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Floyd
5th July 2010, 04:03 AM
A wind farm (12 turbines) has been built quite close (2 miles) to where we sail.Some sailors think its affected wind (in certain directions). Anybody know likely (actual) effect 2 or 3 miles downwind from the turbines ????

mighty
5th July 2010, 01:32 PM
As long as I know there is no effect of wind turbines on wind directions.

Farlo
5th July 2010, 08:39 PM
Hi Floyd, I remember from fluidics tuition that the effect of an obstacle can be noticed away up to seven times its height. 2 miles seem a safe distance.

Roger
5th July 2010, 08:42 PM
Floyd,
My guess would be there is virtually no effect.
Why?
Look at the separation between the wind turbines in the wind field.
At what one of those units cost, I'm pretty sure that they place them so
the upwind turbine does not negatively effect any turbines downwind.
So, the distance between them is probably greater than some calculated or
actually physically tested distance at which the upwind turbine affects the
efficiency and output of the downwind turbines.
You could do your own test...... take a hand held wind meter and a GPS (for elevation/
altitude) and take some readings upwind a mile and downwind a mile as see if there is any measureable difference.
If the turbines are on the top of a hill (which they often are) and your sailing site is lower, I fail to see how there could be any effect at all.
One of the windiest spots in the USA (Cabezon Pass (The Ponds near Palm Springs)
had us windsurfing on small narrow "Perk ponds" right in the middle of a wind farm.
Didn't see any effect there, and that was when "wind farming" in the USA was very much in it's infancy.
Roger

Floyd
5th July 2010, 10:55 PM
General conscencus amongst us is that they have minimal effect but quite a few sailors insist the wind is not as steady as it used to be.
I think the farms are normally arranged perpendicular to the prevailing winds to reduce any effect they might have on one and other but obviuosly there are times when they are downwind.
Could be that quite close to them the wind is actually stronger at ground level (under neath lowest height of bades) ?? So sailing near them may well be
Not sure of power ratings of our turbines but they must take out energy from wind ; wether these amounts removed are significant to total amount passing by I`m not sure.

Floyd
5th July 2010, 10:58 PM
PS
Our turbines are just about at sea level.
If they do have an effect there`s going to be some sad sailors in Tiree;biggest Windfarm in Europe is planned for there !!!

Farlo
5th July 2010, 11:44 PM
Hi Floyd, for over twenty years I've heard sailors insisting the wind is not as steady as it used to be. Even in South of France or places like Tarifa you ear this from time to time. Is it because the trees around their spot have grown, or new buildings have emerged, or the general skill level has improved? It doesn't seem to be related to wind farms. For sure a certain amount of energy is taken out but will there be a sensible effect at ground level two miles away? I doubt. Offshore wind tends to reaccelerate and stabilize a few hundred meters from the beach, unless there are mountains around.

davide
6th July 2010, 11:11 AM
Hard to tell if it is significant but it must have an effect. Some energy is created out of the wind and the wind slows down ... Trees, buildings, ugly turbines ... put down enough and the wind will stop.

Maybe we should start a stop-wind-energy campaign, Turbines do have a huge footprint and who knows what environmental consequences will result when they become more widespread ...

Farlo
6th July 2010, 11:39 PM
Look at this Danish site: http://www.talentfactory.dk/en/tour/wres/shelter/index.htm and plot wind speed after an obstacle. You will find that in most practical cases wind speed at ground level is unaffected after two miles (same as if there was no obstacle). I guess the extra turbulence created by the obstacle disappears as well provided that wind speed is unaffected within ten meters above the ground.

Unregistered
7th July 2010, 02:06 PM
Hi Floyd, for over twenty years I've heard sailors insisting the wind is not as steady as it used to be. Even in South of France or places like Tarifa you ear this from time to time. Is it because the trees around their spot have grown, or new buildings have emerged, or the general skill level has improved? It doesn't seem to be related to wind farms. For sure a certain amount of energy is taken out but will there be a sensible effect at ground level two miles away? I doubt. Offshore wind tends to reaccelerate and stabilize a few hundred meters from the beach, unless there are mountains around.

or kit is more affected by unsteady wind.
20 years ago tops of sails had more drive and power and they were biased more towards the bottom of their wind range
today tops of sails have relatively little drive and power and the sails are biased towards the top of their wind range.

Farlo
7th July 2010, 03:51 PM
This is true and you tend to rig larger now, but modern sails have also a bigger wind range. You don't really need sails every 0.5 m² like in the old days. I guess their ability to handle unsteady wind has grown in proportion. Anyway I remember people already complaining in the early 90's (mostly inland spots) with gear of that time. It seems that wind was very steady before WS actually started.

Unregistered
7th July 2010, 04:58 PM
The Nysted wind farms consist of "Rødsand I" (166 MW total -erected 2003) and "Rødsand II" (215 mW total - under construction). Rødsand I and II are approx 3 km (or 2 miles) from each other and estimates are that "Rødsand II" will reduce the power procution from "Rødsand I" up to 30% (depending on wind direction). As these windfarm have different owners this has caused some discussion about compensation. Experts within the field estimates that there will be a windshadow more than 20 km away from a large windfarm.

http://en.wikipedia.org/wiki/Nysted_Wind_Farm

I could link to some additionals sources for information, but the ones I know are in danish.

A personal experience: I have sometimes sailed approx 5-10 km from Rødsand I, and I feel the wind is more gusty than before 2003.

"Your" windfarm is smaller than Rødsand I - but I still think there will be a difference.

Peter R

Unregistered
7th July 2010, 06:45 PM
Floyd,
My guess would be there is virtually no effect.
Why?
Look at the separation between the wind turbines in the wind field.
At what one of those units cost, I'm pretty sure that they place them so
the upwind turbine does not negatively effect any turbines downwind.
So, the distance between them is probably greater than some calculated or
actually physically tested distance at which the upwind turbine affects the
efficiency and output of the downwind turbines.


There are several reasons that wind turbines are placed pretty close:

1) Infrastructure: The expenses to the power cable to "Rødsand II" is approx. 300 million dKr (50 million dollars). If the wind turbines were dispersed further, the expenses would be higher. Wind turbine service are another example of expenses that would go up, and you will also need infrastructure at land

2) The right bottom structure, (low) water depth

3) Aesthetics


Peter R

Farlo
7th July 2010, 06:49 PM
Hi Peter, wind is more affected in altitude, so the effect at around 100 m of a large wind farm will be sensible several miles away (however 30% is surprising). Close to ground level the situation is different because the wind is slower and less steady anyway. It all depends on roughness between the farm and the spot. If plenty of trees, buildings, hills... the difference will be negligible. If very flat land or open water like Rodsand, the extra turbulence will travel much longer. http://www.talentfactory.dk/en/tour/wres/shelter/index.htm for speed simulations and http://www.talentfactory.dk/en/tour/wres/park.htm for park effect.

Unregistered
7th July 2010, 06:51 PM
Hi Farlo

You are probably rigth about that. I assumed that it was an offshore wind farm.

Peter R