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Venturi wind turbines

Discussion in 'Electronic Design' started by [email protected], Feb 25, 2013.

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  1. Guest

  2. TTman

    TTman Guest

  3. Guest


    It's freaking genius. I can see the EPA maybe requiring a 2-inch-square mesh to prevent hummingbirds from being caught in the draft, but... wow. Wow. And wow. US$0.02/kw-hr, huh.
     
  4. Guest


    It does, but total air flow Q = velocity * cross-sectional area, similar I guess to how total power = voltage * current.

    And, yeah, the cross sectional area at the generator is quite a bit smaller than at the intake.

    Sure looks interesting though.
     
  5. Guest

    I can see it being less noisy and not so many complaints from
    neighbors that
    don't like their house and garden turned in to a blinking disco when
    the sun is low


    -Lasse
     
  6. Guest


    Ah, extractable power is more like 1/2 * (density of air) * (cross-sectional area) * (velocity^3).

    http://uni-leipzig.de/~energy/ef/15.htm

    I vaguely remember power is proportional to the cube of the velocity, and there are some really nasty equations we had to use/derive back in fluid mechanics classes, but this is a good distillation of the relevant equations (and quite elegant, I must add). No macroscopic mechanical energy balances required, haha.

    Michael
     
  7. Tim Williams

    Tim Williams Guest

    Neato, and as obvious as hindsight makes it look, it's about time!

    Seems to me it would suck rather than blow. If you do the old
    blow-across-the-open-end-of-a-pipe trick, you get lift from the Bernoulli
    effect. Specifically, the difference in wind velocity between ground
    level (especially if you hide the intake within a dense forest or
    something like that) and altitude causes a pressure difference

    I suppose the catcher part is baffled and, perhaps, equipped with throttle
    plates to shut off the non-windward sides, so only ram air travels
    through. A passive structure would be possible with lightly sprung check
    valves (air pressure might also provide the action), or perhaps simply
    taking advantage of fluid flow (Coanda effect). If this is the case, it
    leaves much of the head underutilized. I expect further improvements are
    possible, and in development.

    Tim
     
  8. Guest


    The website looks interesting, but it looks like they won't have product shipped until later this year...

    http://sheerwind.com/

    Minnesota... that's pretty close to you, Tim, right?

    Michael
     
  9. Artemus

    Artemus Guest

    I'm not an aero engineer but this looks like pie in the sky claims to me.
    1. It appears that the intake area on this is significantly less than that of
    a propeller style windmill. Therefore it can't extract the same amount
    of wind energy. No?
    2. There will be not insignificant loss of energy due to the aero drag on
    the walls of the venturi. Compressing the air will also add to the losses.

    There do appear to be some benefits, but efficiency isn't one of them.
    Art
     
  10. Tim Williams

    Tim Williams Guest

    In a relative sense, yes. Digikey (Thief River Falls) ships practically
    next day. But it's also a six hour drive.

    For being mostly flat and midwestern, WI gets enough wind that they've
    installed some turbines in various areas. As I recall there's a few
    around the capitol.

    Tim
     
  11. Guest

    The energy of the wind is directly proportional to the air density and
    cross section area and relative to the third power of wind speed.

    The cross section area can be the area covered by a conventional
    horizontal axis wind turbine or the area covered by some vertical
    construction or even the classical Savonius design.

    If the structure shown in the picture is 30 m high and maybe 10 m
    wide, the cross section area is only 900 m², why would anyone expect
    it to generate 1.8 MW ? In a lossless system, that would require at
    least 18 m/s wind, which is rare at 30 m above ground in most parts of
    the world. The situation might be realistic a few hundred meters above
    ground.

    The basic flaw in arguing that a small structure would concentrate the
    air into the turbine. The air is not "so stupid" that it would go
    through the turbine, while it can more easily go around the
    structure:).

    The situation is different, when the structure is kilometers wide
    and/or hundreds of meters tall, e.g. a valley between two mountains or
    when the air flow above a high hill, in which case the speed of air is
    increased (compare this to the faster air flow above the wing of an
    airplane).
     
  12. amdx

    amdx Guest

    Hey Jeff, it does say they tested a 0.3 watt unit. :)

    "The first small scale field unit, rated 300 mW was designed and
    constructed last year and validated the CFD models predictions. A larger
    scale field demo unit rated 1.5 kW to 5 kW also went live last year. "

    I wonder if the pictures shown are the 1.5 kW unit mentioned above.

