You could do this without having to "move" the exhaust back up to the top I think.

Just stack them in a line at different elevations so that one's exhaust turns into the fuel for the next one. If speed of the exhaust increases after a cycle you'd be creating stronger "breezes" as you go down each step.

It wouldn't be 'perpetual' but pods of 3-4 like this might be able to increase the yield substantially.

Then again I don't know much about this and I'm just trying to comprehend it all.