Optimization of an electret-based energy harvester

TL;DR

This paper optimizes electret-based electrostatic energy harvesters, demonstrating their potential to generate up to 200μW from low-level vibrations, and highlights the importance of parameter optimization for efficiency.

Contribution

It presents a comprehensive optimization of electret-based energy harvesters using FEM and Matlab, showing improved power output and challenging assumptions about electret surface potential.

Findings

Harvests up to 200μW with vibrations below 1G

Optimization of geometric, electrostatic, and mechanical parameters

High surface potential electrets are not always optimal

Abstract

Thanks to miniaturisation, it is today possible to imagine self-powered systems that use vibrations to produce their own electrical energy. Many energy-harvesting systems already exist. Some of them are based on the use of electrets: electrically charged dielectrics that can keep charges for years. This paper presents an optimisation of an existing system and proves that electret-based electrostatic energy scavengers can be excellent solutions to power microsystems even with low-level ambient vibrations. Thereby, it is possible to harvest up to 200\muW with vibrations lower than 1G of acceleration (typically 50\mumpp at 50Hz) using thin SiO2 electrets with an active surface of 1 cm^{2} and a mobile mass of 1g. This paper optimises such a system (geometric, electrostatic and mechanical parameters), using FEM (Finite Element Method) software (Comsol Multiphysics) and Matlab to compute the parameters and proves the importance of such an optimisation to build efficient systems. Finally, it shows that the use of electrets with high surface potential is not always the best way to maximise output power.