Empa Teases a Future Where Your Car Charges as Easily as Your Toothbrush — With No Efficiency Loss

Empa, the Swiss Federal Laboratories for Materials Science and Technology, has announced the results of a real-world test for its inductive charging technology — promising a future where electric cars and other vehicles can be charged wire-free at the same efficiency as today's wired systems.

"The aim was to test the existing technology in everyday use, clarify technical and regulatory issues, and demonstrate its potential for the energy transition," Mathias HUber, part of Empa's Chemical Energy Carries and Vehicle Systems Lab, explains of the trial. "The technology works very reliably in practice and is similarly efficient to conventional charging systems."

Inductive charging, in which energy is transmitted wirelessly by energizing a coil that induces a charge in a nearby matching coil, isn't new: the same technology has long been used to charge electric toothbrushes without creating a hole in their casing through which water could creep. While recent advances have taken the technology to the point where it can run at high enough voltages and currents to charge bigger devices like smartphones, electric vehicles are uniquely power-hungry — and a loss of efficiency from wired charging to wireless can mean a big increase in the time it takes to get back on the road.

Empa's system, trialed as part of the INLADE project led energy supplier Eniwa AG, promises the best of both words. A base plate contains a transmitter coil that induces current in the matching coil of the car parked above — retro-fitted to existing electric vehicles for the test, and subject to rigorous electromagnetic compatibility testing. In testing under real-world conditions, Empa recorded an overall efficiency of around 90 per cent — comparable, it says, to wired charging systems.

The team also suggests that the system could help balance power needs on the grid, taking advantage of the fact that most privately-owned vehicles are parked up for around 23 hours a day by taking in excess power from the grid and storing it to feed back in times of need. "The big advantage of an inductive system is that vehicles are connected to the grid much more frequently without the need for any active intervention," Huber explains, "a plus for both convenience and the energy transition."

One key drawback of Empa's system is that it requires that the two coils are aligned as precisely as possible — typically handled via positioning magnets in smartphone charging, which isn't something that really works with an object as heavy as a car. For the trial, drivers were guided to the correct position using an in-car display; in the future, advanced driver assistance systems could position the vehicle automatically.

No timescale has been given for the system's commercialization.