The changing seasons affect solar PV production in two significant ways: the total “Sun Hours” available during the day, and the sunlight’s “angle of incidence” as the light rays strike the solar panel’s surface. The ideal tilt-angle and orientation is subject to the geographic region of the installation; the tilt, orientation, and geographic location will determine the resulting variable sun hours and angles of incidence throughout each year. Solar panels installed north of the equator (ie. northern hemisphere) will be pointed South, East or West. The inclination of the panels and racking will depend on how far away from the equator the system is installed. Extreme Northern latitudes have very low sun angles, meaning the Sun is very low in the sky. This indicates that a South facing array at a steep inclination would best capture the movement of the Sun, from sunrise to sunset. The total sun hours will determine the duration of time that the solar panels will be exposed to the Sun. The Sun’s height in the sky changes throughout the year, and is lowest in the sky during the winter. The low sun angle means that the Sun’s rays must pass through more of the Earth’s atmosphere before reaching its destination, which allows for the gases of the atmosphere to deflect and diminish the strengths of the Sun rays; this is called atmospheric scattering.
