An enhanced electromagnetic energy harvester based on dual ratchet structure with secondary energy recovery

Abstract With the continuous advancement of ultra-low-power electronic devices, capturing energy from the surrounding environment to power these smart devices has emerged as a new direction. However, most of the mechanical energy available for harvesting in the environment exhibits ultra-low frequencies. Therefore, the feasibility of self-powering low-power devices largely depends on the effective utilization of this ultra-low-frequency mechanical energy. Consequently, this work proposes an enhanced electromagnetic energy harvester based on a dual ratchet structure with secondary energy recovery. It converts ultra-low frequency vibrations into fast rotational movements by means of a rack and pinion mechanism, thus achieving high power output while maintaining a simple structure. Experimental tests demonstrate that the proposed harvester exhibits excellent power output under ultra-low-frequency external excitation. Under external excitation with a frequency of 1.5 Hz and an amplitude of 22 mm, with the optimal load matched at 20 Ω, the maximum power output reaches 598 mW, with a power density of 1572.65 μW/cm³. The secondary energy recovery power accounts for 34.4 %, resulting in a 52.56 % enhancement in the energy harvester's output performance. Additionally, hand-cranking tests indicate that the fabricated prototype of the electromagnetic energy harvester can power some common electronic devices, including smartphones, showcasing significant application potential.