Electric vehicle batteries need to be recharged roughly every 160 km, meaning that drivers need to plan their route around charging stations. The availability of stations varies widely in Europe, from nearly 2 000 in France to around 60 in Poland.

The team behind the EU-funded UNPLUGGED project is investigating how to complement traditional charging stations with wireless charging points in public spaces. Two scenarios are under consideration – locations where cars will be stationary for some time, such as supermarket car parks, and those where vehicles will be immobile for a few minutes, such as taxi ranks, bus stops and even traffic lights. Theoretical studies also looked into the feasibility of charging while driving.

“Wireless charging would be very convenient for the driver, and would make it possible to increase the number of charging events per journey,” explains project coordinator Axel Barkow of the Forschungsgesellschaft für Kraftfahrwesen Aachen (fka) in Germany.

Greater range for longer journeys

The concept of wireless charging at home has already reached industry. “Everybody is working on it,” says Barkow. But these endeavours are still focused on private charging points at home. The UNPLUGGED concept of on-the-go charging would extend electric vehicles’ range, meaning they can stay on the road for longer, thus addressing one of drivers’ key concerns.

If a battery can be charged more frequently, it doesn’t need to be large – at the moment, the larger the battery, the greater the distance it will power a vehicle. While the cost of an electric vehicle battery is dropping rapidly, it is still the biggest expense for electric vehicle owners – and the bigger the battery, the higher the cost.

Charging the vehicle would almost be like charging an electric toothbrush, explains Barkow. The vehicle would contain a coil, which would need to be aligned with another coil on the road. This external coil would have a current running through it, generating a magnetic field. This would be captured by the vehicles’ coil, which would transform it into current and then charge the battery.

But unlike a toothbrush, which is placed almost on top of the primary coil, the distance between the two coils is likely to be 10 cm or more. This is one of the UNPLUGGED team’s major technological challenges, along with the fact that the driver must position the car in a very precise position – not so complicated in a car park, but more problematic at traffic lights.

Watch this parking space

Interoperability is another technical challenge. “If you want to charge your private car at the supermarket, you don’t want to have to look for the right model for your car,” says Barkow. UNPLUGGED has already made good progress here, and is confident that it will at least be possible to charge low-power vehicles at high-power charging points.

Interoperability would make it less costly for local authorities to invest in charging points. “At the moment we have a bit of a chicken and egg situation,” says Barkow. Charging points are few and far between because there are very few electric vehicles on the road, but drivers are put off buying such a vehicle by the lack of charging facilities. “Interoperability should encourage investment,” he says.

Local authorities are already expressing an interest in the UNPLUGGED concept, and in particular in how they need to plan for electric vehicles when developing their city’s infrastructure. Several are part of the project’s advisory board, together with car manufacturers.

By the time the project finishes in March 2015, the UNPLUGGED team plans to have answers to interoperability questions, as well as two electric vehicle prototypes able to charge wirelessly – a Fiat 500 and a larger light-duty vehicle manufactured by IVECO. The results will be available to everyone, including car manufacturers and local authorities.