Wind Projects - Site Selection - Rules of Thumb

Estimating annual wind energy output

The forecasting of annual energy generated by a single wind turbine or a wind park at a specific site is a very complex task requiring very much work in advance for wind measurement and the following site evaluation. However, some basic relationships like the increase of wind power with wind speed, the increase in wind speed with height, the dependency of wind power towards air density and general assumptions about the wind speed distribution can be used to create a rough estimation of the annual wind energy output.

The relationship of wind speed to wind power

The power $P$ of a wind stream with the speed $v$ is given by 

$P=1/2\rho AV^{3}$

where $\rho$ is the density of air and A is the swept area by the rotor of the wind turbine. Using air density at sea level $\rho$=1,225 kg/m³ the relationship can be expressed as $P=0,6125AV^{3}$.