While wind energy has shown strong potential as a large-scale, emission-free energy source, bat and bird collisions at wind turbines result in thousands of fatalities annually. Migratory bats, such as the hoary bat, are especially at risk for collision with wind turbines as they fly their routes in the forested ridges of the eastern U.S. This loss not only impacts the immediate area, but is also detrimental to ecosystem health nationwidethat is, bats help with pest management, pollination and the dispersal of numerous plant seeds.
Since turbine towers and non-spinning turbine blades do not kill bats, some scientists have proposed shutting off or reducing the usage of wind turbines during peak periods of migration in the late summer and early fall months when bat activity and fatalities are highest.
In a study to be published online November 1, 2010 in Frontiers in Ecology and the Environment (e-View), a journal of the Ecological Society of America, Edward Arnett from Bat Conservation International in Austin, Texas and colleagues examined the effects of changes in wind turbine speed on bat mortality during the low-wind months of late summer and early fall.
Currently, most wind turbines in the U.S. are programmed to begin rotating and producing power once wind speed has reached approximately 8 to 9 miles per hour (mph)the wind speed at which turbines begin generating electricity to the power grid is known as the cut-in speed. Wind turbines with a low cut-in speed run more frequently than those set at higher cut-in speeds since they begin rotating at lower wind speeds.
The researchers found that, by raising the cut-in speed to roughly 11 mph, bat fatalities were reduced by at least 44 percent, and by as much as 93 percent, with an annual power loss of less than one percent. That is, programming the turbines to rotate only when the wind reached approximately 11 mph or higher caused the turbines to rotate less frequentl
|Contact: Katie Kline|
Ecological Society of America