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Radar Could Save Bats From Wind Turbines
mknewman sends in an MSNBC piece on a promising way to keep bats from straying into wind farms — by using radar. "Bats use sonar to navigate and hunt. Many have been killed by wind turbines, however, which their sonar doesn't seem to recognize as a danger. Surprisingly, radar signals could help keep bats away from wind turbines, scientists have now discovered. ...some researchers have raised concerns that wind turbines inadvertently kill bats and other flying creatures. ... The bats might not be killed by the wind turbine blades directly, but instead by the sudden drop in air pressure the swinging rotors induce... The researchers discovered that radar helped keep bats away, reducing bat activity by 30 to 40 percent. The radar did not keep insects away, which suggests that however the radar works as a deterrent, it does so by influencing the bats directly and not just their food. Radar signals can lead to small but rapid spikes of heat in the head that generate sound waves, which in turn stimulate the ear. A bat's hearing is much more sensitive than ours. It may be so sensitive that even a tiny amount of sound caused by electromagnetic radiation is enough to drive them out."
I can only begin to imagine the complications of wind farms interfering with military radars which scan much closer to the Earth's surface
Turbines are a problem when they reflect signals back to the radar with sufficient Doppler shift to get past filters for static reflections. The emission from this device won't be near the frequency of the military radars (you would think) so there is unlikely to be a problem.
http://michaelsmith.id.au
You have to be very careful with sonic systems and creatures like bats and flying foxes. There are arguments afoot here in Australia that many sonic systems are waayyyyyy overpowered, causing bats to freak out and drop their young, or fall straight out of the sky and hurt themselves. Although technically this is a deterrent, it isn't really a good thing for the bats, which is the main point of the system. It might be like trying to keep humans away from an area by blasting our optic nerves with a near-blinding psychedelic lightshow and being a little miffed when the human falls over backwards in shock, tumbles down a hill and breaks their legs. Whoops.