WIRELESS CHARGING OF FUTURE ELECTRIC CARS

SWEDEN Wireless charging of electric cars will now be tested for the first time in Europe. Vattenfall is involved in a project in which twenty electric cars will be inductively charged in Sweden for a period of a year. “The idea is to move towards automated charging, and electric car owners should in future be able to park their cars and leave them without having to do anything else,” says Johan Tollin, Head of the e-mobility programme at Vattenfall R&D.

Cables are currently an unavoidable part of everyday life for electric car owners. But the future belongs to wireless automated charging.

Vattenfall is now joining several partners, among them the research institute Viktoria Swedish ICT, Gatubolaget in Gothenburg and Stockholm municipality, to take the first step in introducing automated charging of electric cars in Sweden.

Inductive charging
The project, which is supported by the Swedish Energy Agency, will test wireless charging in twenty electric cars for a period of a year.

Johan Tollin explains the technology behind wireless charging.
“Inductive charging uses an electromagnetic field instead of a cable to transfer energy between two objects. The tricky bit with this technology is to get a concentrated magnetic field to where you want it. There are general limits to magnetic fields, in particular their leakage must be effectively limited. We naturally want high efficiency too. The total efficiency of the system is just above 90 per cent, depending on the equipment used. If you charge an electric car today with a cable, its efficiency is about 95 per cent.”

Two coils
There is as yet no standard for wireless charging of electric cars. The project has acquired and inspected American charging equipment.
“What we are doing is to integrate the technology into cars already on the market. That really means we can use only two car models – the Nissan Leaf and the Chevrolet Volt,” says Tollin, and explains that a secondary coil corresponding in size to about two sheets of A4 paper is placed under the booth of the car.

“For charging, we have a plate on the ground or on the garage floor. It contains a primary coil which sets up an invisible link to the secondary coil in the car. The charger is supplied by a regular 230 V connection to a wall outlet or post.”

One advantage of inductive charging is that the charging plate can be placed on asphalt or concrete. The charging will work even if the plate is covered with snow.

Automatic charging
Johan Tollin explains that Vattenfall’s reason for taking part in the project is not to promote the development of the technology.
“The technique of wireless charging is interesting in itself, but automatic charging would be an attractive added bonus for electric vehicles. To park and go, that’s what automatic charging is all about. The driver would not have to do anything, as there’s no need to connect up a cable.”

“At the same time I don’t want us to disparage cables. We will live with them and they will continue to dominate the charging process for a long time to come. I believe in automatic charging as a future option for these cars.”

An attractive solution
Tollin points out that essentially all major vehicle manufacturers are currently working on the development of wireless charging solutions for electric cars.

“It’s hard to know when this technology will finally come onto the market. It still has to handle many challenging limiting conditions and satisfy all relevant standards. Standardisation is also important if this concept is to achieve a significant breakthrough. The first model with inductive charging may be available in 2017 directly from car dealers. It’s a big thing to integrate. But I feel that it’s so attractive that it will be done.”

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