1. Latitude - Due to Earth’s spherical shape, the solar rays have more intensity around the equatorial regions. As we move further away from the equator, the energy density decreases as the solar rays are distributed around a larger geographical region.
2.cloud cover - Clouds have a big impact on the amount of solar radiation reaching the surface of Earth. They reflect and absorb a significant part of the incoming solar radiation
3.aerosols - Aerosols are small particles that float in the atmosphere. By absorbing or diffracting solar radiation, they can act as a filter and decrease the level of solar radiation reaching the surface
4.Elevation - The distance solar rays have to travel through the atmosphere is less at higher altitudes. Therefore there is less atmospheric absorption, and consequently, more solar radiation as the elevation increases.
5.shading - The immediate surroundings of a project site also has a big impact on the level of solar radiation reaching solar energy systems.