Tag: Characteristics of the atmospheric boundary layer
Terrain classification and ground airflow
Topographical features can have such a large effect on wind turbine energy output that the economics of the entire project depend entirely on the appropriate selection of the site. In the previous article, two methods for modeling vertical wind profiles (logarithmic wind profile and power exponential wind profile) were described. But these methods were developed for…
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Steady Wind: Variation of wind speed with altitude
As shown in Figure 1 (van der Tempel, 2006), the actual wind speed varies with space and time. Due to turbulence effects, the actual wind speed at any location will always vary around its average value with time and direction. Most importantly, the graph clearly shows that the average wind speed increases with height, a…
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Turbulence
Turbulence in the wind results from the continuous creation and disappearance of small eddies (or gusts), which convert the kinetic energy dissipation of the wind into thermal energy. Turbulent winds may have relatively stable averages over time spans of an hour or longer, but over shorter periods of time (minutes or less) it may vary…
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Atmospheric lapse rate
The lapse rate of the atmosphere is usually defined as the rate of change of temperature with altitude. As shown in the analysis below, the lapse rate is easily determined by calculating the change in pressure with altitude using conventional thermodynamic relationships. If the atmosphere can be approximated as a dry ideal gas (no water…
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