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New Wireless Power Transmission System for EVs Uses Tires' Steel Wires


When you think of an electric vehicle, batteries are the second thing that comes to mind, since they’re so expensive and inefficient these days. Masahiro Hanazawa and Takashi Ohira from Toyota and Toyohashi University of Technology, respectively, have devised a wireless system that could power electric cars indefinitely while they travel along the road.

However, the idea is not new. While other researchers from all around the world have designed their wireless charging systems to work in a more classical fashion, Hanazawa and Ohira thought that turning the steel wires inside the car’s tires into receivers would make much more sense, since they’re the closest to the electricity-emitting asphalt.

The two researchers practically didn’t invent anything new, as the principle had been discovered by Tesla in early 1900s. They just transformed electricity coming through standard cables from low to high radio frequency, and then transferred the power to small metal plates inside a tire. They also put a small metal plate above the tire, and measured the electrical impedance. Results showed up that this setup doubled the impedance between a plate and a steel belt (just like in picture).

Then they designed a 50-ohm reactance circuit to match the impedance between the plates and the steel wires, and got a transmission system with less than 1 dB loss (versus other systems that had losses >20 dB).

EVs may be powered this way in the future. Some of them may use small batteries that are enough to go for small distances to the nearest electrified road, and others may use normal ones that could get recharged while traveling and then provide extra autonomy where no in-road electrification is available. Both options sound good.

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