Impact of Piezoelectric Material Length on Piezoelectric Cantilever Energy Harvesters: A Numerical Investigation

Abstract

The utilization of piezoelectric cantilever beam energy harvesters is widespread for extracting strain-based energy from vibrations. Ongoing research focuses on enhancing the power output of these energy harvesters. Piezoelectric material length is a vital variable that warrants investigation as it affects the output power. This study investigates the effects of changing the piezoelectric material's length while keeping the base beam and piezoelectric component's thickness and width constant. While maintaining a fixed base beam length, the inquiry modifies the length of the piezoelectric material. The piezoelectric material was positioned at the fixed end of the beam to attain maximum output power for each configuration. Furthermore, due to the dependence of the output power of piezoelectric energy harvesters on the optimal electrical load and resonance frequency, this study also analyzes these contributing elements. The result indicates that the maximum power density of 12.38 µW/mm³ is achieved at a resonant frequency of 40.7 Hz when the piezoelectric material spans the entire beam length. In contrast, the lowest power density, 10.46 µW/mm³, is observed when the resonant frequency reaches 56 Hz for a piezoelectric-to-beam length ratio of 2. These findings highlight that the highest power density, which is also cost-effective, is achieved by coating either a section near the fixed end or nearly the entire surface of the beam. When piezoelectric material is applied to half of the beam, the power density significantly decreases. The resonant frequency of the energy harvester exhibits a completely opposite trend compared to the output power density as the length of the piezoelectric material changes. Decreasing the length of the piezoelectric material leads to a reduction in capacitance, thereby causing an increase in optimal resistance.