Bats, birds and turbines

Sailing out from Copenhagen, on the ferry bound for Oslo, we pass by a long line of wind turbines standing tall out in the water.

As "green" as I am, I have never liked the looks of the modern three-bladed wind turbine. There is something about them that bothers me. When I watch them turn, I find that there is no evenness to their rotation; visually, it looks to me like three Barbie doll legs, one "falling" down after another. (I have rarely seen these things moving so fast you can't make out the individual blades.)

Apparently, these turbines are not as environmentally friendly as we are led to believe. In the county of Rogaland in Norway, one array is noise polluting a nearby neighborhood. I have read that the maximum three blades on modern turbines is chosen because it makes a minimum of noise. Still, anything that big, rotating in the wind, will make some sound.

Another array was put in a white-tailed eagle breeding area two counties north of where I live, in Smøla. Within months after starting up, more than a half dozen birds—a vulnerable species—had died from colliding with the wind turbines. However, it turns out that birds have a tendency to crash into man-made structures, anyway. It's not just wind turbines, and I saw myself a sparrow (most likely) fly right into the side of our office building one day. I have no idea if the poor thing made it, but since it flew straight into concrete, I doubt it. So, the real issue with the Smøla installation is that man-made structures are placed in a known breeding area for several vulnerable bird species, not that the structures are wind turbines. (A similar issue applies to the Altamont Pass energy farm in California.)

It turns out that the slower moving blades I've observed are due to newer turbine design, with larger blades. This slower movement helps birds detect the blades and avoid them.

Sadly, this doesn't alleviate another problem regarding flying animals. Bats are still crashing into wind turbines—or rather, next to them. Echo location means bats will not collide with the turbines themselves so researchers were baffled by bat deaths around turbines. The likely explanation is that because bat lungs are different from birds (i.e. bats have mammalian lungs—a flexible balloon-like structure which can collapse or over-expand), bats are more vulnerable to a sudden change in air pressure. There is a marked difference in air pressure in front of the turbine blades and behind them - like the difference in air speed flow above and below an airplane wing—and this is what affects bats. Bats are vital to insect control and therefore agriculture, and like birds, many bats are migratory. Bat death in one area could adversely affect all ecosystems along the bat's migration route.

I am sad that this is happening to bats. I like them. I have never found them creepy. Rather, this little flying mammal fascinates me. Happily, people are trying to solve the problem.

I started writing about wind turbines because I think they are creepy-looking, but I now have no reason to believe that they represent an energy source that is harmful to us or wildlife—not if we are careful about placement and try to solve the problems that some flying creatures can have with them.


Footnotes:

1. How Stuff Works' article on birds and turbines
2. One of several reports from Smøla wind park on birds
3. Bat death due to barotrauma