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The Car That Runs on Air

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In January, Peugeot announced it had developed a car that ran on air. It officially launched the Hybrid Air vehicle at the Geneva motor show, saying it would be in production by 2016. The car did not run on air only – their new development assisted a petrol engine. However Peugeot believes their hybrid system has significant advantages over battery-powered electric hybrids such as the Toyota Prius. It would be cheaper for one, and further savings would come from a fuel economy of around 81 miles per gallon. _P__6204A From one side, the car looks no different from the compact hatchbacks that Peugeot and Citroën are famous for, but it has been sawn in half to better illustrate the new technology. Most visibly, running down the middle of the undercarriage, there is a blue, four-foot-long  pressurised steel tank filled with around 20 litres of nitrogen, plus some hydraulic fluid. Much like a Prius, Hybrid Air vehicles recover energy every time the driver brakes or decelerates. But instead of using this kinetic energy to charge a battery – as electric hybrids do – the Hybrid Air system has a reversible hydraulic pump that compresses the nitrogen in the tank during braking. When the air is used for acceleration, the nitrogen decompresses to push the oil and the hydraulic components and convert its energy into a force moves the vehicle forwards.

  1. The system doesn’t produce huge amounts of energy at a time. The developers say it is about the amount contained in a kiwifruit. But they also say that repeatedly using and re-using this amount of energy creates significant fuel savings for vehicles driven in stop-start city conditions, and for vehicles such as buses that make regular stops. 
  2. The cars do not require an expensive lithium-ion battery or electric motor and can therefore be manufactured for less.
  3. The parts are simple and easily serviced. This makes them well suited to the emerging markets of China, India and Russia.

Peugeot engineers say that the Hybrid Air is not a radical innovation but simply the result of putting known components together in an innovative way.

  1. First, there is a conventional petrol-powered internal combustion engine. The petrol-driven internal combustion engine is a known technology that has had continual incremental improvements.under the bonnet
  2. This is coupled to an epicyclic automatic transmission. Epicyclic (“planetary”) gears have the advantages of providing high gear ratios in a small volume. They are quieter and generate less vibration. They enable coaxial shafts (as in the example). They have a higher torque and are more resistant to wear because load is distributed across a number of gears. Importantly for energy saving, they are efficient – most of the input energy is transmitted through the gearbox and not wasted on mechanical losses. The multiplying effects of epicyclic gears are commonly applied in desktop pencil sharpeners (but they were also used – albeit for calculation purposes – in The Antikythera Mechanism circa 87BC.) The use of epicyclic gears in automobiles had been hampered by their heavy lubrication requirement and the difficulty of maintaining their closed mechanical system but now their time has come.


  3. The petrol engine is assisted by a hydraulic motor powered by compressed air. The air-compression technique is a known technology that isn’t even particularly technological, but can now be applied to triple the fuel-efficiency of automobiles under certain driving conditions.peugeot2008hybrid2

The fuel efficiency of petrol-powered vehicles is notoriously poor for city driving conditions. Peugeot have taken this as their starting point and developed a car that has excellent fuel efficiency for these worst possible situations. Not only was this an excellent place to start but they have also solved the problem in a way that is simpler and more robust than electrical regenerative braking systems. (I expect the energy loss in converting one form of mechanical energy to another is less than converting mechanical energy into electrical energy and back again.)

Formula I gave the world the automatic transmission, but its quest for a certain kind of performance could not have produced something like what Peugeot has done for it is not really concerned with fuel efficiency under stop-start driving conditions. And nor could the mindset of high-tech innovators such as Venturi have produced this for though Venturi push the boundaries of energy efficiency, they do it for electricity.

Peugeot’s development team were instructed to come up with a disruptive innovation – something that wasn’t an incremental improvement but something that was simply so much better than everything that went before. Their real innovation was to not look for fancy solutions based on new materials or sophisticated electronics, but to put known technologies together in a new way and solve the problem for conditions where it needed solving the most.

We need more of this type of thinking.The automobile has evolved an enormous amount within a very short time. Peugeot’s engineers now believe a fuel consumption of 140 mpg is possible. The creative integration of known technologies may well be responsible for the next leap in automobile energy performance. One cannot compare the performance of today’s automobiles with those of ninety years ago.