Blair Perot Patents Pioneering Airfoils to Make Wind Farms More Efficient

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Professor Blair Perot, head of the Theoretical and Computational Fluid Dynamics Laboratory in the UMass Amherst Mechanical and Industrial Engineering Department, and his collaborator Shujaut Bader of Iowa State University have been awarded a U.S. Patent for their trailblazing concept of a “Wind Turbine Airfoil Structure for Increasing Wind Farm Efficiency.”

The problem addressed by Bader and Perot’s airfoil structure is the significant power loss in wind farms due to substantial “wind wakes” created by upstream turbines effectively neutralizing some of the airflow to downstream turbines. For example, in large offshore wind farms, such power loss ranges from 10 to 20 percent.

Owing to this ongoing problem, wind turbine farms suffer from significant energy deficits in which the downstream turbines generate less power, and/or the front-line turbines are throttled to reduce the downstream power losses.

According to Perot, studies indicate that, across the globe in 2016, $48 billion in wholesale revenue was lost due to this “wind wake” phenomenon. Perot and his research team aim to address this critical problem using their state-of-the-art airfoil and sail technology.  

As Perot and his collaborators explained in a 2018 issue of Wind Energy describing closely related research, which was patented that year: “We focus on possible external modifications that can enhance the wind turbines' performance when they are operating in a farm environment. In particular, this study is interested in enhancing the performance of the downstream turbines in wind farms. The idea is to move each turbine's wake down and away from subsequent turbines.”

Perot and his colleagues concluded that “This goal is achieved by using stationary external airfoils that are placed in proximity to the rotating blades.”

In 2008, the U.S. Department of Energy (DOE) published a report that examined the technical feasibility of using wind energy to generate 20 percent of the nation’s electricity demand by 2030.

“In this paper,” as Perot and his colleagues said in their Wind Energy article, “we pursue an enhancement not mentioned in the DOE report, which is the control and displacement of wind turbine wakes. Modern-day wind farms often consist of a large number of individual turbines arranged in a group or cluster with an inter-turbine spacing of six-to-10 rotor diameters.”

As the Wind Energy paper explained, “The leading (or upstream) turbine in an array is the one to receive the fastest air. After it extracts a part of the energy from the incoming wind stream, it creates a ‘wind shade’ in the region behind it which is referred to as the wake.”

As a result of this wake or wind shade, the wind behind the leading wind turbines is energy deficient and more turbulent than the wind flowing into these lead turbines. Hence, in large wind farms consisting of many rows of turbines, the wakes generated by upstream turbines drastically downgrade the amount of power being produced by the downstream turbines.

According to Perot, “External airfoils can enable partial or full power recovery at turbine separations of as small as three rotor diameters downstream. We will also demonstrate that some devices can also improve the performance of the upstream turbines.”

The prime objective of Perot’s new patent is to facilitate full-velocity recovery by employing the proposed airfoil devices in precise configurations in and around the upstream turbines to control their wake flow in an optimal way for maximizing energy production throughout the wind farm.

As part of Perot’s research related to the new patent, some of his undergraduate students have created models of the airfoil devices and tested them in the UMass wind-tunnel facility, where they worked as predicted. The wind-tunnel experiments were supported through a UMass Acorn funding grant titled “Demonstration of a Wind Turbine Power Augmenter.” (May 2022)