German researchers have developed an innovative technology for wireless electric vehicle charging using inductive coils at the front instead of on the underside of a vehicle.
The team from the Energie Campus Nürnberg believes their approach offers tangible advantages over the currently more explored floor-mounted approach as the car can park virtually touching the inductive charging point.
Though still in its infancy, electromagnetic induction, a process where electrical energy is transferred through the air between two objects connected through en electromagnetic field, is widely considered as the ultimated future of electric vehicle charging.
“Cables are annoying, especially in winter or when it’s raining. Whatever gets on the cable – snow, sludge, water – also gets on your hands,” said Bernd Eckardt, head of the Vehicle Power Electronics department at the Fraunhofer Institute for Integrated Systems and Device Technology IISB in Erlangen, who leads the team behind the new invention.
Eckhardt's system consists of a waste-high, flexible charging column, which is fitted with the charging coils. These coils can be only ten cm in diametre - a considerable reduction compared with those of the floor-based systems, which require extra power to make up for the energy loss caused by the large gap between the charging coil and the underside of the car.
“The car could drive over it if necessary. Touching the charging station causes no damage to the car body,” said 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.
Also, the danger of some objects or even animals blocking the charging process is eliminated. It has been shown that, for example, cats are frequently attracted to the warmth-emanating coils on the ground and tend to lie down and rest in the stream of warmth, blocking the charging process.
Randomly discarded pieces of metallic paper such as chewing-gum wrappers or cigarette packaging can also interfere with the floor-mounted coils, causing fire hazard.
The current technology is a result of a continuous 12-year development.
“We’ve been consistently upping the system’s performance over the past year, and are now in possession of a prototype that is able to transmit three kilowatts (kW) at an overall efficiency of 95 per cent,” the researcher said. “Today’s electric car models can be recharged overnight.”
The team is still working on improving the efficiency of the system by perfecting the design of the coils.