pvlib.pvsystem.sapm_effective_irradiance(poa_direct, poa_diffuse, airmass_absolute, aoi, module)[source]#

Calculates the SAPM effective irradiance using the SAPM spectral loss and SAPM angle of incidence loss functions.

  • poa_direct (numeric) – The direct irradiance incident upon the module. [W/m2]

  • poa_diffuse (numeric) – The diffuse irradiance incident on module. [W/m2]

  • airmass_absolute (numeric) – Absolute airmass. [unitless]

  • aoi (numeric) – Angle of incidence. [degrees]

  • module (dict-like) – A dict, Series, or DataFrame defining the SAPM performance parameters. See the sapm() notes section for more details.


effective_irradiance (numeric) – Effective irradiance accounting for reflections and spectral content. [W/m2]


The SAPM model for effective irradiance 1 translates broadband direct and diffuse irradiance on the plane of array to the irradiance absorbed by a module’s cells.

The model is .. math:

`Ee = f_1(AM_a) (E_b f_2(AOI) + f_d E_d)`

where \(Ee\) is effective irradiance (W/m2), \(f_1\) is a fourth degree polynomial in air mass \(AM_a\), \(E_b\) is beam (direct) irradiance on the plane of array, \(E_d\) is diffuse irradiance on the plane of array, \(f_2\) is a fifth degree polynomial in the angle of incidence \(AOI\), and \(f_d\) is the fraction of diffuse irradiance on the plane of array that is not reflected away.



D. King et al, “Sandia Photovoltaic Array Performance Model”, SAND2004-3535, Sandia National Laboratories, Albuquerque, NM