    Mikek
     
  13. tm

    tm Guest

    Well there you go. Obozo will fund it if they kick some of the money back.
     
  14. mike

    mike Guest

    I'd ask 'em the same thing I'd ask Rossi,
    "why is it so difficult to prove it?"

    Build a uni-directional one out of plywood.
    Bolt it to a flatbed truck, or on top of a bus.
    Drive it down the road.
    Measure volume/pressure with speed as a parameter.
    If you like the numbers, stick a generator in it.
    Then go solve all those pesky issues with omnidirectional behavior.

    If you can't make it work on a truck driving down the road at
    2 or 20 or 60 MPH,
    there's no need to pursue it further.

    That'd be far more useful than a 300mW prototype.
    And you could work on it where there's no wind.
    And it'd cost far less and take less time than setting up their website.
    But it'd garner fewer greedy/uninformed investors.
     
  15. Guest


    I do wonder about maintenance though. There's not much friction in clean, smooth PVC pipe, but in real life bugs are going to get sucked in, and those are going to leave sticky residues in the plumbing that will attract dirt, and next thing you know, the friction factor is way up...

    Michael
     
  16. Guest

    Put the intake on a lazy susan, with a weather vane to point it into
    the wind.

    If you route or switch the exhaust similarly downwind (possibly even
    through a reverse Venturi, for comic investor-suckering effect), you
    can relieve some of the backpressure too. I dub it the double-synergy
    Pushme-pullyou version.

    Please send my checks to Emperor Oblahblah and her Moochelleness.
    (Saves me the trouble.)
    The double-stimulus version could propel the truck faster and faster
    without limit. It uses the energy to print foodstamps on switchgrass
    paper, with enviro-sustainable 200% economic return. Burn the
    foodstamps in its bio-diesel hybrid hyper ion fuel-cell drive, and
    you're on your way to wind-powered LEO.
     
  17. tm

    tm Guest

    Put the intake on a lazy susan, with a weather vane to point it into
    the wind.

    If you route or switch the exhaust similarly downwind (possibly even
    through a reverse Venturi, for comic investor-suckering effect), you
    can relieve some of the backpressure too. I dub it the double-synergy
    Pushme-pullyou version.

    Please send my checks to Emperor Oblahblah and her Moochelleness.
    (Saves me the trouble.)
    The double-stimulus version could propel the truck faster and faster
    without limit. It uses the energy to print foodstamps on switchgrass
    paper, with enviro-sustainable 200% economic return. Burn the
    foodstamps in its bio-diesel hybrid hyper ion fuel-cell drive, and
    you're on your way to wind-powered LEO.
    --
    Cheers,
    James Arthur

    +++++++++++++++++++++++++++++++++++

    Oh, oh, oh... It's got the word "stimulus" in it. It simply can't lose. Just
    think of the military uses for a LEO wind turbine. Hello, DARPA... hello?
     
  18. rickman

    rickman Guest

    The amount of energy a propeller style windmill can extract is limited
    by the design constraints of a propeller. Consider that there is only
    one place on the blade where it is moving through the air at the rate
    that the wind is moving. Any location closer to the hub will be turning
    more slowly pushing the blade faster and any place on the blade further
    out will actually be moving faster than the wind, *pushing* the wind
    faster and so slowing the blade. There is a term for this, but I don't
    remember it. The blade tips are always resisting the motion of the blade.

    I think it is theoretically possible to do better. In practice, I
    believe the egg beater type blades are more efficient, but I'm not certain.

    None of these propeller type designs are 100% efficient. If they were,
    they would *stop* the wind, no? Then all that air would just pile up
    and have to be shoveled away.

    Compared to what?
     
  19. rickman

    rickman Guest

    Really? What do they do about buildings? Do they fold up in storms too?
     
  20. rickman

    rickman Guest

    I think it is funny that you guys think you are aeronautical engineers
    too. Do either of you actually know anything about this?

    Air doesn't have to be "stupid" to go through a pipe. It happens every
    day in the city where wind is redirected and concentrated around
    buildings. You see it often in mountain passes.

    It's easy to criticize. It's not so easy to understand.
     
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