Alternator delete is a very common hack in the ecomodder community (usually coupled with LiFePo or Lithium battery instead of the regular lead-acid). It reduces the complexity and load on the engine, and does give a few percentage better fuel efficiency. But if you mostly ride at night, yeah ...
Everyone except you has approached this discussion with the intent of using the solar power to drive the car, but they should actually be thinking of using it to power the cars electrical system, and thus negating the need for the alternator.
A current gen 2.5L petrol Camry has a 12v 80A alternator. That 80amps likely covers driving at night in the rain (ie headlights on, window wipers going, HVAC fan blowing, etc). Normal daytime driving would be much less demanding, say 50A load, thus 600W power. Then you have to factor in the alternators inefficiencies, which could raise that demand to 1kW.
Next consider what the engine is having to generate whilst cruising, which could be 20kW for the Camry. In this scenario, that 1kW of alternator load is responsible for 5% of the engines load. So ditching the alternator would give 5% fuel efficiency increase on this Camry. A smaller car that only needs 12kW to cruise would see an 8% improvement (8% of a low consumption value though), whilst a much bigger car that needs 50kW to cruise would only see a 2% gain (but that's 2% of a high consumption value).
So if "solar body panels" could generate 500W like people have already guessed in this thread, then that would be close to offsetting the normal day-time electrical load. In this scenario it's probably a good idea to power the vehicles electrical system from a lithium battery, which wouldn't mind the gradual draw-down, because that could then be offset by parking the car in the sun (and possibly even by regenerative braking). Then there could still be an isolated lead-acid battery that is purely for starting the engine (because that needs high cranking amps), and that could be DC to DC charged from the vehicle circuit.
That 12v 80A alternator can generate almost 1kW at max effort. So even if you drive all night in the rain, that's still less than 1/5th of the energy in a Tesla or BYD vehicle battery. So this alternator-less car could get away with a much smaller battery, and it might even be smaller in area than the cars boot!