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Debunk me, please! (Hydo-electric power)

  1. Oct 27, 2005 #1
    I've heard a few people say that if we could translate the flow of a river into angular momentum (ie create a spin/vortex using copper riffling fins) gradually over a long distance of river then we can make equivalent hydro power to a large dam: but without the engineering and environmental cost of the dam.

    The idea that water has the same potential energy regardless of a dam/no dam situation I can grasp. Even the idea that angular momentum can replace pressure as the force that drives a turbine with great power.

    But (1) could a vortex of water really spin up to such speeds? and (2) why does the fins/riffling/tubing need to be made from copper (or as some say, aluminium)? and (3) if it really works, why hasn't someone developed such a hydro-electric plant?

    In other words, please provide me with some de-bunking! :rolleyes: Thanks.
     
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  3. Oct 27, 2005 #2

    russ_watters

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    I'm really not sure what is meant by that. Angular momentum of the river? What I would envision is turbines sunk to the bottom of a fast-moving river.

    Do you have a reference for this?
     
  4. Oct 27, 2005 #3
    Well, I don't have a specific reference other than some absurd "We can make water flow uphill!!!!" claims surrounding a guy called Victor Schauberger (google for links)". So I feel sort of awkward posting that name as a reference (free energy freaks).

    But one day over lunch I talked with a Mech Eng graduate about water, fluid mechanics, vortex spin, angular momentum, etc. Most of it went over my head so I'm on shaky ground.

    But the idea that the same potential enegry is released from a river regarless of what guides, channels, dams and turbines you put in its way was compelling. I just figure that if our old friend Victor was onto something, we'd have harnessed it by now?

    Anyway, I think the idea was copper (again, why copper?) guides that introduce a vortex (not upright like a cyclone, but lying in-line with the flow). The vortex gets faster and faster and (appartently) after a few miles you use a turbine shaped like a shell to capture that enegry -- with the goal being the least turbulent water out the other end (turbulence as proof of some sort of energy going to waste). I think this is a case where the theory is solid until you get your feet wet! :smile:

    Thanks again!
     
    Last edited: Oct 27, 2005
  5. Oct 27, 2005 #4
    What is being proposed is that a vortex somehow has more energy than the system which created it.
    This is not possible.
    Even though a vortex event has speeds and such much greater than its locally immediate environment, the price to pay is with respect to the total environment which created it. All is conserved.
     
  6. Oct 27, 2005 #5
    Oh, I don't think it was seriously about free energy (although just search Victor Shauberger for the free energy freaks!), just converting linear kinetic energy -- a flowing river -- into angular momentum (spinning water) to avoid building a dam to produce hydro power.

    I think a fluid dynamics experts would've cracked this if it were possible.

    The weak point for me is that you still have to FORCE the water over/into the turbine, so pressure is still required: dam it up!
     
  7. Oct 28, 2005 #6
    Your turbines will turn slower because the water is moving slower. You won't get as much usable energy out unless you have a large number of turbines. But a large number of turbines produce greater friction than a small number. The energy content of the water is the same, but the usable amount that you can extract this way is much smaller. Before hydroelectric power stations and dams, there were water wheels doing pretty much as you describe.
     
    Last edited: Oct 28, 2005
  8. Oct 28, 2005 #7

    russ_watters

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    I think I get it now. It sounds like in the end, you'd just have a really long pipe with one end lower than the other. All that twisting wouldn't really help any. And yeah, I think it would work, but it would be incredibly inefficient, since all piping involves friction loss.
     
  9. Oct 28, 2005 #8

    Danger

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    I'm having a bit of trouble figuring out where the exit to this thing would be. If it's spiralling in to a turbine in the centre, where's it go after that?:confused:
     
  10. Oct 28, 2005 #9

    russ_watters

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    I'm envisioning stationary spiral tubes, that just end, and the water coming out is moving and spiraling. Stick a turbine at the end, and...

    But I'm not really sure.
     
