Bat-killing blades

A US group called the Bats and Wind Energy Cooperative (BWEC) has begun testing the effect of stopping wind turbines during low wind conditions to avoid killing bats.

The study, the first of its kind in the US, will also determine the reduction, due to shutdowns, in the amount of electricity generated.

BWEC was formed in 2004 by Bat Conservation International (BCI), the American Wind Energy Association (AWEA), US Fish and Wildlife Service, and the US Department of Energy’s National Renewable Energy Laboratory (NREL) to learn why bats are being killed at wind energy facilities and how deaths can be prevented.

Iberdrola Renewables offered its Casselman Wind Power Project site in Pennsylvania for the research and is also providing funding for it. 'We recognise there is an impact on bats that requires scientific study,' said Andrew Linehan, director of permitting for the company.

Since 2004, BWEC scientists have learned much about patterns of bat deaths and the relationships between weather and interactions of bats with wind turbines. Key findings suggest bat fatalities occur primarily on low wind nights when turbines are operating at low power, but in some cases the turbine blades are rotating at or near their maximum speed.

Scientists hypothesise that shutting down turbines in times of low wind during periods of high bat activity could significantly reduce fatalities, with modest reduction in power production and associated economic impact on project operations.

Bat kills have been high at many facilities, especially in the eastern US, though it remains unclear why some bat species seem susceptible to collisions with the turbines and changes in atmospheric pressure immediately downwind the turbine blades.