Energy Harvesting on AC Power Lines for a Battery-Free LoRa Sensor Node

This paper presents a piezoelectric energy harvesting (PEH) system designed to power a LoRa-based Wireless Sensor Node (WSN). The system integrates a trapezoidal bimorph piezoelectric beam (LiNbO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub>) with a magnetic tip tuned to 50 Hz, optimized for ambient vibrations typically induced around alternating current (AC) power lines. When positioned near AC power lines, the PEH converts oscillating magnetic fields into mechanical vibrations of the beam, which are then transformed into usable electrical power. The lead-free PEH is optimized and characterized in terms of impedance and loading, maximum tensile stress, coupling, and temperature stability. An experimental analysis is then performed to optimize the relative positioning of the PEH for a single-phase AC cable. A normal power density is found to 180 μW · cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> · g<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> which provide about 76 μW in near field of single-phase AC cable under 50 Hz, 220 V and 10.4 A. Subsequently, the PEH is used to power an electronic board capable of transmitting data payloads via LoRa communication technology. This approach opens new possibilities for powering various sensors, enabling real-time environmental data collection and wireless transmission on infrastructures without sectioning multi-wire electrical cables.