windpowerlib.density.barometric

windpowerlib.density.barometric(pressure, pressure_height, hub_height, temperature_hub_height)[source]

Calculates the density of air at hub height using the barometric height equation.

This function is carried out when the parameter density_model of an instance of the ModelChain class is ‘barometric’.

Parameters:

  • pressure (pandas.Series or numpy.array) – Air pressure in Pa.

  • pressure_height (float) – Height in m for which the parameter pressure applies.

  • hub_height (float) – Hub height of wind turbine in m.

  • temperature_hub_height (pandas.Series or numpy.array) – Air temperature at hub height in K.

Returns:

Density of air at hub height in kg/m³. Returns a pandas.Series if one of the input parameters is a pandas.Series.

Return type:

pandas.Series or numpy.array

Notes

The following equation is used [1] [2] :

\rho_{hub}=\left(p/100-\left(h_{hub}-h_{p,data}\right) \cdot\frac{1}{8}\right)\cdot \frac{\rho_0 T_0\cdot 100}{p_0 T_{hub}}

with:

T: temperature [K], h: height [m], \rho: density [kg/m³], p: pressure [Pa]

h_{p,data} is the height of the measurement or model data for pressure, p_0 the ambient air pressure, \rho_0 the ambient density of air, T_0 the ambient temperature and T_{hub} the temperature at hub height h_{hub}.

Assumptions:

  • Pressure gradient of -1/8 hPa/m

References