In the movie Looper (2012) there were multiple scenes with cars with some solar panel kind of stuff on the lid of the cars. Also, some pipe mechanism going through the fuel tank to around. So, was it like some cheap method of running cars in the future that they tried to show? Or am I missing something here?
I don't think they addressed it directly, but it looked like old gas-burning cars that had been retro-fitted with solar power (and electric engines, one assumes.) The "pipes" would presumably just be covering the electric cables that run from the panels to the engine.
If the car no longer uses gasoline, then the cavity where the gas tank was would be a good place for power cells (if they're sizable enough to need it) and that would explain why some of the cables are going in through the gas - it's a pre-made hole that leads right down to where the power cells now are.