A comprehensive energy flow model for piezoelectric energy harvesters: Understanding the relationships between material properties and power output

Piezoelectric materials have significant potential for mechanical harvesting and have an important influence in determining the power output. While the energy harvesting figure of merit (FoMij) is frequently used to evaluate the performance of an energy harvesting material, inconsistencies between the FoMij and power output makes material design and selection complex. To address this challenge, this paper establishes a new comprehensive energy flow model to assess the influence of the mechanical, piezoelectric and dielectric properties of a material on the complete harvesting process. The model is experimentally verified via detailed experimental evaluation at a range of excitation conditions, with piezoelectric materials fabricated to yield contrasting properties. The comprehensive model provides powerful capabilities to enable (i) analysis of the influence of material modification on energy flow, (ii) precise quantification of the dependence of power output on material properties and (iii) prediction of the power output of a harvester, where the energy flow model significantly reduces the maximum error between predicted and measured output power by ∼70%. This work therefore provides a new holistic approach to fill the knowledge gap in understanding the relationships between material properties and harvesting performance to inform future research in material design, selection and modification.