(Pardon if this is a repost.) 'Fish technology' draws renewable energy from slow water currents

[OKIsItJustMe]

http://www.ns.umich.edu/htdocs/releases/story.php?id=6842

Nov. 20, 2008

'Fish technology' draws renewable energy from slow water currents

ANN ARBOR, Mich.—Slow-moving ocean and river currents could be a new, reliable and affordable alternative energy source. A University of Michigan engineer has made a machine that works like a fish to turn potentially destructive vibrations in fluid flows into clean, renewable power.

The machine is called VIVACE. A paper on it is published in the current issue of the quarterly Journal of Offshore Mechanics and Arctic Engineering.

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.

VIVACE 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."

…

(Video and more at the link)

[nashville_brook]

1. -- google Viktor Schauberger

there's a wonderful book on Amazon -- Hidden Nature: The Startling Insights of Viktor Schauberger -- it's an easy read, and presents some intriguing history to this technology.

[zipplewrath]

2. Sounds widely distrubuted

They build dams for a reason. It's to concentrate the energy over space. A slow moving river doesn't have much vertical drop and so to collect the same amount of energy out of the water you'd have to have these things along a huge stretch of the river. Or I suppose a REALLY wide river. I've seen shallow river devices before. They produce extremely small amounts of energy for their size. This type of technology sounds more suited/intended for ocean currents where there is alot of room to work without particularly impacting their environment.

[OKIsItJustMe]

3. You may be surprised. (Watch the video)

http://www.ns.umich.edu/podcast/video.php?id=499

[zipplewrath]

4. I'm not sure what the surprise is

He virtually admits that the energy is highly distributed. The animations show alot of these being spread around to collect the energy. One would have to because each collector isn't exposed to that much energy. This is a difference approach to hydroelectric. Typically we collect the energy in reservoirs and use high vertical drops to extract it. The speed of the current is inconsequential other than the ability to replenish the volume. This is attempting to extrace the energy out of the current speed. It's a "partial dam". The local flow will be slowed which will cause the river to rise. The less the river rises, the less energy they can extract. Basically it is a kinetic energy extractor, instead of a potential energy extractor. Dams work on vertical drops of hundreds of feet. These things will be generating the equivalent of inches of vertical drop. But there will be ALOT of them.

[OKIsItJustMe]

5. I live far from the ocean

The rivers around here are essentially non-navigable, however, I could see installing a large battery of these devices.

I think they're suitable for more than just ocean currents.

[zipplewrath]

6. "large" is the issue

Doing some quick back of the envelope stuff, one of these produces something like 1/3 of a watt-hr. Double that, triple it, whatever, you'll still need alot of them to run one bulb. Small streams don't seem to be the target. Tidal shifts, or ocean currents, yeah.