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one close large white wind turbine in an offshore windfarm with many other wind turbines and a mostly clear blue sky in the background
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Offshore Wind Farms Face Power Challenges

Study shows that new offshore wind turbines can take away energy from existing ones

by University of Colorado Boulder
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Key Takeaways:

  • Wake Effect Reduction: Offshore wind turbines could reduce each other's output by up to 38 percent due to the "wake effect."
  • Energy Supply Capability: Despite wake effect interference, these new turbines could meet 60 percent of New England's electricity needs.
  • Enhanced Predictions: Study contributes to scientists refining models to better predict and manage wind energy integration into the grid.

As summer approaches, electricity demand surges in the US as homes and businesses crank up the air conditioning. To meet the rising need, many East Coast cities are banking on offshore wind projects the country is building in the Atlantic Ocean.

For electric grid operators, knowing how much wind power these offshore turbines can harvest is critical, but making accurate predictions can be difficult. A team of scientists at the University of Colorado Boulder and their collaborators are working to tackle the challenge. 

In a new paper published 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 US plans to build large wind farms, could take away wind from other turbines nearby, potentially reducing the farms’ power output by more than 30 percent. 

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

“The US 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. 

Understanding the wake effect

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 percent to 38 percent 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. 

“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.” 

A balancing act

In early 2024, five looming wind turbines off the coast of Massachusetts from the country’s first large-scale offshore wind project delivered the first batch of wind power to the New England grid. More turbines are under construction off the coasts of Rhode Island, Virginia, and New York. The Biden Administration has set a goal to install 30 gigawatts of offshore wind capacity by 2030, which is enough to power more than 10 million homes for a year.

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. 

As the country continues to expand renewable energy projects and integrates more clean electricity into the power system, grid operators need to know precisely how much energy from each renewable source they can count on.

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. 

In addition to the growing demand for air conditioning and heat pumps, electricity consumption in the US has been rising rapidly in recent years because of the increasing prevalence of electric vehicles, data centers, and manufacturing facilities. Over the next five years, analyses project that electricity demand in the US will increase by nearly five percent, a substantial increase compared with the estimated annual growth rate of 0.5 percent over the past decade. 

“We need a diverse mix of clean energy sources to meet the demand and decarbonize the grid,” Lundquist said. “With better predictions of wind energy, we can achieve more reliance on renewable energy.”

- This press release was originally published on the CU Boulder Today website and has been edited for style and clarity

AI Use Disclaimer: Parts of this text, such as the title and key takeaways, may have been generated using AI. All AI-generated content is fact-checked and edited for clarity.