Oak Ridge National Laboratory researchers develop high power wireless charging solutions that can make the charging of electric vehicles more convenient and efficient.
Electric vehicles are becoming very common and researchers across the globe are trying to make the charging process of these vehicles more efficient and convenient. For increased convenience, electric vehicles employ wireless technologies for charging. At the core of this technology is a power transmitting coil at the charging station. In the vehicle, there is a secondary coil where current is induced due to mutual induction. The efficiency of the wireless charging system is determined by the total power delivered to the receiver over the total power transmitted.
The air gap between the transmitter and receiver is an important parameter and it can significantly affect the coupling efficiency. The researchers from the Oak Ridge National Laboratory (ORNL) have demonstrated that their developed charging system can wirelessly charge both a light-duty passenger car across a six-inch air gap and a medium-duty delivery truck across an 11-inch air gap at the 20-kilowatt level at greater than 92% power transfer efficiency.
In this technology, there is a bidirectional flow of power which means that the power stored in the EV battery can be transmitted back for any external use. This wireless charging capability can send power back into the grid, or a home, or even another electric vehicle. In this way, they can serve as home generators during power outages.
Another important parameter for wireless charging performance is the electromagnetic emissions around the coil. The ORNL researchers developed a solution that uses nano-crystalline materials together with aluminum to create a magnetic-metallic hybrid shielding technology that dampens emissions and the heat they can produce.
There are mainly three levels of charging: slow, fast and rapid charging. The slow chargers have lower energy density and are rated up to 6 KW. The time it takes to reach 100% can vary, depending on the charging unit, and EV being charged. Typically it takes 10-14 hours to fully charge. The fast chargers are rated up to 25kW and can charge an EV within a couple of hours. Rapid chargers are rated more than 50kW and charge an EV within an hour. The charger developed by ORNL researchers is rated 120kW and now researchers are planning to install chargers with 270kW ratings that could charge EVs within 15 minutes.
Moreover, the researchers are now planning for a system called dynamic wireless charging in which vehicles are automatically energized while rolling over specially equipped roadways.
“Now we want to take it a step further. What if you have an EV and never have to worry about having enough of a charge to go anywhere you like? We can accomplish that with dynamic wireless charging,” said Burak Ozpineci, who heads ORNL’s Vehicle and Mobility Systems Research Section.
More information regarding the research studies by the ORNL group can be found at https://www.ornl.gov/news/hands-free-wireless-charging-system-advances-electric-vehicle-convenience.