Maximum Available Efficiency of Undersea Capacitive Coupling in a Wireless Power Transfer System

This paper studies the maximum available efficiency of a capacitive power transfer (CPT) system submerged in seawater. The maximum efficiency for a dissipative CPT system is derived using the network theory, namely the conjugate-image method. Submerging CPT system in seawater gives a coupling capacitance in the nF range, which is higher than that in an airgapped CPT system with similar dimensions. The experimental results demonstrate that the capacitive coupling decrease by 6.3% when the distance increase from 100 mm to 300 mm. The results also show that the efficiency decreases by about 17.5% when the frequency increases from 300 kHz to 1 MHz. These results imply that submerging the CPT system in seawater does not need to operate at a high-frequency range, as in air-gapped CPT counterparts. Thus, a loosely coupled underwater CPT system is a promising solution for wireless charging applications.

Automated summary

This study investigated the maximum available efficiency of a capacitive power transfer (CPT) system submerged in seawater and found that the coupling capacitance in seawater is higher than in air. Experimental results showed that both increasing distance and frequency could decrease efficiency, suggesting that a loosely coupled underwater CPT system does not need to operate at high frequencies.