Single Degree of Freedom Shear-Mode Piezoelectric Energy Harvester

Abstract

An energy harvester operating in the thickness-mode (TMH) or longitudinal-mode (LMH) consists of a piezoelectric element which is sandwiched between a proof mass and a base. The piezo-element is poled along a direction perpendicular to the electrodes. When the base is subjected to a sinusoidal excitation, along the poling direction, a relative motion is generated between the proof mass and the base producing mechanical strain in the piezoelectric element. The resulting strain is converted into electrical power by virtue of the direct piezoelectric effect. In this study, a shear-mode harvester (SMH) is considered as a viable alternative to the TMH and LMH to enhance the harvested output power. The enhancement is generated by capitalizing on the fact that the strain constant of the piezoelectric in shear is much higher than those due to thickness or longitudinal deflections. To achieve such an enhancement, the piezoelectric element is poled along a direction parallel to its electrodes and is sandwiched between a proof mass and oscillating base in a design similar to that of the TMH and the LMH. Sinusoidal excitation of the base, along the poling direction, makes the piezo-element experience mechanical shear strain which when converted into electrical power produces outputs that are larger than those of the TMH and the LMH. The theory governing the operation of this class of SMH is developed for simple resistive electrical loads. Numerical examples are presented to illustrate the optimal performance characteristics of the SMH in comparison with the TMH and LMH. The effect of the piezo-element material, excitation frequency and electrical load on the harvested power is presented. The obtained results demonstrate the feasibility of the SMH as a simple and effective means for enhancing the power output characteristics of conventional TMH and LMH.

Energy Harvesting Research: The Road from Single Source to Multisource

“…In comparison, for the shear mode configuration the polarizations are parallel to the electrodes. The piezoelectric response of the shear mode is even higher than that of the typical electromechanical coupling modes used in other configurations although the fabrication of the materials (e.g., poling, re‐electroding) may become complex.…”

“…Apart from the tuning of the material composition, the rest of the piezoelectric energy harvesting research has focused on the structural design and optimization for different applications. The most popular structures used in piezoelectric energy harvesters include cantilever, stack cymbal configuration, diaphragm configuration, and shear mode configuration . The cantilever structure is suitable for low input force, small acceleration, and mid‐high frequencies (tens of Hz or above), but it allows large amplitude/deformation.…”

High-Performance Piezoelectric Energy Harvesters and Their Applications

“…They considered the ratio of the lateral displacement to the length of the wafer, and neglected the effect of the shear force in the shear strain calculation process. The cantilever PEH with a 13 3 6 3 1 mm 3 PMN-PT element showed a maximum power of 4.16 mW under a cyclic force of 0.05 N. In terms of modeling, Aladwaniet et al 101 developed a single degree of freedom (SDOF) model to analyze the shear-mode operation of piezoelectric materials. Malakooti and Sodano 98 developed a distributed-parameter model for a shear-mode cantilever energy harvester via the Timoshenko beam theory.…”

Electrical Power Generation Using Dynamic Piezoelectric Shear Deformation Under Friction

“…Since the piezoelectric shear constant is usually higher than that along the normal directions [4], many scholars aimed to realize energy harvesting by making good use of piezoelectric materials' shear deformation [5][6][7][8][9]. In addition, there are also some research on the piezoelectric prediction model, the derivation and solution of the electromechanical governing equation, and the calculation and optimization of the output voltage of piezoelectric shear cantilever beams [10][11][12][13][14].…”