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.

  • ghi (numeric) – Global horizontal irradiance in W/m^2.

  • zenith (numeric) – True (not refraction-corrected) zenith angles in decimal degrees.

  • datetime_or_doy (int, float, array, pd.DatetimeIndex) – Day of year or array of days of year e.g. pd.DatetimeIndex.dayofyear, or pd.DatetimeIndex.

  • dni_extra (numeric, optional) – Extraterrestrial direct normal irradiance. [W/m2]

  • 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 degrees.

  • 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.


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

  • dni: the modeled direct normal irradiance in W/m^2.

  • dhi: the modeled diffuse horizontal irradiance in W/m^2.

  • kt: Ratio of global to extraterrestrial irradiance on a horizontal plane.



Orgill, J.F., Hollands, K.G.T., Correlation equation for hourly diffuse radiation on a horizontal surface, Solar Energy 19(4), pp 357–359, 1977. Eqs. 3(a), 3(b) and 3(c) DOI: 10.1016/0038-092X(77)90006-8

See also

dirint, disc, erbs, boland