New type of wind power generator

Discussion in 'Earth Science' started by Sorcerer, Feb 13, 2014.

  1. Sorcerer Put a Spell on you Registered Senior Member

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    Interesting concept. Apologies if already discussed.

    http://www.offgridworld.com/funny-looking-tower-generates-600-more-electrical-energy-than-traditional-wind-turbines/

    Quote:

    The Sheerwind wind turbine promises to produce 6 times the electrical power than traditional wind turbines.

    This funny looking wind tower acts like a funnel, directing the wind from any angle, down through a tube to a ground based turbine generator. The funneling of the wind through a narrow passage effectively creates a “jet effect” increasing the velocity of the wind, while lowering the pressure. This is called the Venturi Effect. This speeds up the wind turbine mounted inside the narrowest portion and generates electricity.

    As such it can capture and generate electricity at a much lower wind speed than current wind power technologies.

    The idea is so simple, so elegant, and promises to produce so much more energy at lower cost and more efficiently, that it might just be the answer to many problems with current wind turbine technology. Aside from the lower capital investment to get started, and increased efficiency and power generation, it also might be a solution to the ever growing problem of birds (and bats) being killed by traditional wind farms. (Yes, that is a problem)
     
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  3. leopold Valued Senior Member

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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    There are more than 5 different reasons why this will not be economical.
    (1) It is more expensive to construct than a simple pole and that gets the driven propellers up into much stronger wind.*

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    A typical curve, but where wind machines are best the curve has higher wind speed before it becomes nearly constant.
    (2) It can not survive a storm. Power in the wind goes as the cube of the wind speed why low to ground is silly; however, all economically feasible wind generators MUST do something to survive strongest wind ever in say 20 years (Feather the props most common, but some smaller ones are with a mounting hinge and spring so tilt the "swept area" to nearly horizontal ( generator axis nearly vertical with little of wind stream impeded.) in strong winds.
    (3) conventional wind machine generators are near the theoretical max of capture of energy from the wind. They slow the wind down to get part of its Kinetic Energy but can not stop it to get all as then there is no flow thru the "swept area." I.e. 600% improvement in efficiency is impossible - a false claim. I forget the theoretical limit but it is more than 50% of the energy in the wind as I recall. This is because even if the machine only slows the wind down to half its entrance speed, you get 3/4 of its KE.
    (4) The drawing showing wind entering from opposite sides is silly. In fact what large static structure the wind can not pass thru will do is to reduce the air pressure on the down wind side and require internal flaps or something to keep the air that does enter on the up steam side for being sucked back up into this reduced pressure zone.
    (5) Air at altitude H > h is there for a reason - that is it was closer to the surface got warmer and rose with adiabatic cooling as it expanded to lower density. To push this air back down requires work be done on it as does compressing it prior to the venturi.
    (6) The systems has a fixed direction it need to eject the air that has passed thru the turbine - that may be "into the ground level wind."

    * Economics sets the height: - When the increased value of the slightly higher speed wind one meter higher is less than one meter taller tower would incrementally cost -that is the optimum height economically. In practice the nature of the soil is very important too - the wind's loss of momentum acting on the tall tower is a torque trying to push the tower over. If it just deep dirt, the foundation may cost more than the tower does. A rocky mountain ridge is an ideal site.

    Note the wind speed graph has 12meters / second at 5 meters height a typical lowest average speed for economical operation. Their 2 Miles Per Hour is 0.894m/s so a convetional machine in that higher 12m/s wind (a typical design speed) is working with (12/0.894)^3 more power potential or gives about 2,418 times more output!

    But thanks for a good laugh.
     
    Last edited by a moderator: Feb 13, 2014
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  7. leopold Valued Senior Member

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  8. iceaura Valued Senior Member

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    Maybe not. Those poles are not that simple, and they have to withstand the full pressure of the wind energy being extracted from the entire propeller swept area at a minimum - they require a serious foundation, fully as large and strong as the tunnel structure requires, and pay at least as much a penalty for height. It may be cheaper to get that height with the larger cage structure and its larger initial footprint, than with a single extraordinarily strong and massively founded pole.

