Parasitic power harvesting in shoes

TLDR

Microelectronics power needs are shrinking, enabling environmental energy sources to replace batteries in some wearable subsystems. This study evaluates three shoe‑integrated devices that harvest walking energy to generate electrical power parasitically. The devices comprise a piezoceramic unimorph strip, a multilayer PVDF stave, and a shoe‑mounted rotary magnetic generator. Tests reveal each device’s performance trade‑offs, suggest improvements, and demonstrate a piezoelectric shoe system that wirelessly broadcasts an RFID tag during walking.

Abstract

As the power requirements for microelectronics continue decreasing, environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this paper examines three different devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking. Two of these are piezoelectric in nature: a unimorph strip made from piezoceramic composite material and a stave made from a multilayer laminate of PVDF foil. The third is a shoe-mounted rotary magnetic generator. Test results are given for these systems, their relative merits and compromises are discussed, and suggestions are proposed for improvements and potential applications in wearable systems. As a self-powered application example, a system had been built around the piezoelectric shoes that periodically broadcasts a digital RFID as the bearer walks.