Scientists tap motion in the ocean for energy

Bryn Nelson Columnist

A sea of potential is lurking just beneath the waves. In a sinuous rubber tube dubbed the Anaconda and in the unusual features of dolphin flukes and humpback whale fins, scientists are looking to the ocean and its inhabitants for a little alternative energy inspiration.

For Frank Fish, humpback whales are inspiring new designs for more efficient windmills and industrial ceiling fans. Why humpbacks? “They actually have these very elongated flippers, about one-third the body length of the animals,” said Fish, a biomechanist at West Chester University in West Chester, Pa.

Along the leading edge of each wing-like flipper, he said, prominent bumps called tubercles modify the flow of water and keep it from stalling. A stall, in either air or water, happens when a wing (or flipper) banks at too high of an angle relative to the oncoming flow, resulting in a dramatic loss of lift. The phenomenon can be catastrophic in airplanes, dropping them from the sky like dead weight.

Humpback fins, however, show that bumpy surfaces can help establish a flow pattern that reduces the likelihood of a stall. Because of the design, the wings can be held at a much higher angle to increase the flow. Fish’s research suggests that at higher angles, the tubercles may actually reduce the drag compared to perfectly smooth wings, flipping conventional engineering theory on its head. Accordingly, Fish sees obvious applications for any lifting, wing-like surface, whether for airplanes or windmills.

Whales and wind turbines
Fish, who presented his research at the Society for Experimental Biology’s annual meeting earlier this month in Marseille, France, has begun applying his work commercially as president of Toronto-based WhalePower. The company’s Web site coyly claims “a million years of field tests” for its humpback-inspired “Tubercle Technology.”

Despite the head start, Fish isn’t quite ready to publish the results with a 30 kilowatt test windmill on Canada’s Prince Edward Island, run by the Wind Energy Institute of Canada. Preliminary tests in wind tunnels, however, have yielded a 4 percent increase in maximum lift, a 40 percent increase in the stall angle and a reduction in drag by as much as 34 percent.

A 4 percent increase in lift may not seem like much, but even small increases can help boost efficiency. Windmills are generally kept far below their maximum lift potential to prevent stalls, which tend to happen asymmetrically so that only one blade falters. The ensuing vibrations can cause a windmill to literally shake itself apart.

Decreasing the attack angle and maximum lift as a precaution means less power generation, but Fish said adding tubercles to the windmill blades requires less of a tradeoff. Beyond the initial test site, Fish would like to scale up the blade design for the larger 3-megawatt wind turbines popping up around the world.

Whales-inspired ceiling fans
If humpback-inspired wind farms are still a few years away, another whale of a design is on tap for industrial ceiling fans by summer’s end.

Stephan Gingras, research and development manager for Seaforth, Ontario-based Envira-North Systems Ltd., said he was initially wary when WhalePower approached his company, one of Canada’s largest industrial fan manufacturers.

“Like everybody else, we were a little bit skeptical,” he said. “What will a whale have to do with blades on fans?”

Plenty, as it turns out. Envira-North’s ceiling fans, varying from 8 to 24 feet in diameter and destined for the likes of aircraft hangars, gymnasiums and shopping malls, can wield up to 10 blades and weigh 500 pounds. The normal angle of attack, or pitch of each blade as it pushes through the air, is about 15 degrees. Adding tubercles to each blade’s leading edge, Gingras said, has allowed the company to increase that angle to 25 degrees, greatly increasing the efficiency.

And as the efficiency increases, costs go down. Currently, a 2 horsepower motor suffices for the biggest fans, which move more than the 380,000 cubic feet every minute. But a new whale-inspired fan in the final stages of testing will push the same volume or more with only four or five blades, cutting about 150 pounds in the process. With a less weighty fan, Gingras said, “maybe we’ll only need 1.5 horsepower.”

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