Why did we not think about this

Discussion in 'Boat Design' started by BertKu, Aug 1, 2013.

  1. BertKu
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    BertKu Senior Member

  2. Leo Lazauskas
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    Leo Lazauskas Senior Member

    I think it's junk.
    Similar "turbines" have been around for quite a while and have not succeeded
    when mounted on a house roof. They are now marketting it to sailors.
    It is essentially a drag device and inherently very inefficient.
     
  3. BertKu
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    BertKu Senior Member

    O.K. , but could somebody not make it for sailors more efficient. I thought the idea is useful. In my opinion any device on a sailing or normal boat, what sticks out, is a drag. Could nobody, really not make something better, what suits the sailors? Bert
     
  4. CDK
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    CDK retired engineer

    This is indeed very useful for marine applications. Seagulls have a habit of sitting on the upper edge and shitting all over the panel. Even if the power generated is minimal, at least it keeps the seagulls away.
     
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  5. BertKu
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    BertKu Senior Member

    O.K. Leo, I was thinking about it, you may be right all the way. At first glance, it looks good, but then the wind changes and indeed, as most solar panels are fixed, very useful energy cannot be extracted. Well another idea down the drain.
    Bert
     
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  6. BertKu
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    BertKu Senior Member

    I had a flipping good laugh!!
    Bert
     
  7. kerosene
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    kerosene Senior Member

    even large scale spiral (vertical axis wind turbines) never pay themselves back. The idea that you could light up a street lamp is ridiculous. I went to design school and it always irritated me to no end when people got away with stuff that is EASY to come up with if NO regard for feasibility is given. I mean if you are visioning year 2050 outdoor jacket and you say its all solar panel - fine. But if you are pretending to solve an immediate problem with today's tech do a little homework.
     
  8. El_Guero

    El_Guero Previous Member

    OK, I went to engineering school.

    And the year 2050 will NOT overcome the basic laws of Physics, unless God suspends them.

    Forget the size, the vanes cannot get the 'lift' they need .... because when in the other direction, the lift of the 180 degree vane cancels out the other lift.

    1+1 = 0 net gain.

    There are ways to overcome that, but not cheap.

    Wayne
     
  9. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Savonius turbines do not rely on lift. They are essentially drag devices. (Think
    of an anemometer which does not rely on lift)
    Darrieus vertical axis turbines use wings with airfoil cross-sections and can be
    categorised as "lift" devices.
     
  10. Leo Lazauskas
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    Leo Lazauskas Senior Member

    No it won't. It will just force seagulls to dance to stay on the turbine.
    If you set yourself up as a predator, your prey will evolve to avoid you.
     
  11. BertKu
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    BertKu Senior Member

    Come on Leo, CDK is pulling our legs, we all have to have sometimes a good sense of humor, and a good laugh, otherwise we will have a boring life. I remember, when our international company sold the first solar panel system to the Telecom company some approx. 40 years ago and it was placed, deliberate between the mountains to get some experience what the worst scenario would give them. Needles to say, that what CDK wrote, happened exactly and very little energy was extracted, until a line was spun over the top of the panels. The seagulls were unable to balance on a thin wire.

    Bert
     
  12. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Actually I made a mistake about the type of turbine.
    It does actually seem more like a Darrieus type, but its solidity is very high and the
    Reynolds numbers are so low that lift will not play much of a role.
    I still would not recommend it.
     
  13. Leo Lazauskas
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    Leo Lazauskas Senior Member

    Huh?
    Of course he was joking.
    What made you think I was being serious when I wrote about dancing
    seagulls?
     
  14. El_Guero

    El_Guero Previous Member

    :)

    Thank you.
     

  15. Leo Lazauskas
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    Leo Lazauskas Senior Member

    That is not correct.
    In fact, with a Darrieus turbine the blades get two "bites" at the wind; once
    on the upwind pass where they extract the most power, and again on the
    downwind side where there is still some energy left.
    The Betz limit for these turbines is a little higher than for propeller type wind turbines.

    Of course there is more to consider than just that measure of efficiency.
    Darrieus turbines use a lot more material;
    they are not self-starting (without special devices, special geometries or in
    special circumstances);
    they can have terrible vibration problems;
    the radial arms contribute large parasitic drag;
    the bending moments on the wings can be enormous; etc etc.

    Darrieus tubines have been around for a long time, and several companies
    have tried to make them viable. All have failed.

    I have studied some special variations for many years and I love their
    aerodynamic complexity, but I'm still not convinced that they are serious
    challengers to HAWT for generating electricity. They might be better in
    water in some circumstances.

    See:
    Lazauskas and B.K. Kirke,
    Modeling passive variable pitch cross flow hydrokinetic turbines to maximize
    performance and smooth operation,
    Renewable Energy, Vol. 45, Sept. 2012, pp. 41-50.

    B.K. Kirke and L. Lazauskas,
    Limitations of fixed pitch Darrieus hydrokinetic turbines and the challenge of
    variable pitch,
    Renewable Energy, Vol. 36, No. 3, Mar. 2011.

    B.K. Kirke and L. Lazauskas
    Experimental Verification of a Mathematical Model for Predicting the
    Performance of a Self-acting Variable Pitch Vertical Axis Wind Turbine,
    Wind Engineering, Vol. 17, No. 2, 1993.

    L. Lazauskas,
    Three Pitch Control Systems for Vertical Axis Wind Turbines Compared.
    Wind Engineering, Vol. 16, No. 5, 1992.

    Kirke, B.K. and Lazauskas, L.,
    Enhancing the Performance of Vertical Axis Wind Turbine Using a Simple Variable Pitch System,
    Wind Engineering, Vol. 15, No. 4, 1991, pp. 187-195.

    Kirke, B.K. and Lazauskas, L.,
    A Novel Variable Pitch Vertical Axis Wind Turbine,
    Proc. Solar '87 Conf. Australian-New Zealand Solar Energy Society,
    Canberra, 26-28 Nov. 1987.
     
    Last edited: Aug 1, 2013
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