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Peugeot Compressed Air Hybrid

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  • Peugeot Compressed Air Hybrid

    Extreme Tech and Popular Science have interesting articles on a compressed-nitrogen/gasoline hybrid power train that Peugeot plans to put in their 2016 model year sub-compact and compact cars. A similar system is in use on some UPS trucks.

    Originally posted by Popular Science
    The Hybrid Air powertrain, which Mokaddem designed with Andrés Yarce, uses a hydraulic pump and a piston to compress the nitrogen gas in a tank called the high-pressure accumulator. Hitting the accelerator releases the pressurized gas, which then moves hydraulic fluid through the same pump in reverse. The pump acts as a motor to power the wheels and the hydraulic fluid ends up in a second tank.

    During normal driving, the system will switch between gas and air power, says Yarce. Much like with hybrid-electric vehicles, the gasoline engine provides a boost up steep hills and on the highway, and it repressurizes the nitrogen tank if the regenerative-braking system hasn’t done so. Yarce and Mokaddem predict that, for urban driving less than 43 miles per hour, between 60 and 80 percent of drive time will be under air power alone. Compared with gasoline-electrics, the Hybrid Air powertrain is lighter and cheaper, and there are no bulky batteries that wear out or intrude on passenger and trunk space. “The system is designed to live for the life of the vehicle,” says Yarce. “The only possible [maintenance] will be an air recharge.”

    Yarce and Mokaddem’s prototype was so successful that PSA Peugeot Citroën has decided to manufacture production vehicles. The Hybrid Air powertrain will appear in all Citroën and Peugeot subcompacts as an option in Europe and possibly other international markets in 2016. The company hasn’t yet released a price, but it says that its air cars will cost around the same amount as other gasoline hybrids.
    Sounds like a cool system, and not as resource intensive as batteries. I know Dodge was looking at a similar system for mini-vans, but I haven't heard anything come of it yet. I could see some of the other manufactures licensing this for their vehicles if its successful.

    I know electric hybrids get cranky/lose range when the weather gets cold Could some of you mechanical/scientific/engineering types comment how this system would be affected by our extreme cold, if there is an effect? Thanks!

  • #2
    From the Exteme Tech article "Any time a fluid is compressed, significant heat is generated, and in many circumstances this would make such a system less efficient than an equivalent electric system" and "Friction in hydraulic system generates significant heat ... dual accumulators and coolers are employed to let the vehicle operate at high duty cycles. On the scale of a compact car ... passive radiation of this heat may in fact suffice allowing the system to be much simpler."

    So in the extreme cold the rubber bladder in the high pressure accumulator might become too rigid and fail, but other parts should work better. The heat generated at stopping (compressing the air) should hopefully keep it warm enough that the cooling which would happen when you accelerate would be somewhat offset. In extreme conditions you could use a metal piston in the accumulator rather than a rubber bladder.