Wind energy is often thought of as "clean" but, in fact, the technology has the blood of thousands – if not millions – of bats on its hands. That's not only because bats can fly into the giant wind turbine blades and die, but because the turbines create a low-pressure field which causes the bats' internal organs to explode when they pass through it. A new drone-mounted system shows promise in rerouting some bats above the turbine blades and away from danger.
While wind turbines kill about 140,000-500,000 birds a year according to the Audubon Society, the death toll for bats is much higher. That's because as the turbine blades spin, they create a five-to-10-kilopascal drop in pressure behind them, according to Scientific American.
When bats fly through this low-pressure zone, their capillaries expand rapidly and the animals die from internal hemorrhaging. Birds tend to have stronger capillaries, so they can withstand the pressure drop more easily.
To combat this negative side effect of a promising energy-producing technology, researchers have experimented with blade-mounted whistles, as well as using ultrasonic waves to keep bats away from the deadly turbines. But the whistle process could prove costly, and the ultrasonic wave devices tested are stationary, which tends to make the system ineffective over time as animals habituate to it.
Researchers at Tel Aviv University and the University of Haifa have come up with a system that could address both issues: brightly flashing lights and ultrasonic pulses delivered from drones that fly in front of the turbines. Flashing lights at bats might seem an odd choice as a deterrent if you have been led to believe that bats are blind, but the creatures do in fact have highly sensitive eyes that can pick up on visual clues.
To see if the light/sound combo would in fact deter bats, the researchers launched their drone in Israel's Hula Valley, which is noted for significant bat activity. For the bulk of the test, the drone flew at a height of 100 meters (about 328 feet), which is the average height of a turbine. Then, it flew back and forth in front of the turbines on a path about 100 meters wide while flashing its lights and playing its sounds.
Next, using a combination of ground-based RADAR, laser-based LIDAR tracking devices, and acoustic receivers, they tracked the bats' flight patterns. The drone was successful in rerouting about 40 percent of the bats above the turbines. During the test (seen in the video below), there was no wind turbine present, but the researchers plan to test the drone again at a turbine as the next phase of the study.
"We hypothesize that if the device is activated near a turbine, it will lead the bats to fly over the turbine and out of harm's way," said Yossi Yovel, head of Tel Aviv University's Sagol School of Neuroscience. "This is an effective and easily-implemented solution that is reasonably priced, with great benefit to all parties: on the one hand, it prevents the killing of bats, and on the other hand, it enables the operation of the turbine and the production of green energy in a safe, continuous and efficient manner."
The researchers' work has been published in the journal, Remote Sensing in Ecology and Conservation.
Source: Tel Aviv University via Phys.org
