Theoretical model of solar incident angle for an optionally oriented fixed flat surface

Abstract

The apparent position of the Sun in relation to any surface is defined by the solar incident angle. The solar incident angle forms the vector of the position of the Sun and the vector of normal to the observed surface. The spatial position of the aforementioned vectors is determined by solar coordinates, which include: declination, latitude, hour angle, longitude, solar elevation angle, solar azimuth angle, azimuth angle of the observed surface, angle of inclination of the observed surface in the north-south direction and angle of inclination of the observed surface in the east-west direction. This article describes in detail the theoretical model for determining the solar incident angle for an arbitrarily placed fixed, flat surface using vector algebra and analytical geometry, as well as solar coordinates. The study model, which was developed by combining, modifying, and supplementing existing models, can be used to determine the thermal performance of solar devices such as: solar collectors, PV panels, and hybrid solar systems.