Theoretical model and performance study of a stacked hydraulic piezoelectric energy harvester under multiple pulsation frequencies excitation

Stacked piezoelectric energy harvesters can be applied to hydraulic systems to convert the pressure pulsation into electrical energy for powering low-power components. A theoretical model is constructed, taking into account the elastic effect of the fluid to mechanical interface. This model is employed to investigate the influence of pulsation frequency excitation on the energy harvesting performance. The findings indicate that the voltage and average power increase with increasing fundamental frequency only at low resistance for single frequency excitation. The harmonic frequency component of pressure is beneficial for improving the harvested electrical energy. When the pressure pulsation contains cavitation high-frequency, the voltage and resistance exhibit a quadratic growth pattern. The increase in fundamental frequency can significantly enhance the voltage and average power of high resistance. Conversely, altering high-frequency affects the energy harvesting performance of low resistance. Furthermore, under small difference between high-frequency and fundamental frequency, the optimal resistance increases initially before decreasing with further increase in the fundamental frequency. However, as this frequency span increases, the effect of the fundamental frequency on the optimal resistance becomes progressively weaker. This paper offers a theoretical practical foundation for selecting fluid regions in hydraulic piezoelectric energy harvesting.