windpowerlib.wind_speed.logarithmic_wind_profile

windpowerlib.wind_speed.logarithmic_wind_profile(v_wind, v_wind_height, hub_height, z_0, obstacle_height=0)[source]

Calculates the wind speed at hub height using a logarithmic wind profile.

The logarithmic height equation is used. There is the possibility of including the height of the surrounding obstacles in the calculation. This function is carried out when the parameter wind_model of an instance of the Modelchain class is ‘logarithmic’ or ‘logarithmic_closest’.

Parameters:
  • v_wind (pandas.Series or array) – Wind speed time series.
  • v_wind_height (float) – Height for which the parameter v_wind applies.
  • hub_height (float) – Hub height of wind turbine.
  • z_0 (pandas.Series or array or float) – Roughness length.
  • obstacle_height (float) – Height of obstacles in the surrounding area of the wind turbine. Set obstacle_height to zero for wide spread obstacles. Default: 0.
Returns:

Wind speed at hub height.
Return type:

pandas.Series or array

Notes

The following equation is used [1]:

v_{wind,hub}=v_{wind,data}\cdot \frac{\ln\left(\frac{h_{hub}-d}{z_{0}}\right)}{\ln\left( \frac{h_{data}-d}{z_{0}}\right)}

with:
v: wind speed, h: height, z_{0}: roughness length, d: boundary layer offset (estimated by d = 0.7 * obstacle_height)

For d = 0 it results in the following equation [2], [3]:

v_{wind,hub}=v_{wind,data}\cdot\frac{\ln\left(\frac{h_{hub}} {z_{0}}\right)}{\ln\left(\frac{h_{data}}{z_{0}}\right)}

h_{data} is the height at which the wind speed v_{wind,data} is measured.

Parameters v_wind_height, z_0, hub_height and obstacle_height have to be of the same unit.

References

[1]Quaschning V.: “Regenerative Energiesysteme”. München, Hanser Verlag, 2011, p. 278
[2]Gasch, R., Twele, J.: “Windkraftanlagen”. 6. Auflage, Wiesbaden, Vieweg + Teubner, 2010, p. 129
[3]Hau, E.: “Windkraftanlagen - Grundlagen, Technik, Einsatz, Wirtschaftlichkeit”. 4. Auflage, Springer-Verlag, 2008, p. 515