Many owners and enthusiasts of electric vehicles dream of charging them without a cable. American engineers have learned how to wirelessly supply 270 kW to a car.
The Oak Ridge National Laboratory (ORNL) has managed to charge a Porsche Taycan sedan with a record capacity. This happened only three months after the laboratory announced a record-breaking 100 kW wireless charging of the Hyundai Kona crossover.
Even from the most powerful 350 kW DC chargers, cars like the Taycan and Hyundai Ioniq 5 can draw approximately 230-250 kW. This power can replenish 10-80% of the battery charge in less than 20 minutes. According to ORNL, its wireless system can increase battery power by 50% in about 10 minutes.
Oak Ridge’s system combines a magnetic resonance transmitter with a receiver mounted on the bottom of the car. The secret of the system is in the multiphase windings — lightweight electromagnetic coils arranged on a coil to create a rotating magnetic field that eliminates current ripple and field damping.
«You have a constant transfer of energy rather than ripples through the air gap, so there is a significant improvement in the spatial and temporal utilization of the magnetic field,» says Omer Onar, ORNL Vehicle Power Electronics Research Group leader.
According to the developer, the system can provide eight to ten times the power density of similar single-phase wireless chargers, with an efficiency of more than 95%.
The system is compact on both the transmit and receive sides. The powerful 270 kW receiver fits into the space that Porsche has allocated for a potential 11 kW wireless charger in future versions of the Taycan. The electromagnetic coils in the receiver have a diameter of less than 50 cm. ORNL says its system is the world’s lightest wireless charger on a per-kilowatt basis at 7.5 kW/kg, compared to 1.9 kW/kg for Brusa’s wireless system, which delivers only 22 kW of power.
The company cited several advantages over wired systems. There is no need to deal with bulky charging cables and plugs, which are a particular burden for the elderly and people with disabilities. There are no cables that can be damaged or stolen because of their copper wiring, as is sometimes the case with charging stations. The wireless charging system is easier to maintain. The liquid-cooled DC cables used in many charging stations require regular maintenance and component replacement. In cable systems, the power output decreases after reaching temperature limits.
Oak Ridge does not require perfect parking like other wireless systems. The car can move more than 12 cm and still receive an effective charge. The system can even use the car’s cameras and built-in guidance to align it.
Wireless systems would be ideal for future generations of robotaxis that do not have a human driver on board. Small fleets of such robot taxis are already operating in China, the United States, and Europe. Currently, many electric taxi and delivery service drivers are not allowed to refuel their vehicles on their own. Wireless charging can be largely automated — you can simply park the car and walk away.
The prototype 270 kW charger can work with cars and trucks with different ground clearance. The relatively low-slung Taycan had a 12-centimeter air gap between the receiver and transmitter. The system can work with a clearance of up to 28 cm.
In terms of safety, ORNL assures that the system meets all electromagnetic field emission limits, emitting a — field of approximately 19 microtesla, and this is without any shielding.
Source: IEEE Spectrum