FROM A DISTANCE, wind turbines can seem sort of peaceful—a 21st century version of the windmill. Get up close, and it’s a different picture. When they get going, the tips of the blades (which can be more than 100 feet long) can move faster than winds in a category five hurricane.
That’s why wind turbines—to the dismay of renewable energy advocates—have been the target of noise and (hard to verify) health complaints. In some cases, the blades are intentionally slowed down, making them less effective at generating electricity.
Now, as they’ve done so many times before, researchers have turned to nature to try to find a solution to the noise problem.
A team at the University of Cambridge has published research based on the wings of large owls, masters at silent swooping—to the dismay of voles—at high speeds, undetected. The team discovered that the birds’ flight feathers, which create lift, have a downy covering, a flexible comb of bristles along the leading edge, and a porous fringe on the trailing edge.
“No other bird has this sort of intricate wing structure,” says Professor Nigel Peake of Cambridge’s Department of Applied Mathematics and Theoretical Physics. Most noise from wings (or fan blades) occurs at the trailing edge, where the air is the most turbulent. An owl’s wing smooths and quiets the air, allowing the birds to hunt more effectively.
So the Cambridge team, working with folks at Virginia Tech, Lehigh and Florida Atlantic Universities, made a prototype material of 3D-printed plastic to mimic the owls’ natural feature. Fitted on full-sized wind turbine blades and tested in a wind tunnel, it reduced noise generation by 10 decibels (a significant amount since noise is measured logarithmically), without significantly affecting aerodynamics.
Of course, just because we’ve figured out how owls fly doesn’t mean we can replicate their tricks today. Testing the coating on a functioning wind turbine is the next step, with the researchers expecting that an average-sized wind farm could generate as much as several additional megawatts worth of electricity without any appreciable increase in noise.
Down the line, the researchers believe this solution could be applied to airplanes. Noise is a serious issue in aviation, as the authorities, plane makers, and airports seek ways tominimize the unpleasant side effect of a vital industry. So the jet of the future may not be able to spin its head around, but it could fly like an owl.