Wvae action generator

Discussion in 'Boat Design' started by buzzman, Mar 23, 2021.

  1. buzzman
    Joined: May 2011
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    buzzman Senior Member

    Hey, all!
    Just been reading a BBC article on electric cars being powered by 'wave action generators' in the Shetlands
    Shetland electric cars can now be fuelled purely by the power of the sea https://www.bbc.com/news/uk-scotland-north-east-orkney-shetland-56482777

    So I got to wondering: tide and waves go up and down. Boats go up and down.

    Would it be theoretically possibly to design some sort of 'wave action generator' that could be attached to the transom that would, say, drive a flap up and down that could in turn drive a generator?

    Or how about a tube built into the hull forward of the mast that would fill with water as the boat goes up and down the waves, funneling that water into a smaller orifice that would be directed onto a pelton type turbine?

    Is this even worth thinking about..??
    I know it would make much, and obviously only when the boat was moving, but it could be useful, maybe...???

    What do the wise heads think?

    Naysayers can just pass....
  2. Heimfried
    Joined: Apr 2015
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    Heimfried Senior Member

    This way the power is generated utilizing the difference in altitude of water plane level against shore (tide or wave). A boat provides typically a very small amount of this difference and only by waves not by tide.
  3. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    It depends on what you want from this electricity generating device, if it is to supply the means of propulsion of the boat in real time, I don't like your chances.
  4. tlouth7
    Joined: Jun 2013
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    tlouth7 Senior Member

    The problem is just the amount of power you can extract. One viable option is to have a tube that is open to the sea at the bottom, and the air at the top. Waves cause the surface of water in the tube to move up and down, driving the air in the tube up and down. A turbine in the top of the tube can extract some energy from this. Specifically the turbine resists movement of the air, increasing its pressure on the up stroke and decreasing pressure on the down stroke. This difference in pressure compared to outside the tube will cause the water surface inside the tube to be at a slightly different height to the outside.

    Lets say you have a tube of diameter 10cm. Lets say a wave passes every 2 seconds (so each stroke takes 1 second), and causes the height of water in the tube to change by 50cm (peak to trough). Imagine the turbine causes enough resistance to displace the water by 1cm from equilibrium (lets call this disp).

    Power = Energy / time = mass of displaced water * wave height * gravity / time = disp * pipe area * water density * wave height * gravity / time

    Power = 1cm * pi * (5cm)^2 * 1.03g/cm^3 * 50cm * 9.8 m/s^2 / 1s

    Power = 400mW

    So you can see that this order of magnitude of power that we can generate is pretty darn small. Even if you came up with something 100x more powerful you would still be competing with a pretty small and cheap solar panel.
  5. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    The article is based on misinformation. It is not powered by waves but by tidal turbines. St. Malo in France has been operating a tidal system for over 50 years. However, the environmental impact is not even mentioned. Seems like the majority of the "green solutions" are worse for the environment that burning fossil fuels, that are simply stored solar energy.
  6. BlueBell
    Joined: May 2017
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    BlueBell "Whatever..."


  7. Skeeter1994
    Joined: Mar 2021
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    Location: Delaware, Ohio

    Skeeter1994 New Member

    This is technically correct, although Solar panels used on cruisers and other vessels are seemingly one place where the ROI makes sense.
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