One of the first studies by Bat Conservation International and the Bats and Wind Energy Cooperative (BWEC) provided strong circumstantial evidence of a potentially powerful and low-cost strategy for reducing bat fatalities at wind-energy facilities.
The 2004 research at the Mountaineer, West Virginia, and Meyersdale, Pennsylvania, wind facilities (operated by key partner Florida Power and Light Energy) found that, of the 64 wind turbines studied, only one produced no bat fatalities. It was out of service, with its blades “feathered,” or left to rotate slowly. This led scientists urged experiments to test the impact and costs of simply not attempting to power up blade rotation until wind speeds reach profitable levels (see BATS Fall 2005).
Those tests had to wait until 2008, when BCI, under the auspices of BWEC, a BCI-led alliance of key federal agencies, wind-industry groups, academia and international experts, initiated the first U.S.-based operational minimization study at Iberdrola Renewables’ Casselman Wind Power Project in Pennsylvania.
We investigated the effects of raising the cut-in speed (the wind speed at which the spinning turbine blades begin to generate electricity) by 1.5 to 3.0 meters per second (4.9 to 9.8 feet per second) above the manufacturer’s preset speed. The result was an impressive 44 to 93 percent reduction in bat fatalities, with only an estimated annual loss of energy production of just 0.3 to 1 percent.
BCI and other researchers have since worked with additional industry partners, including BP Wind Energy, EDP Renewables, Exelon Energy, First Wind and Invenergy, to produce and disseminate results from similar studies. A consistent finding shows that by changing turbine operations during a relatively narrow period of time (the late-summer and fall migration season) and under specific conditions (when wind speeds are low), the numbers of bats dying at wind turbines can be significantly reduced at relatively little cost.
There is even an opportunity to reduce bat fatalities with no loss in power. By simply feathering the blades (pitching them parallel to the wind so they are moving slowly) below that preset speed, bat fatalities can be reduced by an average of 35 percent.
Regrettably, this strategy – a seemingly win-win solution – has yet to be voluntarily adopted by the wind industry.
Of the nearly 905 wind-energy facilities across the United States, only a handful are implementing any form of operational minimization to reduce bat fatalities. Beech Ridge Wind Energy Project (West Virginia), Buckeye Wind Power Project (Ohio), Fowler Ridge Wind Farm (Indiana) and Kawailoa Wind Power (Hawaii) have finalized Habitat Conservation Plans (HCPs) with the U.S. Fish and Wildlife Service to receive “Incidental Take” Permits to protect themselves in case a federally endangered Indiana bat (Myotis sodalis) or Hawaiian hoary bat (Lasiurus cinereus semotus) is killed by their turbines.
In addition, a region-wide HCP is being developed for the Midwest that would provide consistent minimization and mitigation guidelines for participating companies. And with the possible Endangered listing of the northern long-eared myotis (M. septentrionalis), additional HCPs are likely.
While BCI applauds these efforts and encourages all wind companies to work with state and federal agencies, we believe the wind-energy industry has an obligation to pursue scientifically proven minimization strategies to reduce adverse wildlife impacts before they can be considered environmentally “green.”
We support the immediate implementation of feathering blades below the preset cut-in speed and strongly encourage wind-energy facilities to raise turbine cut-in speeds. Meanwhile, we will continue to work closely with our partners to fine-tune current operational minimization recommendations and to develop new strategies to reduce bat fatalities.
By incorporating new data on bat behavior around wind turbines and on activity patterns associated with other weather variables, we can better determine exactly when to alter turbine operations – resulting in a more ecologically sound and economically viable strategy.
BCI also is working with partners to develop a new generation of ultrasonic acoustic deterrents that are designed to steer bats away from turbines. Initial results were promising, and we have redesigned the existing deterrent and improved sound generation and weatherization. Further testing is needed, however, and a commercially available acoustic deterrent is still years away.
Wind-energy development will no doubt continue to expand across North America and around the world, and we will need multiple tools to protect bats – while reducing our dependence on carbon-based fuels. We are grateful to our industry partners who have shown real environmental leadership and supported the pursuit of solutions to this complex issue. We now look to the industry to showcase its environmental stewardship and begin implementing the strategies that have been collaboratively developed.