Masahiro Hanazawa at Toyota Central R&D Labs and Takashi Ohira at Toyohashi University of Technology (Toyohashi Tech) propose a potentially revolutionary solution for powering EVs capable of running unlimited distances.
The basic concept stems from electric railways, where each car of the train is powered from an overhead wire while the car runs on tracks. The researchers imagined how an automobile running along a road could do so without resorting to dangerous contacting devices such as pantographs, and finally came up with an idea: The source of energy from power lines is up-converted into radio frequency (RF) by high-speed inverters implanted along tracks in the road. Then RF voltage is applied to a balanced metal track embedded under the surface of the road. The EV picks up the RF voltage via electrical capacitance between the metal and a steel belt installed inside of the tires of the EV.
The researchers conducted feasibility experiments to test their ideas, and to explore the RFs where such power transfer is effective and practical. In the experiments, the researchers put small metal plates on the floor and inside a tire, and positioned another metal plate above the tire. Finally, they measured the electrical impedance between the two plates. This set-up should be equivalent to double the impedance between a plate and a steel belt.
Experimental results showed the impedance to depend linearly on the RF frequency, and to exhibit 2000-j700 ohm at 1 MHz. Then the researchers designed and implemented a 50 ohm reactance circuit to match this, where 50 ohm is the standard impedance for RF transmission lines. This experimental set-up enabled high transmission efficiency with sub 1 dB loss.
Although these were low power experiments, they demonstrate the feasibility of energy transfer from the road to a running automobile. If this energy transfer could be increased to tens of kW on express ways, then in the future it may be possible to take EV from your house to the nearest interchange with a small battery and then cruise on the expressway via this feeder system as far as you want without concern about battery discharge problems.
Source and image: Toyohashi University of Technology
IDTechEx notes that this idea is exploited in a different form in the Korean KAIST vehicles runnning over metal tape. We have reported how these have been ordered by Boston Logan Airport in the USA. Toyota Central R&D Laboratories is skeptical of such options. Its Massahiro Hanbazawa has recently said that alighniment is a big problem with continuous power transfer. Then there is the problem of energy loss at, "less than 20%" and much worse than batteries, static charging with contacts or even resonant power transfer. Indeed, professor John Boys at the University of Auckland New Zealand, an expert on industive charging, notes that a voltage of around 50,000 volts may be needed and that is the level of a Taser gun. "You wouldn't want to step on that", he observed. Daniel freedman of the University of New South Wales Australia added that the cost of digging up roads is very high but it could be limited to main highways. Smaller batteries could still be used.
For more attend Electric Vehicles Land Sea Air USA 2012 where a large number of electric vehicle manufacturers not seen in conventional EV events will present including WheelTug aircraft electrification, MotoVolta, LLC motorbikes, SolTrac farm tractors, Monterey Bay Aquarium Research Institute AUVs and manufacturers of industrial, commercial, military, e-bike, cars and other EVs.
Also read Electric Vehicle Charging Infrastructure 2011-2021 and