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ORNL achieves 90% efficiency with 20 kW wireless charging for vehicles; looking ahead to 50 kW

A 20-kilowatt wireless charging system demonstrated at Department of Energy’s Oak Ridge National Laboratory has achieved 90 percent efficiency and at three times the rate of the plug-in systems commonly used for electric vehicles today.

ORNL’s power electronics team achieved this world’s first 20 kW wireless charging system for passenger cars by developing a unique architecture that included an ORNL-built inverter, isolation transformer, vehicle-side electronics and coupling technologies—all in less than three years. For the demonstration, researchers integrated the single-converter system into an electric Toyota RAV4 equipped with an additional 10 kWh battery.

Convenience and simplicity are at the heart of the ORNL system, which places a strong emphasis on radio communications in the power regulation feedback channel augmented by software control algorithms. The result is minimization of vehicle on-board complexity as ORNL and partners pursue the long-range goal of connected vehicles, wireless communications and in-motion charging. While the team’s initial focus has been static, or motionless, wireless charging, the researchers also evaluated and demonstrated the system’s dynamic charging capabilities.

We have made tremendous progress from the lab proof-of-concept experiments a few years ago. We have set a path forward that started with solid engineering, design, scale-up and integration into several Toyota vehicles. We now have a technology that is moving closer to being ready for the market.

—Madhu Chinthavali, ORNL Power Electronics Team lead

This ability can help accelerate the adoption and convenience of electric vehicles. Industry partners from Toyota, Cisco Systems, Evatran, and Clemson University International Center for Automotive Research contributed to the technology development demonstrated today at ORNL.

The researchers are already looking ahead to their next target of 50-kilowatt wireless charging, which would match the power levels of commercially available plug-in quick chargers.

Providing the same speed with the convenience of wireless charging could increase consumer acceptance of electric vehicles and is considered a key enabler for hands-free, autonomous vehicles. Higher power levels are also essential for powering larger vehicles such as trucks and buses.

As the researchers advance their system to higher power levels, one of their chief considerations is safety.

The high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded. This means that magnetic fringe fields decrease rapidly to levels well below limits set by international standards, including inside the vehicle, to ensure personal safety.

—Madhu Chinthavali

Energy Efficiency and Renewable Energy’s Vehicle Technologies Office provided funding for this competitively-selected project as part of a broad portfolio in support of DOE’s EV Everywhere Grand Challenge, which aims to make plug-in electric vehicles as affordable to own and operate as today’s gasoline-powered vehicles by 2022.

Toyota provided several vehicles for the research, including RAV4s, a Scion and a Plug-in Prius.

Other members of the ORNL project team are current staff members Steven Campbell, Paul Chambon, Omer Onar, Burak Ozpineci, Larry Seiber, Lixin Tang, Cliff White and Randy Wiles as well as retired staff members Curt Ayers, Chester Coomer and John Miller. The research and demonstration took place at ORNL’s National Transportation Research Center, a DOE User Facility.



The critical take away from the video is that this is very close to the charging efficiency of wired charging.


A 50 KW unit @ 90% would be great for road side restaurants, cinema parking, shopping and Smart centers parking and other places where BEV users may stop for one hour or so?

Charging and parking fees could be coupled-added and automatically charged to the BEV owner credit card.

Unauthorized users would be towed and fined $100+ or so.

Jason Burr

No different than handicap parking fines. But in this case they could install a barrier that lowers/opens/etc when an approved wireless charging vehicle approaches. Maybe make it part of the payment system and if combined with parking fees then should be a cinch.

On the other hand maybe have a warning system that shames the driver if they are not a compatible vehicle. I'm thinking something like electronic tags and the warning system at the doors (Best Buy, Wal-Mart, etc.). So if you park in the wireless charging spot with a Explorer flashing lights and a LOUD recording "this parking is reserved for wireless charging cars, please begin charing your car or park in another parking spot"


this redundant research. Qualcom already has a system they just licensed to Ricardo that does 20kW charging. This needs to be distributed to the the whole Air Fuel consortium
So all the above work for electric cars including Tesla rather getting proprietary charging stations that excludes other brands. May be these could be built into our highway system if they can synchronize charging at 60 mph. This would really drive the consumer to want to switch to electric cars.


Conventional electric rail has contact-based power transmission which operates at highway speeds.  Why try to make something fancy that will cost more?  Just put power and return busbars inside a groove in the guardrail and let the car charge at 200 kW while in motion.

If you're pulling down 200 kW you can charge a 60 kWh battery to 50% in 9 minutes.  Figure a 9 mile section of charging rail every 60 miles is all you need.


Assuming one car every 100 feet for 9 miles = 9 x 52 = 468 cars charging @ 200 KW each = 93600 KW being drawn. The electric guard rail would need rather heavy conductors, even with high (800+) voltage but would be doable if broken into 1/4 mile section or so.

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