[Reading Science] Charging Drones with Magnetic Fields Around Power Lines... Development of High-Efficiency Energy Harvesting Technology

Collecting Circular Magnetic Fields for Power Generation
Expanding into Self-Powered Technology for Ultra-Small Drones and IoT Sensors

A technology that converts weak magnetic fields generated around power transmission lines into electricity has been developed by a domestic research team. This next-generation self-powered technology is attracting attention for its potential applications in ultra-small drones and outdoor IoT sensors, where power supply is challenging.

The Korea Institute of Industrial Technology (KITECH) announced on December 9 that it has developed an energy harvesting technology that efficiently collects the circular magnetic fields around transmission lines and converts them into electricity. The research team led by Senior Researcher Seungha Yoon of the Energy Nano Group at KITECH succeeded in implementing a new structure that can significantly increase power output compared to existing methods.

Research team photo. From left: Jae-woo Park, Seungha Yoon, Yeonhee Yang. Provided by the National Institute for Korean Medicine Development.

Double the Power Output with a Symmetric Oscillation Structure

Energy harvesting is a technology that converts physical energy from the surrounding environment into electricity. This study utilizes the changes in alternating current (AC) magnetic fields generated by power transmission lines. When the magnetic field changes, the force acting on the magnet also changes, and this force bends a piezoelectric material, generating electricity. Since the electrical output of a piezoelectric material increases with greater repetitive deformation, maintaining resonance is crucial.

The research team improved upon the previous design, where only one magnet moved, by fixing the piezoelectric material at the center and placing magnets with opposite polarities on both sides, creating a newly designed "symmetric oscillation structure." Whenever the direction of the AC magnetic field around the transmission line changes, both magnets oscillate in the same direction, maximizing the deformation of the piezoelectric material. This enabled the generation of approximately twice the power compared to conventional methods.

In addition, the team applied a Magnetic Flux Concentrator (MFC) to focus the magnetic field around the magnets, improving power conversion efficiency by more than 20% even under weak magnetic fields.

The team verified the performance by using a Helmholtz coil to create a magnetic field environment similar to that around transmission lines, with intensities below 10 Gauss. Experimental results showed that the developed harvester could generate 25.2 mW/cm³ of power even in weak magnetic fields of about 5.4 Gauss.

This technological achievement was carried out as a flagship project of KITECH, and two domestic patents related to the technology have been registered. The research results were published in the internationally renowned journal in the field of sensors and actuators, "Sensors and Actuators A: Physical."

Senior Researcher Seungha Yoon stated, "This technology enables the generation of electricity using only the weak magnetic fields around power transmission lines. In the future, we plan to develop it into a self-powered platform for continuous operation by applying it to IoT sensors or ultra-small drones near transmission facilities."