Well, an alternator in a car keeps the battery charged, so with maybe compact generators driven from each wheel, plus a turbine and solar panels, I'd say you have a pretty good idea. If you're planning on building on, try it on something like an R/C car first, and proceed from there.
If I'm not mistaken, there have been cars built that run solely on solar power, so having that during the day while the generators charge up another back-up batter for night driving, it should be possible. This is assuming that the car would be intended to be driven for a constant 24 hrs.
And you don't have to worry much about the sky clouding up; last I check, it's brighter outside on a cloudy day than it is in an office, yet solar powered calculators work indoors. So, the clouds wouldn't stop a solar panel from working.
Now, combining these ideas with comfort..well, that's another story....