Damned if you do....

No physical process is free of effects. No physical process is free of consequences or costs. And that is as true of renewable energy as it is of anything else, as an item in New Scientist reminds us.

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 their virtual wind farm in the Great Plains and used meteorological data from Oklahoma for the model.

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.

In fact, at night the ground temperature was around 2^oC. warmer than it would otherwise be and the 24-hour average was about 0.7^oC. higher, plus an increase of about 17% is average ground-level wind speed.

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

Moreover, the findings are backed by real observations of a wind farm in California. Neil Kelley, a meteorologist at the National Renewable Energy Laboratory in Golden, Colorado, said

"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."

It might be possible to modify the turbines to reduce their effect, Baidya Roy says, but while reducing the environmental impact, it would not eliminate it. "There is a price to pay for all kinds of consumption, including renewable energy."

There are no perfect choices, only better ones. Renewables are a better choice, but they do have costs with which we have to be prepared to deal. An even better choice is conservation, simply doing with less, but even that has economic costs in a society built around consumption where people are able to provide for themselves and their families precisely because of the resources other people consume. That doesn't mean those costs are not less than other costs or that they are not worth paying. It means only that we can't forget they are there.