r.sun
Solar irradiance and irradiation model.
Raster (r.*)
ParameterRaster|elevation|Elevation layer [meters]|False
ParameterRaster|aspect|Aspect layer [decimal degrees]|False
ParameterRaster|slope|Name of the input slope raster map (terrain slope or solar panel inclination) [decimal degrees]|False
ParameterRaster|linke|Name of the Linke atmospheric turbidity coefficient input raster map|True
ParameterRaster|albedo|Name of the ground albedo coefficient input raster map|True
ParameterRaster|lat|Name of input raster map containing latitudes [decimal degrees]|True
ParameterRaster|long|Name of input raster map containing longitudes [decimal degrees]|True
ParameterRaster|coeff_bh|Name of real-sky beam radiation coefficient input raster map|True
ParameterRaster|coeff_dh|Name of real-sky diffuse radiation coefficient input raster map|True
ParameterNumber|day|No. of day of the year (1-365)|1|365|1
*ParameterNumber|step|Time step when computing all-day radiation sums [decimal hours]|0|None|0.5
*ParameterNumber|declination|Declination value (overriding the internally computed value) [radians]|None|None|0.0
*ParameterNumber|distance_step|Sampling distance step coefficient (0.5-1.5)|0.5|1.5|1.0
ParameterBoolean|-p|Do not iIncorporate the shadowing effect of terrain|False
*ParameterBoolean|-m|Use the low-memory version of the program|False
OutputRaster|beam_rad|Irradiation [Wh.m-2.day-1] 
OutputRaster|insol_time|Insolation time [h] 
OutputRaster|diff_rad|Diffuse irradiation [Wh.m-2.day-1]
OutputRaster|refl_rad|Ground reflected irradiation [Wh.m-2.day-1] 
OutputRaster|glob_rad|Global (total) irradiance/irradiation [Wh.m-2.day-1]