Active wind turbine controls aim to reduce bird deaths by 80%

It is a tragic but indisputable fact that wind turbines kill birds. It's difficult to determine how many birds fly onto the rotating blades of wind turbines and die - in fact, the topic is too politically charged. The American Bird Conservancy reviewed some of the available evidence and concluded that at least a million birds die each year in the United States alone, which is likely an underestimate.

Of course, this number is significantly lower than the estimated 25.5 million birds killed each year by flying into overhead power lines, or the estimated 980 million birds killed each year by crashing into buildings, or the 1.4 to 3.7 billion birds killed by domestic cats each year. But this is still an unacceptable number and a problem that needs to be solved - because a completely green energy network will require more and more turbines in the coming decades.

Researchers at the Norwegian Institute of Science and Technology (SINTEF) and the Norwegian Research Center for Environmentally Friendly Energy believe they have an idea that could help solve a lot of problems.

The idea is simple: Each turbine will have a camera capable of spotting birds flying directly into the path of the rotor. Software automatically calculates their predicted trajectories, and if they appear to be in danger of being hit, the system sends control signals to slow the blades by adjusting generator torque and blade twist.

In simulations, the system (called SKARV) was able to avoid the vast majority of collisions with individual birds, which moved in predictable paths, flew head-on toward the turbines, and had at least five seconds to detect before impact. Of course, this doesn't tell the whole story. This doesn't stop them from crashing into the central nacelle or tower, nor does it help if they come from the side, or circle around the turbine.

Researcher Paula B. Garcia Rosa said: "Because it is difficult for us to predict the flight trajectories of birds, the new system cannot completely solve this problem. For example, if an inexperienced baby bird shows erratic flight behavior when approaching a turbine, it will be impossible to accurately predict its position a few seconds later. If several birds are approaching at the same time, prediction will also be more difficult."

If a large number of birds are approaching, the system can be set to shut down the turbine completely - although the team notes that large turbines can take up to 20 seconds to come to a complete stop from normal speed.

"Based on our simulations, we believe the SKARV project could help reduce fatal collisions by up to 80 percent," Garcia-Rosa said. "The next step is to further develop existing blade rotation speed control strategies and combine these with methods for identifying bird flight trajectories. We will then conduct practical demonstrations. We believe the SKARV technology can be commercialized within five years, perhaps sooner if we see enough interest from the industry."