At Block Island Wind Farm, researchers measure impact of wind reductions on energy production

Wind turbines are a key component of renewable energy infrastructure, converting wind energy into electricity to power homes and businesses.

However, they are susceptible to an aerodynamic phenomenon called “wake effect” that can reduce energy production by roughly 10 to 20%. In some extreme cases, energy production can be reduced by 40%.

This phenomenon can cause additional loadings on structural components and reduce overall performance, explains Eleonora Tronci, a Northeastern University civil and environmental engineering professor.

Mitigating wake effect is essential for improving the efficiency and longevity of wind farms.

While wake effect has been extensively studied in theoretical and pre-design models, there is still a need for more experimental research at operational wind farms, explains Tronci.

“Understanding wake interactions not only helps us improve wind farm designs before they’re built but also informs how we can optimize energy production,” she says.

That’s why research recently published in Renewable Energy, co-authored by Tronci and Sina Shid-Moosavi, on wake effect’s impact on Block Island Wind Farm is so valuable, especially as global demand for renewable energy continues to rise.

Block Island Wind Farm, which became the first commercial offshore wind farm in the U.S. in 2016, offered an interesting case study, given that its turbines are “aligned in a nearly straight line,” the researchers write. To investigate this, researchers used real-world monitored data to analyze the wake interaction at the site.

How wake effect works

To understand how wake effect works, it’s helpful to visualize a wind farm’s layout and how turbines are positioned next to each other. Oftentimes, turbines are stacked in proximity to one another in a dense area. While that may be an efficient use of space, it also causes problems.

When wind passes through the first turbine in a stack, it creates increased turbulence and reduces wind speed, making the subsequent turbines in the stack less efficient and prone to fatigue damage. Therefore, the term “wake” in wake effect directly refers to the disturbance in the wind as it moves downstream.

What was done at Block Island?

At Block Island Wind Farm, the researchers analyzed several operational and model parameters for wake effect, including turbulence intensity, yaw angle (the rotation of the wind turbine), and power and thrust coefficients.

Among all the factors, turbulence intensity is the most significant parameter driving wake effect. However, it is also the most challenging to measure because lidar sensors are needed for accurate data capture, Shid-Moosavi explains.

Tronci and Shid-Moosavi, using LiDAR measurements from the Woods Hole Oceanographic Institution’s ASIT at the Martha’s Vineyard Coastal Observatory, observed a seasonal variation in turbulence intensity, which correlates with changes in wake effect. They suggest considering these variations by placing lidar sensors near the wind farms and tracking them over several seasons.

More accurate simulation models

That data has been key for researchers to create more accurate wind farm simulation models. Those simulations are important for them to understand “the wake interactions” that significantly impact wake effect.

This research, which was done in partnership with Tufts University, is the first of many studies that Shid-Moosavi and Tronci plan to conduct in the next few years to understand this phenomenon better.

“Once you provide people with a better understanding of this and also prediction tools on how these different interaction dynamics change, it can help inform in the predesign state or if you have an active farm, what is the expected life of these structures due to these interactions,” Tronci says.

This story is republished courtesy of Northeastern Global News news.northeastern.edu.