Feasibility of energy harvesting from thin piezo patches via axial strain (d 31) actuation mode

Abstract

Energy harvesting and structural health monitoring (SHM) are individually very active research fields in themselves. Piezoelectric materials have the necessary capability to perform both the tasks. Surface bonded plate-type piezoelectric ceramic (PZT) patches operating in d31-mode are considered best for SHM. However, for energy harvesting, built-up configurations such as stack actuators are conventionally preferred. The main objective of this study was to explore the possibility of energy harvesting from thin PZT patches operating in d31-mode, so that the patches can serve for SHM as well as energy harvesting. The voltage and the power generated by a PZT patch bonded in the d31-mode on a simply supported laboratory beam are measured experimentally. A coupled PZT-bond-structure electro-mechanical model is developed for predicting the voltage output across the patch under harmonic vibrations. The losses associated with the PZT patch, namely mechanical damping, electrical damping and the shear lag are included and rigorously quantified. Experimental observations are found to match closely with the theoretical predictions. After laboratory verification, a real life flyover (span 25 m) is modelled using finite element model to estimate the power generated by a plate-type PZT patch surface bonded on a typical city flyover. The power output is found to be in the microwatt range. This energy can possibly be harvested during the idle time of the sensor and utilised later for driving the same patch for SHM.