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Do you know of any reports, studies, that kind of thing.  It'd be good (for me at least) to have a sense of how far from (or close to) tangible our maximums might get (and to block scare stories before they get too strong--this guy in the pub was really insistent.  "Nuclear," he said, "not wind.  The wind farms create wind shadows," which change the course of the wind to most deleterious effect.)

If Crazy Horse is reading, I'm sure he's heard this one.    

Don't fight forces, use them R. Buckminster Fuller.

by rg (leopold dot lepster at google mail dot com) on Sat Dec 8th, 2007 at 06:29:40 AM EST
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A wind turbine creates a wind shadow extending about 7 times the diameter of its blade - at which point the wind is such that you can put up another wind turbine. I think that's just nonsense, or FUD.

We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Sat Dec 8th, 2007 at 06:39:32 AM EST
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So if you have to put them at least seven diameters apart how do These work

Any idiot can face a crisis - it's day to day living that wears you out.
by ceebs (ceebs (at) eurotrib (dot) com) on Sat Dec 8th, 2007 at 07:01:02 AM EST
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Park Effect
Park Effect As we saw in the previous section on the wake effect , each wind turbine will slow down the wind behind it as it pulls energy out of the wind and converts it to electricity. Ideally, we would therefore like to space turbines as far apart as possible in the prevailing wind direction. On the other hand, land use and the cost of connecting wind turbines to the electrical grid would tell us to space them closer together. Park Layout As a rule of thumb, turbines in wind parks are usually spaced somewhere between 5 and 9 rotor diameters apart in the prevailing wind direction, and between 3 and 5 diameters apart in the direction perpendicular to the prevailing winds. In this picture we have placed three rows of five turbines each in a fairly typical pattern. The turbines (the white dots) are placed 7 diameters apart in the prevailing wind direction, and 4 diameters apart in the direction perpendicular to the prevailing winds.


We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Sat Dec 8th, 2007 at 07:13:50 AM EST
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If you look at Shadow Casting from Wind Turbines from the Danish wind energy association, the only shadow they consider is the light shadow a turbine will project.

Also, the amount of energy extracted by a wind turbine is, as Jérôme points out, negligible compared with the amount of energy carried by the wind. The only effect I can think of is torque/vorticity generation. But if you make a wind turbine field with half the rotors spinning clockwise and half counterclockwise, the effects should cancel out.

We have met the enemy, and he is us — Pogo

by Migeru (migeru at eurotrib dot com) on Sat Dec 8th, 2007 at 06:44:22 AM EST
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Wake Effect
Since a wind turbine generates electricity from the energy in the wind, the wind leaving the turbine must have a lower energy content than the wind arriving in front of the turbine.

This follows directly from the fact that energy can neither be created nor consumed. If this sounds confusing, take a look at the definition of energy in the Reference Manual. A wind turbine will always cast a wind shade in the downwind direction. In fact, there will be a wake behind the turbine, i.e. a long trail of wind which is quite turbulent and slowed down, when compared to the wind arriving in front of the turbine. (The expression wake is obviously derived from the wake behind a ship). You can actually see the wake trailing behind a wind turbine, if you add smoke to the air passing through the turbine, as was done in the picture. (This particular turbine was designed to rotate in a counterclockwise direction which is somewhat unusual for modern wind turbines). Wind turbines in parks are usually spaced at least three rotor diameters from one another in order to avoid too much turbulence around the turbines downstream. In the prevailing wind direction turbines are usually spaced even farther apart...



We have met the enemy, and he is us — Pogo
by Migeru (migeru at eurotrib dot com) on Sat Dec 8th, 2007 at 07:18:33 AM EST
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I must add to Migeru's notes that there has been a German court case between a wind park and a wind developer, where the former complained that a new farm ahead of theirs would reduce the power theirs generates and thus reduce income.

On a more general note: AFAIK the bulk of wind energy is further above ground, where air moves freely but is still thick, even 60 metre blades atop 150 metre towers would only skirt their downside.

On a hypothetical note: the atmosphere being a nonlinear system, I wouldn't close out climate effects from wind power, it's something to research. But if there is one, I guess it must be comparable to the effect of forest felling or highrise construction. Tho', I'd imagine the effect is dwarfed by the effect of changed thermal conditions (change in surface and air reflection/absorbtion ratio, heat production) -- an effect, hehe, nuclear plant cooling towers have too.

However, that that punter made such a point of wind changing climate is something I heard before, here from engineer colleagues, and I suspect it may come from some nuclear industry propaganda (probably US).

*Lunatic*, n.
One whose delusions are out of fashion.

by DoDo on Sun Dec 9th, 2007 at 12:42:33 PM EST
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