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%.
ORNL didn’t explain how its “polyphasing” differs from the phased electromagnetic fields in traditional inductive charging, but did say “rotating magnetic fields generated by the coil phase windings boost the power.” In addition to the 100-kW rate, the five-inch gap is a big deal; inductive wireless charging is usually constrained to a gap of a few millimeters (note, the Kona EV normally sits 5.9 inches off the ground).
What will it take to get this small, powerful box put into parking spaces and parking garages? The usual: Uniform wireless charging mechanisms and standards, materials vs. costs analyses, and the political and corporate will to foot the bill. Take the standards alone, a paper from December 2023 breaks down eight kinds of wireless power transfer technologies, all with their pros and cons. In contrast to the ORNL solution, for instance, MIT spun off the wireless EV charging company WiTricity that uses magnetic resonance charging for its Halo charger that maxes out at 11 kW. It will be a minute before we can enjoy ORNL’s breakthrough, but the achievement in real-world application gets the clock going.
