Design of novel piezoelectric energy harvester utilizing the force generated from human walking

Abstract

A novel piezoelectric energy harvester (z-PEH) to harness a significant amount of waste energy from human walking is proposed in the present work. The unique feature of the z-PEH is that a greater number of piezoelectric discs are planted in the z-direction without consuming a wide area of the pavement or road surface, hence termed z-PEH. This enables minimum damage to the existing pavements or roads during installation, maintenance and repair works. The power generating piezoelectric bimorphs are glued to aluminum plates attached to the hollow steel structure which is mounted on a spring. The z-PEH module consists of eight commercially available bimorphs, with each bimorph having two circular piezoelectric discs of diameter 25 mm and a thickness of 0.25 mm. The experimental and numerical open-circuit voltages of a single PZT are 9.38, 15.86 and 29.5 V and 9.23, 18.31 and 28.6 V respectively for applied weights of 24.5, 49 and 73.5 N. The z-PEH module occupied an area of 21.1 × 18 cm2. The numerical design is further carried out in commercially available software ANSYSTM with the objective of enhancing output power of the z-PEH module with in the same area. It is found out that, the optimized z-PEH module with square bimorphs, generated an open-circuit Peak-to-peak voltage of 69.07 V and the maximum DC power generated is 0.56 mW for an applied force of 73.5 N. Also, the z-PEH module with 56 bimorphs resulted in an average DC power of 3.95 mW for a step loading of 490 N (equal to 50 kg) under maximum power transfer conditions. The power density in this case is 2.49 W m−3.