Testing how bats and wind energy can coexist


By Kristen Pope

Wind turbines. Photo by Michael Whitby

In a field of spinning wind turbines, a hoary bat lets out an echolocation call in search of an insect to eat. An acoustic monitoring system detects this call and the turbine blades begin to slow, lessening their speed until they are just barely rotating. This technology, called Turbine Integrated Mortality Reduction (TIMR), aims to reduce bat deaths near wind turbines by detecting nearby bats and “feathering” the turbine blades, significantly slowing them down. This is one technique Bat Conservation International (BCI) researchers are studying to help reduce bat fatalities near wind turbines.

Wind energy is a valuable tool in the fight against climate change, but wind turbines can cause significant numbers of bat fatalities. BCI Chief Scientist Dr. Winifred Frick co-authored a paper in 2021 showing how hoary bats and other species are at risk due to wind energy development, and BCI researchers are working to find solutions.

Over the summer, BCI researchers led by Michael Whitby, Bats and Wind Program Director, conducted fieldwork in Iowa to test four potential ways to reduce bat mortality by wind turbines. Now, the team is analyzing the data to see which methods work best.

A team surveys for bat carcasses outside a wind energy facility Photo by Michael Whitby

Vestus Bat Protection System (VBPS) uses an algorithm to feather (slow) the blades at certain times based on parameters like weather and previously recorded bat activity. This is called “curtailment” or “operational minimization” and designed to promote both wind energy and bat conservation.

“We’re looking to optimize when curtailment is put into place,” Whitby says. “We’re trying to essentially produce energy at all opportunities except when bats are at risk.”

The researchers are comparing TIMR and VBPS with a wind-based curtailment regiment, which is currently the conservation standard, that involves feathering when wind is below 5 meters per second. With funding from the Department of Energy, researchers will compare these three methods with normal operations and the manufacturer’s cutting speed.

A trained dog working near windmills. Photo by Rogue Detection Teams

“We’re comparing the fatality rates and energy production among these four different data sets to essentially see which can produce the most energy and cause the least number of bat fatalities,” Whitby says.

To estimate mortality, the teams work with Rogue Detection Teams, which have specially trained dog-and-handler teams who work together to find bat carcasses [learn more about these dog and handlers teams in the October 2022 issue of Bats Magazine]. Dogs are able to detect bat carcasses far more efficiently than humans.

Researchers are also using thermal video monitoring to learn more about bat behavior near wind turbines. Funded by the National Renewable Energy Lab, this project involves using 3D thermal video to try to learn more about why bats are attracted to wind turbines. They are analyzing a number of potential hypotheses, including the leading “roost tree hypothesis,” which suggests bats may confuse turbines—tall structures out alone on the landscape—for roost trees or mating locations. They are wondering if a wind turbine’s patterns might be similar to the wind patterns created by a tree. Using 3D thermal video, they analyzed the area behind the turbine. They positioned three sets of two thermal cameras (for a total of six cameras) at the turbines to create the 3D effect and look at the “wake area” behind the turbine.

Hoary bat in flight. Photo by Michael Durham/Minden Pictures

“We want to look at how bats interact with that space,” Whitby says. The team conducts similar analyses near isolated trees so they can compare them. By coupling video and audio at these sites, they can also learn more about which bat species use these areas.

As Whitby’s team and other researchers work to analyze the data and learn more about how wind energy and bats can have a harmonious existence, he points out the importance of both bat conservation and clean energy.

“There’s potential for rapid and severe population declines of species like hoary bats from the mortality observed at  wind energy facilities in North America,” Whitby says. “We have to balance reducing the direct threat of wind energy to vulnerable bat species with support for renewable energy in the global fight against climate change. The goal of our bats and wind program is to find solutions that achieve that balance.”