We will NOT be able to fuel the cars of the people that will feed the people also using their car in order to build those space solar panel.

Maybe you havent understand that Oil is the energy subside of everything NASA scientist could come up with.

I'm certainly aware of our planet receiving more solar energy than what is used as fossil fuels.  The problem reside in getting it concentrated enough.  

Even if we could (for very not any good reason) power some kind of car, the problem would then reside in getting enough nat gas or coal to keep on manufacturing fertilizers.

The problem is NOT a supply problem, it's a DEMAND problem.  Until the system is working, you will be able to use your car.  Once the system break, you wont need your car.

Actually, the demand problem will be solved rather easily (at least in the USA). Most people won't be buying gasoline because they won't be able to afford it. A trip in the car will be an important journey done for a purpose, because it will be too expensive to waste on anything trivial. There is a giant gap opening in the USA between the haves (top 10%) and everybody else. Rising oil prices are going to put the nail in the coffin.