downstream

Electricity demand in the U.S. continues to grow and, in the summer, homes and businesses crank up their air conditioning which drives demand even further. Many East Coast cities are banking on offshore wind projects that are underway in the Atlantic Ocean to help meet that growing demand. The first offshore turbines are now producing power off the coasts of Massachusetts and New York.

Electric power utilities need to know how much power they can get from offshore wind farms, and this is not that easy to predict. Wind is variable, so there is some built-in uncertainty. But there is also a phenomenon known as the wake effect to contend with.

When wind passes through a series of giant turbines, the ones in front extract some energy from the wind and, as a result, the wind slows down and becomes more turbulent behind the turbines. So, the downstream turbines get slower wind and may produce less power.

A study by the University of Colorado has modeled this phenomenon for planned wind farms in the Atlantic Coast region and has found that power output could be reduced by over 30%. Researchers are installing weather monitors and radar sensors in islands off the New England coast to better understand the behavior of the wind in the area and improve prediction models.

The New England grid covers Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont. Even with the wake effect, offshore wind is predicted to be able to provide 60% of the electricity needs of the grid, but it is important to be able to accurately predict what it can produce.

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How much energy can offshore wind farms in the US produce? New study sheds light

Photo, posted August 31, 2022, courtesy of Nina Ali via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

Offshore wind is booming in Europe. The expansion of wind energy in the German Bight and Baltic Sea has been especially dramatic. At this point, there are about 8 gigawatts of wind turbines in German waters, the equivalent of about 8 nuclear power plants. But space in this region is limited so that wind farms are sometimes built very close to one another.

A team of researchers from the Helmholtz Center Hereon, a major German research institute, has found that wind speeds downstream from large windfarms are significantly slowed down. In a study published in the journal Nature Scientific Reports, they found that this braking effect can result in astonishingly large-scale lowering of wind speeds.

On average, the regions of lowered wind can extend 20-30 miles and, under certain weather conditions, can even extend up to 60 miles. As a result, the output of a neighboring wind farm located within this distance can be reduced by 20 to 25 percent.

These wake effects are weather dependent. During stable weather conditions, which are typically the case in the spring in German waters, the effects can be especially large. During stormy times, such as in November and December, the atmosphere is so mixed that the wind farm wake effects are relatively small.

Based on their modeling, it is clear that if wind farms are planned to be located close together, these wake effects need to be taken into account. The researchers next want to investigate the effects that reduced wind speeds have on life in the sea. Ocean winds affect salt and oxygen content, temperatures, and nutrients in the water. It is important to find out how reduced winds might affect marine ecosystems.

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Are wind farms slowing each other down?

Photo, posted November 23, 2011, courtesy of David J Laporte via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Offshore wind and the wake effect

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Wind Farms Slowing Each Other Down | Earth Wise

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