Analytical model of z-piezoelectric energy harvester for power generation from human physical activities

Abstract

Human physical activities, viz., walking, jogging, jumping, etc on piezoelectric energy harvesters (PEH) have a great potential for the generation of free and clean energy. In the present work, an analytical model is developed to study the performance of a z-PEH, and the results were validated with numerical and experimental results. The distinctive features of the z-PEH are (a) it can be installed in a very small pavement/road surface area, (b) it results in very less damage to the road during installation, and (c) the repair and maintenance works can be carried out relatively easily. The power generation of the harvester can be enormously increased by increasing the number of unimorphs in the vertical (z) direction without increasing in the surface (x-y) directions, hence termed z-PEH. The harvester studied has four unimorphs. Each unimorph has a PZT-5A plate and an Aluminum substrate. The analytical and numerical studies resulted in a harvester with optimum dimensions for the PZT plate and Aluminum substrate of 20 × 20 × 0.4 mm3 and 65.1 × 20 × 1 mm3 respectively. Experiments were carried out on the optimum structure. The z-PEH, for an input deflection of 1 mm generated a maximum power of 0.84 mW, 0.88 mW and 0.80 mW from the proposed analytical model, numerical work and experiments respectively. The percentage of error between analytical and numerical results is 4.55% and between analytical and experimental results is 4.76%. An average human can generate a force of 490 N while walking, thereby allowing the use of 88 unimorphs in the z-PEH. From the analytical model, the resulted DC power of this harvester is 18.39 mW and the power density is 10.09 W m−3.