SUPRA: Supply underground power to running automobiles: Electric Vehicle on Electrified Roadway exploiting RF displacement current through a pair of spinning tires

Abstract

This paper presents an experimental RF characterization for a proof of concept called "Electric Vehicle on Electrified Roadway (EVER)", where the energy is fed through dielectric coupling between a steel belt in a tire and a metal plate laid under the road surface. We first put a round aluminum plate of 1,000 mm in diameter directly under a tire whose inner surface is covered with a copper tape. This structure is regarded as an electrical one-port circuit having two electrodes. An RF impedance analyzer is connected between the copper tape and the aluminum plate. Measured complex impedance at frequency 1 MHz exhibits 700 ohm in real and -2000 ohm in imaginary. Based on this result, we then proceeded to experiments with a more pragmatic configuration having a pair of wheels set up on a pair of rectangular ground metal plates of 2,000 mm × 1,000 mm. This one is regarded as a two-port RF network having four electrodes. Applying an RF network analyzer, the two ground plates are excited with a sinusoidal wave in the differential mode, and the RF voltage is detected between the tires. Transmission coefficient successfully achieved -1.0 dB at 1 MHz and -2.5 dB at 13.56 MHz. They are equivalent to 80 % and 55 % respectively in power transfer efficiency. We conclude that this is a major step to pave the way toward a promising solution of electric vehicle on electrified roadway.