The amount of power generated by a wind turbine depends largely on the wind speed, but that’s not the only factor that comes into play. Individual turbines in a wind farm can experience the same wind speeds but different wind profile “shapes,” such as turbulence and wind shear (the difference in wind speed and direction over a relatively short distance in the atmosphere)—with significant impact.
New research finds that these factors, collectively referred to as “atmospheric stability,” can be used an indicator for power production. By developing forecasts of atmospheric stability measures at wind farm sites, scientist can help operators better estimate how much power a facility is likely to generate at a given time.
These findings are the result of a year’s worth of data collected from 80-meter-tall turbines at a West Coast wind farm. In addition to power production data, Lawrence Livermore National Laboratory (LLNL) scientist Sonia Wharton and colleague Julie Lundquist of the University of Colorado at Boulder and the National Renewable Energy Laboratory also gathered meteorological data from an 80-meter-tall tower and a Sonic Detection and Ranging (SODAR). They found that, at a fixed wind speed, turbines generated up to 15 percent more power under stable conditions than under strongly unsteady conditions at the same location.
“The dependence of power on stability is clear, regardless of whether time periods are segregated by three-dimensional turbulence, turbulence intensity or wind shear,” Wharton said in a statement. “We also found that wind turbines experienced stable, near-neutral and unstable conditions during the spring and summer. But, daytime hours were almost always unstable or neutral while nights were strongly stable.”
Although similar research on the effects of atmospheric stability on power output has been performed previously, few studies have analyzed power output from modern turbines over 60 meters tall. The new research highlights the increased accuracy achieved by observing wind speed and turbines across the turbine rotor disk.