An investigation into how owls silently fly and hunt has enabled researchers to develop a prototype coating for wind turbine blades that could significantly reduce the number of decibels they generate.
The first wind turbines were installed in France nearly fifteen years ago. Progress towards non-polluting energy? Not so sure...
According to the Federation of Sustainable Environment, the Ministry of Ecology would receive many complaints about the nuisance of these new windmills: wind turbine neighbors would complain of numerous physical pains such as violent headaches, dizziness, nausea,... Noise pollution on which British and American researchers have focused through the in-depth study of owl flight and the characteristic silence of their wings.
The magazine Enerzine.com reveals that initial tests of the material, which mimics the complex structure of an owl's wing, have shown that it could significantly reduce the amount of noise produced by wind turbines and also by other types of wings, such as those found in computers (fan blades) or an airliner.
Extensive microscopic study of owl wings has indeed allowed the composition of the feathers to be observed in minute detail, revealing a downy or fluffy covering, a flexible "silk comb" evenly spaced along the leading edge (front part of the wing) and a porous and elastic edge on the trailing edge (rear part of the wing).
However, much of the noise caused by a wing comes from the turbulent passage of air over the trailing edge. "The structure of an owl's wing serves to reduce that noise, soften the passage of air over the wing, diffuse the sound so that their prey can't hear them coming. "says Professor Nigel Peake of the Department of Applied Mathematics and Theoretical Physics at the University of Cambridge, and director of the study project.
Wind turbine blades like wedding sails...
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This study of how owls fly and hunt silently has allowed researchers to develop a prototype coating for wind turbine blades that could significantly reduce their noise level. Mimicking the complex structure of owl wings, this new technology (also applicable to aircraft wings or computer fans) could significantly increase the speed of the turbines and thus optimize silent production.
This particular coating, developed by researchers at the University of Cambridge, in collaboration with researchers at Virginia University of Technology, Lehigh University and Atlantic University in Florida, consists of scattering the noise generated by the turbine. The first experiments, based on a material identical to that used for wedding sails, have reduced the underlying roughness of the surface, thereby reducing the noise by 30 decibels.
However, while the bridal veil works relatively well, in practice it is not applicable to a wind turbine or an aircraft. The researchers have therefore developed a prototype plastic material with the same characteristics that has been tested on a segment of a wind turbine blade. During the wind tunnel tests, the treatment applied reduced the noise generated by a wind turbine blade by 10 decibels, with no noticeable impact on aerodynamics.
According to the researchers, the coating still needs to be optimized to hopefully one day apply it on an aircraft. Before then, the coating could be used on a different range of wings and blades. The next step will therefore be to test the coating on a wind turbine under real operating conditions. (Source : EDF June 2015)