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Researchers harness wave energy in research simulations

  • Published
  • By John Van Winkle
  • U.S. Air Force Academy Public Affairs
U.S. AIR FORCE ACADEMY, Colo. --  Researchers here recently harnessed more than 99 percent of the energy in a simulated ocean wave and are preparing to take their emerging technology to the next level.

The energy research is part of a National Science Foundation-funded project to create the world's first free-floating, fully submerged wave-energy converter that generates electrical power from deep-ocean waves.

The Air Force Academy's department of aeronautics began this project in the fall of 2008. The aeronautics department professors have decades of experience researching feedback flow control and fluid dynamics for various military aircraft and NASA spacecraft, which is the rare and necessary expertise to create a successful wave-energy converter.

The latest tests are experimental confirmation of the computational simulations that began the project.

"Now, everybody looks at simulations and says, 'Well, you're making all those assumptions and deriving the equations,'" said Dr. Stefan Siegel, who is leading the Academy's wave energy research effort. "Nobody believes simulations, other than the guy who did it. So ... we set up a very small, about 1:300 scale version of the deep-ocean wave in the lab. We built a wave tank and we built a scale model of our wave energy converter that we will use in the open ocean.

"What came out of those initial experiments is that we were able to get 95 percent of the wave's energy," he said. "That is, in a sense, confirming and replicating the results that we got out of the simulations."

That remaining 5 percent was lost to harmonic waves, but improved feedback flow control increased the efficiency to 99 percent in subsequent tests.

"There's pretty good reason to believe that when we scale up the experiment, it will behave in a similar fashion," Dr. Siegel said.

The computational and physical research both took place at the Academy. In many research environments, one of these two options is available, but rarely do researchers have access to both.

"This is really one of the great benefits of working in this environment," Dr. Siegel said. "We have both outstanding computational support, and the lab has excellent experimental facilities."

Cadets who major in aeronautical engineering must conduct research, which they do alongside Academy professors. One of those cadets recently introduced to this is Cadet 1st Class Caitlin Miller, who joined the wave energy project last year.

"Last semester, we pretty much worked in parallel with researchers, providing experimental results to validate the computational simulations they'd done," Cadet Miller said. "It was a lot cooler than I expected. I thought it was especially interesting, because renewable energy is one of the big things people are looking at, especially considering the finite supply of natural resources. The potential wave energy has to become the next big renewable energy source is a pretty cool thing to be part of."

She said she will further her research into wave energy this semester, as part of an independent study course.

The current three-year NSF grant runs through September.

The Department of Energy has provided another $400,000 of follow-on funding to take the wave energy converter to the next level: two testing campaigns with 1:10-scale models at the Offshore Technology Research Center at Texas A&M University, Dr. Siegel said.

The center has one of the world's largest wave tank facilities, which will allow the test of a larger wave energy converter and eventually permit testing of three wave energy converters simultaneously.