Wind power, in order to be more effective on a national level as an energy source, will need continued growth of wind farms, large and small. On these farms it will probably be common practice to fit in as many wind turbines as possible in order to maximize acreage. The question that arises as a result is – what is best spacing policy between turbines for optimal energy production? Teams from the U.S. and Belgium working together believe they have an answer.
Charles Meneveau, who studies fluid dynamics at Johns Hopkins University, and his collaborator Johan Meyers from Leuven University in Belgium, are said to have developed a model to calculate the optimal spacing of turbines for the very large wind farms of the future. Using as example 5 megawatt-rated machines and “some reasonable economic figures,” a statement related to the study says, Meneveau calculated that the optimal spacing between turbines should be about 15 rotor diameters instead of the currently prevalent figure of 7 rotor diameters.
The blades of a turbine distort wind, creating eddies of turbulence that can affect other wind turbines farther downwind. Starting with large-scale computer simulations and small-scale experiments in a wind tunnel, said Meneveau, his new model considered the cumulative effects of hundreds or thousands of turbines interacting with the atmosphere.
It was found the energy a large wind farm can produce depends less on horizontal winds and more on entraining strong winds from higher in the atmosphere. A 100-meter turbine in a large wind farm must harness energy drawn from the atmospheric boundary layer thousands of feet up. With the right configuration, “lots of turbines essentially change the roughness of the land — much in the same way that trees do — and create turbulence. Turbulence, in this case, isn’t a bad thing. It mixes the air and helps to pull down kinetic energy from above.”
“The optimal spacing between individual wind turbines is actually a little farther apart than what people use these days,” said Meneveau in a statement.
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