This model calculates the direct solar radiation on a tilted surface (general model).
The direct solar radiation forms an angle with the vector normal to the earth Zen
.
The same direct solar radiation forms an angle with the normal vector of a tilted surface Inc
.
Based on trigonometric relations, the model calculates the direct normal irradiation.
IrrDirNor = IrrDirHor/cosAngleZen
, Which maximum value is limited for numerical reasons to the solar constant 1367
W/m2.
the amount of direct solar radiation incident on a tilted surface is equal to
IrrTotTil = IrrDirNor * cosAngleInc