Hybrid air system cuts fuel cost

Technology will help to create an 'attractive hybrid range', says PSA

Engineers at French carmaker PSA Peugeot Citroën are developing full-hybrid technology that uses compressed air for energy storage.

The hybrid air system is being touted as a key step towards achieving petrol consumption figures of 2 litres/100km by 2020.

The technology combines a petrol engine and compressed air for energy storage instead of a battery. A hydraulic pump-motor unit recovers energy generated by the internal combustion engine at top efficiency and during braking and deceleration, storing it in compressed-air tanks. 

The system is modular and can be packaged beneath the passenger compartment, with no need to surrender boot space. The system can operate in three modes, depending on driving conditions. The vehicle can use petrol power, with the petrol engine operating as the sole source of propulsion; air power, with the hydraulic motor alone transmitting energy to the wheels when pressure is released from the tanks; and combined power, with the engine and hydraulic motor working together.

According to PSA, fuel savings can be as much as 45% in city driving conditions, offering a 90% increase in range compared with conventional engines with the same power rating. Certified fuel consumption stands at 2.9 litres/100km in combined-cycle driving, with CO₂ emissions of 69g/km for standard body style models such as the Citroën C3 or Peugeot 208. In comparison, PSA’s three-cylinder petrol engines with manual transmissions produce 104g/km CO₂ in combined-cycle driving. 

Vehicles equipped with hybrid air technology could run on air power alone 60-80% of the time in city driving, depending on traffic density, thanks to the optimal efficiency of energy recovery during braking, claimed the company.

PSA has filed more than 80 patents around the world for its hybrid air system. The company will continue to refine the technology and wants to achieve performance of 2 litres/100km by 2020. It said: “This innovation will make it possible to offer an attractive hybrid range, with broad coverage of all car and light commercial vehicle segments in and outside Europe.”