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These nearly silent wind turbines have owl-inspired ‘feathers’
Noise from wind turbines limits where they can be built. But a design that mimics the shape of owl feathers can make wind farms quieter and help renewable energy grow faster.
On a recent winter day on a wind farm in Germany, workers scaled 544-foot-tall wind turbines and started adding fringe-like attachments to the massive blades. The design, inspired by the shape of owl feathers, aims to solve one of the wind industry’s biggest challenges: the noise that turbines make as the blades slice through the air.
“Noise is really the biggest limiting factor for the placement of turbines,” says Ryan Church, founder and CEO of Biome Renewables, the startup that designed the new owl-inspired attachment. Modern turbines keep getting louder as they get bigger. And the sound of the turning blades is noticeable enough that it limits the size of wind farms, how close they can be to cities, and the schedules that they can operate.
Like airplane wings, wind turbine blades are shaped so that air flows faster on one side and slower on the other, creating lift. At the trailing edge of the blade, where the air mixes, there’s noisy turbulence. To help, blades are designed with a serrated edge that helps break up the airflow. But Church, who has also developed other nature-inspired designs for renewable energy, realized that it was possible to go farther.
Church started developing the design, called FeatherEdge, after watching a nature documentary that demonstrated how quietly owls fly. In the film, other birds fly across a room over a series of microphones that record the sound of their flapping wings. “Then the barn owl comes along and it goes back and forth, and they wonder if the recording equipment is even on,” he says. “It’s absolutely silent.”
Owls use a variety of strategies for silence, but Biome’s design is inspired by the shape of the fringe on the trailing edge of some owl feathers. The FeatherEdge’s shape uses the same principles of physics to cut noise. The engineers customize the design for each specific wind turbine, applying the flexible attachments at key locations to control how the air mixes.
The design works. The standard serrations on wind turbine blades cut noise by 1.5 to 2 decibels; in early tests, FeatherEdge reduced noise by an additional 3.4 decibels. (It’s possible that the latest installation, on massive turbines, may show even greater reductions when the results are in.)
“The frequency range that we target with our product is the low-frequency range,” says Church. “It is the hardest part of the sound spectrum to quiet down. And that’s where we have most of our impact. And that’s what matters because it’s the low-frequency sound that travels to someone’s house.”
Right now, some projects get permits but then have to run in a noise-reduced mode at night—sometimes forfeiting as much as half of the power that they otherwise could have generated. Noise restrictions also sometimes mean that projects can’t move forward because they aren’t financially viable.
With the new design in place, it could be possible for projects near communities to run effectively at night, adding more power to the grid. Because the wind turbines would be so much quieter, it also could be possible to put 30% to 50% more turbines on the same plot of land, he says. That’s especially important because many of the best locations for wind farms have already been developed, and the world is currently grappling with how and where to quickly build more renewable energy to meet demand.
The new commercial pilot, for a company called Schierloh Engineering, will be followed by more installations later this year. (The design recently received a certification that means it can be used on any turbine globally.) Biome is also in talks with wind turbine manufacturers about incorporating the design.
