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Need slow flow high pressure wind generator fan design

  1. Apr 27, 2009 #1

    I have been toying with the idea of producing electricity from the cross winds that build up in my house.

    Basically when I leave a window open one one side of my flat and open a window on the other the wind blows through the house very strong.

    I want to place a wind generator on one of the windows and tie into the grid (the tie in bit I already know about) to get power.

    The problem is that I dont want lost of wind flowing through my house, what I want is to use the pressure that builds up and let the air flow slowly but that has lost of pressure behind it.

    Im getting confused myself but basically what I need is a fan design that will work well with low wind speed but high air pressure, imagine the old watermills turning slowly but with lots of power due to the water.

    Any ideas

    Albert Pizzarello - Gibraltar
  2. jcsd
  3. Apr 27, 2009 #2


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    Staff: Mentor

    Welcome to PF!

    Wind doesn't have a high pressure behind it, otherwise your house would blow up like a balloon and the power available in the wind is what it is - any power taken from it reduces the flow through the house by exactly the fraction of the volume you have flowing through the house. IE, if you recover half the power, you cut your flow rate in half.

    Why not locate the turbine outside?
  4. Apr 27, 2009 #3

    Thanks but we cant place any object like dishes etc outside, due to community regulations etc.

    Would a turbine type prop be more efficient under these circumstances ?

  5. Apr 27, 2009 #4


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    Staff: Mentor

    More efficient than what and what do you mean by efficient? There are an awful lot of variables that go into designing a wind turbine and no single "efficiency" number. Your biggest limitation here is that you've got a very small cross sectional area exposed to the wind, so a very small amount of available wind energy. I'd just see what the specs are on wind turbines of the size of your window openings.
  6. Apr 28, 2009 #5
    Ok, Lets look at this a different way.

    If I had a motor and wanted to produce high pressure (for example to inflate a car tyre) and the speed at which it pumps that up is not important.
    Assuming same motor, same power applied to the motor, what prop type would produce the highest pressure more psi. An airplane type prop or a ducted fan type prop ?

    What Im getting to is that why do jet engines use "props" with many blades all near each other, I assumed that that design produces more compression in the jet engine whilst a normal 2 or 3 bladed prop would not.

    In my simple mind I would then use that configuration but inverse.

    The problem is I dont know much about fan designs so I might be talking bu??it. :) Which is not the first time.

  7. Apr 28, 2009 #6


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    Science Advisor

    OK OK, you have some bad terminology here. If you are trying for a really high pressure with low flow using a motor (e.g. your inflating car tires example), you would typically use a positive displacement pump. Other than this, there are things like centrifugal compressors which act on the same principle to increase pressure.

    When you're talking about jet engines, I'm assuming that you're referring to the fan rotor. The thing you see in the front. The design for the fan rotors is really to suck air into the engine. They typically do not have very high pressure ratios.

    The first question I would ask is what type of wind velocities do you expect through the window? Is it possible to duct between the windows (even possibly going up along the ceiling, then back down)?
  8. Apr 28, 2009 #7
    I think a feasability study would be in order.

    Wind-turbines are expensive, and yield little for the cost, well thats my opinion.

    I looked into buying one, and it would take 5 years to pay for its-self.

    OK, making one can be a fair bit cheaper, but when you consider time you need to put in, is it really?

    Loads of threads on here about Wind Generators/Turbines, so you should find all the calculations one would ever need.

    I have seen one of these things using a type of turbine blade, but its far of the blades of the fan on an aircraft, more like Water Turbine Blades.

    I would find out what you can expect to yield first, if its 10watts then your going to be able to power 1 energy saving light-bulb only, i doubt you'll get much above 50watts with the C.S.A that would be available.

    Wind power is great, just expensive, even though its free in theory.
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