There kind of seems to be a debate on here whether solar panels are worth the additional weight on a car. I have seen some members do it and others say that it is a waste. This guy added them to his Prius and insists they help:
Green Car Congress: Solar-Power-Augmented Prius Takes the Grid Out of Plug-in
On a house, you would want them angled to be at 90° with the sun, but on a car, I would think that you would want them to be flat, and one of the comments that I have read is that there is very little usable space on a car.
Well, if you need a flat area, wouldn't louvres provide that?
If I bought solar panels, I would put them on my house, and then park my car in the garage.