Texas may be known for oil, but it is also the nation’s largest producer of wind energy. And while renewable energy is generally a good thing to most people, it’s not great for bats. Those towering wind turbines that harness the wind’s power kill a lot of bats every year.
When you drive by a wind farm out in the countryside, populated with soaring white turbines, their blades slowly spinning, it’s a bit of an illusion. Texas Christian University biologist Amanda Hale says those blades may look like they’re lazily twirling along, but the tip of a 120-foot blade is moving fast, creating a kill zone.
“Those blade tips, at wind speeds at which bats will be flying, are well over 150 to 200 miles an hour,” says Hale, who is leading a team trying to find ways to keep bats from being killed by turbines. “And so as they’re echo-locating and they’re flying, there’s nothing there. And then bam, the blade comes and kills them.”
Now, bats may give you the creeps. The winged mammals have gotten a bad wrap -- Dracula and all that – but Hale says they play a big role in the eco system. For one, the same agricultural pests that farmers battle are dinner for bats.
“They also are good at keeping down mosquito populations and so having bats in our communities is probably a really good thing,” she says.
Exactly how many flying bats fall victim to wind turbines is a mystery, Hale says. Maybe a half million every year in the US. Maybe more. Researchers just don’t know, but more wind turbines are built every year and so the risk is growing.
“I think the consensus is that we know it’s a problem, but we don’t know how much of a problem, and that’s why there’s such a push right now for technologies to reduce fatalities while we figure out how many bats there are,” Hale says.
To create those technologies, though, you have to understand why bats are drawn to turbines, and migratory bats are notoriously hard to study. One theory is that they think they’re trees. Another idea: The light colored surfaces attract bugs, which makes wind farms attractive to hungry bats. Hale’s intervention comes from watching the way bats interact with the turbines’. Essentially, she thinks bats are confusing the smooth surface of the turbine for water.
“These migrating bats are in unknown territory, they come into this tower for whatever brings them there, and now their echo-location information is telling them it’s water,” Hale says. “We think they’ll stay in that risk zone, that rotor-swept zone, longer than they would otherwise.”
Hale’s team is testing that theory. They capture neighborhood bats and put them in a huge mesh-enclosed area inside of a retro-fitted white barn tucked away in a corner of the TCU campus in Fort Worth. The building looks more like a warehouse than a cutting-edge bat research facility. But that’s what it is.
The team watch the bats for four to seven days before releasing them. At night, they use high speed cameras to see how their bats interact with different surfaces.
“The evidence is accumulating that how they’re approaching these smooth surfaces is not different than how they’re approaching water,” Hale says. “And they’re coming across and then it’s not water and sometimes they seem to get a little confused and do sort of a belly bounce on the surface, but they’re certainly touching the surface with their face.”
Hale’s idea to help bats survive around turbines is really pretty simple: put a textured coating on the surface that’ll make the turbines less attractive to the bats. They key is to find the right texture so that bats don’t confuse the surface for tree bark, and to make sure the treatment is durable but not overly expensive.
“What we’re going for is something that bats show little interest in but that can last the lifetime of a turbine,” Hale says. “Right now, when you see these big utility scale turbines built, those have the lifetime of 20 or 30 years.”
Hale’s research will likely get its biggest test next summer at a wind farm near the Oklahoma border. Her team will apply the textured surface to some of the turbines, and leave the others smooth. Then they’ll see if texture-treated turbines mean more bats live to fly another day.