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Charging Electric Vehicles Through Tires?

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Schematic of EVER project

A schematic of the proposed power transfer system shows the transmission of electric power thorough a capacitor composed of a steel belt and a metal plate attached to the road. Notably, the leakage electromagnetic field is small, and the infrastructure can be set up at low cost compared with coils.

Engineers at Japan’s Toyohashi University of Technology have developed a potentially revolutionary way for electric vehicles to recharge through their tires as they move along roadways. Their work might eventually solve one of the main problems plaguing electric vehicles, as Adam Westlake writes in his July 9 article in The Japan Daily Press: the fact that drivers of such vehicles have to pull off the road to recharge the batteries, limiting how far they can drive continuously.

An article about the research in Tech-Overtures, the Toyohaski University of Technology’s e-Newsletter, notes that electric vehicles provide many environmental benefits, such as high energy efficiency, low noise, low temperature while operating, no emission of exhaust, plus the ability to regenerate power from kinetic motion when a vehicle slows down. Among the problems with electric vehicles that are driving the researchers’ work, the article says, are that:

…it takes an impractical long time to recharge the batteries, and loading larger batteries increases the onboard load, which leads to greater consumption of energy to move vehicles. And notably, batteries are too expensive for use in replacing all existing cars, buses, and trucks.

Rollin Bishop for Geekosystem reports for Mashable Tech that the Toyohashi research team, led by Takashi Ohira, has found a way to send up to 60 watts of electricity through almost four inches of solid concrete. He writes: “The technique they are using isn’t exactly new, but the fact that they managed to squeeze out between 80 and 90% efficiency is.”

Tech-Overtures describes the system:

The basic concept stems from electric railways, where each car of the train is power[ed] 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 a profound and novel 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. The 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 — who call their project EVER, for Electric Vehicle on Electrified Roadway — demonstrated their work with a prototype at the Wireless Technology Park 2012 trade show held in Yokohama. Westlake writes the following about the demo:

In their demo, four-inch blocks of concrete, to represent the road’s surface, were placed under full-size car tires, with metal plates in-between. Electricity measuring from 50 to 60 watts was transmitted to the tires, and then used to turn on a light bulb that had been attached to the tires [to provide a visual cue that the energy transfer was occurring].

Ohira worked with Toyota Central R&D Labs last year on a similar project, which made it apparent that a lot of electricity is lost through the rubber, Westlake writes: “As of their test last year, less than 20% was dissipated, but it’s still a significant amount.” Ohira said the energy output needs to be multiplied by 100 in order to power a car. Thus any practical use of this technology is “still a ways off,” writes Bishop, although the research shows that it is possible. Bishop goes on to say: “According to the researchers, the high conductivity of the concrete used in roads and the cheap cost of materials could eventually lead to much more massive amounts of energy being produced and transmitted through as much as eight inches of concrete.”

Image by Tech Overtures, used under Fair Use: Reporting.


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