Scientists from the Fraunhofer Institute for Integrated Systems and Device Technology IISB in Erlangen, Germany, have devised an efficient and cost-effective approach for charging electric vehicles (EVs) featuring a new wireless electromagnetic induction technology.
Cords are fast disappearing from our daily lives and the notion of being wires-free has taken portability to a whole new dimension. The computer mouse has already lost its tail, our telephones and headphones have become wireless – even electric toothbrushes and cellphones don’t need cables anymore. It’s a bright new world of power needs being met via an electromagnetic induction supply system.
Now it’s the turn for EVs to join the wireless fraternity thanks to the new approach developed by the Fraunhofer community.
“Cables are annoying, especially in winter or when it’s raining. Whatever gets on the cable – snow, sludge, water – also gets on your hands,” says Dr. Bernd Eckardt, head of the Vehicle Power Electronics department at the IISB. “It would be much more convenient to charge these plug-in vehicles remotely with contactless technology. And it’s possible. The way to do it is using electromagnetic induction, whereby electrical energy is transferred over the air between two objects via an electromagnetic field.”
Dr. Eckardt explaining the physics behind the new technology said: “Any wire that carries a current generates a magnetic field. As the English physicist Michael Faraday demonstrated in the 19th century, this magnetic field generates voltage or electromotive force as well. By correctly positioning two wires in relation to one another inside a magnetic field, it is possible to transmit energy over the air. In principle this works just like a transected transformer.”
Familiar examples of products that use this kind of energy transfer include charging stations for electric toothbrushes and smartphones, and induction hobs.
Researchers from the scientific and industrial communities have been working for several years to find ways to use induction to charge electric vehicles. Last month, Toyota revealed plans to release a plug-in electric Prius in 2016 that needed no plug at all to recharge, thanks to wireless technology from a U.S. company called WiTricity. A new partnership between BMW and Daimler is also aiming to develop the concept of wireless charging for electric vehicles.
All such approaches involve mounting induction coils on the underside of the vehicle and installing charging stations in the ground. But this brings with it a number of significant challenges. The coils need to be very powerful for the method to work because of the significant gap of up to 15 cm between car and ground. Powerful coils are large in size – and large coils are expensive, which pushes up costs.
There is also the problem of objects or animals impeding the charging process by blocking the transmission of power. Another particularly problematic issue is that metallic paper such as chewing-gum wrappers or cigarette packaging can blow under the car and into the induction zone, where it can get so hot that it bursts into flame.
Researchers at the IISB began pursuing an alternative approach in a bid to resolve these problems. Working as part of the Energie Campus Nürnberg research platform it took them less than a year to develop a system for charging electric vehicles from the front end. Since this allows the car to be driven much closer to the induction source – essentially touching it – the coils themselves are much smaller in diameter than in the floor-based version, coming in at 10 instead of 80 cm across.
The system is thus more efficient, more cost-effective and makes it less probable that obstacles will disrupt the flow of energy. The charging column is approximately waist-high and made of plastic. It bends backwards if pushed by the vehicle, and is even designed to flip down and out the way if the pressure applied is too strong.
“The car could drive over it if necessary. Touching the charging station causes no damage to the car body,” says Eckardt.
The coils are arranged in such a way that charging can take place even if the driver has not positioned the vehicle exactly in front of and centrally to the column. Clusters of coils that overlap vertically in the column and horizontally behind the license plate allow the current to flow irrespective of the vehicle’s size or height.
Today’s electric car models can be recharged overnight,” says Eckardt. The researchers are now looking to further increase the power of the coil, primarily to keep up with developing battery technology, and to cut the cost of the charge spot even further. “Nowadays, charge spots are offered as part of the sales package when customers buy an electric vehicle. This technology will only become a mass product if the price is right,” Eckardt explains.
In a parallel scenario, Alliance for Wireless Power (A4WP), Power Matters Alliance (PMA), and the most well-known Wireless Power Consortium (Qi), are developing non-electromagnetic induction and alternate induction methods that could herald the “next generation” of wireless charging technology.
A4WP uses a transfer technology called Rezence, based on magnetic resonance, which is basically the opposite of magnetic induction charging used by the competitors; the magnetic resonance also ensures multiple-device charging. PMA’s powermat is another wireless tech being embraced by companies like Starbucks and AT&T.
The Wireless Power Consortium, or WPC, backs an induction standard called Qi (pronounced chee) which so far has the widest global distribution and penetration, from charging plates to automotive cradles.
Image courtesy of Fraunhofer IISB