Comparison of monolithic and composite piezoelectric material–based energy harvesting devices

This study presents a comparison of the energy harvesting capacity of monolithic and composite piezoelectric materials, especially in the same energy harvesting configuration. The energy harvesting device was composed of a cantilever beam with active piezoelectric materials, a full-bridge rectifier circuit and an electrical load (resistance). Two energy harvesting devices were fabricated, both of which had piezoelectric patches mounted on top and bottom of the cantilever vibrating element. The first energy harvesting device utilized PZT-5H patches as a monolithic piezoelectric material, and the second energy harvesting device used macro-fiber composite patches as a composite piezoelectric material. The vibrating element used in this study was a stainless steel cantilevered beam with the same dimension as the patch. Characteristics of the energy harvesting devices, including generated power, current, and voltage, were compared in frequency domain and evaluated with respect to the electrical load under different excitation levels. In addition, the effects of the natural frequencies of the energy harvesting devices to the harvesting performance were evaluated. The power density (i.e. power over volume) and specific power (i.e. power over mass) of the energy harvesting devices were compared. In addition, the current density (i.e. current over volume) and specific current (i.e. current over mass) were also presented. Finally, the charging and discharging performances of the energy harvesting devices were also evaluated using a polymer Li-ion battery as the electrical load.