Reduction of the collision risk of bats on onshore wind turbines (RENEBAT II): Results of a research project

  • Published source details Behr O., Brinkmann R., Korner-Nievergelt F., Nagy M., Niermann I., Reich M. & Simon R. (2016) Reduktion des Kollisionsrisikos von Fledermäusen an Onshore-Windenergieanlagen (RENEBAT II): Ergebnisse eines Forschungsvorhabens. Institut für Umweltplanung, Hannover report, Umwelt und Raum Bd. 7, 369pp.


This study is summarised as evidence for the following.

Action Category

Automatically reduce turbine blade rotation when bat activity is high

Action Link
Bat Conservation
  1. Automatically reduce turbine blade rotation when bat activity is high

    A replicated, paired sites study in 2012 at eight pairs of wind turbines in Germany (Behr et al 2016) found that using automated ‘bat-friendly’ operating systems that reduced turbine blade rotation speed resulted in fewer bat fatalities than at conventionally operated wind turbines. Total bat fatalities and average collision rates were lower at automated turbines (total 2 bat fatalities, 0.01 fatalities/turbine/night) than at conventionally operated turbines (total 21 bat fatalities, 0.06 fatalities/turbine/night). At automated turbines, predictive models identified periods of high fatality risk and low energy yield from bat activity and wind speed data. During these periods, rotor blades were moved parallel to the wind to reduce rotation speed according to a target bat fatality rate (0.012 fatalities/turbine/night). Conventionally operated turbines rotated freely. At each of eight sites, automated and conventional operating modes were alternated weekly between two paired turbines over 14 weeks in July–October 2012. Carcass searches were carried out daily. Carcass counts were corrected to account for searcher efficiency and removal by scavengers. If applied to all turbines, it was estimated that automated operation would result in annual energy losses of 2.1%.

    (Summarised by: Anna Berthinussen)

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