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German offshore wind construction aims to limit noise impact on porpoises

Effects of Noise on Wildlife, News, Ocean, Ocean energy, Wind turbines Add comments

Aggressive offshore wind energy plans in Germany are pioneering innovative new approaches to reducing the noise impacts of wind turbine construction, according to a recent Bloomberg News article.  It’s a good, long piece, well worth a read.  A few highlights:

“Quite a large proportion of our sea area will probably be used for offshore wind farms,” said Hans-Ulrich Rosner, head of the Wadden Sea Office for WWF in Germany. “This will have a serious impact on nature, which needs to be mitigated.”  Harbor porpoises, common in the North and Baltic Seas, appear to be especially sensitive to noise, adding to the challenges. 

Construction of the 108 MW Riffgat offshore wind project is nearing completion; it’s been utilizing a double-walled, water-filled casing in which bubbles are produced to absorb some of the sound from pile-driving of the turbine foundations into the seabed.  In addition, a less intense vibration method is being used for almost half the depth of the piles, with the louder hammering of classic pile driving being used for only the last 40 meters.  These noise reduction techniques amount to half of one percent of the total cost of the wind farm.

Germany’s Federal Maritime and Hydrographic Agency, or BSH, has set a noise limit of 160 decibels for 750 metres around offshore wind construction work. Developers regularly overshoot the limit, which is not applied to detonating old bombs, the BSH’s Christian Dahlke said.  “Our regulations are creating a new industry,” Dahlke said. “If environmental rules to protect animal life are tightened in other countries as well, our companies may even export these technologies.”

At the Nordsee Ost project, a large hose perforated to produce a curtain of air bubbles around each of the 48 turbine foundations to absorb the noise from pile driving, which “brought the noise level much closer” to the 160 decibel cap.  But RWE, a utility involved in the project, said that more research and development is needed “to meet the limit reliably in the future.”

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