bsrn.utils.calculations.calc_kt#

bsrn.utils.calculations.calc_kt(ghi, zenith, bni_extra, min_mu0=0.065, max_clearness_index=2.0)[source]#

Calculates clearness index ($k_t$) following pvlib conventions [1] [2] [3].

$k_t = G_h / (E_{0n} cdot max(mu_0,; text{min_mu0}))$

Parameters:

  • ghi (numeric or Series) – Measured global horizontal irradiance ($G_h$). [W/m^2]

  • zenith (numeric or Series) – True (not refraction-corrected) solar zenith angle ($Z$). [degrees]

  • bni_extra (numeric or Series) – Extraterrestrial beam normal irradiance ($E_{0n}$). [W/m^2]

  • min_mu0 (float, default 0.065) – Minimum $mu_0$ for the denominator (equiv. ~86.3 deg).

  • max_clearness_index (float, default 2.0) – Upper clamp for $k_t$; 2.0 allows sub-hourly over-irradiance.

Returns:

kt – Clearness index ($k_t$), clamped to [0, max_clearness_index]. [unitless]

Return type:

numeric or Series

References