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The world’s first offshore wind farm employing floating turbines is taking shape 25 kilometers off the Scottish coast and expected to begin operating by the end of this year.
[...] Wind power generation is obviously contingent on how fast and how often winds blow. But only over the past decade have scientists and wind farm developers recognized that the winds measured prior to erecting turbines may not endure. For one thing, dense arrays of wind turbines act as a drag on the wind, depleting local or even regional wind resources.

It is now generally accepted that drag from wind turbines in the boundary layer (where the atmosphere interacts with Earth's surface) limits the kinetic energy that large land-based wind farms can extract to about 1.5 megawatts per square kilometer (MW/km2). "If your average turbine extracts 2-6 MW, you really need to space those turbines 2-3 kilometers apart because the atmosphere just doesn’t give you more kinetic energy to extract,” says Carnegie postdoctoral researcher Anna Possner.

Wind speeds over open ocean areas are often higher than those in the windiest areas over land, which has motivated a quest to develop technologies that could harvest wind energy in deep water environments. However, it remains unclear whether these open ocean wind speeds are higher because of lack of surface drag or whether a greater downward transport of kinetic energy may be sustained in open ocean environments. Focusing on the North Atlantic region, we provide evidence that there is potential for greater downward transport of kinetic energy in the overlying atmosphere. As a result, wind power generation over some ocean areas can exceed power generation on land by a factor of three or more.

https://spectrum.ieee.org/energywise/green-tech/wind/rechargeable-wind-power-over-the-open-ocean?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+IeeeSpectrum+%28IEEE+Spectrum%29 [ieee.org]

Research Article: http://www.pnas.org/content/early/2017/10/03/1705710114 [pnas.org]

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