pvlib.irradiance.haydavies

pvlib.irradiance.haydavies(surface_tilt, surface_azimuth, dhi, dni, dni_extra, solar_zenith=None, solar_azimuth=None, projection_ratio=None)

Determine diffuse irradiance from the sky on a tilted surface using Hay & Davies’ 1980 model

\[I_{d} = DHI ( A R_b + (1 - A) (\frac{1 + \cos\beta}{2}) )\]

Hay and Davies’ 1980 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, extraterrestrial irradiance, sun zenith angle, and sun azimuth angle.

Parameters:

surface_tilt : float or Series

Surface tilt angles in decimal degrees. The tilt angle is defined as degrees from horizontal (e.g. surface facing up = 0, surface facing horizon = 90)

surface_azimuth : float or Series

Surface azimuth angles in decimal degrees. The azimuth convention is defined as degrees east of north (e.g. North=0, South=180, East=90, West=270).

dhi : float or Series

Diffuse horizontal irradiance in W/m^2.

dni : float or Series

Direct normal irradiance in W/m^2.

dni_extra : float or Series

Extraterrestrial normal irradiance in W/m^2.

solar_zenith : None, float or Series

Solar apparent (refraction-corrected) zenith angles in decimal degrees. Must supply solar_zenith and solar_azimuth or supply projection_ratio.

solar_azimuth : None, float or Series

Solar azimuth angles in decimal degrees. Must supply solar_zenith and solar_azimuth or supply projection_ratio.

projection_ratio : None, float or Series

Ratio of angle of incidence projection to solar zenith angle projection. Must supply solar_zenith and solar_azimuth or supply projection_ratio.

Returns:

sky_diffuse : float or Series

The diffuse component of the solar radiation on an arbitrarily tilted surface defined by the Perez model as given in reference [3]. Does not include the ground reflected irradiance or the irradiance due to the beam.

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] Hay, J.E., Davies, J.A., 1980. Calculations of the solar radiation incident on an inclined surface. In: Hay, J.E., Won, T.K. (Eds.), Proc. of First Canadian Solar Radiation Data Workshop, 59. Ministry of Supply and Services, Canada.