Bat fatalities have long posed difficulties for wind farm operators, and have often been the subject of criticism from environmental and wildlife groups. In fact, a single bat fatality caused Duke Energy to halt operation of its North Allegheny wind facility in Pennsylvania last September.
But now, researchers at the U.S. Department of Agriculture's (USDA) Forest Service have developed a new technology to help wind farm operators tackle this issue. The interactive tool, created by ecologist Ted Weller and statistician Jim Baldwin from the USDA Forest Service's Pacific Southwest Research Station, is designed to help wind energy project operators make informed decisions on efficient ways to reduce wind farms' impacts on migratory bats.
The tool allows users to visualize how changes in date and weather conditions affect the probability of bat presence.
‘Increasing the wind speed at which turbines begin to spin and produce energy to the grid has proven to be an effective way to reduce bat fatalities; however, bat activity levels depend on more than just wind speed,’ says Weller, who led the research. "Our work demonstrates the use of a decision-making tool that could protect bats when fatality risk is highest while maximizing energy production on nights with a low chance of fatalities."
Weller and his research team used devices that detected the bats' echolocation calls, and then linked the presence of bats to the weather conditions measured on-site on a given night. They found that echolocation detectors placed at 22 meters and 52 meters above ground were more effective at characterizing migratory bat activity than those located closer to the ground.
Moreover, multiple echolocation detectors were required to accurately characterize bat activity at the facility. The researchers then built models to predict the presence of bats based on date and weather variables.
"Properly deployed echolocation monitoring can be an effective way to predict bat activity and, presumably, fatalities at wind energy facilities," Weller explains. "These days, pre-construction echolocation monitoring is as common as meteorological monitoring at wind energy facilities, so the basic building blocks for these models are available at most proposed sites."
The researchers conducted the study at a wind energy facility in the San Gorgonio Pass Wind Resource Area near Palm Springs, Calif., and was a collaborative effort among government, industry and a nongovernmental organization. Other participants included PSW, Iberdrola Renewables, and the Bats and Wind Energy Cooperative. The primary funding was provided by the California Energy Commission Public Interest Energy Research program.
More findings from the study can be found here.