Re: Solar panel used to power fan directly
Probably not--The typical brushed motor is pretty voltage tolerant. Go ahead and connect--measure the fan voltage and see if it is OK.
It is very possible though, that you will need a larger solar panel to start the fan and run it under less than full sun... The "proper" way to run a blower is with a Linear Current Booster (more or less the MPPT of the battery less DC world).
7 amp Linear Current Booster/Pump Driver
But, they are not cheap... It may cost less to just buy a second solar panel and connect it up.
Poster 2manytoyz--On his website, he has a solar attic fan project which is similar to what you are probably looking at:
20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.