Solar Radiation is electromagnetic radiation emitted by the Sun. Solar Radiation comes to earth in form of Visible Sunlight, Electromagnetic radiation, Ultraviolet radiation, Infrared radiation, Radio Emmission.
Solar Gain is the Increase in Thermal Energy of a Object, ( in this case Assembly – Panel), as it absorbs incident Solar Radiation.
When Electrical Distribution Panel – Assembly OR LV Busduct is installed outdoor, it is exposed to direct sunlight and that object faces Solar Gain effect.
Due to Solar Gain, Electrical Assets like HT Panel, LV Panel, Transformer, LV Busduct, absorbs incident Solar Radiation and Increase in Thermal Energy is Observed. This Increase is in Addition to Thermal Energy of Panels due to Current flow from Busbar and Switchgear.
As we know each Switchgear and Busbar Produces heat, due to Resistance and Watt loss, even for Indoor Panel or Busduct. And Even in case of Indoor Assembly Panel need to be designed to ensure Thermal Stablity.
Normally LV Panels / Busduct are designed for Indoor Application which Ambient Temperature from 35 *C to 45 *C. With this Ambient Temperature Temperature Rise tests are been performed, which considers effects of Watt Loss, Busbar Resistance, Panel Volume, Panel IP degree etc. When Assembly – Panel/Busbar to be installed outdoor, in addition to standard Temperature rise test.