Offshore Wind “Wake Effect”

From MasterResource

By Robert Bradley Jr.

The media bias in favor of industrial wind turbines is a sight to behold. Simple reporting of the facts, from costs to environmental tradeoffs, could inform the public and voters to quite possibly eliminate the government gravy train that disadvantages virtually all of us. That is, everyone except for wind developers and other constituencies of the Climate Industrial Complex.

It is uncommon to see a break in the narrative of “the energy transition.” This was recently done at E&E News’s Energywire, “‘Wake effect’ could drain 38% of offshore wind power, study says“. This piece by Heather Richards (May 5, 2024) is worth revisiting at length. Key quotations follow:

The findings from national lab and university researchers upend assumptions about how turbines interact with each other.

Wind turbines off the East Coast might significantly drain energy from each other, lowering the power output of an offshore farm by up to 38 percent, according to a new study that challenges early assumptions about the nascent industry’s electricity contribution.

The findings add to growing research about the “wake effect,” which is when offshore turbines in close proximity affect each other’s energy output.

Researchers from the University of Colorado and the National Renewable Energy Laboratory (NREL) found that entire wind farms can impede neighboring projects, decreasing the power production of adjacent farms by up to 15 percent under some conditions.

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In the research paper, “New offshore wind turbines can take away energy from existing ones,” Science Direct reports on the findings, with the authors offering apologetics (“We need a diverse mix of clean energy sources to meet the demand and decarbonize the grid”) and (“With better predictions of wind energy, we can achieve more reliance on renewable energy”). The article states:

In a new paper published March 14 in the journal Wind Energy Science, a team led by Dave Rosencrans, a doctoral student, and Julie K. Lundquist, a professor in the Department of Atmospheric and Ocean Sciences, estimate that offshore wind turbines in the Atlantic Ocean region, where the U.S. plans to build large wind farms, could take away wind from other turbines nearby, potentially reducing the farms’ power output by more than 30%.

Accounting for this so-called “wake effect,” the team estimated that the proposed wind farms could still supply approximately 60% of the electricity demand of the New England grid, which covers Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, and Vermont.

“The U.S. is planning to build thousands of offshore wind turbines, so we need to predict when those wakes will be expensive and when they have little effect,” said Lundquist, who is also a fellow at CU Boulder’s Renewable and Sustainable Energy Institute.

When wind passes through turbines, the ones at the front, or upstream, extract some energy from the wind. As a result, the wind slows down and becomes more turbulent behind the turbines. This means the turbines downstream get slower wind, sometimes resulting in lower power generation.

The wake effect is particularly prominent offshore, because there are no houses or trees that stir up the air, which helps dissipate the wakes, said Rosencrans, the paper’s first author.

Using computer simulations and observational data of the atmosphere, the team calculated that the wake effect reduces total power generation by 34% to 38% at a proposed wind farm off the East Coast. Most of the reduction comes from wakes formed between turbines within a single farm.

But under certain weather conditions, wakes could reach turbines as far as 55 kilometers downwind and affect other wind farms. For example, during hot summer days, the airflow over the cool sea surface tends to be relatively stable, causing wakes to persist for longer periods and propagate over longer distances.

There is another problem for offshore wind ….

“Unfortunately, summer is when there’s a lot of electrical demand,” Rosencrans said. “We showed that wakes are going to have a significant impact on power generation. But if we can predict their effects and anticipate when they are going to happen, then we can manage them on the electrical grid.”

Compared with energy sources derived from fossil fuels, wind and solar power tend to be variable, because the sun doesn’t always shine and the wind doesn’t always blow. This variability creates a challenge for grid operators, said Lundquist. The power grid is a complex system that requires a perfect balance of supply and demand in real-time. Any imbalances could lead to devastating blackouts, like what happened in Texas in 2021 when power outages killed nearly 250 people.

To better understand how the wind blows in the proposed wind farm area, Lundquist’s team visited islands off the New England coast and installed a host of instruments last December as part of the Department of Energy’s Wind Forecast Improvement Project 3. The project is a collaboration of researchers from CU Boulder, Woods Hole Oceanographic Institute and several other national laboratories.

The instruments, including weather monitors and radar sensors, will collect data for the next year or more. Previously, offshore wind power prediction models usually relied on intermittent data from ships and satellite observations. The hope is that with continuous data directly from the ocean, scientists can improve prediction models and better integrate more offshore wind energy into the grid.

Or not. Wind is the perfect imperfect energy for the grid, and offshore wind more so.