Tyres play a starring role in Japanese EV research

If work being carried out by Professor Takashi Ohira and his team at Toyohashi University of Technology can be successfully applied to the real world, the day may come when we drive electric cars powered by current flowing through their tyres. The Toyohashi team is working on a project known as EVER, or Electric Vehicle on Electrified Roadway, and it says the technology being developed applies the same basic concept used on suburban electric railways for more than a century. On 5 July the Ohira and the Toyohashi team demonstrated its prototype technology at the WTP2012 trade show in Yokohama.

The Toyohashi project’s stand out feature is that, as opposed to electric railways powered directly from a live rail, it enables electric vehicles to obtain current from under a concrete roadway. The system utilises inductive coupling; Toyohashi University of Technology reports that while standard 50/60Hz current is not suitable for this purpose as it cannot flow through a tyre’s rubber, a frequency of 10MHz or higher delivers successful results. The demonstration given at WTP2012 involved illuminating a 100w light bulb, with the current reaching the bulb through 10 centimetres (3.9 inches) of solid concrete. The current was transferred to a steel belt within a passenger car tyre and then sent through the axle to a centrally-mounted light bulb.

The technology shown at WTP2012 still needs to be perfected, however the Toyohashi team reports power dissipation is now less than 20 per cent. While Ohira explains that power used would have to be increased 100 times in order to be practical, he believes that if energy transfer could be increased to tens of kW, it may be possible to drive an electric vehicle with a small battery to the nearest motorway and then drive long distances without worrying about battery range limitations.