A flexible piezoelectric energy harvester featuring an eccentric pendulum via frequency up-conversion for human motion

This paper presents an innovative design of a flexible piezoelectric energy harvester featuring an eccentric pendulum (FPEH-P), which has two major characteristics: frequency up-conversion and large deformation that can improve output capacity. To clarify operational principles, we establish a dynamic model of the pendulum, and the vibration of the flexible piezoelectric plate is analyzed. Then, the two major characteristics of the FPEH-P are verified by experiments and simulations. Furthermore, it is verified that the FPEH-P can work at a low frequency (about 2 Hz) experimentally. Due to the large deformation of the piezoelectric plate, the maximum peak open-circuit voltage can reach 6.82 V. At an excitation frequency of 1.9 Hz and amplitude of 100 mm, the maximum average power can reach 6.06 μW. The FPEH-P can efficiently harvest energy from individuals engaged in walking, jogging, and running, as evidenced by the output load voltage and average power. Moreover, it can also output voltage under multiple motion actions. Finally, it has been verified that the high-instantaneous voltage characteristic of the harvester can provide sustainable power to a timer.