A University of Michigan engineer has made a machine that works like a fish to turn potentially destructive vibrations in fluid flows into clean, renewable power. Called VIVACE for Vortex Induced Vibrations for Aquatic Clean Energy, the hydrokinetic energy system relies on vortex-induced vibrations, undulations that a rounded or cylinder-shaped object makes in an air or liquid flow. Fish have long known how to put the vortices that cause these vibrations to good use.

"VIVACE copies aspects of fish technology," said developer Michael Bernitsas, a professor in the U-M Department of Naval Architecture and Marine Engineering. "Fish curve their bodies to glide between the vortices shed by the bodies of the fish in front of them. Their muscle power alone could not propel them through the water at the speed they go, so they ride in each other's wake."

The system could harness energy from most of the water currents around the globe because it works in flows moving slower than 2 knots (about 2 miles per hour.) Most of the Earth's currents are slower than 3 knots. Turbines and water mills need an average of 5 or 6 knots to operate efficiently. According to Bernitsas, VIVACE energy would cost about 5.5 cents per kilowatt hour - less expensive than clean energy alternatives such as wind and solar power.

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