Hydrokinetic power

A University of Michigan professor has developed a machine that can generate power from slow moving water.

The so-called VIVACE machine (Vortex Induced Vibrations for Aquatic Clean Energy) could, it’s claimed, harness energy from most of the water currents around the globe because it works in water flows moving slower than two knots.

A working prototype of the machine, developed by Michael Bernitsas, a professor in the University of Michigan Department of Naval Architecture and Marine Engineering, comprises just one sleek cylinder attached to springs that hangs in a tractor-trailer-sized water-filled tank across the direction of the water flow.

When water flows over the cylinder, the presence of the cylinder causes alternating vortices to form above and below it. The vortices push and pull the passive cylinder up and down on its springs, creating mechanical energy. Then, the machine converts the mechanical energy into electricity.

Just a few cylinders may be enough to power an anchored ship, or a lighthouse. An array of VIVACE converters the size of a running track and about two stories high could power about 100,000 houses. Such an array could rest on a river bed or it could dangle, suspended in the water under the surface.