Wind Turbine Noise: New Reports

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The German Wind Energy Institute (DEWI) in conjunction with the Martin Luther University  Halle–Wittenberg’s environmental psychology department has conducted measurements, data evaluation and a survey of 200 people living close to a wind farm near Wilstedt in Lower Saxony. The farm comprises nine 2MW turbines operated by wind developer WPD. The 200 were asked questions about the effects of turbine noise, if any, on their daily lives, including sleep,  and their mental and  physical well-being.
The results indicated that it wasn’t noise level that was the issue, but the fluctuating noise occurring in the rhythm of the rotating blades, known as amplitude modulation. Further work will focus on avoiding critical amplitude-modulation situations and reducing noise disturbance, DEWI said. Only a small number of wind farms are affected by this type of noise problem caused when blades stop moving as wind speed drops, increases or changes direction. In the UK only about 3% of wind farms are likely to produce a low-frequency sound that can be heard up to a kilometre away.
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The deep thumping-like sound, produced when the blades on a turbine partially stall because of changes in wind speed and direction, is about as loud as the noise from a single carriageway road. This sound is not the same is the “whooshing” effect of the blades being turned in the wind when you get closer to a turbine.

A report commissioned by RenewableUK into this issue found the problem to be infrequent, and more importantly, able to be remedied with changes to software which rectifies the stalling problem.

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RenewableUK’s deputy chief executive, Maf Smith, pictured above, said:

“The research shows that this only affects a limited number of wind farm sites, and when it does occur it can be resolved using a software fix which controls the angle of the turbine blades. It’s right that the wind industry should take the lead in investigating issues like this when they arise.”

 

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