Improving the performance of a piezoelectric energy harvester using a variable thickness beam

In recent years, researchers have shown a growing interest in the possibility of harvesting mechanical energy from vibrating structures. A common way to proceed consists of using the direct piezoelectric effect of a bimorph cantilever beam with integrated piezoelectric elements. Several studies focused on the development of analytical models describing the electromechanical coupling. Historically, most of these models have been limited to simple structures such as a constant cross-section cantilever beam harvester. This paper studies the effect of a variable thickness beam harvester on its electromechanical performance. A semi-analytical mechanical model was developed using Rayleigh–Ritz approximations with a trigonometric functions set. The model was next validated by a finite element (FE) modeling. Numerical simulations were then performed for different beam slope angles in order to find the optimum for a given maximal strain across the piezoelectric elements. For the case under study, it is shown that tapered beams lead to a more uniform strain distribution across the piezoelectric material and increase the harvesting performance by a factor of 3.6.