Researchers at the DOE’s Oak Ridge National Laboratory (ORNL) recently demonstrated a 20-kilowatt bi-directional wireless charging system installed on a UPS medium-duty, plug-in hybrid electric delivery truck.
In the demo, the system transferred power at more than 92% efficiency between the truck and a charging pad across an 11-inch air gap, using two electromagnetic coupling coils.
The system incorporates ORNL’s custom electromagnetic coil design, control, system and wide-bandgap power conversion system. The team tested the system using grid and battery emulators before installing it in the vehicle.
The system’s bi-directional design supports use of the vehicle’s batteries for energy storage in a V2G application. ORNL says its bidirectional technology is fully compliant with grid power quality standards. Bi-directional charging capability would allow fleet owners to manage on-site generation such as solar power. “Scaling the technology to a fleet of 50 trucks gives you megawatt-scale energy storage,” said team leader Omer Onar.
ORNL has been working on wireless charging for some time. In 2016, researchers demonstrated a 20 kW wireless charging system on a light-duty passenger vehicle. In 2018, they created a 120 kW system that operated over a 6-inch air gap. The latest version of the system represents a further refinement. “There’s no off-the-shelf solution that can deliver 20 kilowatts across an 11-inch air gap with these efficiencies,” Onar said.