pvlib.irradiance.klucher(surface_tilt, surface_azimuth, dhi, ghi, solar_zenith, solar_azimuth)[source]

Determine diffuse irradiance from the sky on a tilted surface using Klucher’s 1979 model

$I_{d} = DHI \frac{1 + \cos\beta}{2} (1 + F' \sin^3(\beta/2)) (1 + F' \cos^2\theta\sin^3\theta_z)$

where

$F' = 1 - (I_{d0} / GHI)$

Klucher’s 1979 model determines the diffuse irradiance from the sky (ground reflected irradiance is not included in this algorithm) on a tilted surface using the surface tilt angle, surface azimuth angle, diffuse horizontal irradiance, direct normal irradiance, global horizontal irradiance, extraterrestrial irradiance, sun zenith angle, and sun azimuth angle.

Parameters
• surface_tilt (numeric) – Surface tilt angles in decimal degrees. surface_tilt must be >=0 and <=180. The tilt angle is defined as degrees from horizontal (e.g. surface facing up = 0, surface facing horizon = 90)

• surface_azimuth (numeric) – Surface azimuth angles in decimal degrees. surface_azimuth must be >=0 and <=360. The Azimuth convention is defined as degrees east of north (e.g. North = 0, South=180 East = 90, West = 270).

• dhi (numeric) – Diffuse horizontal irradiance in W/m^2. DHI must be >=0.

• ghi (numeric) – Global irradiance in W/m^2. DNI must be >=0.

• solar_zenith (numeric) – Apparent (refraction-corrected) zenith angles in decimal degrees. solar_zenith must be >=0 and <=180.

• solar_azimuth (numeric) – Sun azimuth angles in decimal degrees. solar_azimuth must be >=0 and <=360. The Azimuth convention is defined as degrees east of north (e.g. North = 0, East = 90, West = 270).

Returns

diffuse (numeric) – The sky diffuse component of the solar radiation.

References

 Loutzenhiser P.G. et. al. “Empirical validation of models to compute solar irradiance on inclined surfaces for building energy simulation” 2007, Solar Energy vol. 81. pp. 254-267

 Klucher, T.M., 1979. Evaluation of models to predict insolation on tilted surfaces. Solar Energy 23 (2), 111-114.