There are plans to add solar panels to a car like Lightyear. Its solar panel area is only 5 m2 (53.8 ft2). Here we can see new "kleinbus". The back area is about 23 m2 (247.6 ft2). I assume that the effective solar paner area could be as much as 20 m2 (215.3 ft2). Even the whole 20 m2 area can't be in the sunlight at the same time four times more area would still give much more energy. Solar panels receive indirect sunlight too.

You might think that the car is dark inside? No problem, there is a solution. The windows can be replaced with TV screens. At the outside of the car there are video cameras that the passengers can see out of the car. These screens supposed to look very close to the windows.