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Underwater Windmill

Extract power from ocean currents
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Synopsis:
See title and subtitle :)

Background and Details:
I just did a Search here for "underwater" and "windmill" and it came up blank, so if this idea really has been posted here using some other verbiage, I apologize.

Anyway, this Idea should be somewhat obvious in hindsight. We build ordinary windmills to extract useful power from wind energy. We put turbines in rivers (usually accompanied by dams) to extract useful power from downhill water flow. The second is more "energy intensive" than the first, which is why we all know that dams are great sources of electrical power, while electric-generator windmills spent decades in the economic doldrums (return on investment --ROI-- is relatively tiny, and only recently proved viable on a large scale).

Anyway, putting the equivalent of a windmill in a steady ocean current, say the Gulf Stream, should have an automatically-viable ROI that is intermediate between windmills and ordinary hydropower. This is because water is something like a thousand times denser than air, so a volume of flowing water contains a thousand times the energy of an equal volume of equally-flowing air.

Do note that the ocean has different currents at different depths. I once read somewhere that near the seafloor underneath the Gulf Stream is another current going the opposite direction. If true, then we can buld towers on the seafloor, just like ordinary windmills, to extract power. Being so deep will protect them from ships, and most sea life is found at other depths, so they won't be bothered. Also, another thing that protects sea life is the fact that underwater windmills will have a SLOW rotation rate, due to that same greater density of water over air. This means we can also put windmills in the rich-life upper ocean currents; animals will have time to dodge the blades. (Some life forms, like barnacles, need to be discouraged; probably everything needs to be coated with Teflon or something even more slippery.)

Consider buoyant windmill modules can be anchored by cables to the bottom. They float up to perhaps fifty meters beneath the surface, in the midst of the ocean current. There they stay and generate power (which flows down those same anchor cables, and then toward shore).

Finally, it may be necessary to build all underwater windmill modules in counterrotating pairs. Again, this is because the water is denser than air; and for every unit of force that tries to rotate the blade, there will be reactive force against the generator assembly, Counterrotating blades will let such forces be canceled.

Vernon, Sep 14 2003

Like this? http://www.bbc.co.u...tidal_turbine.shtml
[RoboBust, Oct 04 2004, last modified Oct 21 2004]

(?) Tidal stream oscillating hydroplane http://www.engb.com/Pages/demo.htm
[FarmerJohn, Oct 04 2004, last modified Oct 21 2004]

(?) They talk about it here too. http://europa.eu.in.../nn_rt_oes1_en.html
Can't be bothered looking any more. [RoboBust, Oct 04 2004, last modified Oct 21 2004]

(?) water turbine for use in currents http://www.eeca.gov...Mar02/Renewable.htm
"Gorlov" type double-helix turbine [Laughs Last, Oct 04 2004, last modified Oct 21 2004]

Blue Energy http://www.bluenerg...ishydroturbine.html
“- the Davis Hydro Turbine 'Ocean Class' system, which will link 7-14 MW units across ocean and estuarine passages” [Shz, Oct 04 2004, last modified Oct 21 2004]

(??) Darrieus patent http://windturbine-analysis.com/
[Fussass, Oct 04 2004, last modified Oct 21 2004]

Baking in progress! http://www.science....le18/phase2/062.htm
Here's an outfit that has obtained US Govt grant money for developing the idea. [Vernon, Oct 04 2004, last modified Oct 21 2004]

Baked in Hammerfest, Norway http://www.newscien...s.jsp?id=ns99994188
Sep 24 2003: "The first commercial subsea power station to harness the tidal currents of the sea was hooked up to an electricity grid on Saturday....The power station, which resembles an underwater windmill, began generating electricity for the town of Hammerfest." [krelnik, Oct 04 2004, last modified Oct 21 2004]

Open Centre Turbine by Florida Hydro http://www.floridah....com/Technology.htm
I believe this is in the process of being baked, with US Navy money. [goodasdead, Oct 04 2004]

