Altering turbine speed reduces bat mortality at wind-energy facilities

  • Published source details Arnett E.B., Huso M.M.P., Schirmacher M.R. & Hayes J.P. (2010) Altering turbine speed reduces bat mortality at wind-energy facilities. Frontiers in Ecology and the Environment, 9, 209-214


This study is summarised as evidence for the following.

Action Category

Increase the wind speed at which turbines become operational (‘cut-in speed’) to reduce bat fatalities

Action Link
Bat Conservation
  1. Increase the wind speed at which turbines become operational (‘cut-in speed’) to reduce bat fatalities

    A randomized, replicated, controlled study in 2008–2009 at a wind farm in a forested area of Pennsylvania, USA (Arnett et al. 2010) found that increasing the wind speed at wind turbines become operational (‘cut-in speed’) resulted in fewer bat fatalities than at conventional wind turbines. Average bat fatalities were lower at turbines with increased cut-in speeds (5 m/s: 0.3–0.7 bats/turbine; 6.5 m/s: 0.5–0.6 bats/turbine) than at turbines with conventional cut-in speeds (3.5 m/s: 2 bats/turbine). In July–October 2008 and 2009, two treatments (cut-in speed increased to 5 m/s or 6m/s) and one control (cut-in speed of 3.5 m/s) were randomly assigned to three groups of four turbines for 25 nights/treatment. Daily carcass searches were conducted along transects in 120 x 126 m plots centred on each of 12 turbines. If applied to the entire wind farm (23 turbines), annual power output losses were projected to be 0.3% with cut-in speeds increased to 5 m/s, and 1% with cut-in speeds increased to 6.5 m/s.

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