pvlib.irradiance.grounddiffuse¶

pvlib.irradiance.grounddiffuse(surface_tilt, ghi, albedo=0.25, surface_type=None)[source]¶

Estimate diffuse irradiance from ground reflections given irradiance, albedo, and surface tilt

Function to determine the portion of irradiance on a tilted surface due to ground reflections. Any of the inputs may be DataFrames or scalars.

Parameters:

surface_tilt : numeric

Surface tilt angles in decimal degrees. 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).

ghi : numeric

Global horizontal irradiance in W/m^2.

albedo : numeric

Ground reflectance, typically 0.1-0.4 for surfaces on Earth (land), may increase over snow, ice, etc. May also be known as the reflection coefficient. Must be >=0 and <=1. Will be overridden if surface_type is supplied.

surface_type: None or string

If not None, overrides albedo. String can be one of 'urban', 'grass', 'fresh grass', 'snow', 'fresh snow', 'asphalt', 'concrete', 'aluminum', 'copper', 'fresh steel', 'dirty steel'.

Returns:

grounddiffuse : numeric

Ground reflected irradiances in W/m^2.

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.

The calculation is the last term of equations 3, 4, 7, 8, 10, 11, and 12.

[2] albedos from: http://pvpmc.org/modeling-steps/incident-irradiance/plane-of-array-poa-irradiance/calculating-poa-irradiance/poa-ground-reflected/albedo/ and http://en.wikipedia.org/wiki/Albedo