A novel dual piezoelectric-electromagnetic energy harvester employing up-conversion technology for the capture of ultra-low-frequency human motion
Ge Shi, Xing Liang, Yinshui Xia, Shengyao Jia, Xiangzhan Hu, Mingzhu Yuan, Huakang Xia, Binrui Wang
Abstract
As the realm of smart wearable electronic devices undergoes continuous evolution, tapping into the energy generated by everyday human movement presents a compelling alternative to conventional batteries for powering these devices. However, conventional energy harvesting devices face limitations in capturing energy from ultra-low frequency mechanical excitation. This paper proposes a novel dual piezoelectric-electromagnetic energy harvester (DHEH). The DHEH consists of two PZTs comprising the piezoelectric energy harvesting unit (PEH), arc-shaped driving magnets, and two sets of coils constituting the electromagnetic energy harvesting unit (EMEH). The arc-shaped driving magnet facilitates coupling between two units, serving to generate a relative motion with the coils for energy harvesting and triggering the operation of the two PZTs. The excitation magnets can penetrate the coils completely. Meanwhile, employing two arc-shaped magnets with a repelling orientation can effectively enhance the power generation efficiency of the EMEH. Experimental findings indicate that under an external excitation of 2 Hz and an acceleration of 0.6 g, the optimal load resistance for the Piezoelectric Energy Harvester (PEH) is 80 kΩ, yielding a maximum output power of 0.306 mW. For the EMEH, the best-matched load is 96 Ω, resulting in a maximum output power of 10.65 mW, with a power density of 86.3 μW/cm3. Compared to the non-hybrid solution, adopting a hybrid approach increases the efficiency of the PEH by approximately 23-fold. Furthermore, hand-shaking tests reveal that the fabricated prototype of the DHEH can power common portable electronic devices, demonstrating its significant potential for practical applications.