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Forum Index : Windmills : 25 rotor turbine

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azland00123

Newbie

Joined: 24/02/2008
Location: United States
Posts: 23
Posted: 01:42am 16 May 2008
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hello again,
I have enjoyed reading all of your posts. I am learning allot each week. Thank you for sharing.

Have any of you seen this windmill?

He claims that he can get 2k from a two rotor turbine.

Is the motor in the pic half the size of the f&p?

If it is, then this blade design might increase the power on the f&p considerably.
http://www.popsci.com/scitech/article/2008-05/ten-times-turb ineEdited by azland00123 2008-05-17
Bob
 
azland00123

Newbie

Joined: 24/02/2008
Location: United States
Posts: 23
Posted: 01:48am 16 May 2008
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The space in "turbine" will not go away I tried to edit it but it returns every time. Make sure you remove the space from turbine after you paste it in the address bar.

Bob
 
GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 04:44am 16 May 2008
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Hi Bob,

I stacked kites to increase the lifting power. I got to 3. I have seen photos where there were hundreds on the same line.

There has been a windmill design with 2 rotors, that was claimed to harness power above Betts Law. This had one shaft, with a rotor on each end, with the generator inbetween.

It is hard enough getting planning approval for a fixed object. Imagine what it would be like for something like a giant sky hook that moved, with blades on it.

I imagine it would be difficult to match the rotors for the different air velocities as the height increased as well. .. .. Gordon.
become more energy aware
 
azland00123

Newbie

Joined: 24/02/2008
Location: United States
Posts: 23
Posted: 09:27am 17 May 2008
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Betts law says you can harness around about 53 percent but I thought that applied only to a given area of each rotor not the entire unit.

So A set of blades that covers more, then the percent in betts law, would become ineffective or not work at all.

Would it be true that if the blade were far enough apart that they acted independently of each other and each harnessed 40 percent that you could go over betts law with out breaking it? Thank you
Bob
 
GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 11:52am 17 May 2008
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Hi Bob,

I believe the 100m+ turbines get around 50% extraction efficiency of energy from the wind. My mill is pretty good at around 28%. If in a two rotor setup each rotor was in clean air, then the total area of wind exposure would be x2. Betts law would still apply for the total area. The only benefit I can see is for the continued high rpm, that can be achieved by a small rotor diameter, without having to use a gearbox, or high pole count generator. The high rpm allows a high power density from a small generator.

I will wait for some published comparison data. STD turbines are still pretty good value. .. .. Gordon.
become more energy aware
 
azland00123

Newbie

Joined: 24/02/2008
Location: United States
Posts: 23
Posted: 07:19pm 17 May 2008
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Thank Gordan.
Bob
 
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