as long as we don't have pured fish, diced dolfin or sliced wale I'm all for it!

I suppose the manatees don't have things bad enough...perhaps they can make a guard for them...fashioned out of recycled 6-pack rings

I'm kidding..this is a great idea if it doesn't mess with the local wildlife

I assume they had the forethought to put it out of a whales path but I'd worry about dolphins and sharks

Like modern wind turbines, these things are probably big enough that the blades spin very slowly and are easy to see (or hear? detect) by the local fauna.

Lets hope, anyway.

Six turbines to provide half the power for one store? Seems like this technology has long way to go.

Good point, Ferris. These are probably pretty small, then.

But there's no reason why bigger ones couldn't be built.

Personally, I'm a big fan of wave-generators.

This looks interesting, and my reaction was similar to others here; "That doesn't seem like very much power for six turbines" and "I hope those turbines don't slice up marine life."

The Business week article does say that the turbines spin at a "fish friendly 35 Mph." Most details would be nice, but let's assume that's correct. The store is also a supermarket - likely a big consumer of electricity with all the freezers, etc.

The company's website isn't that detailed, but I think if you all peruse it it may clear up some misconceptions about how much power these things put out etc.

My guess is that the reference to the store getting half their power from this means they're contracting to get 50% of their electricity from the utility that comes from the Verdant Power equipment.

You can do the same thing with wind power contracts through your utility - buying in blocks of 100 or 200 kWh per month, or even simply signing up for "100%".

For example, Verdant is claiming their East River field will eventually be 10 MW:
http://www.verdantpower.com/initiatives/currentinit.html

That's enough to fully power about 7,500 average US households.

Great Idea. I do not worry about the fish. They will go around.

We should line the whole river with these, it would power several stores! Really, anything to stop pollution.

small correction: "a fish friendly 35 rpm" is claimed, not 35mph. . .

It might seem like this energy is practically coming out of no where. But it's not. The energy that we get from these turbines is coming from the motion of the ocean. I sincerely hope we don't become dependant on this type of energy along with "wave generators" for our new energy need because it has the possibility to alter the natural motions of the ocean which are vital to the stable climate of the planet. No matter where we get our energy it has consequences. This may not have pollution, but on large scales, this type of energy could be just as dangerous I think.

These things are moved by tidal pressure: The cannot move faster than the water around them, and thus in order to spin fast enough to injure marine life the current would have to be extreme.

You could surround these things with manatees, none would be harmed. IF the current was strong enough to turn them with anything approaching a speed hazardous to a swimmer then the swimmer would have moved to calmer waters long before.

The biggest hassle involving these things would be the constant maintence required to keep them free of barnicals.

I agree with wos. This energy isn't coming from nowhere. Setting up these turbines is creating resistance during ocean movements, which will disturb the resonant tide wave and create a kind of gravitational resistance (just like the electrical kind). With only a small number of these turbines the effect is probably insignificant. What this is really doing is converting the stored potential kenetic energy of the moon. If we pull enough of it, the moon will slow down, it's orbit will shrink and it'll eventually crash into the earth. It might be quite a while before that happens though, someone should crunch the numbers before we start with this endevour.

What you guys say about creating resistance to the flow of water is true, but lets keep things in perspective.

First of all, you have to realize just how big the ocean is and how insignificant even thousands and thousands of turbines would be in comparison.

You also have to remember that turbines creating resistance to water currents wouldn't be anything special; the uneven terrain on all ocean floors already does that, just like trees and mountains create a lot more wind resistance than all the wind turbines we could build in the next 100 years.

dan, thats just plain wrong. this will not affect the moons orbit. the tides move because of gravity, but changing the tides will not change gravity, nor will it affect the moons potential or kinetic energies. gravity is determinted by distance, mass, and some gravitational constant, which is really small. by affecting water flows, we would only be able to change the distance between the water and the moon, and that change would be insignificant because it would be a couple of meters. this could affect tidal patterns, which could do bad things, but it will not cause the moon to fall down. ever.

I am going to hope that dan, if not wos, really meant thier posts in the spirit of The Onion

Otherwise I am sad.

A couple comments:
- There is a power plant in France that works on this principle. It's been operating for decades and it works great.
- This energy is *NOT* renewable. It's basically gravitational potential energy. Thoses of you familiar with physics know about the principle of action and reaction, which in this case imply that such energy tapping would in return have an impact on the relative motions of the Earth and Moon. Of course this effect is very very small and probably safe to ignore but we do have a precedent: the Moon itself now always shows the same face to us because the dissipation of the tide energy into deformations of the crust quickly forced it into the minimal energy position which is the one where the tidal bulge on the rock always faces the direction of the tidal force.

