pvlib.irradiance.clearness_index_zenith_independent¶
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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