Study

Bat monitoring studies at the Fowler Ridge Wind Energy Facility, Benton County, Indiana, April 1 – October 31, 2011

  • Published source details Good R.E., Erickson W., Merrill A., Simon S., Murray K., Bay K. & Fritchman C. (2012) Bat monitoring studies at the Fowler Ridge Wind Energy Facility, Benton County, Indiana, April 1 – October 31, 2011. Western EcoSystems Technology, Inc. (WEST) report.

Actions

This study is summarised as evidence for the following.

Action Category

Prevent turbine blades from turning at low wind speeds ('feathering')

Action Link
Bat Conservation

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

Action Link
Bat Conservation
  1. Prevent turbine blades from turning at low wind speeds ('feathering')

    A replicated, randomized, controlled study in 2011 at a wind farm in an agricultural area of Indiana, USA (Good et al 2012) found that preventing turbine blades from turning at low wind speeds (‘feathering’), and feathering along with increasing the speed at which turbines become operational (‘cut-in speed’), resulted in fewer bat fatalities than at conventional control turbines. Total bat fatalities were 36% lower when turbine blades were feathered below the conventional cut-in speed (66 fatalities) compared to control turbines without feathering (105 fatalities). Total bat fatalities were 59% and 75% lower when blades were feathered and cut-in speeds increased to 4.5 and 5.5 m/s respectively (42 and 25 fatalities). Differences in total bat fatalities between treatments were significant. Seven bat species were found, although 81% of bat carcasses were eastern red bats Lasiurus borealis and hoary bats Lasiurus cinereus (see original report for data). Three treatments (turbine blades feathered below cut-in speeds of 3.5, 4.5 and 5.5 m/s) were each randomly assigned to a group of 42 turbines. Two control groups of nine and 42 turbines were left unaltered (blades rotated freely below cut-in speed of 3.5 m/s). Treatments were rotated between turbine groups nightly in July–October 2011. Carcass searches were conducted every 1–2 days along transects in circular plots (80-m radius) around each of the 177 turbines.

    (Summarised by: Anna Berthinussen)

  2. Increase the wind speed at which turbines become operational (‘cut-in speed’)

    A replicated, randomized, controlled study in 2011 at a wind farm in an agricultural area of Indiana, USA (Good et al 2012; same site as Good et al 2011) found that increasing the wind speed at which turbines become operational (‘cut-in speed’), along with preventing turbine blades from turning at low wind speeds (‘feathering’), resulted in fewer bat fatalities compared to conventional turbines. Total bat fatalities were 59% and 75% lower (42 and 25 fatalities) when cut-in speeds were increased to 4.5 and 5.5 m/s respectively, and blades were feathered below these speeds, compared to conventional control turbines (105 fatalities). Differences in total fatalities between the two treatments were significant. Six bat species were found, although 80% of bat carcasses were eastern red bats Lasiurus borealis and hoary bats Lasiurus cinereus (see original report for data). Two treatments (cut-in speeds increased to 4.5 and 5.5 m/s and blades feathered below these speeds) were each assigned to a group of 42 turbines. Two control groups of nine and 42 turbines were left unaltered (blades rotated freely below cut-in speed of 3.5 m/s). Treatments were rotated between turbine groups nightly in July–October 2011. Carcass searches were conducted every 1–2 days along transects in circular plots (80-m radius) around each of the 135 turbines.

    (Summarised by: Anna Berthinussen)

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