If someone wants to use solar energy in hot places, temperature is a problem. So, what's the solution for cooling the solar panel?
The answer depends on quantity. The more complex the system, the more potential modes of failure. The article mentioned by @Aryan Firouzian goes into great detail on several of these methods, but as a general rule, in order of increasing complexity:
- Passive air cooling- heat exchangers on the back of the panel transfer heat to ambient air, airflow is provided by local air currents or convection. There is no electricity cost to this method.
- Active air cooling- same as above, but some of the energy from the panels is used to power fans. I would imagine that other than in a few DIY arrangements, as soon as the complexity of fans are added, it becomes better to switch to water cooling.
- Passive water cooling- Water circulates between panels and a radiator/evaporative cooler due to convection.
- Active water cooling- Open loop- Water is pumped or sprayed over the surface of the panels. This can be used to help with dust issues as well. Does not necessarily require a radiator. Water evaporating from the surface of the panels can transfer more heat away that the water could carry away with its thermal capacity alone.
- Active liquid cooling- Closed loop- In it's simplest form, water is pumped through a heatsink on the back of the panels, through a radiator and back to the panels. Optionally, the heat from the water can be used directly, harvested, and a system can also be built without photoelectronics being involved at all.
The increase in output is quite substantial, and can justify a fairly complex system if enough wattage is present.