Wind turbines are deadly to bats—maybe even more deadly even than they are to birds. A new paper in Frontiers in Ecology and the Environment showing how the industry might minimize or even eliminate bat mortality at wind turbine sites. Experimenting with small changes in turbine speeds, researchers were able to reduce bat deaths by as much as 93 percent while reducing power generation by only 1 percent or less.
Currently most wind turbines in the US are programmed to begin rotating and producing power once wind speeds reach ~8 to 9 mph—what’s 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.
But by raising the cut-in speed to ~11 mph, bat fatalities were reduced by between 44 percent and 93 percent, with an annual power loss of less than 1 percent. The exeriments were conducted during months with seasonably low wind speeds, so the overall energy loss was marginal when calculated against annual power output.
The researchers monitored 12 of the 23 turbines at the Casselman Wind Project in Somerset County in the Pennsylvania Appalachians and recorded bat fatalities for 25 summer and fall nights in both 2008 and 2009. They analyzed fatalities following nights when the turbines were fully operational and when they were set to 11 mph and 14.5 mph, reporting mortality rates on average 3.6 to 5.4 times higher at the fully functioning turbines compared with higher cut-in speeds.
– from motherjones