Nonlinear electrostatic energy harvester using compensational springs in gravity field

Abstract

This paper presents an experimental proof-of-concept of an innovative design of electrostatic vibration energy harvester based on a double bistable curved beam whose mechanical behaviour is significantly modified by additional linear springs. The basic analytical model for a curved beam with dynamical and quasi static behaviour is introduced and validated by finite element modelling. It is shown that the static force offset due to the gravity field can provide an important increase in the sensitivity to external acceleration. The device is fabricated using silicon on glass technology without the need of a wafer bonding technique. Energy harvesting experiments are performed with various orientations of the device relative to the gravity field direction. The electrical power output is derived from the output voltage measured across a storage capacitor. It is shown that the maximum power output of the energy harvester reaches 10 µW under 50 Hz, 10 m s−2 sine excitation, and is sensible at accelerations with amplitudes less than 1 g (down to 3 m s−2) and operating at a very low frequency range (5–100 Hz) with an overall device size of 1 cm × 1.5 cm × 200 µm.