Range anxiety is set to be a thing of the past with the Volvo C30 Electric as the Swedish company is developing a range extender engine for its plug-in electric car.

The 60bhp petrol engine will sit under the boot floor and be used to charge the batteries supplying power to the 111bhp electric motor. This means the C30 Electric can run solely on electric power or a combination of petrol charging and electric power.

Volvo says the range extender engine can run on normal petrol or E85 bio-fuel and adds up to 620 miles to the range - on top of the car's existing 68-mile range on battery power alone.

The Swedish firm is also testing a concept with a 190bhp three-cylinder turbocharged petrol engine and 111bhp electric motor. Power from the petrol engine will be sent to the rear wheels via a six-speed manual gearbox, while the electric motor will drive the front wheels. This would result in a C30 capable of 0-62mph in less than six seconds.

A third option for Volvo is the V60 with range extender engine, using the same 111bhp electric motor and 190bhp petrol engine as the C30 concept. It will have a 30-mile electric-only range and be able to cover more than 620 miles on a single fill of petrol to its 40-litre tank.

Derek Crabb, Vice President Powertrain Engineering at the Volvo Car Corporation, said: "This is an exciting expansion of our increasing focus on electrification. 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."