I'm a beginner myself, but have a post (that no one answered either about a solar fan lol). I believe I understand how these things work now, and will let you know how I see it. The specs of that fan didn't list the watts or voltage only that the fan runs on DC.
You want to look for a 12v or 24v DC ceiling fan (doesn't have to be solar, just 12v or 24v DC). I learned you can't connect direct to a solar panel (unless the item plugged in can handle multiple voltages) as solar panels put out all sorts of voltages depending on the current sunlight. In the morning without much sun your 12v panels may be putting out only 8v. As the sun rises, so does the voltage and at noon your 12v panels might be outputting 17v+ and as the sun goes down so does your panels voltage. Since the voltage varies we need something to stabilize it. We have 2 options.
If we're going to use a battery, then you get a solar controller (some are cheap, $15... 12v or 24v and battery either 12v or 24v). Solar controllers typically have 2 inputs for the solar panel, 2 for the battery, and 2 for the load. All that I've seen you can not skip the battery, the controller handles trying to keep the battery charged (without damaging it, overcharging, etc.) and the load pulls off said battery through the same controller. Most require lead battery types. The good here is, you may be able to use a smaller panel and draw off the battery but the battery matters too. A typical car battery is meant to stay charged to 95%+ else it gets damaged and be junk quickly. Deep cycle marine batteries are designed to be drained down more, but even discharging below 80% will shorten their life a little, some can go down to 20% with minimal damage repeatedly. So a deep cycle battery makes the most sense, and the panel big enough to keep it over 80% charged.
If we're not going to use a battery, then we need a voltage regulator instead of controller. This is useful for times we want something to run only when there's enough sunlight (attic fan for example). A voltage regulator takes the unstable voltages from the solar panel and outputs a stable voltage for the device (these are cheap as well, $8-$12). They also take some of the volt(s) out of the panel to work, that is if you want 12v out of the voltage regulator the regulator will only turn on the output when the solar panel has enough sunlight to produce 13v+ (because it uses 1v give or take). Also a warning USB ports on voltage regulators are typically tied to what you set the output volts to. So, if you set the output to 12v to run something out of the voltage regulator the USB ports (if it has them) will also be 12v DC and fry anything you plug into them.
Since panels typically state their best lab specs (not real world) you want to overshoot. If the fan uses 12v DC and 6A, that's 72 watts. Add inefficiencies of stated claims and some loss to the controller and I would think you'd need a 100 watt panel. But, depends on how many amps/watts and voltage of the motor.
