Towards the Feasibility of Long Range Wireless Power Transfer over an Ocean Surface

In this work, we have realized Zenneck’s style of wireless power transfer over a seawater surface. Method: The problem can be thought of as a surface electromagnetic wave propagating along an interface between a low-loss non-polar medium and seawater. A 10 m long water-filled plastic duct was connected to two separated water tanks, with one tank identified as the transmitting end and the other the receiving end. At the transmitting end, the water tank was excited with a 100 kV plasma from a spark gap transmitter at 44 MHz. At the receiving end, surface power was harvested in an open-circuit manner with the help of a suspended monopole antenna. Results: Without any antenna, no power was received at the receiving end. However, when two monopole antennas were individually connected to the transmitter and the receiver, a power was noticeably detected and successfully delivered to multiple loads even if the water’s conductivity was low. As the salinity level increased from 0 to 5 g/L, the transmission efficiency was increased from 10% to 99%. Consistent with Marconi’s law of transmission, the transmission distance leading to the first maximum efficiency was found to be approximately proportional to square of the antenna heights. Conclusion: A vertically mounted monopole antenna enables power to be wirelessly transmitted along the interface between a low-loss dielectric medium and seawater.