The Future of EV Charging is Wireless
Wireless charging technology is poised to revolutionize the way we charge electric vehicles (EVs). Instead of plugging in a cable, wireless charging allows EV owners to simply park over a charging pad and let the battery charge automatically through electromagnetic induction. This hands-free, convenient approach to charging is gaining traction as companies bring wireless charging systems to market.
How It Works
Wireless EV charging relies on resonant electromagnetic induction to transmit electrical current between two coils – a transmitter coil in the charging pad and a receiver coil installed in the vehicle. When parked over the pad, the coils form an electromagnetic field, allowing energy to transfer wirelessly to the vehicle’s battery. This process is highly efficient, with most systems achieving over 90% efficiency, comparable to plug-in Level 2 charging.
The charging pads can currently deliver power levels up to 11 kW, providing Level 2 charging speeds and adding around 20-25 miles of range per hour. While slightly slower than the fastest plug-in chargers, wireless charging eliminates the need to plug/unplug, improving overall convenience.
Advantages Over Plug-In Charging
Wireless charging offers several key advantages over traditional plug-in charging methods:
- Improved safety by eliminating exposed cables that can be tripped over
- Weatherproof operation as there are no ports or connections exposed to the elements
- Autonomous charging without requiring the driver to plug in the vehicle manually
- Reduced maintenance by avoiding wear and tear on charging ports and cables
- Future-proofing for technology advancements like dynamic charging without hardware changes
The convenience of wireless charging can reduce range anxiety, enabling more spontaneous trips and allowing for smaller, lighter battery packs in future EVs. Frequent wireless charging also keeps batteries in their optimal 20-80% state of charge, potentially extending battery life.
Efficiency Comparison
Wireless EV charging operates within an efficiency band of 88-93%, equivalent to Level 2 plug-in charging (typically 83-94% from grid to battery). The air gap between the ground pad and vehicle pad serves the same safety function as plug-in isolation transformers, with minimal power loss due to the highly resonant design.[1]
Some argue that plugged charging is still slightly more efficient overall due to factors like cable resistance. However, technological advancements have allowed wireless charging to virtually match the efficiency of plugged charging at around 90%. Ultimately, while individual results may vary, wireless EV charging is generally considered to be on par with Level 2 plug-in charging in terms of efficiency and speed.
Key Players
WiTricity, a Massachusetts-based company, has partnered with automakers like BMW, Hyundai, and Honda to integrate their Halo™ wireless system into production vehicles. The system offers charging rates from 3.6 kW to 11 kW.
Plugless Power, based in Texas, commercialized their L2 wireless charging system in 2014, allowing compatible EVs to charge at up to 7.2 kW. The company plans to expand compatibility to cover 80% of EVs in North America by 2024.
Challenges and Barriers
While promising, widespread wireless charging adoption faces hurdles like high upfront costs, efficiency limitations compared to the fastest wired chargers, electromagnetic safety concerns, lack of standardization across systems, regulatory hurdles, and the need for further technology maturation.
Establishing interoperability standards is crucial for seamless integration across all EV makes and models. The Society of Automotive Engineers (SAE) published official wireless charging standards in 2020 to facilitate wider industry adoption.
Future Developments
Several exciting advancements are on the horizon for wireless EV charging:
Dynamic wireless charging would allow EVs to charge while driving by installing charging coils under roadways, reducing the need for dedicated charging stops on long trips. Michigan has already announced plans for a wireless charging road pilot.
Vehicle-to-grid (V2G) capabilities would enable EVs to receive power wirelessly and discharge stored energy back to the grid when needed, turning them into mobile energy storage assets to help balance grid loads.
Continued efficiency improvements are expected, with researchers at Oak Ridge National Lab recently demonstrating a 120 kW wireless system with 97% efficiency. Cost reductions through economies of scale will also make the technology more affordable as it matures.
Conclusion
While challenges remain, wireless EV charging promises to revolutionize the ownership experience by making charging more convenient, autonomous, and accessible. With its potential to reduce range anxiety, extend battery life, enable dynamic charging, integrate with smart grid capabilities, and provide a seamless charging experience, this innovative technology is poised to play a key role in accelerating mainstream EV adoption in the coming years.
