Alternator With A Solar Panel

We show you how to install a basic 200 watt solar system.
Alternator with a solar panel. Alternator 160a or less 120a cyrix alternator more than 160a 230a cyrix. Additionally when a charge is applied to a house battery bank the cyrix will close and allow current to flow to the starter battery. As the name says it a solar charge controller is intended to be connected to a solar panel. Just wondering if the alternator is somewhat reducing gas mileage or if it does reducing the full capacity of the engine coz the alternator is using mechanical energy from the engine to convert it to electrical energy the alternator uses the rotating energy from the engine.
Car alternators and pv panels do not have similar characteristics. Now i have an idea if i remove the alternator and replace it with solar panels would i get more gas mileage or gain. If so would i gladly spring for the extra 150 or 250 amp alternator. We install this on top of our 2012 mercedes sprinter custom conversion van.
If you need a separate controller because you want to charge a li battery it is difficult to answer. It depends on the charge controller and alternator. So if i didn t want any solar panels on the roof would i be able to consume about 50 amp hours per day from 300 amps of lithium batteries by just charging off a dedicated and separate alternator in a ford transit if i drive an average of 2 hours per day.