Integration of a High Frequency Inductive Power Transfer System to Energize Agricultural Sensors Through Soil

This paper describes the design and integration of a 13.56 MHz inductive power transfer (IPT) system and an in-house underground soil sensor network. The transmitter of this wireless power system was retrofitted on a Matrice 100 drone for periodic fast-charging missions, and the receiver was designed to fit into a sealed underground enclosure. The experiments reported in this paper involve a 40-day agricultural field trial where power was fed wirelessly to the soil sensor network. During this trial, the receiver’s enclosure was buried at a depth of 200 mm in soil. These experiments feature an average charging efficiency (from the drone’s battery to the underground station) of 33.5% (5% peak) with a peak power transfer of 35 W. Compared to laboratory testing, a significant increase in the end-to-end losses (of around 30 W) was observed in the field tests due to the presence of soil.The work reported in this paper is part of a collaborative project which looks to enable state-of-the-art high-frequency wireless power technology in agricultural applications.