Abstract

During the last decade, driven by the need, energy harvesting has drawn considerable attention due to the cost-effectiveness and simplicity of the structure. The most important feature or advantage of energy harvesters is their energy sources which are coming from the energy that would be wasted otherwise to the ambient surroundings. Among the three types of energy conversion methodologies, piezoelectric energy harvesters (PEHs) have been highlighted as a self-power source of energy for small wireless sensors with low required power input due to their simple converting structure.
While conventional piezoelectric materials possess ideal sensing properties, the microfabrication of these structures typically requires access to the sophisticated equipment and cleanroom facilities. Moreover, the fabrication process is time-consuming and expensive, researchers found it interesting to resort to micro-electromechanical system (MEMS) designs with inexpensive, simple and green-based materials and simple fabrication techniques such as paper.
Generally, the paper-based devices have offered significant benefits but their recorded performance is significantly below that of the ones of the commercial smart structures. Their development is still in the early stage of growth and they need to be properly designed to satisfy the general requirements of the commercial products. Geometry optimization, sizing and functionalizing are among the strategies which can be adopted to boost the performance of all types of piezoelectric energy harvesters including the paper-based piezoelectric energy harvesters (PPEH).
Therefore, the major contributions of this work are improvement of the performance of piezoelectric energy harvesters using the geometry modification, sizing analysis and functionalizing. In this work, the governing equations of piezoelectric cantilevers based on both Euler-Bernoulli and Timoshenko beam theories are developed and solved using one type of element with a great rate of convergence called superconvergent element (SCE). The theoretical analysis was validated against results published in the open literature and the results indicate that the proposed method yields higher accurate results. Further, the effect of non-uniformity on the electrical output and efficiency of Piezoelectric Energy Harvesters (PEH) are studied. Then, the influence of sizing and application of a series of piezoelectric cantilever energy harvesters on the performance of structure are studied. The effect of the shape of the piezoelectric elements is also investigated below. Eventually, development of functionally graded piezoelectric materials (FGPMs) for non-uniform beams are presented to evaluate the effect of functionalizing.