Static wind turbines at low wind speed could save bats from gory end

One of the main beneficiaries of the turbine standby would be the European free-tailed bat which flies at high-altitude Raphaël Arlettaz

A study conducted by researchers from the University of Bern shows that the risk of bats being killed by wind turbine blades falls to 5% if the machines are kept on standby at night as soon as wind speeds drop to below 5.4 metres per second.

This is because most bat species observed at the study site – Lower Rhône valley in southwestern Switzerland – stop flying high once a certain wind speed threshold has been reached. This was ascertained by placing ultrasonic detectors (Batloggers) along cables that stretched from the ground to the top of a telescopic crane, up to 65 m high. By extrapolating the flight profiles at different altitudes, the scientists were able to show, firstly, that only a few bat species are active at heights swept by the turbine blades (50-150 m) and, secondly, that most species avoid flying so high when the wind speed exceeds 5.4 m/s.

“This simple adaptation of the night time operation of wind turbines would greatly limit the risk of bats colliding with the blades,” said studyExternal link leader Raphaël Arlettaz.

According to the scientists, such a measure would be easy for wind turbine operators to implement, especially as it involves only a marginal loss of electricity production, which is quite low anyway at wind speeds below 5 m/s.

One of the main beneficiaries of the turbine standby would be the European free-tailed bat (Tadarida teniotis) which travels long-distances in search of insects and flies at high-altitude. The activity of the nocturnal creature, which is also active in winter, drops to 5% in the danger zone (less than 65m) once wind speeds exceed 5m/s.