Wind turbine adjustments reduce bat deaths

A study at the Casselman wind park in Pennsylvania found that raising the wind speed threshold for turbine activation significantly reduced bat mortality. Researchers adjusted the start speed on some turbines, which kept the blades still during low wind conditions, leading to a drop in bat deaths by up to 93 percent.

Study methods and findings

The research, published in 2010 in Frontiers in Ecology and the Environment, monitored 12 turbines over 25 nights in 2008 and 2009. Bats were found dead near normally operating turbines at rates 5.4 times higher in 2008 and 3.6 times higher in 2009 compared to turbines that were stopped during low wind periods.

Energy production impact

Despite the adjustments, the wind park's electricity production loss remained below 1 percent, even when the threshold was raised to 14.5 mph. This is because low wind conditions generate little electricity, so the overall impact on power output was minimal.

Broader research and recommendations

A 2013 synthesis of 10 studies found that increasing the start threshold by 1.5 meters per second reduced bat deaths by at least 50 percent. A 2024 North American review estimated a 33 percent reduction in bat mortality per meter per second of threshold increase. The Casselman study authors suggested applying these adjustments in areas where bat conservation is a priority.