Offshore wind turbines at Barrow Offshore Wind off Walney Island in the Irish Sea.
Offshore wind turbines at Barrow Offshore Wind off Walney Island in the Irish Sea. Image credit: Andy Dingley

Click either choice below to hear a 500 kW turbine operating at the Bockstigen-Valar offshore wind farm in Sweden:
 
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Underwater recording taken less than 50 m from a 500 kW turbine operating at the Bockstigen-Valar offshore wind farm (Baltic Sea, Sweden). Sounds were recorded at a water depth of 10 m.
Sound credit: Aarhus University, National Centre for Energy and Environment. Sound file released under Creative Commons license, NonCommercial-NoDerivs.
Click either choice below to hear a 2.3 MW turbine operating at the Samsoe offshore wind farm in Denmark:
 
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Underwater recording taken less than 50 m from a 2.3 MW turbine operating at the Samsoe offshore wind farm, Kattegat, Denmark. Sounds were recorded at a water depth of 12m.
Sound credit: Aarhus University, National Centre for Energy and Environment. Sound file released under Creative Commons license, NonCommercial-NoDerivs.
Click either choice below to hear a 450 kW turbine operating at the Vindeby offshore wind farm in Denmark:
 
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Underwater recording taken less than 50 m from a 450 kW turbine operating at the Vindeby offshore wind farm (Western Baltic Sea, Denmark). Sounds were recorded at a water depth of 4m.
Sound credit: Aarhus University, National Centre for Energy and Environment. Sound file released under Creative Commons license, NonCommercial-NoDerivs.
Description
Wind energy (or wind power) refers to the process by which turbines convert the movement of wind into electricity. Wind turbines are built high (80+ m) above the ground or water to take advantage of faster, less turbulent wind than occurs at the surface. Offshore wind power has become one of the fastest growing energy technologies and is the focus of development in many countries around the world. Winds tend to be stronger and more uniform at sea than on land. In addition, there are large, potentially productive areas available offshore. It is predicted that by 2020 10% of Europe’s electricity demand could be met by offshore wind farms.[1] Europe is the global leader in offshore wind power.

Underwater sound is generated during the construction, operation, and decommissioning of offshore wind turbines. Construction of wind turbines involves a variety of activities such as seismic exploration (with airguns), excavation with explosives, dredging, ship and barge operations, and pile-driving. All of these activities produce underwater sounds of varying intensity and duration. As a turbine operates, vibrations inside the nacelle (the housing that contains the generator, gearbox, and other parts) are transmitted down the main shaft of the wind turbine and into its foundation. These vibrations then propagate into the water column and seafloor. Mechanical noise generated by offshore turbines is concentrated at low frequencies below 1kHz, generally below 700 Hz. The level slightly increases as wind speed increases.
 
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References

  1. Xiaojing, S., D. Huang, and G. Wu. 2012, "The current state of offshore wind energy technology development." Energy. 41: 298-312. 
  • "Proceedings of the ASCOBANS/ECS Workshop on Offshore Wind Farms and Marine Mammals." (Link)
  • Dennis Y.C. Leung and Yuan Yang. 2012, "Wind energy development and its environmental impact: A review." Renewable and Sustainable Energy Reviews. 16: 1031– 1039. 
  • H. J. Lindeboom, H.J. Kouwenhoven, M.J.N Bergman, S. Bouma, S. Brasseur, R. Daan, R. C. Fijn, D. de Haan, S. Dirksen, R. vanHal, R Hille Ris Lambers, R. terHofstede, K.L. Krijgsveld, M. Leopold, and M. Scheidat. 2011, "Short-term ecological effects of an offshore wind farm in the Dutch coastal zone; a compilation." Environ. Res. Lett. 6, 13pp. 
  • Jakob Tourgaard, Peter T. Madsen, and Magnus Wahlberg. 2008, "Underwater noise from construction and operation of offshore wind farms." Bioacoustics. 17(1-3): 143-146. 
  • Jennifer C. Wilson, Mike Elliott, Nick D. Cutts, Lucas Mander, Vera Mendão, Rafael Perez-Dominguez, and Anna Phelps. 2010, "Coastal and Offshore Wind Energy Generation: Is It Environmentally Benign?" Energies. 3: 1383-1422. 
  • Meike Scheidat, Jakob Tougaard, Sophie Brasseur, Jacob Carstensen, Tamara van Polanen Petel, Jonas Teilmann, and Peter Reijnders. 2011, "Harbour porpoises (Phocoena phocoena) and wind farms: a case study in the Dutch North Sea." Environ. Res. Lett. 6. 
  • P. T. Madsen, M. Wahlberg, J. Tougaard, K. Lucke, and P. Tyack. 2006, "Wind turbine underwater noise and marine mammals: implications of current knowledge and data needs." Marine Ecology Progress Series. 309: 279–295. 
  • Paul M. Thompson, David Lusseau, Tim Barton, Dave Simmons, Jan Rusin, and Helen Bailey. 2010, "Assessing the responses of coastal cetaceans to the construction of offshore wind turbines." Marine Pollution Bulletin. 60: 1200–1208. 
  • Ryunosuke Kikuchi. 2010, "Risk formulation for the sonic effects of offshore wind farms on fish in the EU region." Marine Pollution Bulletin. 60:172–177. 
Additional Resources

  • "A review of offshore windfarm related underwater noise sources." (Link)
  • "European Wind Energy Association." (Link)
  • US Department of Energy, "How do Wind Turbines Work." (Link)