Article: Weather hots up under wind farms

[Guest guest]

Very interesting stuff IMHO ... even the environmentally friendly energy

sources aren't friendly to some aspects of the environment ...

I suppose though, the more we strive to understand it and work on it,

the better we'll get at it

 

*Smile*

Chris (list mom)

 

http://www.alittleolfactory.com

 

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http://www.newscientist.com/news/news.jsp?id=ns99996608

 

 

 

 

 

Weather hots up under wind farms

 

 

10:34 04 November 04

 

 

 

 

Wind farms can change the weather, according to a model of how these

forests of giant turbines interact with the local atmosphere. And the

idea is backed up by observations from real wind farms.

 

Somnath Baidya Roy from Princeton University, and his colleagues

modelled a hypothetical wind farm consisting of a 100 by 100 array of

wind turbines, each 100 metres tall and set 1 kilometre apart.

 

They placed the virtual farm in the Great Plains region of the US, an

area suitable for large wind farms, and modelled the climate using data

from Oklahoma.

 

During the day, the model suggests that wind farms have very little

effect on the climate because the warmth of the sun mixes the lower

layers of the atmosphere. But at night, when the atmosphere is stiller,

the wind turbines have a significant effect.

 

“At hub height the turbine gives an extra input of turbulence to the

wind, which increases the vertical mixing,” explains Baidya Roy. This

brings down to ground level the warm night air and higher wind speeds

that are normally found at 100 metres.

 

At 3 am the average wind speed in Oklahoma is 3.5 metres per second, but

it increased to around 5 m/s in the model wind farm. The model also

suggested that the temperature would increase by around 2°C underneath

the 10,000 turbines. Over the course of a day this averages out to an

increase in ground-level wind speed of around 0.6 m/s and a rise in

temperature of around 0.7°C.

 

 

Heat of the night

 

 

How such a change might affect local wildlife and agriculture is not

clear.

 

The findings are backed by real observations. Neil Kelley, a

meteorologist at the National Renewable Energy Laboratory in Golden,

Colorado, has gathered data from a wind farm in California.

 

“Although the wind farm was more dense and the turbines smaller we still

found that the turbines tended to pull down heat and momentum from

above, particularly during the night-time hours,” he says.

 

Meanwhile, Gustave Corten from the Energy Research Centre in Petten in

the Netherlands is carrying out experiments with a model wind farm

inside a wind tunnel. “I think the study is of much interest and I can

confirm that large wind farms will affect the microclimate,” says

Corten.

 

Baidya Roy says it may be possible to modify the wind turbines so that

their effect on the weather is not so extreme. “If engineers can reduce

turbulence then the turbine would become more efficient and the

environmental impact would be reduced,” he says.

 

But no amount of engineering will change the fact that energy is being

removed from the wind. “People tend to think that renewable energy is

for free, but it isn’t. There is a price to pay for all kinds of

consumption, including renewable energy,” says Baidya Roy.

 

Journal reference: Journal of Geophysical Research Atmospheres (DOI:

10.1029/2004 JD004763).

 

 

 

Kate Ravilious

 

 

 

 

 

 

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