Recharging your electric car while driving will soon be possible

Lack of autonomy is the most important obstacle to the widespread use of electric cars. The solution could come from technologies that can charge your car while driving. U.S. researchers are announcing a significant breakthrough today.

Seeking a solution to the lack of autonomy of electric vehicles, researchers at Stanford University (USA) have developed a technology based on magnetic resonance coupling. Their goal: to successfully charge car batteries remotely.

Let us first recall the principle of magnetic resonance coupling. When a coil of wire rotates between magnets, the electricity that passes through these wires creates an oscillating magnetic field. A field capable of causing electron oscillations in a nearby coil, and thus transferring electricity... Wireless. The efficiency of this transfer is optimized when the frequencies of the coils are tuned and they are deftly positioned.

Efficiency to be confirmed

This principle is difficult to implement with moving objects, precisely because the frequencies of the coils must be continuously tuned. To solve this problem, Stanford researchers have added a counter-reaction voltage amplifier like those found in commerce to the system. Enough to allow it to automatically detect the appropriate frequencies.

So far, they have only been able to transmit electricity wirelessly to a moving LED bulb. That's a charge of about 1 milliwatt. Electric cars, on the other hand, typically require tens of kilowatts. But U.S. researchers say that by replacing the commercial amplifier with a specially designed amplifier, they could increase efficiency from about 10% to more than 90%!
Encouraging first tests for wireless charging

Will it soon be possible to recharge your electric car while driving? In any case, this is what Stanford researchers are trying to develop and the first trials are conclusive. Enough to get around the major obstacle of the electric car.

Reducing transport pollution is one of the technological challenges of our time, with a positive impact on public health and the environment. Among the range of green transport, the electric car seems interesting, but it has no shortage of drawbacks, starting with a very low autonomy. Like all devices that work with a battery, it is necessary to recharge it regularly. While this is not an obstacle for short urban journeys - although an electric bollard is still needed - the situation becomes much more complicated on long journeys.

Hence the development of hybrid cars that use not only electric energy, but also fuel to compensate, among other things, for the lack of autonomy of the electric motor.
Wireless electricity

One of the ways explored is to recharge the battery while moving. This is the one borrowed by Shanhui Fan and his colleagues from the Stanford lab. The system they are testing - presented at a symposium on renewable energy - is based on a transfer of energy between the road and the vehicle. Thanks to a couple of coils placed under the asphalt and the other in the car, the scientists were able, in the laboratory, to shift the energy from the first to the second. The two coils are associated thanks to a very precise wavelength.

In 2007, an MIT team used this system to power a light bulb 2 m from its power source. It was the beginning of wireless electricity. But is this applicable for a car on the move and - even more interestingly - at high speed? Yes, according to the calculations of the team of scientists. They measured that 10 kilowatts could be transferred after 7 microseconds, with 97% efficiency, which is sufficient to charge at the speed allowed on a highway.

This is good news when you consider that the fleet is growing. In France, the number of registrations (all vehicles combined) rose from 33 million in 2000 to 37.5 million in 2010, an increase of about 13% in ten years, going hand in hand with an increase in greenhouse gases (up 23% between 1990 and 2004 imputab transport). It's time to find a solution.

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