A long, detailed article in Windpower Engineering provides a fascinating look at current efforts to understand the complex wind flows in and around wind farms. Recent research at NREL, Sandia National Laboratory, and Texas Tech is highlighted in the article, which also includes several compelling graphic representations of the patterns of turbine wakes inside wind farms. For the first time, researchers are now able to measure wind speed and direction in three dimensions in working wind farms, using multiple dopplar radar units; this data has led to new and far more detailed computer models that can be used to investigate how small changes in turbine operations may reduce stresses on downwind turbines.
Read the whole thing at the link above; here are a few teasers:
“It’s almost as if we added a dye into the wind that changes color with speed,” says Moriarty, commenting on the video he presented. “The images show high winds in red or hot colors, and slower winds speeds in blue, and how well downstream turbines are working.
What has been known for a while, he says, is that under certain atmospheric conditions, turbines are getting beat up by what’s called a mildly stable atmosphere. “Even though this has been known for a while, we don’t know exactly what is happening in the flow that influences damage events” says Moriarty.
Although tuning a wind plant is difficult, Moriarty’s simulations suggest adjustments. “We have run several simulations, for example, that de-rate (reduce the power) the first row to let more energy through. That works under some conditions. And then there’s wake steering, moving a wake. Changing the yaw on one or more turbines allows controlling where the wake flows, ideally away from downstream turbines. Depending on yaw angle, results show a 4.5% increase in energy capture.”
UPDATE, 10/17/13: Here’s more on turbulence research, this time in India, where the Tamil Nadu province has some insane turbine densities (check out the image at the link; note the 2km bar at the bottom right).