pvlib.irradiance.klucher#
- 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 the Klucher (1979) model.
- Parameters:
surface_tilt (numeric) – Panel tilt from horizontal. See surface_tilt. [°]
surface_azimuth (numeric) – Panel azimuth. See surface_azimuth. [°]
dhi (numeric) – Diffuse horizontal irradiance, must be >=0. See dhi. [Wm⁻²]
ghi (numeric) – Global horizontal irradiance, must be >=0. See ghi. [Wm⁻²]
solar_zenith (numeric) – Apparent (refraction-corrected) zenith angles. [°]
solar_azimuth (numeric) – Sun azimuth angles. See solar_azimuth. [°]
- Returns:
diffuse (numeric) – The sky diffuse component of the solar radiation. [Wm⁻²]
Notes
The Klucher (1979) model [1] [2] 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, global horizontal irradiance, sun zenith angle, and sun azimuth angle. The expression for the sky diffuse irradiance, \(I_d\), is as follows:
\[I_{d} = DHI \frac{1 + \cos\beta}{2} (1 + F' \sin^3(\beta/2)) (1 + F' \cos^2\theta\sin^3\theta_z).\]DHI is the diffuse horizontal irradiance, \(\beta\) is the surface tilt angle, \(\theta_z\) is the solar zenith angle, and \(\theta\) is the angle of incidence. \(F'\) is a modulating function to account for when the sky changes from clear to overcast, and is defined as follows:
\[F' = 1 - (DHI / GHI)^2,\]where GHI is the global horiztonal irradiance.
References