

The Department of Energy has provided another $400,000 for follow on testing with a 1:10 scale models at the Offshore Technology Research Center at Texas A&M University, taking the technology another step closer to full size tests in the open ocean.

Update for 7:40 p.m. ET: In a follow-up phone conversation today, Siegel explained his optimism for the scale-up of the technology. “Things actually get better for us as it gets bigger,” he said. There’s a lot of friction at the current scale, and the waves themselves are not very powerful. “In a sense, the experiment we just completed is almost, I would say, the worst-case scenario,” Siegel said.

What’s more, Siegel and his colleagues are about to publish numerical full-scale simulation results that demonstrate how this will work. Since the model-scale simulations and experimental results match up, they are confident the full-scale experiment will match the full-scale simulations as well.

Siegel now splits his time between the Air Force Academy and a startup dedicated to the wave energy technology. Visit the company website to learn more: Atargis Energy Inc.

More stories on wave energy:

* $28 billion in wave energy projects proposed * Scientists tap motion in the ocean for energy * Oregon eyes wave buoys to generate power

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John Roach is a contributing writer for Connect with the Cosmic Log community by hitting the “like” button on the Cosmic Log Facebook page or following’s science editor, Alan Boyle, on Twitter (@b0yle).


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