[link]






       fogfreak, you are describing something else, than this idea. Yes, I know that there are many schemes for extracting power from the ocean, such as thermal (OTEC), tidal, and wave-action, and all of them are actually in use (though OTEC is only at pilot-plant level). This idea is NONE of those! And, I've never heard of any such thing as windmill, specifically intended for ocean currents, actually having been built anywhere. So, if you insist on this being baked, provide a link! Thanks!
Vernon, Sep 14 2003
  

       Just thought I'd mention that those currents are probably important to certain ecosystems and by impeding the flow of the water you are disrupting them. But obviously this has never stopped us before.
DeathNinja, Sep 14 2003
  

       I don't know if anybody has built a big turbine that takes energy from ocean currents. I do know that any search for 'underwater windmill' is likely to turn up a blank no matter since, once you put a turbine under water, you no longer call it a windmill.
st3f, Sep 14 2003
  

       RoboBust, your first link is partly right and partly wrong. It is a windmill blade designed for water, true, but it is specifically stated as being intended to catch water flowing toward and away from the shore, as part of the tides. Tides are not ocean currents! Your second link is better, but it appears to simply be an independently-invented idea like this one, and does not describe an actual implementation. (Hey! Where'd it go?!) Ditto for your third link (except it hasn't disappeared). Thanks, though!   

       FarmerJohn, that idea seems like it could work in an ocean current, but again it seems that they are concentrating only on using it in tidal flows.   

       DeathNinja, yes, I'm aware that extracting too much energy from ocean currents will cause problems. The Gulf Stream keeps Northern Europe from having weather like Siberia, for example. But, there are quite a few ocean currents, and we should be able to safely extract some reasonable amount from each of them....   

       st3f, I basically agree, except that in any basic explanation of this idea, I'd expect the writer to compare it to windmills. So, while the exact phrase "underwater windmill" may be a fruitless seach, the individual words should come up with something. They didn't, here at the HalfBakery, and so I posted this.
Vernon, Sep 14 2003
  

       Oh, sorry about that Vernon. I deleted it 'cause I thought it was a bit plain.   

       To my understanding though, it doesn't matter if something has been actually implemented or not here at the halfbakery. If I was to post an idea about how we should construct a huge solar sail and attach it to a spacecraft, I would be boned to hell, regardless of whether or not I claimed to have come up with it independently.
RoboBust, Sep 14 2003
  

       [Vernon]:   

       You’ve hit upon a great scheme to extract a constant flow of power from a reliable source. Not only could we harness this concentrated source of solar power fairly easily, but we could use the generators to monitor oceanic currents, perhaps revealing an unbeknownst correlation with weather patterns.   

       Some obstacles to construction would be: (1) finding a site that isn’t too deep, yet has reliable currents, (2) transmission loss over the vast distances that’d probably be involved, and (3) maintenance of the turbine. These are all surmountable obstacles, and worth the effort in my opinion. Anything but dino-fuel please!   

       The only invention that I’ve come across that is remotely similar, was done by the US Navy. Although I briefly looked around, I couldn’t find any links – perhaps someone else will.   

       Their system used, what could best be described as, a flag on a pole. The flag would ripple as the ocean current flowed past, and this would generate electricity – great for stealthy passive-sonar recorders. The material of the flag was something that generated voltage in response to mechanical stress.   

       As far as I know, it is still being tested. One problem with the flag idea was that large sea creatures may see the flag as another sea creature swimming, and either try to eat it, or attack it. An elegant idea though… Very simple, and a huge array could be place anywhere there was water flowing.
TIB, Sep 14 2003
  

       I saw plans for (if they were up in the air they would be termed) Darrious (sp?) turbines suspended from a surface float, hanging in the Gulf Stream. Yeah, `cause the water is so dense, even moving more slowly than the winds, the blades rotated much, much more slowly. Maybe 20 rpm, so yeah, easy on the wildlife.   

       Also have read that in four days the world oceans absord as much energy from the sun as humans use in a year.   

       If the floating platform was large enough for a farm of turbines underneath, it might serve as an offshore airport, resort, etc. Habitable.   

