pvlib.irradiance.haydavies#
- pvlib.irradiance.haydavies(surface_tilt, surface_azimuth, dhi, dni, dni_extra, solar_zenith=None, solar_azimuth=None, projection_ratio=None, return_components=False)[source]#
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 (numeric) – 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 (numeric) – 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 (numeric) – Diffuse horizontal irradiance in W/m^2.
dni (numeric) – Direct normal irradiance in W/m^2.
dni_extra (numeric) – Extraterrestrial normal irradiance in W/m^2.
solar_zenith (numeric, optional) – Solar apparent (refraction-corrected) zenith angles in decimal degrees. Must supply
solar_zenith
andsolar_azimuth
or supplyprojection_ratio
.solar_azimuth (numeric, optional) – Solar azimuth angles in decimal degrees. Must supply
solar_zenith
andsolar_azimuth
or supplyprojection_ratio
.projection_ratio (numeric, optional) – Ratio of angle of incidence projection to solar zenith angle projection. Must supply
solar_zenith
andsolar_azimuth
or supplyprojection_ratio
.return_components (bool, default False) – Flag used to decide whether to return the calculated diffuse components or not.
- Returns
numeric, OrderedDict, or DataFrame – Return type controlled by return_components argument. If
return_components=False
, sky_diffuse is returned. Ifreturn_components=True
, diffuse_components is returned.sky_diffuse (numeric) – The sky diffuse component of the solar radiation on a tilted surface.
diffuse_components (OrderedDict (array input) or DataFrame (Series input)) –
- Keys/columns are:
sky_diffuse: Total sky diffuse
isotropic
circumsolar
horizon
Notes
When supplying
projection_ratio
, consider constraining its values when zenith angle approaches 90 degrees or angle of incidence projection is negative. See code for details.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.