A question: Are these turbines pulling enough to skew the winds? I'm remembing a guy in the pub a year ago. "The shadow!" behind the turbines. I thought at the time that a turbine sticking up is like a tall tree. But these farms are large, so is there a danger limit, where planting more will affect the winds, or are we so small compared to the wind that we can't have any tangible effect? Don't fight forces, use them R. Buckminster Fuller.
If Crazy Horse is reading, I'm sure he's heard this one. Don't fight forces, use them R. Buckminster Fuller.
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.
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
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...
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...
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). *Traitor*, n. A benighted individual who perceives an illusory distinction between serving his nation and abetting the criminals who govern it.
