# Question On Those 350' Wind Turbines Popping Up Everywhere



## drizler (Sep 29, 2008)

We have them sprouting up like sunflowers around here.    What is the minimum speed those things have to turn to make any usable power?   They seem to be turning around 10 RPM most of the time even when there is no noticeable breeze.   Looking at the published literature all they seem to talk about is averages.


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## Redox (Sep 29, 2008)

I believe most of them are using inverter technology that allows them to generate power with very little movement.  It may not be much, but it's power.  10 RPM isn't much but the torque must be incredible on a blade that big.

Chris


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## webbie (Sep 29, 2008)

The gearboxes make that MUCH faster!
If they are turning constantly, they are making electric......pretty well. It is when they are not turning that we have to be concerned. 

There may be no breeze where you are, but go a couple hundred feet up in the air and things change.


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## bayshorecs (Oct 3, 2008)

Webmaster said:
			
		

> There may be no breeze where you are, but go a couple hundred feet up in the air and things change.



No kidding.  Reminds me of the days I used to work on radio towers.


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## 2.beans (Oct 6, 2008)

the towers around here are going to produce 2 megawatts each . they're installing 12 of them and thats supposed to produce enough power for 10,000 homes or one walmart supercenter.


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## NoPaint (May 27, 2009)

2.beans said:
			
		

> the towers around here are going to produce 2 megawatts each . they're installing 12 of them and thats supposed to produce enough power for 10,000 homes or one walmart supercenter.




Haha or enough power to run a single pump at the Playboy mansion grotto.


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## Delta-T (May 27, 2009)

a lot of the engineerings is done to keep the RPM's down around 10 or so. One of the "problems" with smaller faster blade configurations is chopping birds into tenders. Low RPM is much friendlier. In the off chance that something catastrophic happens to the blades I imagine one moving at say 300rpm is likely to fly off somewhere and do some crazy damage too.

Agree with Redox, the torque must be awesome. All we need to do is put a harness on the blades and we can turn it into a sweet carnival style ride.


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## Highbeam (May 27, 2009)

They are much noisier at speed too.


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## webbie (May 27, 2009)

People in Portsmouth (RI) have been asking why the new BIG turbine is still while the smaller turbine is still spinning.

The answer was given and is this - the older and smaller one turns even when there is not enough power to engage the transmission and generate electric. The newer one saves a lot of wear and tear by not allowing the blades to spin until electric will be made.

BTW, I hear it generated over $80K worth of electric in the first two months. At that rate, it will be ahead of projections.


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## Hakusan (May 28, 2009)

The important factors to turbines are the cut in speed and the swept area. The greater the area the blades sweep, the greater the power they produce--the speed of the blades are not important in power generation, but in whether the design can take the forces. Classifying a turbine by watts is not a very good measure of its power. Large turbines can have blades that can change pitch to control speed (small turbines have mechanisms to move them out of the direction of the wind). Also the height of the turbine is important as the higher it is, the more energy it catches. The air is less turbulent and provides consistent power--small turbines can have a shorted life span because they are located on shorter towers where the wind turbulence is high. 

Turbine speed and bird strikes, as far as I know, are unrelated. The speed of a turbine has nothing to do with whether it would hit a bird. Turbine blades also spin faster than wind speed would suggests if it were a drag system--the blades actually produce lift like an aircraft wing. This is why these thin blade are so efficient. As stated above, large turbines have gears and windings to increase power to the generator; small turbines have direct drive and so are faster because turbines do not have a great deal of mechanical torque. Small turbines can get away with faster blade speed because the stresses are less.


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## JustWood (May 28, 2009)

Delta-T said:
			
		

> a lot of the engineerings is done to keep the RPM's down around 10 or so. One of the "problems" with smaller faster blade configurations is chopping birds into tenders. Low RPM is much friendlier. In the off chance that something catastrophic happens to the blades I imagine one moving at say 300rpm is likely to fly off somewhere and do some crazy damage too.
> 
> Agree with Redox, the torque must be awesome. All we need to do is put a harness on the blades and we can turn it into a sweet carnival style ride.



Too bad the Chinese didn't have windmills when bird flue was a problem.
Maybe Mexico should look into wind turbine  technology just in case pigs fly . :cheese:


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## mayhem (May 28, 2009)

Even at just 10 rpm, the tips of those blades are moving at a couple hundred miles an hour.


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## mbcijim (May 28, 2009)

I've had a tour of a 'farm' and even been up in one.  Pretty cool.

If memory serves me right the one I was in was around 1.2 MW and needed 9 MPH wind to generate that much power.
It had a little regular old PC in the base, he changed the pitch of the blade via the PC, and the blades immediately stopped turning.  By immediately I mean <5 seconds from a click on the mouse.  

They turn very easily to face into the wind and change the pitch as well to get them running quickly and easily.  They are also designed to shut down in high wind.  They pitch the blades away from the wind and they just don't turn.  

Interestingly, I am involved in a solar project that might run into a few million dollars.  The return on solar without subsidies is a joke.  Wind power on the other hand, is on the verge of being cost effective without subsidies.  That, to me, is very exciting.  And I don't believe in the whole green BS movement.


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## Jackpine Savage (May 28, 2009)

Has everyone seen the video of what happens when they spin too fast?


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## Delta-T (May 28, 2009)

Preused ufO brOKer said:
			
		

> new windmills have an electric braking system. wonder if that one had one



this one has the new-fangled electric "breaking" system.


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## flyingcow (May 28, 2009)

mbcijim said:
			
		

> I've had a tour of a 'farm' and even been up in one.  Pretty cool.
> 
> If memory serves me right the one I was in was around 1.2 MW and needed 9 MPH wind to generate that much power.
> It had a little regular old PC in the base, he changed the pitch of the blade via the PC, and the blades immediately stopped turning.  By immediately I mean <5 seconds from a click on the mouse.
> ...



On the residential windmills I'd hold off a while. I've got a small unit and its only producing about 250 kw/hrs a month. Even with the tax breaks its a crap shoot. I''ve got good elevation, good exposure to the prevailing winds, limited turbulance factors, etc.

I've told everybody at least I'll have a nice 45ft flag pole if this doesn't work out. :coolsmile:


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