According to a US Geological Survey estimate, anywhere from tens of thousands to hundreds of thousands of bats are killed by wind turbines annually – in the US alone. New technology may help reduce those numbers, however, by causing the turbine blades to whistle at the animals.
Bats are killed either when they collide with the blades, or when the air pressure difference produced by rotating blades causes the creatures' lungs to explode.
Existing efforts at keeping this from happening have involved installing loudspeakers at the center of turbines, where they produce bat-deterring ultrasonic acoustic fields. Unfortunately, though, in some cases those fields don't reach all the way out across the span of the blades, plus a power source is required.
With those limitations in mind, scientists from Texas A&M University have produced 3D-printed whistles modelled after a bat's larynx, that can be mounted on wind turbine blades. The idea is that as those blades turn, air passes through the whistles, causing them to create a noise similar to the ultrasonic echolocation signals used by bats. Oncoming bats will hear that sound (which is inaudible to humans), and change their course in order to avoid a collision with the other bat that they assume is making it.
Recordings of the whistles have already been played back in the field, in order to ascertain if they do indeed deter bats. Depending on the results of those experiments, the next step may be to actually mount the whistles on wind turbines. Unfortunately, the installation process would currently be rather expensive, although that may change as the technology is further developed.
"Our approach focuses on producing a sound bats could easily recognize and locate, thereby making it easier for them to avoid the moving turbine blades," says A&M's Prof. Michael Smotherman. "I'm hopeful that using this neuroethological approach to the design and implementation gives us a better chance for success."
Smotherman is presenting his team's research at the 177th Acoustical Society of America meeting in Louisville, Kentucky.
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