Wireless charging for smartphones has become a reality—but can the same be achieved for electric vehicles (EVs)?

A research team led by Dr. Jiang Zhaoqiang, Assistant Professor in the Department of Electrical Engineering at the City University of Hong Kong, has developed a novel high-power 22 kW nano-crystalline intelligent wireless charging technology. This innovation achieves a remarkable 96% charging efficiency while reducing the system's size by 20% and weight by 14%, paving the way for widespread adoption of wireless charging for EVs.

How Wireless Charging Works

Wireless charging, or inductive charging, transfers energy wirelessly from a charger to a battery using electromagnetic fields. Its key advantage lies in the elimination of physical connectors—simply park an EV in the designated charging area to start charging, significantly enhancing convenience and reducing the failure rate of charging interfaces.

“Wireless charging technology is already used in some premium EVs. With technological advancements and cost reductions, it is likely to become mainstream in the future,” says Dr. Jiang.

Challenges of Current Wireless Charging Technologies

Most EV wireless chargers rely on ferrite cores, which suffer from poor thermal stability and high magnetic losses. To address these limitations, redundant designs are often added to the chargers, resulting in low power density, increased weight, and higher costs—obstacles to broader adoption.

Breakthrough with Nano-Crystalline Materials

Dr. Jiang’s team optimized the design of magnetic materials and circuits by integrating nano-crystalline alloy strips (thinner than 18 microns) into the magnetic coupling mechanism, replacing traditional ferrites.

Advantages of Nano-Crystalline Materials:

High Saturation Magnetic Flux Density: Achieves up to 1.2 Tesla, significantly higher than ferrite's 0.45 Tesla.

Enhanced Thermal Stability: Reduces sensitivity to environmental temperature fluctuations.

Lower Magnetic Core Losses: Improves efficiency and enables compact charger designs.

Overcoming Challenges:
Nano-crystalline materials exhibit high electrical conductivity, which can lead to elevated eddy current losses in high-frequency magnetic fields. To maximize their potential, the team:

Precisely designed the geometry and magnetic properties of the core.

Optimized the magnetic coupling mechanism for more direct and efficient energy transfer.

Created multiple combinations of magnetic permeability to achieve an optimal balance of electrical, magnetic, and thermal properties tailored to various applications.

Applications and Future Prospects

This wireless charging technology is suitable for parking lots, shopping centers, and home garages, enabling “park-and-charge” without cables. It could also be embedded into roadways, allowing EVs to charge while driving—ideal for long-haul trucks and buses.

As autonomous driving technology matures, self-driving cars could autonomously park in charging areas, eliminating the need for manual intervention and enhancing operational efficiency.

In the context of smart cities, wireless charging could integrate with intelligent power grids, optimizing energy management through load balancing and smart scheduling, contributing to grid stability.

Beyond EVs

With continuous advancements and cost reductions, wireless charging technology could extend to drones, robots, and other domains, driving broader adoption and innovation in the future.

This breakthrough not only revolutionizes EV charging but also offers a glimpse into a sustainable and interconnected smart city ecosystem.