Researchers Seek to Reduce Bat Deaths from Wind Turbines

November 5, 2008

The Bats and Wind Energy Cooperative (BWEC) announced in mid-October that it has begun testing a procedure to stop wind turbines during low-wind conditions to avoid killing bats. Bat deaths from wind turbines are a relatively recently discovered phenomenon, and although they are not fully understood, recent studies have suggested that most bat deaths occur on low-wind nights when the turbines are producing low amounts of power, but may be rotating near their maximum speed. Based on that finding, Iberdrola Renewables has agreed to shut down the turbines at its Casselman Wind Power Project in Pennsylvania during low-wind conditions. The experiment will provide information on how the new operating procedure will effect both bat deaths and power production at the 34.5-megawatt facility, which is located southeast of Pittsburgh. The BWEC is a unique alliance of Bat Conservation International, the American Wind Energy Association (AWEA), the U.S. Fish and Wildlife Service (FWS), and DOE's National Renewable Energy Laboratory. See the BWEC press release (PDF 90 KB) and Web site. Download Adobe Reader.

Iberdrola Renewables isn't just helping out the BWEC experiment; the company has also committed to responsibly developing wind power while addressing wildlife concerns. Last week, Iberdrola released a company-wide Avian and Bat Protection Plan, modeled on a similar plan to address the impacts of power lines on birds. Preparing in consultation with the FWS, the plan establishes a process for contact with government agencies and non-governmental organizations early in the site assessment stage of new wind power projects. It also includes policies for pre- and post-construction monitoring and other measures to reduce and mitigate bird and bat deaths. See the Iberdrola Renewables press release and plan (PDF 2.9 MB).

While bat deaths remain poorly understood, a recent study by the University of Calgary suggests that it's not an actual impact with wind blades that kills bats, but rather the effects of the pressure drop caused by the moving blades. Large numbers of migratory bats are being killed by some of the turbines in southern Alberta's wind facilities, and a study of the dead bats at one of those sites found that the bats suffered severe injuries to their respiratory systems consistent with a sudden drop in air pressure, a condition known as barotrauma. While only half of the dead bats showed signs of being struck by wind turbine blades, 90% had injuries consistent with barotrauma. The study was published in the August 26 online edition of Current Biology. See the University of Calgary press release.