Solar geometric angles vary with respect to the time of day and year due to the Earth’s rotation and orbit around the sun. The solar altitude angle (α) and solar azimuth angle (γ) change throughout the day, while the tilt angle (β) remains constant for a fixed surface. The incident angle (θ) and surface azimuth angle (ψ) also vary with the time of day and year. Accurate calculations must account for these changes to determine the energy balance across any time scale.