New Machine Harnesses Renewable Energy From Slow Water Currents

November 25th, 2008

A University of Michigan engineer has been able to emulate fish technology to produce a renewable source of energy from slow water currents. These potentially destructive vibrations in fluid flows are being used with the help of fish observation to produce usable energy.

Michael Bernitsas, a professor in the U-M Department of Naval Architecture and Marine Engineering, has developed a machine called VIVACE, which stands for Vortex Induced Vibrations for Aquatic Clean Energy. It doesn’t depend on waves, tides, turbines or dams. It’s a unique hydrokinetic energy system that relies on “vortex induced vibrations.”

The machine called VIVACE is the first known device that 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.

Vortex induced vibrations are undulations that a rounded or cylinder-shaped object makes in a flow of fluid, which can be air or water. The presence of the object puts kinks in the current’s speed as it skims by. This causes eddies, or vortices, to form in a pattern on opposite sides of the object. The vortices push and pull the object up and down or left and right, perpendicular to the current.

These vibrations in wind toppled the Tacoma Narrows bridge in Washington in 1940 and the Ferrybridge power station cooling towers in England in 1965. In water, the vibrations regularly damage docks, oil rigs and coastal buildings.
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“For the past 25 years, engineers—myself included—have been trying to suppress vortex induced vibrations. But now at Michigan we’re doing the opposite. We enhance the vibrations and harness this powerful and destructive force in nature,” said VIVACE developer Michael Bernitsas.

“VIVACE copies aspects of fish technology,” Bernitsas said. “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.”

Bernitsas doesn’t believe that this will solve all of our energy needs, but it can help provide quite a bit of energy if we can harness some of the ocean’s unlimited energy.

“There won’t be one solution for the world’s energy needs,” Bernitsas said. “But if we could harness 0.1 percent of the energy in the ocean, we could support the energy needs of 15 billion people.”

We certainly can use all the options we can get when it comes to re-usable energy sources. I have to say this is a pretty interesting, and ingenious study. Certainly good thinking on his part to come up with the machine using known observations in nature. I always wonder what kinds of weird projects guys like this have stored on their external hard drive when I see these kinds of stories. Just the way inventors think is amazing to me. I have so many little things in my documents folders that occur to me from time to time and always wonder what kind of strange ideas other people have…lol