Back in 2016, the US Department of Energy's Oak Ridge National Laboratory developed a 20-kW wireless charger for electric vehicles with a reported 90 percent efficiency. That was for passenger EVs, and now researchers have successfully tested a system for a medium duty, plug-in hybrid delivery truck.
The grid-connected 20-kilowatt bi-directional wireless charging system was tested on a UPS delivery truck, transferring power from a charging pad over an 11-inch gap using two electromagnetic coupling coils at more than 92 percent efficiency.
The setup comprises the lab's custom coil design and control system, and wide bandgap power conversion systems. It draws from the grid and converts energy to direct current voltage, before a high-frequency inverter switches that to alternating current. A magnetic field is subsequently created and this sends power over the gap where it's converted back to direct current to charge the truck's 60-kWh batteries.
The research team notes that where it might take up to six hours to charge the vehicle's battery over a conventional wired charging setup, the wireless charging system could do so in around three hours.
Since it's a bi-directional system, the truck's batteries could be used to store energy from on-site renewables like solar panels or wind turbines. Technical team lead on the project, Omer Onar, reckons that scaling up the technology to a 50 truck fleet could give operators megawatt-scale energy storage options.
"UPS appreciates the Department of Energy’s support on this effort," said VP of Global Energy and Procurement at UPS, Mike Whitlatch. "This project demonstrates innovative ways to utilize vehicle battery storage at fleet scale to power the vehicle, add resiliency to our facilities and support the grid."
Further testing and data analysis is now being undertaken, but as the passenger prototype has already been scaled up to 120-kW at 97 percent efficiency over a six-inch gap, perhaps a future where wireless battery charging for light and medium duty all-electric or plug-in hybrid vehicles takes around the same time as filling up with fuel at a gas station is not too far off.
Source: ORNL
