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    New Checkerboard Optimization Scheme Could Reduce Wake Effects In Wind Turbines
    By News Staff | April 2nd 2014 03:00 AM | Print | E-mail | Track Comments
    As long as mandates and subsidies continue, wind turbines will continue to be part of the alternative energy mix. 

    That means going beyond hype and potential and focusing on physical design, such as spacing and orienting individual turbines to maximize their efficiency and minimize any "wake effects," where the swooping blades of one reduces the energy in the wind available for the following turbine. 

    Many considerations go into the design of a wind farm.  Political and social considerations factor into the choice of sites but after that, ideal turbine arrangement will differ depending on location. The specific topology of the landscape, whether hilly or flat, and the yearlong weather patterns at that site both dictate the specific designs. Common test cases to study wind-farm behavior are wind farms in which turbines are either installed in rows, which will be aligned against the prevailing winds, or in staggered, checkerboard-style blocks where each row of turbines is spaced to peek out between the gaps in the previous row. 

    Staggered farms are generally preferred because they harvest more energy in a smaller footprint, but what Stevens and his colleagues showed is that the checkerboard style can be improved in some cases.

    Optimally spacing turbines allows them to capture more wind, produce more power and increase revenue for the farm. Knowing this, designers in the industry typically apply simple computer models to help determine the best arrangements of the turbines. This is fine for small wind farms but for larger wind-farms, where the wakes interact with one another, the overall effect is harder to predict.

    Researchers from Johns Hopkins University say they have developed a new way to study wake effects that takes into account the airflow both within and around a wind farm and challenges the conventional belief that turbines arrayed in checker board patterns produce the highest power output. Their study provides insight into factors that determine the most favorable positioning. This insight is important for wind project designers in the future to configure turbine farms for increased power output -- especially in places with strong prevailing winds.

    "It's important to consider these configurations in test cases," said Richard Stevens, who conducted the research with Charles Meneveau and Dennice Gayme at Johns Hopkins University. "If turbines are build in a non-optimal arrangement, the amount of electricity produced would be less and so would the revenue of the wind farm."

    Specifically, they found that better power output may be obtained through an "intermediate" staggering, where each row is imperfectly offset -- like a checkerboard that has slipped slightly out of whack.

    Citation:  Richard J. A. M. Stevens, Dennice F. Gayme and Charles Meneveau, 'Large Eddy Simulation studies of the effects of alignment and wind farm length', Journal of Renewable and Sustainable Energy, DOI: 10.1063/1.4869568.