Environment

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Wade Payne/AP

Technology Extracts Energy From Ocean’s Currents

December 15, 2008 10:33 AM
by findingDulcinea Staff
A new device that uses cylinders inspired by the movements of fish has the potential to produce more energy at a cheaper cost. Scientists hope to ride the wave.

Watery Source of Energy Looks Promising

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Scientists say that the VIVACE system, or “vortex-induced vibrations for aquatic clean energy,”  is more effective than existing technologies that use the movement of waves, tides or currents created by dams, according to a study published in the November issue of the Journal of Offshore Mechanics and Arctic Engineering.

“This is a totally new method of extracting energy from water flow,” said Michael Bernitsas, a professor of naval architecture at the University of Michigan, to The Telegraph. “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.”

In the VIVACE system, water flows past a system of cylinders that are placed horizontal to water flow and attached to springs, creating vortices that move the cylinders up and down to produce vibrations that can be converted into electricity.

Scientists say that, compared to other devices, it can generate more power at a cheaper cost, requires less ocean acreage, and is less harmful to aquatic life as its parts move slower than other devices. It also has a broader range of uses because it can be used in bodies of water that do not have a fast flow of water. It can be placed far below the ocean’s surface, scientists say, so it is less disruptive to shipping and recreational boats.

Background: Tidal energy

While VIVACE’s creators say that tidal energy is less effective than their device, it continues to gain momentum. New York City’s Roosevelt Island became the site of the first major tidal power project in the U.S. two years ago when the company Verdant Power first started operating an “underwater windmill” to transmit energy from the East River to area businesses.

“What we love about tides is that they are very predictable,” said Trey Taylor, president of Verdant Power, to New York University’s Scienceline. “We can look at a clock and a tidal chart and know exactly when power is coming on and going off.” 

At first, however, the East River’s tides looked like they might be too powerful for the fledgling technology. Last year, the first set of turbines installed underwater had to be removed for redesign and repair, creating a temporary setback for the project. “The good news is that there’s more power in the East River than we thought,” Verdant Power geologist Mollie E. Gardner said to The New York Times.

And in May, SeaGen Tidal System near Northern Ireland was to become the first deepwater tidal energy plant in the world to start providing commercial electricity to homes in the area.

Related Topics: The alternative energy debate

Everything from car exhaust to do-it-yourself fueling devices are being mined for energy, in addition to more mainstream alternative energy sources such as wind power. How does energy derived from the world’s bodies of water stack up against the myriad alternative fuel sources available today?

Most devices that extract energy from water bodies such as ocean currents, flowing water from rivers, tidal streams and artificial waterways like canals, operate “like windmills underwater,” said Douglas Hall, program manager of the water energy program at Idaho National Laboratory, to LiveScience.

These water-based technologies, or hydrokinetic devices, produce renewable energy and do not emit pollutants into the air like fossil fuels. They also provide power more consistently than wind or solar power devices, which have more variability, and because they operate underwater, they have less visual impact than wind turbines.

But Hall, cautions that hydrokinetic technologies are at the moment less developed than solar or wind power, and their longterm environmental impact is unknown.

Reference: Scientific study

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