       Great stuff Vernon. We are definitely missing out on this option.
lock, Sep 14 2003
  

       The turbines are in the oven, see link for "Gorlov" water turbine, or google for "Gorlov". Basically, you hang a couple of these on a line with flotation device at the top of the line, and perhaps an anchor at the bottom. Admittedly, these turbines are not yet widely used, but can be used anywhere with a reasonable current.
Laughs Last, Sep 14 2003
  

       [reensure]: If sending power to the land is too expensive, then how about sending hydrogen. All that would be required is a pipe from the generators.   

       An electrolysis device would have to reside near the network of generators, and would exhaust quite a bit of oxygen into the surrounding ocean. Dunno if this is good or bad…
TIB, Sep 14 2003
  

       Davis Hydro Turbine = Underwater Windmill <link>
Shz, Sep 14 2003
  

       The Darrieus patent of 1931 also covered water power. His cage version looks just like one of the other links.
Fussass, Sep 14 2003
  

       Well, folks, thanks for the links. Part of the reason that I posted this was that I was going through some 25-year old notes (old mad ideas), and this was one of them. So, I thought I might be able to claim a little more than mere independent originality -- I might actually have been first! However, I do know that the Darrieus patent is quite old, and I did not know that it also covered water power. I might quibble a bit and ask if it was referring to water power as in rivers with/without dams only, or if "ocean currents" were specifically mentioned as an extra source for water power. See, I consider tapping the ocean currents to be at least as important a notion as that of putting underwater windmills in them, to do the tapping.   

       What I shall do, therefore, is wait for the votes to accumulate for another week or two, and if it the result is a fishbone, then I'll delete this idea as not being sufficiently original.   

       Until then, there are still things that can be discussed. Getting the power tranmitted to land is an important issue. As it happens, one of my other mad ideas concerns a way to directly generate high-voltage power, no transformer needed. It is well known that high voltages are necessary to carry electric power long distances. Perhaps that will solve the problem. Alternately, a "field" of water-mills could all send their ordinary power to an underwater transformer facility, which then sends power ashore. Alternately AGAIN, such a field of water-mills might feed power into a superconducting cable (no transformer needed).   

       (Transformer rationale: Electric power can usually be roughly figured as Volts multiplied by Amperes. Amperes describe the total quantities of electrons that are actually flowing inside a wire. The more amps, the more electrical resistance to that current flow, and the more power lost. A transformer changes the volts/amps ratio --remember, if 100Volts x 10Amps=1000Watts of power, then 10000V x .1A also =1000W-- so that high-voltage-and-minimal-amperage can be carried for long distances with minimal resistance losses. At the end, another transformer again changes the volts/amps ratio, to what we can safely use in homes/industies. Note that transformers require Alternating Current to work (and they work at 95%+ efficiency), and this is ultimately why Thomas Edison lost his bid to electrify the world with Direct Current.)   

       I suppose I'll have to hunt down that high-voltage generator of mine, and post it. Sometime....
Vernon, Sep 15 2003
  

       The first mills worked from water. So technically it could be an underwater mill. If you modify the idea to have it grind grain underwater or something you would have a less baked idea.
sartep, Sep 15 2003
  

       Perhaps I should have mentioned in my last annotation that I think the idea, posted by TIB, about electrolyzing seawater and sending the hydrogen ashore to be an adequate alternative to direct electric transmission. Indeed, the released oxygen, especially from watermills located near the ocean bottom, would also be beneficial to sea life. However, if one directly electrolyzes seawater, then chlorine (from the salt in the water) and not oxygen will be produced. Oxygen is more chemically reactive than chlorine, so in this situation the oxygen stays chemically combined (water + salt + electricity yields hydrogen + chlorine + sodium hydroxide). Obviously, the seawater needs to be purified before being electrolized (we do NOT want to add lye to the seas! -- and we don't want that chlorine to get loose, either, because in the upper atmosphere, it causes ozone-depletion.) Well, the free energy to do that purification is right-there-available, from the watermills....
Vernon, Sep 24 2003
  

       Interesting coincidence that you posted on this idea today, Vernon, because I just this morning read about a power plant of this type going online in Norway this week. See link.
krelnik, Sep 24 2003
  

       krelnik, sorry, "tidal currents" (see Bay of Fundy for extreme example) are not the same thing as "ocean currents" (such Gulf-Stream/North-Atlantic-Drift).
Vernon, Sep 24 2003
  

