An experimental investigation of wireless power transfer under water via capacitive coupling technique

In the last decade with the wide spread use of cellular phones and many other mobile devices including biomedical implants, the need for charging batteries and wireless powering of electric circuits, devices were obvious to grow significantly. Around hundred years ago, Tesla demonstrated [1] wireless power transfer (WPT) through magnetic resonance and near-field coupling of resonant coupled coils. In fact, even the induction machines, microwave heating and similar power devices are based on wireless power transfer. however even multi-frequency multicoil power transfer is being developed not only for short- distance but also for mid-range applications. (wpt) can be radiative or nonradiative depending on how the energy transfer mode is made and its applications [2] .Capacitive coupling power transfer is one of the wpt modes that can be valuable alternative to inductive coupling technique due to its simplicity ,less components , robustness to surrounding metallic elements , better EMI performance and less eddy currents in the water Autonomous underwater vehicles(AUV) operating essentially using the electrical energy stored in batteries to perform critical missions , oceanic research, search and recovery operations, and some military purposes ,since traditional charging methods requires removal of the AUV from the water and power is provided through a cables. The conductors are usually copper or aluminum which corrode in the presence of salt water. Removal of the AUV from the water requires a larger vessel with a crew operating it, increasing the operating cost. The contact less power transfer to the batteries while the AUV is underwater provides a solution to these operational complications. It is obvious that deeper researches must be done in order to understand clearly the behavior of (wpt) in the water using capacitive coupling technique. Water has very particular electric properties and anomalies that is really merit to be investigated. In this work based on laboratory experiments and simulations a capacitive coupling model made of copper plates fully isolated with polyamide situated in water container is created and immersed in different types of water like tap water seawater and deionized water Measurements are made also in air medium to analysis and examine the behavior of the power transfer at different distances and a wide range of frequencies in order to observe the response of the circuits.