Wireless charging has already transformed how people power phones, wearables and even electric vehicles. The next leap is advancing wireless technologies to not merely deliver electrical energy, but to enable direct non-electrical outputs, such as optical, thermal and mechanical energy, directly according to actual needs, building an energy delivery network as flexible and efficient as the internet. To drive this transformation, researchers at The Hong Kong Polytechnic University (PolyU) have conducted a groundbreaking study that sets out a technical roadmap for "wireless energy internet", guiding the industry from "wireless power transfer" toward direct "wireless energy conversion".
Conventional wireless power transfer systems typically receive electrical energy and store it in a battery or supercapacitor before producing light, heat or motion. By contrast, direct wireless energy conversion transforms transmitted electric power directly into chemical, optical, thermal, or mechanical energy. In other words, the energy sent from the transmitter can become light for illumination, heat for warming, or force for driving motion — without first charging a battery — thereby eliminating intermediate storage and conversion stages, reducing energy losses, improving overall efficiency and simplifying receiver-side hardware. The study also establishes a unified framework that integrates near-field and far-field transmission with different applications such as wireless charging, lighting, heating, and motoring (mechanical energy), and summarises the common design principles and future directions of the underlying technologies.
The research was led by Prof. CHAU Kwok Tong, Chair Professor of Electrical Energy Engineering of the Department of Electrical and Electronic Engineering and Co-Director of the Research Centre for Electric Vehicles (RCEV), together with Prof. LIU Wei, Assistant Professor of the same department and Manager of RCEV at PolyU. The research team has identified the common technical principles and key engineering bottlenecks of wireless energy conversion systems, and proposed development directions in areas including standardisation, cybersecurity, energy harvesting and emerging applications, while outlining the challenges that must be overcome to provide an important reference for future large-scale deployment. Their study has been published in Nature Reviews Electrical Engineering and received Gold Medal with Congratulations of the Jury at the 50th International Exhibition of Inventions Geneva in Switzerland and a Grand Prize and a Gold Medal at the 4th Asia Exhibition of Innovations and Inventions Hong Kong.
Prof. Chau said, "Our review delivers impacts on two levels: first, establish practical design routes to cover core technologies such as primary-side control, multi-frequency compensation networks, secure transmission and field-directed transmission; and second, provide strategic guidance on future industry standards, security and application priorities. This will help industry select viable product architectures, while enabling policymakers and investors to identify the infrastructure required to drive commercialisation and mass adoption."
At present, transferring electricity to batteries is the most mature and widely adopted energy transmission and storage technology, already seen in portable electronics and biomedical implants, and developing rapidly in electric vehicles and rail transit. By comparison, wireless lighting, heating, and motoring demonstrate unique value in special application scenarios, such as sealed motors for harsh environments, mobile robots that require less onboard storage, and capacitive ultrasonic motors for magnetic-resonance-compatible robots. In these scenarios, conventional cables, batteries, or receiver electronics are hard to maintain or undesirable. These systems can also offer lightweight designs, convenience, high efficiency, flexibility, and improved safety.
At the consumer level, batteries can fail due to cell defects, internal short circuits, overcharging or poor thermal management, posing safety risks. In contrast, wireless power operates more flexibly and sustainably, and holds the potential to reduce battery-pack sizes or eliminate the need for onboard storage in vehicles. The smaller the battery and the less chemical energy stored, the lower the associated energy-storage risks — the most direct significance of wireless energy conversion for everyday life.
However, while direct conversion can ease energy-storage risks, it introduces a different safety consideration. Wireless energy networks still face a number of challenges, foremost among them the safety of energy transmission itself. The potential effects of prolonged human exposure to electromagnetic fields, and electromagnetic interference with nearby electronic devices, are of particular concern in environments such as public spaces and medical facilities. The study also notes that system complexity and performance limitations, especially in high-power wireless charging and wireless motoring, constitute barriers to application.
Prof. Liu added, "Our study highlights a key commercialisation challenge: most existing standards cover only specific applications, particularly wireless electric-vehicle charging. Comprehensive safety, emission and interoperability frameworks across broader wireless energy conversion remain incomplete. We therefore advocate designing wireless energy systems in a systematic and holistic manner, rather than optimising individual energy conversion stages in isolation."
The research team classifies wireless energy conversion into four categories: chemical for charging, optical for lighting, thermal for heating and mechanical for motoring. Together, these four categories encompass most application scenarios spanning domestic homes, industry and biomedical use, as well as extreme environments such as deep-sea and deep-space exploration. Looking ahead, a wireless energy network could automatically recognise the specific energy needs of different devices – whether chemical, optical, thermal or mechanical, and dynamically adjust transmission frequency, field distribution and power level accordingly.
The study also identifies four major engineering challenges: safety, scalability, complexity and performance, and, in response, outlines four priority directions for development. First, standard interfaces should be developed to enable devices to negotiate power, identify receivers, exchange data, control systems, handle faults, and interoperate. Second, energy encryption should progress towards integrated physical-layer security. Third, for aerospace applications, lightweight, sealed and radiation-tolerant couplers, converters and relay transmitters should be developed to connect satellites, stations, rovers and planetary bases. Fourth, electromagnetic harvesting should be strengthened, focusing on sensitive receivers, ultra-low-power rectification and hybrid architectures combining ambient energy harvesting with dedicated wireless power.
