Bats and wind energy - significance threshold, tower microphone

Up to now, there has been no nationwide recommendation on how to deal with the individual-related prohibition of killing bats in accordance with § 44 para. 1 no. 1 of the Federal Nature Conservation Act (BNatSchG) in connection with the approval of wind turbines. A science-based recommendation and transparent consultation are intended to contribute to nationwide standardisation.

For several years, the question has been discussed how the combined effect of rotor diameter and turbine height of a wind turbine affects the collision risk of bats. A central issue here is how much knowledge can be gained by using additional microphones on the tower of the wind turbine for so-called nacelle monitoring (i.e. acoustic recording of bats in the rotor area).

Procedure

Sub-project: Significance threshold

Based on scientific and legal principles, a "significance threshold" recommendation is developed and discussed with the central actors in the field of nature conservation and wind energy. This is based on extensive research and analysis of the literature on the effects of wind turbines on bats, including knowledge of population biology. In addition, administrative regulations and court rulings (national and European) are researched and evaluated. A proposal is then developed based on the current state of scientific knowledge and the legal discussion. This is then consulted with relevant federal and state authorities, representatives of nature conservation and (wind) energy associations, and bat experts, and finally updated.

Tower microphone sub-project

In 2022 and 2023, three (nationally representative) wind turbines will be equipped with an additional tower microphone in the vicinity of the lower rotor tip. In addition, data from the wind test field in Baden-Württemberg and from impact assessments will be evaluated. The aim is to determine how much knowledge can be gained from an additional microphone on the tower of a wind turbine for the prediction of collision risk and for the calculation of operational algorithms for the protection of bats. Specifically, the question is to be answered to what extent the data of an additional microphone can represent the effect of different hub heights and rotor diameters on the calculated impact risk. As a result, practical recommendations for the planning and approval of wind turbines will be derived. If necessary, the results available in 2024 should also lead to an adjustment of the calculation algorithms of the ProBat software.