Did you see this?
On Friday, ABC News had the story of British inventor Peter Dearman and his car that runs on air. To be more exact, the car runs on air that has been super-cooled into a liquid state and then stored in a pressurized container — in this case, a beer keg — in the car.
The air is then returned to a gaseous state, which creates the pressure that powers the car.
Because the only “fuel” involved is air, there are no emissions, but nothing is said here about how much energy is required to super-cool the air in the first place, which is what will determine whether this type of engine actually saves on fuel.