Both bald eagles and golden eagles are federally protected species, and both are vulnerable to dying in collisions with wind turbines stretching hundreds of feet in the air. A team of researchers hailing from Oregon State University’s College of Engineering along with the College of Earth, Ocean and Atmospheric Science are developing technologies to both prevent and sense collisions with these majestic birds. Lead author Roberto Albertani says while any bird-strike is “sad,” his team is focusing on these species because they are protected and because their strikes can lead to turbine downtime and revenue loss for operators.
There are approximately 40,000 golden eagles and 143,000 bald eagles in the U.S. There are more than 50,000 wind turbines operating in the country and they inadvertently kill between about 140,000 and 328,000 birds every year.
One of the OSU projects is to improve the means of capturing data on bird strikes.
"At land-based wind farms, carcass surveys and long-term visual monitoring have been the typical ways of assessing collisions and mortality rates. Factors like surveyor error and carcass removal by scavengers can make the data inaccurate,” Albertani says. He adds that carcass surveys are costly and also impractical and basically infeasible at many locations, including offshore turbine setups, densely vegetated areas and agricultural fields.
Albertani and his colleagues tested a prototype that can auto-detect collisions with avian species. Within this system, the turbine’s blades, of which there are typically three, are outfitted with vibration sensors. A camera is positioned on the tower base and an acoustic sensor is located on the generator housing to catch bird sounds. At the National Renewable Energy Laboratory Wind Technology Center in Boulder, the researchers shot tennis balls at turbines with a compressed-air launcher to simulate the deadly encounters with wildlife.
While only 14 of 29 blade strikes were accurately detected, Albertani says the hits that were missed were probably low-impact and that the rate can likely be “significantly increased.”
"This study demonstrates the feasibility of an impact detection system based on vibration sensors,” he also says of the project, the results of which were published in Wind Energy. The U.S. Department of Energy provided financial support for the study.
In a related undertaking, Albertani et al. received DOE funding to deter eagles from coming near wind turbines. In this endeavor, they are developing an eagle-sensing-system that will also use visual stimuli, much like a virtual scarecrow, to send birds in another direction. A camera will watch specifically for eagle species approaching the turbines. If one is detected, “randomly moving, brightly colored facsimiles of people, designed to play into eagles' apparent aversion to humans,” will be projected at ground level, according to an OSU press release.