Monday, July 11, 2005

Wind-turbine based bird deaths found to be less than thought likely

While wind power is getting economically feasible, it's facing one repetitive criticism. That the turbines kill lots of birds.

I saw a study once describing this. The idea is based on the wind farm in California's Altamont Pass. The experience there is that those turbines do kill lots of birds, especially rare raptors. However further study showed several fixable problems with the Altamont Pass wind farm, and the solutions have been put into use in newer wind farms. Why the solutions haven't also been put into use in the Altamont Pass is beyond me.

Basically the problem was twofold: 1) the turbines in Altamont Pass are located primarily on ridgelines, a place where the birds frequently fly, placing them in more frequent proximity to the turbines; 2) the turbines in Altamont Pass are small, with fast moving blades, and the tower design also gives many places for birds to roost, all of which contributes to more frequent contact between birds and turbine blades.

Wind turbines not so deadly for birds -Dutch study (Tue Jul 5,12:00 PM ET, AMSTERDAM (Reuters))

In The Netherlands and other parts of Europe they've been installing massive wind turbines. The blades on these are often 100 meters in diameter, and each tower produces around 1 megawatt of electricity.

And, their experience with bird deaths is that they're a lot less frequent than expected. e.g.

The new study suggests the Netherlands' 1,700 wind turbines kill about 50,000 birds a year. About 2 million birds perish each year on Dutch roads, it said.

This was predictable from the study I read of the Altamont Pass. With the larger turbines, the blades actually move a lot slower, making it easy for birds to dodge the blades. Further, when the tower makers pay attention, they make sure there's no ledges for birds to sit on, making it less likely the birds will stay around the towers in the first place. Finally, siting of the towers makes a difference, simply by putting the towers in places the birds don't stay in.

Several years ago Home Power Magazine published this summary of research into bird death around wind turbines. The article concludes the issue is overblown - for example, the recorded bird deaths in Altamont Pass are small compared to the birds killed in collisions with buildings or radio towers and the like.

Further the rates of bird death at other wind farms in California are a fraction of the rates at Altamont Pass, so there must be something special about Altamont Pass. Namely, the population growth in the San Francisco Bay Area is causing an out-migration of wildlife, and the Altamont Pass area is pretty open (other than the wind turbines) giving refuge to the out-migrating wildlife.


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