All energy goes somewhere. If it crashes on the beaches it pusing the panet that way; if its going into a grocery store and heating up your hot pockets it isnt movin anything.
Conservation of energy, nothing lost and nothing is free.

Hey Kids --

The tides (both in the water and in the earth's crust) are actually transferring energy to the moon from the earth. Recall that the earth revolves once a day, while it takes the moon 29.5 days to go around. Frictional forces between the tidal bulges and the crust accelerate the bulges and slow the earth -- resulting in a longer day and a moon accelerated by the bulges (which are ahead of it in a rotational sense).

So:
1. If there were to be any difference, more drag by these wonderful, clean, safe, out-of-sight turbines would cause a longer day and shorter moon-month.
2. How much difference does a generator of this kind make to the length of the day? Any AP Physics or college Physics student should be able to solve this problem. Not much, but how much?

How often do the blades need to be cleared of marine growth?

How fast will the efficiency deteriorate with marine growth?

Tangles?

I love renewable, but I'm dubious about the chance for long term success here. It looks expensive to maintain in the real world. Underwater maintenance is not cheap.

The costs for the concrete base foundations on the seafloor would be huge (environmentally, as well as economically).

For extracting energy from the ocean, the most impressive technology, in my opinion, is the Wave Dragon. http://www.wavedragon.net/ The only impact to the seafloor is where the anchor lands. (other than the undersea electric substatation -- which this would need as would the turbine from this article.)

Lets zoom in a bit before we become cosmologically challenged. The local effects are worth more attention. By slowing water down, and making flow less laminar, more turbulent, there will be a small scour pocket downflow of each turbine, just like from a rock in a stream. Further downflow still, there will be a zone of increased deposition: a sand bar in other words. Fish typically love the scour zones to hang out in and feed from. There will have to be navigation markers to prevent boating accidents and keep fishermen from snagging the turbines.

My hunch would be that a large field of these small turbines would have a macro effect of increasing flow velocites around the edges, causing some added stream and bank scouring. But surely none of this would exceed the effects of dredging and of the sediment deposition being increased by development and by elevation of the ocean levels due to glacial melting.

Great idea; not much different than one I worked on and proposed 25 years ago.
What you have will work; much better suited for lower depths where marine life casualties are much reduced and barnical infestation would not occur, or to be less of a problem because of the fact marine life lives at different strata in the ocean not necesserly at all levels. Even at a five mile per hour water flow, the speed of travel at the tips of the impeller blades would have an effect of chopping up the marine life to come in contact with the blades; the longer the blade the faster the tips travel. There are places in the oceans where your approach would work great, generate desired electrical power at lower costs and to be cost efficient. For higher depths and entrances to waterways, it would be better to stand the pod on end and use a different impeller design simular to a revolving door approach, and it can be done. It would take away from the idea of making minch meat out of the marine life. While the rotation (RPM'S) of the impeller may be slow, it's the intensity, the amount of water pressure/power applied of the water to pass by the impeller that will prove important; can be achieved by the positioning of the generator pod where the water is "funneled" either by the natural underwater topography of the location or by means of artifical inducement; the idea that with a long enough lever or pry bar, you can move the world. Keep me posted; I might even be interested in taking some stock. with best regards,
Jim Young

Your physics comments are incorrect.

The moon is currently losing kinetic energy. Some of this energy is tranferred to the oceans; not all of it.

Still, unless we change the amount of mass on Earth or the moon, the moon will orbit us for another several billion years.

The majority of energy this product will harness will come from local phenomenon, but in aggregate, they could cause environmental change by shifting currents.

Please, search before you type (although avoid the creationist arguments; the first hit I got on Google about moon/Earth energy transfer was for 'scientists against evolution').

The moon is receeding naturally at about 3.8 cm per year. This is due to tidal friction.

As the Moon creates two bulges in the earth's oceans the earth rotates independently of them. When the earth's continents rotate into these high tides there is a braking effect to the earth's rotation and the moon is moved into a higher orbit.

The end result is a nominal decrease in earth's rotational speed and a nominal increase in the moon's potential energy.

The tides happen, we can't do anything about it. Being worried that we're exhausting "lunar power" is like arguing the sun should stop shining because so much of its output is wasted, that is-not used on earth.

If the tide doesn't slow down hitting a propeller, it'll slow down when it hits new york.

This is a very good idea, I hope many thousand of these generators will be forthcoming

THe reading I have done offers an interesting side effect if enuf are placed in the Gulf Stream: the slowing of Global Warming by slowing the conveyance of warm water to the north polar region... Not sure if it wouldn't maybe go too far and freeze out the UK though.... ;)

kk