       Yes, tidal currents are a bit different, but is the technology needed all that different? The Norway project that went online this week is described as an "underwater windmill" in the article. ("I come not to mfd Caesar, but to praise him")
krelnik, Sep 24 2003
  

       krelnik, there is a reasonable difference between tidal and oceanic currents: Oceanic currents are reliably continuous, while tidal currents ebb and strengthen. Which do you suppose is better suited for electric power generation?
Vernon, Sep 25 2003
  

       Perhaps you should ask that question of the people of Hammerfest, Norway.
krelnik, Sep 25 2003
  

       Well, I can bet that for them, having the generators close by is more beneficial (servicing issues regarding new technology; power-transmission issues as already described here) than having them however-far-away the nearest oceanic current is located. In due time, though, the tech will mature and the desire for steady power will lead to oceanic currents....
Vernon, Sep 25 2003
  

       Well, folks, until today this Idea has been running with votes of +5 and -5, so, since the result wasn't a fishbone, I've been retaining and watching it (see my Sep 15 annotation). Today I noticed that somebody has made it -6, so, unless someone else thinks this Idea should be retained by giving it a +, I shall be deleting it, probably tomorrow. Thanks!
Vernon, Nov 14 2003
  

       This is a great concept, and the annotations add a lot of better ways to implement it. It got me thinking, which is why I come to this site.   

       I think the main reason for the fishbones was lack of 100% originality. I'm not a purist like that. I know that the patent office is chock-full of great inventions that are just a liiiittle bit different than similar thoughts from the past. That little difference in thought can really make or break an implementation.
sophocles, Nov 14 2003
  

       [tsuka], thanks for the info. And [sophocles] is right, in that annotations like yours can be a quite adequate reason to retain ideas that are otherwise insufficiently original.
Vernon, May 12 2004
  

       geez, six months later and you are still on the ball as far as watching replies. You get a + from me just for the quick response time.
Bamboo, May 12 2004
  

       Thank you, [Bamboo]. It's not a complicated trick. At the bottom of the www.halfbakery.com screen you will see a small "Overview: EDIT" thing that you can click on. You can customize the display and either save it so that becomes your default HB page, or save it under a unique title, in which case that title will appear in the upper-left "IDEA" area of the default HB page, where you can click it any old time. I have one that hunts down recent annotations to my ideas, just so I can respond in a timely way. MUCH easier than wading through those dozens of ideas personally, looking to see if anyone added something.
Vernon, May 13 2004
  

       I was watching a show on discovery channel. The scientist on the show claimed that ocean currents are crucial in regulating global temperature...keeping another ice age from happenning. This being the case, I personally wouldn't want to mess with them ;)
nomel, Jun 09 2004
  

       [nomel], I agree, to some extent. Extracting SOME energy from ocean currents is probably fine. Trying to extract it all will just cause trouble. "Moderation in all things" applies here!
Vernon, Jun 22 2004
  

       I would think that taking ANY would cause the slowing of the currents, which would mean a shorter time to the next ice age. I personally would rather take energy from the waves...since them hitting the shore doesn't have any crucial role that I'm aware of (besides errosion and supporting some sea life).
nomel, Jul 02 2004
  

       It will be intersting to know how much energy can be harnessed from natural phenomenon such as ocean current before it causes negative impacts. I assume that complex relations of processes that drive the phenomena would cause multiplier effects on the mangnitude of negative impacts.
eilathean, Jul 04 2004
  

       This would be great... if you needed power way out in the ocean. It's my understanding that the Gulf Stream and other such major ocean currents are pretty far from shore. It's also my understanding that there is a big problem with transporting power over long distances, since power cable is basicly a big resistor. I would not be suprised if by the time your power got back to shore you would only have enough to power a radio.   

       Also, never underestimate the power of water, there's no way you could build a turbine large enough to effect the currents. Imagine the weight of a wall of water a mile high traveling at the speed of a river. To think that you could effect such a force is overestimating your ability to effect the world around you by a vast margin.
dvddecrypter, Jul 05 2004
  
      
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