Although wind turbines may be a valuable source of eco-friendly energy, they do have at least one drawback – bats are frequently killed by their spinning blades. A promising new system is designed to help keep that from happening, however, by producing an ultrasonic acoustic field.

As most people likely already know, bats find their way around in the dark by emitting ultrasonic calls. Based on the time that it takes for those calls to echo back to the bat's ears, along with the direction from which those echoes come, the animal is able to determine the distance and direction of obstacles – or of the flying insects upon which it feeds.

Developed by Vermont-based NRG Systems, the Bat Deterrent System emits an ultrasonic field in the same range as bats' natural calling frequencies. As bats approach that field, it gradually starts causing them to be unable to hear the echoes of their calls. The idea is that when this happens, the animals will begin to become disoriented, and respond by leaving the area.

The system was recently evaluated by a team from Texas State University, in partnership with Bat Conservation International, at the Los Vientos Wind Energy Facility.

Two years after being installed on 16 of the facility's 255 turbines, the technology was determined to have reduced overall bat fatalities by 54 percent. While the study particularly notes a reduction in deaths of Brazilian free-tailed bats and hoary bats, NRG states that its system is designed to work on all bat species native to North America, and most found in Europe.

It is also claimed that the system isn't harmful to bats or other wildlife, and that bats should not develop a tolerance to it.

The Bat Deterrent System will be commercially available starting next year.