Oak Ridge National Laboratory demonstrates 100-kW wireless charging from a parking space

The white coats at Oak Ridge National Laboratories (ORNL) in Tennessee have hit a research milestone for the world of electric vehicles that seems like a plausible reality in the coming decade. Earlier this month, after parking a Hyundai Kona EV over a new wireless charger design, the scientists and engineers registered a max wireless charging rate of 100 kW across a five-inch air gap at a claimed efficiency of 96%. In an earlier bench test, researchers hit 120-kW wireless charging speeds, but this test used a production car parked atop the prototype coil. The power registered is equivalent to a lower Level 3 plug-in system using a good cable, trouncing the best commercially available wireless chargers and wall-mounted Level 2 systems — potent enough to restore about 350 miles in an hour of charging compared to around 42 miles. In the case of the Kona EV, a full charge at the max rate would take less than an hour.

The magic comes from a polyphase electromagnetic coupling coil, a design ORNL's been working on for at least three years. A paper the lab put out in 2022 claimed, "High-power wireless power transfer (WPT) systems with polyphase electromagnetic couplers" can be a better solution thanks to "very high surface power density," high efficiency, more compact form factors, and the ability to integrate automated charging processes that could serve autonomous vehicles.

The wireless charging for dummies explanation is that a sending coil takes AC (alternating current) electricity from the wall and turns that electricity into an alternating magnetic field. A second coil inside the device to be charged then turns that magnetic field into electricity to charge the battery. 

The ORNL unit, at only 14 inches wide, contains coils made of various materials that create a magnetic field in the same way used by consumer devices like cellphones and toothbrushes, called inductive charging. Receiving coils built into a unit on the underside of the Kona EV turn that stronger, more uniform magnetic field into electricity, at a higher efficiency than most wireless charging setups are capable of. In fact, a range of EV charging tests showed plugged-in Level 2 and Level 3 charging losses of around 14% to 20%.