  11. Oct 28, 2005 #10

    Integral

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    New York City is generating power from the river without a dam. This does not require magic, just an underwater turbine.
     
  12. Oct 28, 2005 #11

    Danger

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    Yeah, Int... that makes good sense. What I got from RunDMC's description was a conche-shell shape, like a spiral bullet trap, with a turbine in the middle. I thought that maybe the tubing narrowed funnel-wise in order to accelerate a large volume of water through a small generator. It would have to exit either up or down, because there's no sideways open, and the resistance as it hits the ambient water would mess things up. Maybe a picture would help.
     
  13. Oct 28, 2005 #12

    Cliff_J

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    Integal's link is a pretty decent idea as presented on a Discovery Science channel program.

    The main advocate said that according to their preliminary data they expect to easily be profitable selling their energy at 10 cents/KWH and that its attractive because of the currently high electricity costs in that market.

    While not as efficient, it is a great idea since the enviromental impact is near zero. The blades turn slowly enough to prevent any fish damage (according to speaker the fish won't even know the blade is there) so aside from maybe some scour or other tiny side effect its a great idea if it can be done cheap enough. The rivers are going to flow regardless as an untapped energy source and if the rise caused by the extra restriction is negliable then why not do it?
     
  14. Oct 28, 2005 #13

    Integral

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    The turbines will do 2 things, slightly raise the river behind them and slow the river down. This should not be a problem but it does but some interesting limits on how many you can put in a river.

    I wonder how well they would do with large debris, think 1m diameter, 30m long log?

    I live on the banks of the Willamette River, it is a very powerful river even 100km from the confluence with the Columbia. Unfortunately it is not extremely deep, somehow I do not think a horizontal version would work as well. :biggrin:

    One effect that needs to be carefully considered is the amount of turbulence created in the river, if you were to produce strong rotational currents you might cause erosion damage to the river bottom and banks, this would not be desirable.
     
    Last edited: Oct 28, 2005
  15. Oct 29, 2005 #14
    Just out of curiosity; would this be more salmon friendly?

    KM
     
  16. Oct 29, 2005 #15

    Cliff_J

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    I think compared to the massive impact of daming up the river, a few well placed turbines that may lead to a small amount of erosion from turbulence scour is pretty minimal. Is there really much of an ecosystem completely dependant on the river bottom that would be displaced?

    Don't logs float? :smile:

    Kinda funny to think of how capturing energy from the natural flow of a river with a waterwheel was utilized many decades ago, and now its finally getting close to being economically viable again without needing to create a giant reservior.

    While not as efficient as typical hydrodynamic power, it does offer many advantages over wind power generation, and that was one of the advantages touted in the video clip.

    I can't imagine it to be too difficult to create an enviromental arguement to make its impact (if any) to be far less than burning coal, especially with the current hysteria over global warming. I know I personally feel better knowing my power comes from a dam, and still try to do my part to conserve so any excess can be fed back into the grid and reduce natural gas/coal consumption.
     
  17. Oct 29, 2005 #16

    russ_watters

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    I didn't know people were actually trying to do it, but it sounds like a good idea to me. --- Yes, K-M, it would be salmon friendly.

    The type of turbine discussed in the article - like a windmill - is low speed and low pressure. It wouldn't change much about the flow of the river.
     
    Last edited: Oct 29, 2005
  18. Oct 30, 2005 #17

    Integral

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    Sure logs float, I was just trying to put turbines in the Willamette River, but I am afraid that it is to shallow. I don't think it is 3m deep on the average in this area. At that depth a 1m diameter log floating past, needs to be planed for!

    How much water do the turbines need?
     
  19. Nov 1, 2005 #18
    Interesting replies & links -- Thanks!. Seems the various clearances and environmental impact statements are more important than getting the actual method of generation up to spec.

    I hadn't thought about the poor fishies! Slow blades seem to be the best answer.
     
  20. Nov 2, 2005 #19

    Danger

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    Naw, just open a sushi restaurant downstream.
     
  21. Nov 5, 2005 #20

    GENIERE

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