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.

  • 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.


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