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Researchers demonstrate dielectric coupling between steel belt in tire and metal plate in roadway for EV power

Researchers at Toyohashi University of Technology (Japan) have demonstrated the transfer of electric power from wheels to power an electric car using dielectric coupling between a steel belt in a tire and a metal plate in a roadway. A paper on their work is published in IEEE MTT-S International Microwave Workshop Series on Innovative Wireless Power Transmission.

The approach exploits the steel belt usually embedded in rubber tires. The steel belt collects power excited from a pair of electrodes buried beneath the road surface. Since the steel belt is electrically insulated by the rubber tread, the researchers used a displacement current at high frequency to penetrate from underground to the steel belt.

The researchers constructed a 1/32 scale EV as a proof of concept. The car moved successfully with a power penetration efficiency exceeding 75% at 52 MHz—the first demonstration of electric power transfer via the car-wheel to the vehicle.


  • Y. Suzuki, T. Sugiura, N. Sakai, M.Hanazawa, and T. Ohira (2012) Dielectric Coupling from Electrified Roadway to Steel-Belt Tires Characterized for Miniature Model Car Running Demonstration. IEEE MTT-S International Microwave Workshop Series on Innovative Wireless Power Transmission, IMWS-IWPT2012, pp.35-38 doi: 10.1109/IMWS.2012.6215814



Very impressive, imagine what you could do with dedicated equipment on the bottom of the car.


I would imagine that the very close proximity of the tyre and the plate underneath the road is what makes this work.

Before battery only advocates get too excited about the loss of efficiency, making and lugging around batteries all cost money and energy, and this would still be hugely better than ICE.


75% is a huge efficiency, especially if 'The approach exploits the steel belt usually embedded in rubber tires.'


This goes back to the item about Hanazawa's scheme from August last year.

75% transmission is Good Enough For Government Work.  We could build a petroleum-free transport system based on this, so it's time to start doing full-scale feasibility and safety testing to see just how well it's suited to deployment.


"at 52 MHz" That's one huge and powerful short wave transmitter.


There are designated ISM (Industrial, Scientific, Medical) bands at 27 MHz and 42 MHz.  Either of those would do; other users must tolerate any interference from ISM equipment.


Wonder if enough power could be transferred directly from in-road transmitters to the in-wheel e-motors winding to extend EVs range while travelling on equipped roads?


The type of motor appears to be irrelevant.

Even if the power transfer isn't sufficient for continuous cruising at full speed, it might be worthwhile.  If a Leaf could get 2/3 of its cruising power requirements through the road it would go from a 100 mile vehicle to a 300 mile vehicle.  Quick charging to 80% would allow another 240 miles of cruising, making the Leaf a contender for many more uses.

At even lower power levels, the applications are still good.  Being able to transfer a couple of kW to a vehicle would power the air conditioning and keep the hybrid battery charged, allowing hybrid cars in traffic jams to operate with engines off.  The reduction in fuel consumption and emissions could be significant, both for economics and public health.

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