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As mainstream as hybrids are right now, the technology is still seen with a lot of public scepticism, especially with regards to its batteries. Cue PSA with its revolutionary hybrid system that works without the dreaded power cells or in fact, electric motors and yet manages to deliver exceptional fuel economy of less than 3 litres per 100 km.

Eh, how’s that work then? Not like a conventional hybrid for starters. At least not as we know it.

Fundamentally it’s simple enough to explain: instead of using battery-powered electric motors to assist the internal-combustion engine, PSA’s Hybrid Air technology utilises a compressed air energy storage unit driving a hydraulic pump/motor to provide driving power to the wheels.

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Going without the worrisome battery, Hybrid Air promises a reduced environmental footprint (bypasses the need for rare raw materials), more affordable pricing (it’s less complicated hence cheaper to manufacture) and effectively no impact on cabin space (no more large and weighty battery to be packaged into the vehicle).

Further benefits include a constant level of efficiency, regardless of weather or driving conditions while servicing operations and end-of-life recycling are also simplified as compared to conventional battery-laden hybrids.

Citroën will be showcasing a full-scale C3 VTi 82 prototype fitted with the system at its stand at the Geneva Motor Show. The Citroën C3 Hybrid Air produces CO2 emissions of just 69 grammes per kilometre with fuel consumption reduced by a third to achieve a record-breaking 2.95 litres per 100 km over a combined cycle. In urban driving, fuel consumption and CO2 are reduced by 45% compared with a vehicle solely fitted with the same internal combustion engine.

It autonomously and continuously cycles between three different driving modes – Air, Petrol and Combined – to optimise energy efficiency. In Air mode which is limited to 70 km/h, it’s a zero-emission vehicle using just the compressed air as fuel. With both the system and the three-pot 1.2 litre petrol engine working in tandem, a combined output of more than 120 hp is on offer.

The compressed energy tank is filled in two ways. On deceleration (on braking or releasing the accelerator), the speed is reduced not by application of the brake pads to the brake discs but by the resistance to the compression of the air in this accumulator. The alternative consists of using the petrol engine to compress the air. In both cases, the maximum energy capacity of the unit is reached very quickly – in just ten seconds.

PSA and Citroën in particular aren’t strangers to pioneering automotive breakthroughs. The new Hybrid Air technology joins a long list of PSA world firsts, including the diesel particulate filter, engine stop/start system and most recently, diesel/electric hybrid vehicles.