12v attic fans

It depends on what the rating is for those fans. I currently have a DC fan connected directly to a 10Watt panel and it runs pretty good. I will say that the fan and panel were sold together as a solar roof cooling system so the output voltage/current of the panel was matched to the fan's requirements.

So if you can determine what those 3 fans require and see if the 100w panel can provide that output I would say you just need to protect each set of wires going to each fan with a fuse or circuit breaker and then you should have a complete system. Or if you want to run the fans off of a battery system then look into a battery rated about 10 times what the Imp rating is for that panel and get a PWM CC to charge the battery system from the panels. Then you will just need a distribution block with fusing for each of the fans.

It's a 30 watt 12v 12" fan. It's not the ones with the solar panel mounted on it. I was going to put 3 of them in the attic mounted to the roof vents but wanted to use 1 solar panel to run all 3. I have a 30w panel that if a bird flies over its enough to slow the fan down. So I wanted to mount 1 mono panel and power all 3.but wasn't sure what all I would need to make it work.

Have you sized the fan(s) with any idea of how much heat you want to remove from the attic ?

I have a pair of 12 volt radiator fans installed in my garage roof. They're hardwired to a 65 watt 12 volt solar panel. as long as the sun shines they operate. The stronger the sun hitting the panel, the faster the fans spin. Couldn't be simpler. They've been running in the extreme Baja heat for about 7 years now.