A geared-pendulum-based electromagnetic energy harvester with dual one-way bearing and synchronous magnet arrangement for enhanced performance under ultra-low-frequency excitations

Abstract Battery replacement for hydrological monitoring sensors is often time-consuming and costly, particularly in remote or offshore environments. To address this challenge, this study proposes a high-performance geared-pendulum-based electromagnetic energy harvester (GP-EMEH) that can harvest wave energy to enable self-powered sensing. The proposed harvester features a dual one-way bearing (DOWB) a synchronous magnet arrangement (SMA). The DOWB in the GP-EMEH converts wave-induced motion into unidirectional rotation, thereby maintaining counter-rotation between magnets and coils. Meanwhile, the unique design of the SMA not only achieves non-contact magnetic locking transmission which eliminates the necessity of mechanical connection of two magnet layers, but also amplifies the rate of magnetic flux variation, enhancing the electrical output under low-frequency excitations. A simplified finite element analysis is conducted to validate the working principle of the energy generation module. The experiment of the GP-EMEH prototype further confirms the simulation results, demonstrating a positive correlation between open-circuit voltage and excitation frequency (0.8–1.6 Hz). At an excitation frequency of 1.6 Hz with a 60 mm amplitude, the GP-EMEH prototype delivers a maximum power output of 130 mW. To demonstrate its feasibility in practical application, the GP-EMEH is employed to power an integrated sensing system for temperature, humidity, and pH monitoring installed on a buoy in a water tank, successfully initiating three measurement cycles within 220 s. These results highlight the potential of the GP-EMEH as an efficient and practical solution for self-powered ocean monitoring.