A synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America. A report submitted to the National Renewable Energy Laboratory
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Published source details
Arnett E.B., Johnson G.D., Erickson W.P. & Hein C.D. (2013) A synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America. A report submitted to the National Renewable Energy Laboratory. Bat Conservation International report.
Published source details Arnett E.B., Johnson G.D., Erickson W.P. & Hein C.D. (2013) A synthesis of operational mitigation studies to reduce bat fatalities at wind energy facilities in North America. A report submitted to the National Renewable Energy Laboratory. Bat Conservation International report.
Actions
This study is summarised as evidence for the following.
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Increase the wind speed at which turbines become operational (‘cut-in speed’) Action Link |
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Increase the wind speed at which turbines become operational (‘cut-in speed’) Action Link |
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Increase the wind speed at which turbines become operational (‘cut-in speed’)
A replicated, randomized, controlled study in 2010 at a wind energy facility in an agricultural area in the Midwest region, USA (Arnett et al 2013) found that increasing the wind speed at which turbines become operational (‘cut-in speed’) resulted in fewer bat fatalities than at conventional turbines. Bat fatalities were estimated to be 47% and 72% lower at turbines with cut-in speeds increased to 4.5 and 5.5 m/s respectively compared to control turbines with conventional cut-in speeds (data reported as statistical model results). A total of 25 and 14 bat carcasses were found at turbines with cut-in speeds of 4.5 and 5.5 m/s respectively, whereas 53 carcasses were found at control turbines. Two treatments (cut-in speed increased to 4.5 and 5.5 m/s from 1 h before sunset to 1 h after sunrise) and a control (conventional cut-in speed of 3.5 m/s) were each randomly assigned to four turbines. Treatments were rotated weekly between turbines over nine weeks in August–October 2010. Daily carcass searches were conducted in plots (80 x 80 m) centred on each of the 12 turbines.
(Summarised by: Anna Berthinussen)
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Increase the wind speed at which turbines become operational (‘cut-in speed’)
A replicated, randomized, controlled study in 2012 at a wind energy facility in a desert scrub area in the Pacific Southwest region, USA (Arnett et al 2013) found that increasing the wind speed at which turbines become operational (‘cut-in speed’) did not result in fewer bat fatalities compared to conventional turbines. Total numbers of bat fatalities were reported to be 20–38% lower for four different treatments with increased cut-in speeds than at conventional turbines, but none of the differences were significant. The authors report that sample sizes were small (numbers not reported). Three bat species were found, although 74% of bat carcasses were Brazilian free-tailed bats Tadarida brasiliensis (see original paper for details). Four treatments (cut-in speed increased to 4, 5 or 6 m/s for 4 h after sunset, or cut-in speed increased to 5 m/s all night) and a control (conventional cut-in speed of 3 m/s) were randomly rotated each night between four groups of 10 turbines in August–September 2012. Daily carcass searches were conducted along transects in plots (126 x 126 m) centred on each of the 40 turbines.
(Summarised by: Anna Berthinussen)
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