Of Foxes, Birds And Wind Turbines

Collisions of birds with wind turbines are one of the biggest criticisms regarding the use of wind energy. A study was therefore commissioned by the Federal Office of Energy (SFOE) to investigate this question. Their conclusions were published in November 2016. (See links at the end of the article.) According to this, around 21 birds per year would be killed on each wind turbine. An expert opinion from an engineering office for renewable energies and nature conservation also came to the conclusion that the actual number of collisions would be much smaller and that only one bird sacrifice per system and year would be complained of. All these surveys are ultimately intended to confirm, according to the BFE study, that bird collisions are rare exceptional events.

Naturschutzbund is disappointed

On the occasion of these publications, the Naturschutzbund Deutschland (NABU) criticized in a message that the wind energy industry is trying to give the impression that there is no conflict between wind energy and bird of prey protection.

"NABU is disappointed by the unwillingness to recognize a real existing species protection problem and to work together on sensible solutions for a nature-friendly energy transition that are covered by applicable law. Violations of the species protection law will not be cured by discussing the problem away and have no chance in court, "said NABU federal director Leif Miller in a press release. According to NABU, part of the wind industry hopes to be able to expand wind energy without having to take species protection into account. For the whole of Germany, NABU assumes over 1,000 deaths per year from the endangered red kite alone and up to 12,500 from the common buzzard - a total of more than 100,000 birds would die.

Fox, you stole the evidence

However, Hermann Hötker from the Michael Otto Institute in the Naturschutzbund Deutschland (Nabu) can explain how the BFE study comes to such a small number of 21 birds killed per year: “Small animals in particular are immediately carried away by scavengers in many cases. It is extremely fast."

Could industry, so to speak as a mediator, not deliver applications that protect nature from renewable energies on the one hand, and on the other hand not significantly reduce the already narrow profit margin? Repowering measures on old systems would be an option to retrofit such applications. A specific idea comes from the sensor manufacturer and Bavarian founder award winner Indtact from Würzburg: Through targeted acoustic excitation of the rotor blades, the entire wind turbine could be transformed into an "acoustic scarecrow" to keep birds out of the danger area. A possible system could direct the sound waves that are already occurring in a targeted manner into the desired frequency spectra by means of the pitch control of the system. Depending on the size of the wind turbine, the sound cone would have a range of 300 m to 500 m. Enough,to keep flying animals away. This sound cone would not be perceptible to humans because the frequencies used would be below the perception limit. Studies would have to find out which frequencies would make sense. Similar considerations already exist when keeping bats away, which are also endangered by wind turbines.

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What would be possible today with sensors like those from Indtact: an absolutely reliable count of bird strikes per rotor blade and wind turbine. These sensors are already installed in the blades today in order to increase the efficiency of wind turbines via vibration analysis, force and strain measurements. The size of the animal could even be determined on the basis of the strength of the impact in order to draw any conclusions about the species.

On this basis, it could be argued based on facts and already today, if it were desired, the actual number of bird victims can be determined, in order to then initiate suitable protective measures for birds and bats alike. (br)

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