I think I get it.
I was sceptical at first, but that was when I was thinking sailboat. You have to think airplane. The wheels drive the prop, which pulls the vehicle through the air. Now, in zero wind, this arrangement would slow down and stop due to under 100% efficiency. BUT, we have the energy of the wind behind us. So, if the car is going, say, 30mph, it only needs the energy to go 20mph if there is 10 mph wind behind it.
It does need a very efficient system with little drag apart from air resistance, but it can be done!
druid