Vortex Induced Vibrations to generate energy from river flow
The Detroit River is the site of an unusual experiment. Whirlies in the water that the river carries form around cylindric 'wings' that are forced to move up and down in alternation. It is the imbalance of the attractive forces of vortices that form when water flows by the round obstacle that do the moving. Mike Bernitsas, director of the Marine Renewable Energy Laboratory at the University of Michigan and inventor of the device is ready to deploy a three kilowatt pilot plant that will prove his concept in a real-life setting.
PESWiki has a page that explains the Vivace concept, including some drawings and videos of a test set-up:
Vivace or Vortex-Induced Vibrations for Aquatic Clean Energy is a rather unique system that puts the power of vortices forming in flowing water to positive use. The formation of a vortex alternately above and below the cylindric 'obstacle' forces an alternating vertical motion of the cylinder, the energy of which can be harnessed.
Another one of those systems that use the normal flow of river water is the invention of Austrian engineer Zotloterer, where the water forms a snail's vortex, which is then directly converted into electricity by shedding its power to turn a slow-running turbine. See Water Vortex Drives Power Plant.
Other systems that utilize slow water flow are described in PESWiki's Low Impact Hydro page.
While such use of slow flowing water seems much less efficient than using the water pressure built up by a dam, the number of sites that can potentially be used is almost unlimited. This more than compensates for the relatively low efficiency. An advantage that should not be underestimated is the fish-friendly nature of these technologies, as well as their adaptability to an infinite variety of local conditions. They make it possible to produce our electric energy right where we need it - close to cities and villages - rather than in some remote region from whence it then has to be transmitted to reach the point of consumption.
Here is an article about the VIVACE project in Michigan from Phys.org, as first published by the Detroit Free Press - http://www.freep.com
- - -
Scientists to tap river currents to create clean energy
Whirligigs of illuminated particles form as the water pours over and under the cylinder in rhythmic patterns.
It looks simple, but it's revolutionary. This is VIVACE, a device to harness energy in slow-moving water currents across the globe and turn it into electricity.
VIVACE, which mimics the way fish swim in currents, is to debut next year in the Detroit River, powering the light for a new wharf between Hart Plaza and the Renaissance Center.
"Everybody is excited by this," said Mike Bernitsas, director of the Marine Renewable Energy Laboratory at the University of Michigan and inventor of the device.
It's one of a handful of new techniques - the first in more than 100 years - to use water to create clean, renewable energy. Since late November, the device has been filmed by Canada's Discovery Channel and discussed in science blogs, journals and the British Sunday Telegraph.
Unlike water-driven mills, turbines or dams, VIVACE doesn't require fast-moving water - most streams on the globe are slow-moving - and doesn't harm the environment.
VIVACE means "lively" on a musical score, but in this case is an acronym standing for Vortex-Induced Vibrations for Aquatic Clean Energy.
Bernitsas said he is thinking small so far, but someday an array of 1,000 cylinders offshore could produce the same energy as a large nuclear plant. A smaller grouping, as big around as a running track and as tall as a two-story building, could power 1,000 homes.
He came up with the idea four years ago and is developing it with a team of more than 30 students and researchers for commercial use. He patented it and started a company that hopes to manufacture it in Michigan in a few years.
In a stream, small eddies, or vortices, are created above and below an object the current hits. These vortices alternate, creating an up and down lift.
For example, a moored boat will bob up and down, and a stick caught underwater in a stream will quiver. Vortices in the air make your car antenna shake if you drive fast.
In air or water, the vibrations can be dangerous if not controlled.
Bernitsas, 57, has worked for two decades on ways to control these vibrations on offshore oil rigs.
"He was famous for how to kill vortex-induced vibrations," said U-M doctoral student Jim Chang, who works on VIVACE. "Now he'll be known for using them."
What Bernitsas envisions is groups of cylinders in frames on the ocean bed or in streams, perpendicular to currents. As the water flow hits the cylinders, it creates vortices that cause the cylinders to move up and down. That energy drives generators to make electricity, which goes through cables to the electrical grid on land. The size, number and placement of the cylinders depends on the body of water.
In the Detroit River, he plans 21 cylinders, each about 10 inches in diameter and 16 feet long, suspended in frames mid river on the U.S. side, which will create 3 kilowatts of energy around the clock to power lights on the dock.
This electricity is clean, infinitely renewable - "as long as the sun, the Earth and the moon move as they do now," he jokes - and doesn't harm the environment.
The cylinders will be far enough apart that fish can swim through them and deep enough to avoid ships, boats and fishing lines.
"It's a really creative project," said John Kerr, director of economic development for the Detroit/Wayne County Port Authority.
VIVACE's electricity will be cheaper to produce than solar or wind energy - at 5.5 cents per kilowatt hour - and cheaper than coal plants if controlling their carbon emissions is accounted for, he said, because the devices are simple and require little maintenance.
The cylinders should go into the Detroit River within 12 to 14 months, followed by further testing.
Bernitsas said he can't jump up and down until then, since challenges remain.
"Once it's in the Detroit River, I'll be screaming, 'Eureka!' " he said.
See also related: