pvlib.irradiance.clearness_index_zenith_independent

pvlib.irradiance.clearness_index_zenith_independent(clearness_index, airmass, max_clearness_index=2.0)

Calculate the zenith angle independent clearness index.

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