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. When it comes to solar energy, it’s a definite advantage to be close to the equator.
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. Therefore, two sites at the same latitude may have drastically different solar radiation levels depending on the cloud cover. On average, clouds absorb or scatter about 20% of the incoming solar radiation.
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. Atmospheric pollution and sand storms also have similar impact. While aerosols degrade the performance of photovoltaic systems, their impact is more severe on the performance of concentrating solar applications and solar thermal systems.
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.
The immediate surroundings of a project site also has a big impact on the level of solar radiation reaching solar energy systems. Vegetation, buildings, even certain landscape features such as hills can block incoming radiation and cast a shadow, drastically reducing the usable solar radiation.