The effects of varying meteorological conditions on power production at a central North American wind farm

Wind energy is playing an increasing role around the world in providing power to electrical grids. It is important to both the provider and consumer of wind energy to maximize power generation yields. One way to improve these yields is to have a more complete understanding of meteorological conditions at wind farms. This study contains an analysis of farm yields compared to atmospheric conditions in order to quantify the effect that atmospheric stability can have on power generation from wind.

For three months, meteorological data were recorded by ten stations as well as a radar wind profiler at a wind farm in the Plains of Central North America. From these data, two measures of atmospheric characteristics are calculated: the bulk Richardson number and a power law exponent (α) for wind variation with height. Stable, neutral, and convective stability classes are defined, and power curves are generated based on these chosen classes. At this farm, convective conditions provide better yields for low wind speeds below 8m/s, while neutral and stable conditions provide better yields above that threshold. Cases in which low yields were found correlate well with α: higher values, and thus higher shear, lead to lower power generation. This correlation is the opposite from those seen in a West Coast North America wind farm (Wharton and Lundquist, 2010). We surmise that the Plains site is influenced by nocturnal Low Level Jets which induce elevated levels of turbulence and could decrease power performance at the wind farm. An investigation of wind profiles with height at the site confirmed the presence of these jets during many of the times featuring low yields.