pvlib.irradiance.aoi_projection(surface_tilt, surface_azimuth, solar_zenith, solar_azimuth)[source]

Calculates the dot product of the sun position unit vector and the surface normal unit vector; in other words, the cosine of the angle of incidence.

Usage note: When the sun is behind the surface the value returned is negative. For many uses negative values must be set to zero.

Input all angles in degrees.

Parameters
• surface_tilt (numeric) – Panel tilt from horizontal.

• surface_azimuth (numeric) – Panel azimuth from north.

• solar_zenith (numeric) – Solar zenith angle.

• solar_azimuth (numeric) – Solar azimuth angle.

Returns

projection (numeric) – Dot product of panel normal and solar angle.