20kW wireless charging system, demonstrated at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL), has achieved 90% efficiency at 3x the rate of the plug-in systems commonly used for electric vehicles, potentially accelerating adoption of battery powered cars.
“We have made tremendous progress from the lab proof-of-concept experiments a few years ago,” says Madhu Chinthavali, ORNL power electronics team lead. “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.”
ORNL’s power electronics team achieved the 20kW wireless charging system for passenger cars in less than three years, developing an architecture that included an ORNL-built inverter, isolation transformer, vehicle-side electronics, and coupling technologies. Researchers integrated the single-converter system into an electric Toyota Rav4 equipped with an additional 10kWh battery.
The researchers are already looking ahead to their next target of 50kW 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 higher power levels are essential for powering larger vehicles such as trucks and buses.Researchers say safety is a key concern for the wireless chargers.
“The high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded,” Chinthavali says. “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.”
Radio communications in the power regulation feedback channel, augmented by software control algorithms, minimize on-board complexity. While the team’s initial focus has been static wireless charging, the researchers also evaluated dynamic charging capabilities.
The DOE’s Vehicle Technologies Office provided funding for the project as part 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.
“Wireless power transfer is a paradigm shift in electric vehicle charging that offers the consumer an autonomous, safe, efficient, and convenient option to plug-in charging,” says David Smith, vehicle systems program manager. “The technology demonstrated today is a stepping stone toward electrified roadways where vehicles could charge on the go.”
Toyota provided several vehicles for the research, including Rav4s, a Scion, and a plug-in Prius. Industry partners from Cisco Systems, Evatran, and Clemson University International Center for Automotive Research contributed as well.
The research and demonstration took place at ORNL’s National Transportation Research Center, a DOE user facility. UT-Battelle, a partnership between the University of Tennessee and Columbus, Ohio-based research company Battelle, manages ORNL for the DOE’s Office of Science.
Oak Ridge National Laboratory
UT-Battelle
Toyota Motor Corp.
Clemson University International Center for Automotive Research
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