chemosavi wrote:When kiteboarders start worrying about wind farms wrecking their precious spot they need to get a job in a coal mine somewhere and start a meth addiction.
As in, something ain't meshing down in the engine room.
They have quite a few in the Netherlands and you don't hear them complaining about them ruining their kiting. Bit of an oxymoron, in other words. Better to have a noxious coal burning powerplant somewhere else far away doing the polluting that runs the refineries that make the petroleum for the plastic everything you use to kite with is made of.
SSK wrote:At first I assumed that no way a wind farm could have that big of an effect downwind. However, there seems to be quite a lot of studies on wake and downwind effects. You can download a lot of technical information. These articles cite a large ocean grid off Denmark (9 by 8 grid) the velocity loss at 0-3km was 10%. This recovered by 8-20km to within 2% of the upwind velocity. Also energy loss was estimated at up to 15% at 5KM. So depending on the size of the farms and actual location, I would not dismiss it as not having a real impact. I did not read anything that suggests it could "wreck" it.
http://books.google.com/books?id=VKGF-E ... ts&f=false
http://www.gl-garradhassan.com/assets/d ... akes_paper)_-_FINAL.pdf
A loss of 0-3km doesn't sound that bad to me
frankm1960 wrote:A loss of 0-3km doesn't sound that bad to me... check out some of the light wind kites in "various" threads on this forum if you're worried you're gonna miss some light wind sessions.
SSK wrote:A loss of 0-3km doesn't sound that bad to me
Sorry for not being clear. At a distance of 0-3KM downstream, there was a velocity loss of 10% on average. It seems at lower winds the percent loss was greater. As people have pointed out it is probably not the velocity concern as much as it is the downwind turbulence resulting in greater wind energy loss.
@Laughingham. The effect of a wind farm is actually much more significant than "kiting behind a treeline" because of wake turbulence caused by the blades. The posted image show contrails in relation to wake turbulence. The contrails are caused by condensation caused by the pressure change caused from the blades. In aviation this causes many accidents as a large aircraft produce enough "dirty air" to flip a smaller aircraft.
I am not saying that this is a major impact or something we should worry about. But it does appear that a large wind farm can have real effects on downwind conditions even at a pretty surprising distance. Also NOAA has been looking at other micro climate effects caused by wind farms such as precipitation and temperature differences. I would not dismiss the possibility of some adverse effects, but I would not suspect it would wreck the wind. But under certain conditions like a valley and smaller distances, this could be a real issue.
SSK: you've just shown why it is a non-issue.
I agree with most of the posters...anyone start worrying about a wind farm 6 miles away for a kiting session...I dunno.
With a new power source comes an impact to our environment. Roy says, "Large wind farms can significantly affect local meteorology." He studied these massive machines and believes wind farms can actually impact our weather because wind turns the blades of the turbine around a rotor, which helps generate electricity the blades create a lot of turbulence in the wake. Roy says, "It's something like the wake from the propeller of a boat. Now this added turbulences mixes air up and down and creates a warming and drying effect near the ground." He says the affects can be felt for miles. These studies suggest that while large wind farms can affect local hydrometeorology, there are smart engineering solutions that can significantly reduce those impacts.
If you dislike windfarms for other reasons then that is a different discussion
SSK: The safe contrails behind a plane is way less than 3 km. This occurs at much much higher speeds than wqe are talking about.
As air flows through the blades of a gigantic, 300-foot wind turbine tower, the wind energy turns the blades. This energy is robbed from the atmosphere, effectively slowing the wind speed proportionally. The greater the array of wind turbines, the more energy is removed from the atmospheric flow and the slower the ambient wind will travel. Slowing wind speeds by 5 or 6 miles per hour – while it sounds negligible, could have significant impacts on the large-scale atmospheric flow and yield consequences we do not yet understand.
When air flows through wind turbine blades, the path that the flow takes is slightly altered. The net result is that there is turbulence down wind from the turbine blades. When this turbulence occurs, rather than the ordinary laminar flow, the surface of the ocean is impacted. This turbulence over the ocean water can cause a phenomenon known as upwelling whereby deeper ocean water is drawn up to the surface as surface water is driven down to replace it. When the ocean “turns over” in this manner temperature flow within the body of water is altered. Altering the upwelling patterns of an otherwise undisturbed body of water may have impacts on the currents that naturally exist as part of the large-scale flow. As with the atmospheric air flow impacts of large-scale wind farms, the overall impact of increased ocean current upwelling is not fully understood.
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