A new study conducted by an international research group has raised the question of what happens when too many wind turbines begin affecting the low atmosphere.
Over the last decade there have been several attempts to determine the impact of wind farms on the atmosphere and regional and global climate. The concern rests primarily with the way wind turbines affect the wind that powers them. As a wind current hits a wind turbine to move the blades the strength of that current is lessened — so scientists have long since determined that turbines should not be placed directly one behind the other in line with prevailing wind currents if the wind farm is to be as efficient as possible. Therefore, concerns have been raised over what impact this will have on regional, and even global climates — whether or not daytime or night time is adversely affected by too many wind turbines, etc.
New research that was recently published in the Proceedings of the National Academy of Sciences (PNAS) has similarly attempted to answer the question, “What happens to the wind when a larger number of wind turbines removes more and more of the energy of atmospheric motion?” Two atmospheric science professors from the University of Kansas were part of the international research group which co-authored the paper, which “evaluated the effects of large wind farms on atmospheric flow and its implications for how much renewable energy the turbines can generate.”
“Wind turbines generate electricity by removing energy from the wind, so a larger number of wind turbines should result in a slowdown of the winds in the lower atmosphere,” explained David Mechem, who along with Nate Brunsell, represented the University of Kansas on the team. In the abstract for the report, the authors explain further, saying that “wind turbines remove kinetic energy from the atmospheric flow, which reduces wind speeds and limits generation rates of large wind farms” — which appears to be the focus of the report, rather than any attempt to dismiss wind energy as a valuable renewable form of energy. Furthermore, the authors of the report note that “the limited replenishment of kinetic energy from aloft limits wind power generation rates at scales sufficiently large that horizontal fluxes of kinetic energy can be ignored.”
The report evaluates these factors and demonstrates by use of a regional atmospheric model based on the central United States the scale that is required for such a drop off to occur. The researchers noted that there is currently no current or planned wind farm that even comes close to the size or concentration necessary to begin pushing towards diminishing returns, they are nevertheless cautious to advise developers of the possibility, and the need for this new research to be incorporated into further planning.
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