Wind Converters Theory

Habil Oyugi


From the viewpoint of energy conversion, the most important properties of the wind at a particular location are the velocity of the airstream and the air density. The air density varies with altitude and with atmospheric conditions such as temperature, pressure, and humidity. At sea level and at standard atmospheric temperature and pressure, the value is: ρ = 1.201 kg/m3 at 1bar or 101.3 kilo Pascal (kPa) pressure and temperature 293K.In the UK, a useful figure for the atmospheric air density is: ρ = 1.29 kg/m3). In the USA, a commonly quoted figure, for sea level under dry conditions at a temperature of 0◦C (273 K), is: ρ = 1.275 kg/m3. There is a lot of local variation of the values of the air density in different areas of the world. It is found that the temperature, pressure, and density of the air decrease with altitude. For wind-turbine applications, the range of interest is mostly within a couple of hundred feet above ground level. Within this range, it is adequate to use the density values above.


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