Grounded golden eagle

Vibration sensors improve detection of turbine bird strikes

Image credit: Dreamstime

Researchers at the University of Oregon have demonstrated a system capable of detecting birds approaching wind turbines. This could be combined with a deterrent to reduce deaths of protected birds.

While wind power has the potential to be a significant renewable source of green energy, there remain concerns around the impact of wind turbines on wildlife; birds and bats are regularly killed in collisions with wind turbine blades, which tend to be twice as long as a Boeing 747 wingspan, move at nearly 320km/h, and are mounted 90m in the air.

There are particular concerns around the welfare of bald eagles and gold eagles, which receive federal protection in the US. According to the US Fish and Wildlife Service, there are roughly 143,000 bald eagles and 40,000 golden eagles in the US. The bald eagle is the national animal of the US, and appears on its seal.

“If a turbine strikes a generic bird, sad as that is, it’s not as critical as striking a protected golden eagle, which could potentially trigger down time in turbine operations and losses in revenue, and most [importantly] the loss of a member of a protected species,” said Professor Robert Albertani, co-author of the study.

“At land-based wind farms, carcass surveys and long-term visual monitoring have been the typical ways of assessing collisions and mortality rates,” he said. “Factors like surveyor error and carcass removal by scavengers can make the data inaccurate. And carcass surveys are expensive or not feasible at remote locations or other sites like agricultural fields, dense shrub habitats, or in offshore turbine operations.”

As an alternative to carcass surveys, Albertani and his colleagues designed an impact detection system that uses vibration sensors mounted at the base of a blade, an optical camera on the tower base and an acoustic sensor on the generator housing to pick up bird sounds.

This combination of sensors makes it possible to identify when a bird or a bat has collided with a turbine, and determine the species of the unfortunate creature (using recorded video data).

The researchers tested a conceptual design of the system by firing tennis balls at turbines. Out of 29 field tests, the system confirmed 14 incidents, mostly at the leading edge of the blade and halfway between midpoint and tip. The researchers believe that the system’s accuracy could be significantly improved, and say that the study demonstrates the feasibility of a detection system based on vibration sensors.

The US Department of Energy (DOE), which supported Albertani’s research, is supporting his companion project, which will look into protecting eagles by detecting them as they approach and triggering colourful images of people at ground level to deter them.

Meanwhile, researchers at the DOE’s Pacific Northwest National Laboratory have developed thermal imaging software capable of surveying potential wind farm sites for birds and bats, ensuring minimal disruption of wildlife when selecting sites.

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