Saturday, November 22, 2008

Slow water currents and renewable energy

A new way to harness the power of moving water comes from something we've known about for hundreds of years: Vortex Induced Vibrations (VIVs).

Read about the new technology at ENN

First observed by Leonardo DaVinci, these vibrations result from spinning water flows forming and breaking up ("shedding") on the downstream side of a rounded ("bluff") mass that sits passively in a current of moving water.

A vortex is a spinning flow of liquid or air. We all see vortices (vortexes? vorteci?) each day as the water in the commode spins away. Other examples include tornados, hurricanes and black holes in space. A wind vortex creates the drag that moves sailboats. Anyone who has seen eddies (little cyclones of spinning water) form around rocks in a river or stream knows about this phenomenon, and has observed that water in the eddy spins on itself faster than the current is moving.

Scientists at the University of Michigan observed the way fish swim through the vortex created by the fish swimming in front of them (similar to drafting or slipstreaming in car or bicycle racing), and have figured out how to harness the power of slowly moving water by mimicking that process. Fish aren't the only animals to do this. We see geese and other birds flying in a "V" formation for the same reason. Lift force from the vortex created by the leader bird helps the trailing birds move along using less energy.


The U Michigan folks found that by placing a passive rounded cylinder in the water such that two vortices are created (above and below the cylinder), slowly moving water creates vortices that cause the cylinder to move like a piston. Presto! A renewable power source.

The thing that comes to mind for me is seeing a crab trap buoy move back-and-forth in a quickly moving tide, just like a piston. Why didn't anyone think of this before?

7 comments:

Chris R. said...

Wow, that's a really inovative idea. Does anyone know the implications of this as far as potential output? I guess since the idea is in it's fledgling stages that those type of statistics are just being calculated. These are definetley the kind of ideas the government needs to invest in if we are ever to free ourselves of the shackels of big oil. Way to go Michigan!

EASON said...

? I failed fluid dynamics.

Vinny Torregrossa said...

I think there is more renewable energy in everything around us than we realize. It's just a matter of time before we learn how to harness it. An example that comes to mind is the city of Greensburg KS. After seeing the show on TV explaining how this small rural town was destroyed by a massive tornado, the people of the town are building it "green". They are going above and beyond not only to save themselves on utility cost but to make less of an impact on the environment. They are doing things like using ICF walls, windmills, geothermal heating and cooling features and using the sun for natural light and heating in the winter months. This technology and these ideas are fairly new and are already being implemented. If we figure out how to harness more energy in the things around us we will soon be able to power cities with clean, renewable energy.
I don't believe anyone but the oil companies can disagree with me when I say we need to go this route. As for the upfront costs, they would be pricey to implement the new technology, but we would save and possibly make money on utilities in the long run. I don’t remember if we talked about it in class but I know LIPA (Long Island Power Authority) gives you money if your electric meter spins backward. In other words if someone had solar panels and it power their house plus some, the power would go back into the system powering someone else’s home and they would receive money for doing so. The ideas and possibilities in this field are endless. We just need to start taking actions. Hopefully it WON’T take a massive hurricane in this area to convince us to start a change like Greensburg.

Anonymous said...

(rachel bisesi)
sounds pretty cool, especially since it utilizes the slower water currents of around 2 knots and less- which would work in most areas.

It said that they don't think the cylinders will cause much damage to marine life- I wonder if this will really be the case-?

also, how much is it going to cost for these things to be made, or installed?
-the generating power costs for the device seems to vary from website to website but I guess they haven't really gotten all the logistics worked out yet so it will be neat to see what happens with this idea.

Mandy Isaac said...

I learned about this briefly in my Oceanography class. It's renewable energy without being an eyesore (like wind farms). Based on what my teacher said in class, there are no major negative side effects this would have on sea life. Hopefully in the next 10 years we can see this take off!!!!

Mandy Isaac said...

http://www.sciencedaily.com/releases/2008/11/081121125604.htm

That's the article we reviewed in Oceanography on the issue in case anyone is interested.

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