Investigation of Subsurface Current Flow Using an Active Front-End Converter for Through-the-Soil Long-Range Wireless Power Transfer

There is a strong demand for buried sensor networks in industries including mining, agriculture, geothermal energy, and oil/gas. However, the integration of these sensors is bottle-necked by the need for electric power which cannot be delivered by conventional means, i.e., cables, photocells, and batteries. To mitigate this bottle-neck, a recent technique was developed that utilizes conduction currents through the soil and subsurface (TTS) to transfer power wirelessly over large distances. The work presented here further investigates changes in conducted power signals as they flow over a 50m radius around a buried TTS Transmitter. An Active Front-End (AFE) converter in tandem with an integrated inverter output is used for creating signals with large spectral densities in order to study attenuation effects throughout the subsurface. The changes in the signals’ spectral content over distance are analyzed and discussed. The abilities to separate attenuation from current spread (divergence) from attenuation due to resistive loss are given, allowing the identification of frequencies best suited for long range power transfer.