A novel composite multi-layer piezoelectric energy harvester

A typical linear piezoelectric energy harvester (PEH) is represented by a unimorph or bimorph cantilever beam. To improve the efficiency of linear PEHs, classical strategies involve the increase of the beam length, tapering or adding additional cantilever beams to the free end. In this work we discuss the design of novel type of composite linear multi-layer piezoelectric energy harvester (MPEH). MPEHs here consist of carbon fibre laminates used as conducting layers, and glass fibre laminas as insulating components. We develop first a electromechanical model of the MPEH with parallel connection of PZT layers based on Euler-Bernoulli beam theory. The voltage and beam motion equations are obtained for harmonic excitations at arbitrary frequencies, and the coupling effect can be obtained from the response of the system. A direct comparison between MPEH and PEH configurations is performed both from the simulation (analytical and numerical) and experimental point of views. The experiments agree well with the model developed, and show that a MPEH configuration with the same flexural stiffness of a PEH can generate up to 1.98-2.5 times higher voltage output than a typical piezoelectric energy harvester with the same load resistance.