Drive

Peugeot Citroën's new set of wheels to run on compressed air

Cars can’t run on air — or at least, not yet. But an experimental gasoline-air hybrid powertrain being developed by PSA Peugeot Citroën harnesses the power of compressed air for propulsion.

“It’s the first hybrid based on air,” says Hugues Barlow, electrical and electronics director for the company’s research centre in Shanghai, China. “It’s much cheaper than a battery. And, in the city, it could have a 45 per cent (fuel) saving and reach 2.9 L per 100 kilometres.”

In a gasoline-electric hybrid car, an electric motor either runs the vehicle by itself, or works alongside the gas engine to provide maximum power.

The hybrid battery that powers the motor is recharged both by the gas engine and through regenerative braking, which captures kinetic energy created during deceleration and converts it into electricity.

The air hybrid is similar, but instead of an electric motor, it has a hydraulic pump/motor unit and an air tank. The motor and pump recover kinetic and engine energy and use it to compress air in the tank.

The compressed air is then used to run the vehicle by itself, or to augment the gas engine for more power.

“The range on air is quite small — a few hundred metres,” Barlow says.

“But it only takes a few seconds to recharge each time. You can use it quite often, and, in the city, you could have 70 to 80 per cent of the time when you are on air mode.”

As with a regular hybrid, the Air Hybrid’s electronic monitoring system continually and automatically adjusts to the driving conditions, and uses the gasoline engine, compressed air, or a combination to suit the current need.

Thriving under pressure

• In addition to concept cars for auto show displays, Peugeot Citroën has some 15 prototype Air Hybrid vehicles in testing in France.

• A similar hybrid system that uses compressed hydraulic fluid instead of air is already in use in a small number of garbage trucks in the U.S.

• PSA Peugeot Citroën has filed more than 80 patents worldwide for its Air Hybrid technology.

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