Investigation of a d15 mode PZT-51 piezoelectric energy harvester with a series connection structure

A d15 mode piezoelectric energy harvester (PEH) with two PZT-51 elements in series connection (SC), in which the elements are arranged along the width direction, was fabricated, and it is compared with the traditional d15 mode PEH with a single PZT-51 element (SPEH) to discuss the output peak-to-peak voltage (Up−p). The energy harvesting performances of PEHSC are modeled by combining the single degree of freedom model and the electrical model with the piezoelectric constitutive equation of the d15 mode. The energy harvesting performances of PEHSC were systematically measured at various frequencies and load resistances, and Up−p and output power are 12.4 V and 8.7 μW at a load resistance of 2.2 MΩ and resonance frequency of 73 Hz. The experimental Up−p of PEHSC and SPEH are 25.4 and 15.6 V at the resonance frequencies under open circuit condition, and this indicates that the SC structure can improve the energy harvesting performance for d15 mode PEH. The experimental Up−p, output power and the transient voltage-time curve of PEHSC are in agreement with the results of finite element numerical solutions and theoretical modeling, so they are acceptable. The d15 mode and SC structure could potentially improve the energy harvesting performance of PEHs.