Failure Mechanisms of Four-Plate Seawater Capacitive Power Transfer: A Poynting Vector Perspective

Existing research indicates that conventional four-plate Capacitive Power Transfer (CPT) system can hardly realize power transmission when the plates are fully submerged in seawater. However, the root cause of this failure in power transmission has not been investigated currently, still relying on simulation and experimental results, leading puzzles for scholars. Therefore, this article attempts to elucidate the failure mechanisms from the perspective of electromagnetics (EM) theory. It reveals that the high conductivity of seawater leads to significant attenuation and a dominant real part in CPT near-field complex Poynting vector, preventing effective reactive power coupling crucial for CPT. Then, an equivalent circuit model of seawater CPT is developed based on Poynting's theorem, establishing a fundamental connection between EM phenomena and lumped circuit models. Finally, the significant influence of conductivity on CPT is proved by simulation in COMSOL and experiments in lab and actual ocean, validating the feasibility of the theoretical analysis.