    The claims of 600% improvement in capture efficiency are indeed misleading - any large gain in overall efficiency would come from other factors. But those other factors exist - most obviously: nothing is wasted aiming the thing or lost in suboptimal direction of capture, less is lost in air resistance and aerodynamic factors, rain and so forth are more efficiently dealt with, and so forth.

    It is less vulnerable to storms than current propeller designs - wind energy can simply be vented, in an emergency, more reliably and effectively than propellers can be feathered etc, and having the turbine close to the ground makes possible far more robust and easily maintained designs - allowing generation from those higher wind speeds. As for ice loading and similar storm factors, the advantages over a long, thin, exposed, hundred foot propeller of necessarily sophisticated aerodynamic shape are obvious.
    That isn't significant in the common - prairie - situations in which wind power is captured in my region. The first couple hundred feet of altitude is a single air mass continually mixed by wind turbulence, with any layering past two or three meters coming from a boundary layer of friction slowed air. Gliders cannot take off from the ground using ambient wind alone, for example.

    No, it doesn't - the direction can be easily varied (much more easily than aiming a propeller setup by rotating the entire turbine system with servo motors on high-load bearings a hundred feet up on a pole), and could even be adjusted to create further venturi gains (sideways or downwind into any ambient ground level wind, say).

    It is completely adequate in principle for almost all houses, actually, but the economics of storage intervene. One of the interesting possibilities of a wind tunnel as opposed to a propeller design is its greater adaptability to different storage setups. An air pressure storage setup , for example, scaled up from the common pressure tank used to provide water pressure to any well supplied house, could be used to drive the turbine directly at need.
     
  9. leopold Valued Senior Member

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    there is no wind at my location right now and there has been very little all day.
    a wind driven generator would be useless on days like this.
    analysis: unreliable.
     
  10. Sorcerer Put a Spell on you Registered Senior Member

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    That's what the man said: you need some storage options....
     
  11. Read-Only Valued Senior Member

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    Therein lies the major rub in many locations. In mine - interior of Georgia, USA - there are less than 5 days per month that the windspeed reaches 12mph. I would haft to invest a tremendous amount in storage. Beyond what would be practical. And yeah, unfortunately mine is one of the few locations where the power company is not required to buy power from individuals.

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  12. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    To iceauraIn your post 5 you disagree with four of my points only by making claim the are wrong. I claim all your points are wrong. For example wind passing around a vertical right circular cylinder with perfectly smooth skin in theory does not have any net force on it. In reality there is some, but very much less than an apartment of equal height building does. That "better" wind machine would be more like an apartment building if it were higher to get into economically useful air stream. The conventional wind machine's "foundation" can be just a deep hole of diameter equal to the base diameter of the wind poll, which could have guy wires if they were needed, but rarely are. I'll let you pick first - Chose any one point and try to support your claim my point is wrong with more than just assertion.

    The idea is not even new. Mac, now dead poster had some what similar concept - but much more practical. His was basically a cheap concrete cone growing smaller in diameter with it height. The cone's sides had rigid vertical slots (wind catchers as extending outside at an angle) and some ventri effect as part of the entering air did escape thru much smaller turbine at the top, already with some rotation to its flow. He had enough understanding to know that you don't get much more than stagnate the air without some flow thru and the up steam - down stream pressure differential on that large area will blow it over in modest wind. No wonder they need a large, expensive steel structure.
     
  13. Gage Registered Senior Member

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    Wind power isn't meant to be a sole provider of electricity in the U.S. people..... It's intent is to provide a portion of the nation's needs in a broad renewable portfolio that eliminates the need for non-renewables.
     
  14. iceaura Valued Senior Member

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    The foundations necessary for the wind turbines in western Minnesota are massive concrete platforms poured to exacting requirements (they have to be dead level) due to the very high and dramatically variable (buffeting) wind loads placed on such structures even in normal operation - the idea that all you need is a deep hole is ludicrous, and what are you talking about with "guy wires"? You understand the propeller axis revolves 360, with the blades in vertical sweep a couple of meters from the pole, right?

