sounds crazy. it is. I have tried to figue this one out. watch how an old train moves. burn wood to boil water to create steam to push a piston that moves the wheels. my idea is like that. instead is burning anything a small electric motor geared right pushes a piston. the piston is moved by water which works like the train. 2 lines connect to a transmission which creates the needed tourque to drive the wheeles. one line is supply the other is return. solar panels on the car can help gererate electricity to get the motor going. don't know if I describe it right. drawing it was easier.