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

$F' = 1 - (I_{d0} / GHI)^2$

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

1

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

2

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