Electric fans used for ventilation may be powered by solar panels instead of mains current. This is an attractive option because once the capital costs of the solar panel have been covered, the resulting electricity is free. Also, electricity is always available when the sun is shining and the fan needs to run.
During the absence of electric power solar powered fan is operate the air flowing and maintain environmental condition. 
A typical example uses a detached 10-watt,  solar panel and is supplied with appropriate brackets, cables, and connectors. It can be used to ventilate up to  of area and can move air at up to . Because of the wide availability of 12 V brushless DC electric motors and the convenience of wiring such a low voltage, such fans usually operate on 12 volts.
The detached solar panel is typically installed in the spot which gets most of the sunlight and then connected to the fan mounted as far as  away. Other permanently-mounted and small portable fans include an integrated (non-detachable) solar panel.