    Guy wires would be more useful with the caged tunnel setup, allowing a lighter and cheaper cage - as with the 300 meter towers used for communication relays. Remember, the weight and rigid support/orientation of precision moving turbine parts and their support motors, bearings, tracks, etc, is not way up off the ground as it is with propeller designs.

    http://schwing.com/wind-farms-fill-the-sails-of-a-minnesota-concrete-pumper/
    That's one.

    two:
    It's obvious from the picture of the one OP design that the ejection tube is flexible and can be curved away from a prevailing wind. But beyond that, a moment's thought will produce a variety of ejection schemes including a smaller duplicate of the intake with optionally blocked apertures - why would you claim only one direction of outflow is available?
     
  15. Russ_Watters Not a Trump supporter... Valued Senior Member

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    (7) The device is relatively small and wastes space with a bunch of structure that doesn't collect wind, making it capture a ton less wind than a conventional wind turbine. Yah - the 2m turbine produces 6x as much power as a conventional 2m turbine.....or about 1/4th of what a conventional 10m turbine (my guestimate of the height of this monstrosity) produces!
     
  16. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Lol, are the tower support structure and fence flexible too?
     
  17. iceaura Valued Senior Member

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    The propeller design captures wind strike area equal to the area of the blades perpendicular to the wind.

    The tunnel design captures wind strike area equal to the area of intake aperture perpendicular to the wind.

    Obviously as one's dimensions expand one gets larger areas much quicker with squarish or roundish shapes than long thin ones. The tunnel isn't as small as it looks, compared with a large propeller.

    Dunno. I'd just bend the exit tube a little bit at need, but whatever floats your boat.
     
  18. billvon Valued Senior Member

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    Sure; you could likely choose your cases where that would be true. Of course I could also choose a wind turbine that produced 600 times the electrical power than the Sheerwind.

    There are two things, and two things only, that contribute to wind power generation - wind speed and swept area. If this thing can have the same intake area as a large wind turbine, and can be as high as a large wind turbine, then it could produce a similar amount of power. (Somewhat less due to drag.) There's no way around that equation, no clever design that will let you "suck" more power out of the air. This has been proven over the course of over 1000 years of wind power.

    Let's take an example, the Vestas V164-8.0. This is a turbine that generates 8 megawatts. Its rotor is 500 feet across and 750 feet tall and costs about $10 million to build and install.

    Now let's take one of these new turbines. You need a similar size to capture the same power, so you'd need a building 750 feet tall and 400 feet across each opening (you get some advantage from the rectangular form factor over a circular swept area.) That's equivalent to a 60 story building. As a reference, the Commerzbank Headquarters building in Germany is about 400 by 400 feet but 1000 feet tall (so a bit taller) and cost $414 million. Let's say that this turbine is much, much easier than an office building to build - no elevators, windows, escape stairways, water coolers etc etc. So let's say it costs only 10% of a building like this. You're still at $41 million, more than 4 times more for just the STRUCTURE. That isn't even counting the turbines.

    Why wouldn't this cause just as much problem? Birds collide with apartment buildings all the time, and this is going to be way bigger than an apartment building.

    (BTW wind turbines are the #1 way to fail at renewable energy for people who try to go off-grid - primarily due to gimmicky machines mounted on too-short towers.)
     
  19. leopold Valued Senior Member

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    wind energy alone cannot power your house on a daily basis, you MUST have some kind of storage system.
    this implies batteries and the additional charging circuits.
    you also must supply some kind of automatic disconnect from the batteries to keep the generator from draining the batteries when there is no wind.
    wind turbines and the associated mounting structures must withstand any tornadoes or hurricanes that happen to pass your way.
    so, what does all of this add up to.
    in my opinion, what is needed is a few small cheap turbines that are easily replaced instead of one monster.
    the monster turbines would be best suited for supplying power directly to the grid.
     
  20. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    On "two" I doubt the exit tube is flexible as it would buckle if you tried to bend it; but even is that were possible, there are 8 or so steel (painted yellow) support anchoring it to the ground visible in the post 3 photo - Impossible to move the exhaust direction even only 10 degrees in less than hour and very expensive to do so - (keep a construction crew there 24/7 ?) and the wind , especially one blowing at their design speed of 2mph, can change its direction greatly in less than 10 minutes.
    You are posting economic non-sense in this reply. Try again to show economic viability.

