pvlib.irradiance.orgill_hollands#

pvlib.irradiance.orgill_hollands(ghi, zenith, datetime_or_doy, dni_extra=None, min_cos_zenith=0.065, max_zenith=87)[source]#

Estimate DNI and DHI from GHI using the Orgill and Hollands model.

The Orgill and Hollands model [1] estimates the diffuse fraction DF from global horizontal irradiance through an empirical relationship between hourly DF observations (in Toronto, Canada) and the ratio of GHI to extraterrestrial irradiance, Kt.

Parameters:

ghi (numeric) – Global horizontal irradiance. See ghi. [Wm⁻²]
zenith (numeric) – True (not refraction-corrected) zenith angles. See solar_zenith. [°]
datetime_or_doy (int, float, array or pd.DatetimeIndex, optional) – Day of year or array of days of year e.g. pd.DatetimeIndex.dayofyear, or pd.DatetimeIndex. Either datetime_or_doy or dni_extra must be provided.
dni_extra (numeric, optional) – Extraterrestrial normal irradiance. dni_extra can be provided if available to avoid recalculating it inside this function. In this case datetime_or_doy is not required. See dni_extra. [Wm⁻²]
min_cos_zenith (numeric, default 0.065) – Minimum value of cos(zenith) to allow when calculating global clearness index Kt. Equivalent to zenith = 86.273°.
max_zenith (numeric, default 87) – Maximum value of zenith to allow in DNI calculation. DNI will be set to 0 for times with zenith values greater than max_zenith. [°]

Returns:

data (OrderedDict or DataFrame) – Contains the following keys/columns:

dni: the modeled direct normal irradiance. [Wm⁻²]
dhi: the modeled diffuse horizontal irradiance [Wm⁻²].
kt: Ratio of global to extraterrestrial irradiance on a horizontal plane. [unitless]

References