Secret vortex energy harnessed in ocean currents

A machine that works like a fish could turn slow-moving ocean and river currents into an affordable and reliable renewable energy source.

The technology – called Vivace (Vortex Induced Vibrations for Aquatic Clean Energy) – has been invented by an engineer at the University of Michigan.

It works in water flows moving slower than two knots (about two miles per hour), compared with turbines and mills which need an average of five or six knots to operate efficiently.

How does the technology work? A cylinder-shaped object in the water current causes alternating vortices to form above and below the cylinder. 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 (see artist’s impression in the image on the left).

Vivace developer Michael Bernitsas, a professor in the university’s Department of Naval Architecture and Marine Engineering, estimates 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 – all be under the surface.

Bernitsas claims the energy would cost about 5.5 cents per kilowatt hour – cheaper than wind and solar (but still more expensive than nuclear).

Vivace copies aspects of how fish work – they 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 says:

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

More from the University of Michigan here.

Illustration credit: Omar Jamil