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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Thu Jan 03, 2013 11:35 pm 
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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.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 12:32 am 
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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.


I'll admit I never thought much of wind power and solar power effects on the environment till I started kiting but still, it's worth a discussion. Does anyone really know the effect on the environment by using the energy stored in wind and solar? A few km/h is easily compared to a few degrees change in ocean temp... Global warming... Should we also not worry about that?
I don't, simply because I'm a selfish sob and I figure I'll be gone long before I need to really be concerned, but there could be an immediate effect on usable wind down stream of major wind farms.
Part of the reason I started this thread is to get the feed back from those who kite downstream of major wind farms... So let's have it... OBX is just talking about it at this point... Lake Erie on the other hand has been slated for about 200 turbines off of long point... I cannot see how this will be good for wind enthusiasts in the area.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 12:34 am 
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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.

[url]
http://books.google.com/books?id=VKGF-E ... ts&f=false
[/url]

[url]
http://www.gl-garradhassan.com/assets/d ... akes_paper)_-_FINAL.pdf
[/url]

Image


Yay, someone did their homework before forming an opinion. thanks for your constructive input!


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 12:37 am 
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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.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 12:39 am 
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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.


Not too worried about the light wind sessions... If you study the diagram on the first page of this thread you will see that the effect of friction on wind increases as the velocity of the wind increases.... Remember those awesome smooth consistent winds you once kited in... Are they in jeopardy if your local spot is downstream of a major wind farm... I think it may be a factor...


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 12:58 am 
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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.

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.

Remember we're talking 6 miles. About 10 km...not the 0-3km you are talking about.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 1:20 am 
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SSK wrote:
Quote:
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.


Sorry... you're right I miss understood that... you lose 10% of wind speed 0-3km downstream. I got it now. So if it's blowing 10km/hr upstream of turbines... it's gonna blow 9km/hr 0-3km downstream of turbines... I don't know if I could live with that. If it's blowing 60km upstream of turbines it's gonna blow 54km 0-3km downstream of turbines... I would kill myself if that ever were to happen here. The surfers might like it though.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 6:04 pm 
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SSK: you've just shown why it is a non-issue.


No I did not show it was a non-issue at all. I simply showed some values that a single study reported, for a specific grid, at a specific location. Thats it. How a potential grid off the NC coast would effect weather and wind, no one knows. But scientist have shown that there are potential impacts, and that is why a whole lot of money is being spent studying it and ways to mitigate any adverse effects. Some of these effects could be positive for kiting and the environment while other could be negative.

Quote:
I agree with most of the posters...anyone start worrying about a wind farm 6 miles away for a kiting session...I dunno.


It seems that many scientists to include those involved in power generation, NOAA, and NASA are concerned of possible impacts. They believe this concept is worth understanding. It is more than just kiting that could be affected. And again these effects could be positive, negative, minimal, or even large. But to say we should not study it or be interested in possible impacts is not a good position. We built hundred of hydroelectric dams in this country without considering the impacts because of course clean electricity is completely a good thing. In many cases the destruction to the environment and the way of life for those affected outweighed the benefit and now we are ripping them out. On the Outer Banks we have hardened the beaches and dredged inlets to save the beaches. These turned out to cause the oppositte result and are the cause of massive destruction to the island.

Quote:
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.



Quote:
If you dislike windfarms for other reasons then that is a different discussion


What? Who said that? I got a whole lot of money invested in wind turbines. No one in this thread has suggested that we should be against wind farms or the proposed ones off of the NC coast. Just by saying there could be an affect on the local weather does not make you against something. Somehow by wondering about potential effects you "should get a job in a coal mine", "start a meth addiction", or you are a "hypocrite." There are a lot of dedicated environmentalists who are interested in studyin and understanding of wind farm effects. I do not see how that makes them hypocritical.

Quote:
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.


That is incorrect. Wake turbulence, wing tip voritices, and contrails can and do occur at low speeds. See the below image

Image

That aircraft has a takeoff speed around 140-150 mph. The wingtip velocity of a large turbine seems to be around 120 - 130mph. The aircraft wingtips are creating the same contrails as the image of the Horns Rev 2 wind farm only on a massive scale. That wind farm is 12 square miles.

I threw out some numbers on the Horns Rev 2 study, not to say I was in dire concern of a possible decrease in wind speed. Only to show that there are measureable downstream effects of wind farm. This is a huge mass of disturbed air with pressure, temperature, momentum, velocity, density, and moisture changes. Also there is an effect on the water caused by upwelling and temperature change. The downstream effects could be bigger than a simple slowing of airspeed

Quote:
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.


http://www.sciencedaily.com/videos/2005/1012-wind_farms_impacting_weather.htm

http://www.atmos-chem-phys-discuss.net/9/2917/2009/acpd-9-2917-2009.pdf

So bottom line there are some real possibilities, that we are only just understanding, and are worth understanding and considering. Does not mean that you should boycott wind farms, club a baby seal, take meth, work in a coal mine, be a hypocrite, lose sleep worried that kiting will be canceled on the OBX, or lose sleep hoping for a newly formed thermal or surf spot. But denying the possibility based on a "gut feel", is like those who deny climate change simply because they do not believe that man could possibly alter the environment on a grand scale. Assuming is has to be all good simply because it is alternative energy is dangerous as shown with hydroelectric. Everything has tradeoffs, but you should at least understand them going in.


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 6:28 pm 
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Well done SSK, a picture tells a thousand words


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 Post subject: Re: Offshore wind farm may wreck NE winds for the Outer Bank
PostPosted: Fri Jan 04, 2013 6:45 pm 
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WOW SSK thanks so much for your input.
These things are popping up all over our local spots. Whenever I see them I always wonder if anyone really knows what the long term effects of them are on the environment. There is a lot of opposition to them here, mostly people who are concerned with effects on health and property value.Ironic that the one thing we are doing to try and protect the environment "may" actually be equally as bad for it or worse...
...for those of you who don't read... I said "may" not "will" or "is"


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