Oak Ridge National Laboratory (ORNL) has developed a 20-kilowatt wireless charging system at 90% efficiency, yielding roughly three times the charging rate of the plug-in systems commonly used for electric vehicles today.

Industry partners Toyota, Cisco Systems, Evatran and Clemson University International Center for Automotive Research contributed to the technology, which they say will help boost the adoption and convenience of electric vehicles.

ORNL demonstrates its 20-kilowatt wireless charging system. Image credit: ORNL.ORNL demonstrates its 20-kilowatt wireless charging system. Image credit: ORNL."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, ORNL vehicle systems program manager. "The technology demonstrated today is a stepping stone toward electrified roadways, where vehicles could charge on the go."

ORNL’s power electronics team achieved the world-first 20-kilowatt wireless charging system for passenger cars by developing an architecture that included an ORNL-built inverter, isolation transformer, vehicle-side electronics and coupling technologies. For the demonstration, researchers integrated the single-converter system into an electric Toyota RAV4 equipped with an additional 10-kilowatt-hour battery.

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.

Safety is a chief consideration as the researchers advance their system to higher power levels.

"The high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded," says Madhu Chinthavali, ORNL Power Electronics Team lead. "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."

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