What happens when you look in the sky even when its cloudy? There is a sort of glare in the sky that makes it difficult to keep your eyes wide open, right? That is irradiance, in simple terms! And the Solar PV panels use this irradiance for the generation of Solar Power. It is this light that is composed of photons that hit the panels and cause the semiconductors cells (generally composed of Silicon, Germanium, Indium, Tellirium or a mix of them like CdTe, CIGS) to generate electricity.
The abundance of Sunlight is no good to panels if the temperature is very high, as the efficiency decreases. That is why it is seen that the generation in hilly and cooler areas with good sunlight is greater. The optimum temperature (as rated on panels) is around 25-27 deg C. That is why, in order to try to keep them cooler, power producers grow plantations beneath the panels to reduce the heat, thus increasing efficiency.
Written 8 Feb 2014 · View Upvotes