pvlib.irradiance.erbs

pvlib.irradiance.erbs(ghi, zenith, doy)[source]

Estimate DNI and DHI from GHI using the Erbs model.

The Erbs model [1] estimates the diffuse fraction DF from global horizontal irradiance through an empirical relationship between DF and the ratio of GHI to extraterrestrial irradiance, Kt. The function uses the diffuse fraction to compute DHI as

\[DHI = DF \times GHI\]

DNI is then estimated as

\[DNI = (GHI - DHI)/\cos(Z)\]

where Z is the zenith angle.

Parameters:
ghi: numeric

Global horizontal irradiance in W/m^2.

zenith: numeric

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

doy: scalar, array or DatetimeIndex

The day of the year.

Returns:
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.

See also

dirint, disc

References

[1](1, 2) D. G. Erbs, S. A. Klein and J. A. Duffie, Estimation of the diffuse radiation fraction for hourly, daily and monthly-average global radiation, Solar Energy 28(4), pp 293-302, 1982. Eq. 1