On the Effectiveness of Vibration-based Energy Harvesting

TLDR

Vibration‑based energy harvesting research has surged, yet most studies focus on a single technology, hindering cross‑design comparisons. The study seeks to develop a general theory that enables systematic comparison of diverse vibration‑generator designs. The theory shows that power output depends on vibration parameters, coupling coefficient, quality factor, generator mass density, and load matching, and it derives an effectiveness expression applied to electromagnetic, piezoelectric, magnetostrictive, and electrostatic transducers. Predicted maximum theoretical power densities range from 0.5 to 100 mW cm⁻³ for 1–10 m/s² vibrations at 50–350 Hz, and these predictions align with experimental results from two piezoelectric generator designs.

Abstract

There has been a significant increase in the research on vibration-based energy harvesting in recent years. Most research is focused on a particular technology, and it is often difficult to compare widely differing designs and approaches to vibration-based energy harvesting. The aim of this study is to provide a general theory that can be used to compare different approaches and designs for vibration-based generators. Estimates of maximum theoretical power density based on a range of commonly occurring vibrations, measured by the author, are presented. Estimates range from 0.5 to 100mW/cm 3 for vibrations in the range of 1–10 m/s 2 at 50–350 Hz. The theory indicates that, in addition to the parameters of the input vibrations, power output depends on the system coupling coefficient, the quality factor of the device, the mass density of the generator, and the degree to which the electrical load maximizes power transmission. An expression for effectiveness that incorporates all of these factors is developed. The general theory is applied to electromagnetic, piezoelectric, magnetostrictive, and electrostatic transducer technologies. Finally, predictions from the general theory are compared to experimental results from two piezoelectric vibration generator designs.