Turning the tide: Magnetic coupling enables safer, smarter powering of ocean robots

Autonomous underwater vehicles (AUVs) play a vital role in ocean exploration, offshore infrastructure inspection, environmental monitoring, and defense applications. However, their mission duration remains restricted by limited battery capacity and the need for resurfacing or manual retrieval for charging. Underwater wireless power transfer is further challenged by seawater’s high conductivity, which induces significant eddy current losses and weakens electromagnetic fields. Moreover, waves and ocean currents cause inevitable misalignment between transmitter and receiver coils, reducing transfer stability. Growing requirements for real-time sensing and communication during charging add additional complexity. Due to these challenges, deeper research is required to develop more efficient and robust underwater wireless power transfer technologies.

Researchers from Fuzhou University, Tsinghua Shenzhen International Graduate School, and Nanyang Technological University published (DOI: 10.26599/OCEAN.2025.9470008) a comprehensive review in November 2025 in Ocean, summarizing the state of underwater wireless power transfer based on magnetic coupling. The review evaluates eddy current loss mechanisms, misalignment-tolerant coil architectures, compensation-network design, and emerging SWPDT strategies. The findings outline how optimized electromagnetic structures and control schemes can dramatically improve power transfer efficiency and operational reliability for AUVs.

The review first explains how seawater’s high conductivity creates strong eddy currents that dissipate power and distort electromagnetic fields. Simulation and analytical models show that losses increase almost exponentially with frequency, motivating the development of low-frequency, low-leakage coupling structures. Approaches such as three-coil transmitters, phase-shift control, and frequency modulation are shown to effectively suppress eddy current losses by reducing net electric-field intensity in surrounding seawater.

The review then examines misalignment tolerance—a critical issue because docking platforms drift and AUV posture fluctuates in currents. Clamp-type magnetic couplers, such as jar-shaped and cone-shaped cores, offer high efficiency but require precise docking. Open-type structures, including coaxial, cone-planar, arc-type, and multi-coil arrays, provide far greater tolerance to rotational and axial offset—some maintaining stable output at ±25 mm axial or ±10° rotational deviation.

Compensation networks further enhance robustness. Hybrid topologies combining series and LCC compensation stabilize power output across large coupling-coefficient fluctuations, while advanced control schemes using H-bridge inverters or variable inductors/capacitors deliver adaptive regulation without sacrificing efficiency. Finally, the review highlights four major SWPDT schemes—FDM, TDM, hybrid transmission, and load modulation—capable of enabling real-time sensing or command exchange during charging.

According to the authors, underwater wireless charging is transitioning from conceptual demonstrations to engineered systems capable of supporting long-endurance robotic missions. They emphasize that the integration of magnetic-coupling design, compensation-network optimization, and intelligent control will be essential for achieving reliable, kilowatt-level transfer in real ocean environments. The team also highlights that simultaneous power–data transfer will redefine how AUVs communicate, enabling continuous monitoring and decision-making without interrupting energy flow. These advances, they note, could significantly expand the operational envelope of next-generation marine robotics.

High-efficiency underwater wireless power transfer will enable AUVs to operate for months without surfacing, improving mission continuity for deep-sea mapping, ecological monitoring, pipeline inspection, and national-defense operations. Misalignment-tolerant couplers reduce the need for expensive precision docking, lowering deployment costs and improving reliability in turbulent waters. Meanwhile, SWPDT technologies could integrate energy supply and communication into a single interface, simplifying AUV architectures and enabling persistent, networked ocean-sensing systems. These innovations collectively move the field closer to fully autonomous, maintenance-free underwater robotics capable of supporting scientific, industrial, and security applications on a global scale.

Funding information

This work was supported in part by the Natural Science Foundation of Fujian Province (Grant No. 2022J06011) and in part by the National Natural Science Foundation of China (Grant No.52107183).

About Ocean

Ocean is an international, peer-reviewed, open-access journal that provides a multidisciplinary platform for cutting-edge research and practical applications in the fields of ocean science, marine technology, and marine engineering. The journal publishes articles, reviews, and perspectives aimed at advancing theoretical, numerical, site-based, and experimental developments to promote global sustainability.