pvlib.irradiance.clearness_index_zenith_independent#

pvlib.irradiance.clearness_index_zenith_independent(clearness_index, airmass, max_clearness_index=2.0)[source]#

Calculate the zenith angle independent clearness index.

See 1 for details.

Parameters
  • clearness_index (numeric) – Ratio of global to extraterrestrial irradiance on a horizontal plane

  • airmass (numeric) – Airmass

  • max_clearness_index (numeric, default 2.0) – Maximum value of the clearness index. The default, 2.0, allows for over-irradiance events typically seen in sub-hourly data. NREL’s SRRL Fortran code used 0.82 for hourly data.

Returns

kt_prime (numeric) – Zenith independent clearness index

References

1

Perez, R., P. Ineichen, E. Maxwell, R. Seals and A. Zelenka, (1992). “Dynamic Global-to-Direct Irradiance Conversion Models”. ASHRAE Transactions-Research Series, pp. 354-369