Hi Triple
Been using fans on a number of boats for years with great results.
No more mildew or mould and they also cut down on moisture levels too.
A mate had a solar fan and it was just OK in that it only moved a little air compared to the ones I've used for years.
If you in your driveway why not go the 240V route and be done with it? My 20 odd year old fans are 240 V units that started life as computer cooling units. They are simply mounted in old ice cream tubs with a hole cut for the fan and a hunk of wire suspends them so they blow where required ie one forward into the cabin and one facing rearward to cover the area under the stern seats and batteries. They run 24 7 and have done for many years except when the boat leaves the 240 v power.
Go for it; it works well.
Cheers
Chimo