In order to run a solar fan directly from solar panel without battery you need to select whole system carefully.
How to use a solar panel to run a fan.
What is a solar powered fan.
Similarly to how solar lights works a small solar fan is powered by a solar panel that is either mounted on the device or wired to a separate installation.
It would be good to put a dc controller in between panel and dc fan.
Great for a variety of uses.
The pc fan needs a voltage of 12v with at least 0 3a 300ma to run.
Western harmonics solar powered fan kit 1505 hg features a great fan running directly off a 10 watt solar panel.
This circuit is a voltage doubler that doubles or triples the voltage to make the fan run but the power watts stays same even smaller a little.
The solar board is 1 2v and 300ma.
A fan having 12vdc and 25 watt need a panel of 12vdc and 30watt.
Video shows the basic hookup of a standard 80mm computer case fan to a solar panel.
I use these fans in many things that i make so i wanted to cut this video to show the basic hook up from fan to.