Capacitive Coupler Utilizing Electric Double Layer for Wireless Power Transfer Under Seawater

Abstract

This paper presents a capacitive coupler utilizing an electric double layer for wireless power transfer under seawater. Since seawater is an electrolyte solution, an electric double layer (EDL) is formed on the electrode surface of the coupler in direct current. If the EDL can be utilized in RF frequency, it is possible that high power transfer efficiency can be achieved under seawater because a high Q-factor can be obtained. To clarify this possibility, first, the frequency characteristics of the complex permittivity in seawater is measured and the behaviors of the EDL and electric conductivity are elucidated from the results. Next, it is clarified that EDL leads to an improvement in the Q-factor of seawater. Finally, it is demonstrated that the efficiency with the designed coupler under seawater can achieve about 91.1% by the single-ended model and 55.3% by the differential model.