mmm...lots of ideas here but for your information:
In nature, you get nothing for free. Moving the same amount of air, be it from a mechanically driven fan or an electrically driven fan, draws the same amount of power . However, you may use a less powerful electric fan and run it for more time, so the instaneouos power required is less. That is not opinion, that it physics.
You think driving an alternator is easy? how many times have you had to tighten that belt to stop it from screeching driving the alternator: nothing like that for the fan...yes, the fan pulley diameter is larger, so you need less pull from the belt, because you have more leverage. Anyway, those electric fans require 25-30 amps Ó 14.5 volts ( regulated voltage with engine running), so about 400-450 watt: the regulator will maintain voltage so for that, it will excite the alternator to provide the additional 30 amps as required, not the battery; driving belt plus alternator combinaison has about a 60% efficiency so you will need about 750 watt from the engine, which is 1 h.p. This is not a loss less that what a mechanical fan requires.
Also, when the mechanical fan runs idle at 60 mph, well the windstream will make the fan rotate almost as much as if it were driven, so no real strain in fact on the system.
A normal car running at 60 mph requires about 20 hp to maintain constant speed. (I,ll offer you an easy test for that soon). So no way that fan requires 10 hp.
ALL in all, it is a question of preference: I might have fun installing an electric fan, whatever the reason, and if I like that, I'd do it. SO no problem.
