The panels normally sold for home use have a glass sheet on top of them, are about 50lb each, and are 200-300 watts, and about 5.5' x 3'. The glass rules them out for any kind of auto use IMO. A mild accident would cost $$$$.
You also have flexible thin film solar stuff. Look up Unisolar on Ebay or Amazon. This stuff is amazing. You can roll it up like carpet, walk on it, put nails in the edges of it, etc. It's 128w, 15" x 17', and 17 lb? It's intended to be used as roofing shingles, and built into the house. However, the output is about 8% efficiency and normal silicon solar chips are about 17%. So it takes up twice as much room. I have one of these that will soon power the lights in my trailer with a battery. It wasn't going to be useful because of the square feet required. It would be the safest.
So I found semi-flexible panels about 4' x 2' that use the silicon chips. These are mounted on aluminum sheet, weigh 6.5lb, and produce 105w (measured after MPPT) at noon. 19.0v x 5.56 amps. I bought 10 of them, which is 80 sq ft. I had also bought just raw solar chips, and was going to solder them together. These things are as fragile as butterfly wings. When I first tried to measure one, it broke in my hand. It was about .004" thick IIRC. For the number of cells I'm going to need, this would be silly. If you break one in the middle of a chain, you must try and replace it.
When I first hooked a panel to a motor, it did nothing. Here's the funny thing about them. They only produce power if they have the perfect load. No load voltage was 20.8v, but zero amps. Dead short made 0.2v at 5.56 amps. The circuit that puts the perfect load on them is called a MPPT (Max Power Point Tracking). This adjusts the resistance the panel sees to optimize the watts it produces. After I put one of these on, it will make power.
When you do a house, you are running a series of panels at 400-600v DC into a MPPT on-the-grid controller. Make a mistake hooking a 5000w array together can kill you dead. Series system are dangerous, since if somehow they see the right load and you're touching it, you lose. Cover panels when working with them.
Another weird thing about solar panels, is that you cannot block a small area at all. If I put my hand in the corner of the panel, the output falls from 105w to 20w instantly. In some cases it can drop to 10w.
The frame is at Mitch Fabrications being welded up out of aluminum. We first need to do balance testing with dummy weights. This is a two wheeler. It will have a 25' long wheelbase and be 4 feet wide. Time to take the kids to school. Will finish later.