Looking at Iberdrola's Casselman Wind Power Project in Pennsylvania from July to October of last year (during bat migration season in the area), researchers found that 32 bats were killed. Of those, 21 were killed when the turbines were left on during the night and 11 on nights where the turbines were turned off:
Nighttime Shut Down Decreases Productivity 1%
In terms of loss in productivity, over the year the wind farm would see about a 1% decline—translating to some 1000 megawatt-hours less electricity being produced. That works out to be about $90,000 per year at current electricity rates.
Changes in Air Pressure Main Bat Threat
It's not really getting hit by the blades that is the issue with bat deaths and wind turbines: In a study done at the University of Calgary, 90% of bats killed by wind turbines were found to have been killed by internal bleeding caused by sudden drops in pressure caused by the blades.
Bat Deaths Could be Bigger Problem Than This One Study Indicates Though only 32 bats were killed at this particular wind farm during the study period, the original article cites figures from Bat Conservation International that another recent study has shown that about 2,000 bats were killed at wind farms in Pennsylvania and West Virginia over a six week period.
Here's the original report: Effectiveness of Changing Wind Turbine Cut-in Speed to Reduce Bat Fatalities at Wind Facilities (PDF)
photo: -5m via flickr
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