As part of the research, the manufacturer has developed three technical concepts, each using a three-cylinder petrol engine that can also run on E85 ethanol, and all featuring brake energy regeneration. Volvo claims an additional 620 mile range for each model, compared to running on electricity alone.

The project is backed by a £1.06m (€1.2m) grant from the Swedish Energy Agency, and forms part of Volvo’s participation in an EU-supported carbon reduction programme in which it is the only car manufacturer.

Derek Crabb, vice president of powertrain engineering at the Volvo Car Corporation, explained: ‘Battery cost and size mean that all-electric cars still have a relatively limited operating range. With the Range Extender, the electric car has its effective range increased by a thousand kilometres – yet with carbon dioxide emissions below or way below 50 g/km.

‘These three projects allow us to evaluate the Range Extender's various possibilities. As with the C30 Electric and V60 Plug-in Hybrid, the goal is to make the cars exceptionally CO2-lean without compromising on customer requirements such as comfort, driving pleasure and practicality.’

Two of the concepts are based on the C30 Electric, adapted to run on a smaller battery pack to make room for the range extending engine. One features a 60bhp unit under the boot floor, used purely to charge the battery when it’s running low, and returning 690 miles from a combination of battery power and its 40-litre fuel tank.

The second C30 has a more powerful 190bhp turbocharged version of the same engine, and it can be used as an on-board generator to keep the batteries topped up while driving on the electric motor. But it also functions as a source of power, either to keep the car moving once the batteries are flat or to give a combined 300bhp when used alongside the electric motor.

It gives blistering straight line performance – Volvo claim this parallel-connected setup lets the C30 reach 62mph from rest in under six seconds, but with a 668 mile range using a combination of electric and conventional power. The system behaviour is governed by driver-selected modes.

Unlike the C30-based concepts, the third setup places a full range extending setup under the bonnet of the V60, using a 190bhp engine and 111bhp electric motor with a battery pack under the boot floor.

Different again, this has two driving modes – one that uses the petrol motor to provide power and generate electricity only when the batteries are depleted, and the other two combine both units for maximum power. It offers 30 mile pure electric range, with up to 620 extra miles using the range extender.