Bat
Conservation International News
Efforts
to reduce the alarming number of bats that are being killed
at wind-energy facilities took a big step forward when
scientists demonstrated that bat-mortality falls sharply
when wind turbines are temporarily stopped during low-wind
conditions during the night.
The research was conducted by the BCI-led Bats & Wind
Energy Cooperative at partner Iberdrola Renewable’s
Casselman Wind Power Project in Pennsylvania. BWEC
Coordinator Ed Arnett, BCI’s co-director of programs, said
the study found that bat kills were reduced an average of
73 percent when turbines were left off-line until wind
speed reached between 11.2 and 14.5 miles per hour (5 - 6.5
meters/second). That’s compared with mortality at turbines
that remained fully operational, starting up at a wind
speed of 7.8 mph (3.5 m/s).
The low-wind mitigation is recommended at night (when bats
are active) and during the bat-migration season from late
July through mid-October. The research found that
temporarily stopping all Casselman turbines at low-wind
periods during these time frames would have resulted in the
lost electricity output of just 0.3 to 1.0 percent of total
annual power production.
This first U.S. study of reduced fatalities and economic
costs of low-wind mitigation was funded by the U.S. Fish
and Wildlife Service, BCI, the National Renewable Energy
Lab and Iberdrola Renewables. It grew out of previous BWEC
research that showed bat kills increased as wind speed
slowed and fatalities were greatest during migration
season. The Fish and Wildlife Service is funding the second
year of this study at Casselman in 2009.
These results could prove critically important by providing
developers of wind-power projects in areas of high risk for
bats with reliable scientific data for evaluating a
documented option for reducing bat mortality.
The risk is great, with tens of thousands of bats dying at
wind farms each year, and the number of turbines increasing
rapidly in the United States and around the world. The
industry reports that installed wind-energy capacity now
exceeds 28,000 megawatts, up from about 16,000 just
eighteen months ago.
BWEC, a unique alliance of government, industry and
conservation groups, was founded in 2004 by BCI, the
American Wind Energy Association, the U.S. Fish and
Wildlife Service and the U.S. Department of Energy’s
National Renewable Energy Laboratory to learn why so many
bats are being killed at wind-energy facilities and how the
deaths can be prevented.