    BTW, I don't claim only one direction of flow is available. In fact I noted the post 3 figure showing wind entering the machine from opposite sides at the same time is ridiculous - but which side it enters from can be "wind selected" but that duplication of mainly wind blocking structure is costly compared to a conventional wind machine small tail that automatically turns it directly into the wind. (Some very large machines do sense the wind direction and use a motor to turn.)

    BTW2, a two or even one blade machine is slightly more efficient than the three blades used. They are used as their moment of inertia against rotation is nearly a constant. If it is not, changing direction induces stresses as the blade(s) rotate. This greater efficiency is partly why small prop air planes have only two propeller blades. Many blades are used when you are more interested in low speed torque than efficiency as in wind power farm water pump applications.

    On one: Yes some low strength soils do require a massive weight base. I installed a North Wind generator for the US Coast Guard at their Norfolk VA station in sand. It was a test / demo - not intended to be economical as power company energy was available. Their main applications were off shore island light houses, where diesel generators run 24/7 and not just at idle speed even during the day as they get "clogged up" with carbon, if you do that. Some light-house stations can not even get their drums of diesel fuel deliver by transfer from delivery ship to its small boat, but must use helicopters for delivery from their large, expensive to operate, "cutter" ship. - This was back when gasoline was about $0.75 / gallon but their delivered diesel was at least $300 /gallon or >$1000 / gallon if a helicopter was used.

    I.e. The wind machine + battery economy was great, without question as it allowed the diesel to be off when there was wind - i.e. almost always. The question was what was the expected down time each decade - that was the object of the Norfolk site test. I doubt the North Wind machine is still there, but that concrete cube in the beach sand still is, I'm sure. North Wind does not still seem to exist - I tried to find photo of the machine as it shed wind by rolling back to near horizontal. We choose this design as it is very reliable way to shed excessive wind power compared to more standard but more complex feathering of the props. - just a large coiled spring resisting roll back pivot so no failure modes exist except 100+ years of rusting. I went down from work ( at APL/JHU in Maryland) during near hurricane storm - saw it rolled back with spin axis less than 5 degrees off vertical but still slowly turning.

    Yes, guy wires would need to attach at less than 1/4 the pole height and need their own massive anchor points - why they are not used, ever AFAIK.

    Point you avoided was what is the cost of a massive block of concrete? Especially one that is with four corner steel tie-down bolt points but more than half just solid rocks dumped in for mass in central volume? - Compared to the expensive steel structure that can at least get that huge, mainly wind blocking structure to at least to twice the height of taller trees. Rock filled concrete base with < 1% of that steel in it than that new type wind machine would need.Rock filler is very cheap - I.e. cuts the cost of already cheap concrete base in half. Try again, and keep in mind the question is about economics, not how large the torque resisting base block must be, even in sand.

    Note also, when you do so, that a large steel base which can also resist strong wind from toppling that mainly wind blocking machine over is 10 or so times more costly than in-earth, half rocks filling concrete, except at the corner tie down points.
     
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  21. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Right, but the intake is only about 25% of the height of the whole tower (using a finger to measure from the picture), compared to a conventional turbine which is about 75%. So it captures only a little more than 1/3 as much wind as a conventional turbine of a similar height and width.
    Again, it is much worse than that because of what I said above. To have the same swept area as that normal turbine, assuming a square cross section gives 440x440 feet for the intake and a total height of 1700 feet. That's a billion dollar skyscraper.
     
  22. leopold Valued Senior Member

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  23. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    No this just reflects you poor understanding. The energy in the ENTIRE "swept area" even if only one blade were used, is reduced as the wind in that "tube of wind" is slowed down, giving up kinetic energy. - Actually slightly larger "tube" of wind is slowed as if it were not there would be great turbulence at the boundary.

    I have professionally worked in this area - know what I am talking about. By your false ideas, one would expect wind machine to used many blades - they use three for reason I explained in prior post even though only one is slightly better at collecting energy from the wind.
     

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