A solar fan is a mechanical fan powered by solar panels. The solar panels are either mounted on the device or are installed independently. Solar fans mostly do not require secondary power sources other than solar power, as most of them are used for cooling purposes during day time. Some types are also used for heating purposes. It runs the fastest when it is the hottest outside providing savings on air conditioning costs.
Attic heat is caused by the sun baking down on the roof surface. This sunlight causes the roofing material to heat up, thus transferring the heat into the attic via thermal transfer. The buildup of heat is generally dissipated by normal convection.
A typical roof-mounted solar attic fan will be effective in removing excessive heat from the attic. When mounted near the peak the solar fan forces hot air out while pulling fresh air in via eave/soffit vents. This exchange of air keeps the attic space from overheating.