Influence of Beam Geometry on the Power Capacity of a Cantilever Beam Based Energy Harvester
Authors: Mohiuddin Md. , Ahmed Zahir Uddin , Ahmed Riaz 
Published: February 2024

Abstract
The cantilever beam structure is the most conventional setup for strain-driven energy harvesting. While energy harvesting has found tremendous focus in many areas of engineering such as self-powered wireless sensors, radio transceivers, implanted biomedical devices, health monitoring, autonomous charging, automotive applications, etc., researchers are constantly working to improve the power scavenging capacity while maintaining the basic configuration of the energy harvester. This work aims to propose an optimal cantilever beam design for obtaining maximum electrical energy. To achieve this goal, a number of cantilever beams are investigated with different shapes (e.g. trapezoidal, concave, convex, triangular, V-shape) and geometric configurations. Each shape has been analyzed by varying different geometric parameters while the surface area, volume, and mass of the beam are kept the same. Such an approach was crucial to find the optimal geometric configuration for a specific beam shape. A similar approach was also adopted for the piezoelectric material attached to the beam, as an energy conversion medium, to minimize the effect of PZT on the power capacity of the beam. One-third of the beam surface area was coated by the piezoelectric material following the unimorph setting. The placement of the piezoelectric material was selected such that maximum power can be scavenged. The energy output from the beams was computed in terms of power density, as the energy capacity of a beam can be significantly dependent on geometric parameters (e.g. surface area, thickness) of a piezoelectric material. Hence, power density can be a reliable measure to understand the true effect of beam geometry on the power capacity of the harvester. In finding the optimal cantilever beam design, at first, a comprehensive analysis was performed to understand the geometric influence on power capacity for each beam type. Next, for each shape, an effective design was selected to achieve an increased power output. Finally, understanding the physics laying underneath in getting an increased output from each beam type, a unique design is proposed that can offer an increased power output compared to any conventional cantilever beam shape or the shapes analyzed in this work. The proposed beam isn’t a conventional shape, however, a composite design that is a combination of multiple shapes. To ensure a rational comparison with the conventional/studied shapes, a similar surface area, thickness, volume, and mass is considered for both the proposed model and the attached PZT material. While for a conventional shape, it has been found that, a trapezoidal shape with a winder apex compared to the fixed end can generate maximum power compared to any other conventional shape, the newly proposed composite design is capable of suppressing the power capacity of the trapezoidal beam with a considerable margin. The model proposed in this work can be a crucial addition to the energy harvesting domain as the technology is continuously thriving for increased power output.