A Multi-Directional Pendulum-Based Energy Harvester for Self-Powered and Distributed Ocean Environment Monitoring

Ocean environment monitoring is essential to timely assess marine conditions and climate change, as well as promote the exploration of marine resources. However, the distributed ocean monitoring systems still face challenges in energy autonomy, as most of the systems are widely distributed and powered by batteries. To address the challenges of sustainable energy supply in distributed ocean environment monitoring systems, this paper proposes a multi-directional pendulum-based energy harvester to effectively harness low-frequency random ocean wave energy. This harvester consists of a fixed iron ball, a moving magnetic ball tethered by the fixed iron ball, and a multi-coil array to realize multi-directional harvesting of ocean wave energy. The fixed iron-ball and rolling magnetic ball configuration allows the magnetic ball rolling freely on the surface of the shell, avoiding complexity of using universal-joints. The developed energy harvesting device generates approximately 4.18 mW across a 220 Ω load under single-axis sinusoidal excitation at 3 Hz and 0.7 g. Under dual-axis excitation, it can charge a power management module with an 800 μF storage capacitor to 3.8 V within 60 seconds. This study provides a potential solution for the self-powered operation of distributed monitoring nodes in the Internet of Ocean Things.