E-Cars – Wireless Charging System Successfully Tested

ORNL’s power electronics team achieved this world’s first 20-kilowatt wireless charging system for passenger cars (Oak Ridge National Laboratory)

Wireless charging systems move electric mobility into a completely new light. It enhances convenience and acceptance by customers for this technology. However, wireless charging systems are still far from being a reality. Therefore, it is all the more important that research facilities, such as the Department of Energy’s Oak Ridge National Laboratory (ORNL), search for real-world solutions. The largest US Department of Energy science and energy laboratory ORNL demonstrated a 20-kilowatt wireless charging system with a 90 percent efficiency at three times the rate of the plug-in systems usually used for electric vehicles nowadays.

Together with the industry partners Toyota, Cisco Systems, Evatran, and Clemson University International Center for Automotive Research, ORNL developed in less than three years an architecture that includes an ORNL-built inverter, isolation transformer, vehicle-side electronics and coupling technologies. The researchers integrated a single-converter system into an electric Toyota RAV4 for a functionality test. For this purpose, the car was equipped with an additional 10-kilowatt hour battery.

“We have made tremendous progress from the lab proof-of-concept experiments a few years ago,” said 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.”

“The high-frequency magnetic fields employed in power transfer across a large air gap are focused and shielded,” Chinthavali said. “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.”

The researchers are already going one step further and prepare a 50-kilowatt wireless charging system. According to ORNL, it matches the power levels of commercially available plug-in quick chargers. The higher power levels are also needed in order to charge larger vehicles such as trucks and buses.

“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,” said David Smith, vehicle systems program manager. “The technology demonstrated today is a stepping stone toward electrified roadways where vehicles could charge on the go.”