Wireless electric car charging – via tyres

Japanese university demonstrates dynamic charging through the wheels

By Will Dron on July 11, 2012 10:18 AM

The Toyohashi University of Technology has demonstrated a new method of wirelessly transmitting electrical power to a car via its tyres.

Shown at the WTP Wireless Technology Park 2012 in Yokohama, Japan, the technology can transfer current from a metal plate embedded under 10cm of concrete – the thickness of public roads in Japan – to metal rings in the tyres, using inductive coupling. It could be used for dynamic charging, or charging whilst on the move, meaning that electric cars could, potentially, have unlimited range if they run on suitably-equipped surfaces.

Power transfer is said to be 80-90% efficient, according to Takashi Ohira, professor at the university's Department of Electrical and Electronic Information Engineering.

There are a couple of major problems with the technology on show at WTP, though, not least that the 50-60W current demonstrated is only enough to power a lightbulb and nowhere near powerful enough to charge an electric car. Qualcomm Halo, which is leading the first large-scale pre-commercial trial of Wireless Electric Vehicle Charging (WEVC) has installed 3.3kW systems in test vehicles, which are roughly 60 times more powerful.

“We also installed a 7kW system in the Rolls-Royce Phantom 102EX and a 20kW system in the 200mph Lola-Drayson B12/69EV racing car that ran at Goodwood this month,” says Joe Barrett, Senior Director of European Innovation Development at Qualcomm.

But as power is increased, there’s an even bigger issue to address – one of electrical ‘emissions’ which could potentially interfere with other electrical devices, such as pacemakers.

“One thing that is vital to consider is the practicality of any system, since it needs to be compliant to regulatory requirements on emissions,” says Barrett. “The Qualcomm Halo system has the on-vehicle pad centrally placed under the vehicle. This means that the vehicle chassis acts as a shield to any emissions to the side of the vehicle. With a WEVC system implemented in the wheels, there is no shielding possible for these emissions, especially at the high power values that are being suggested.”

Let’s hope Professor Ohira addresses that before he ramps up the power.