Electrostatic Conversion for Vibration Energy Harvesting

This chapter focuses on vibration energy harvesting using electrostatic converters. It synthesizes the various works carried out on electrostatic devices, from concepts, models and up to prototypes, and covers both standard (electret-free) and electret-based electrostatic vibration energy harvesters (VEH).Comment: This is an author-created, un-copyedited version of a chapter accepted for publication in Small-Scale Energy Harvesting, Intech. The definitive version is available online at: http://dx.doi.org/10.5772/51360 Please cite as: S. Boisseau, G. Despesse and B. Ahmed Seddik, Electrostatic Conversion for Vibration Energy Harvesting, Small-Scale Energy Harvesting, Intech, 201

Adjustable Nonlinear Springs to Improve Efficiency of Vibration Energy Harvesters

Vibration Energy Harvesting is an emerging technology aimed at turning mechanical energy from vibrations into electricity to power microsystems of the future. Most of present vibration energy harvesters are based on a mass spring structure introducing a resonance phenomenon that allows to increase the output power compared to non-resonant systems, but limits the working frequency bandwidth. Therefore, they are not able to harvest energy when ambient vibrations' frequencies shift. To follow shifts of ambient vibration frequencies and to increase the frequency band where energy can be harvested, one solution consists in using nonlinear springs. We present in this paper a model of adjustable nonlinear springs (H-shaped springs) and their benefits to improve velocity-damped vibration energy harvesters' (VEH) output powers. A simulation on a real vibration source proves that the output power can be higher in nonlinear devices compared to linear systems (up to +48%).Comment: Please refer to paper "Nonlinear H-Shaped Springs to Improve Efficiency of Vibration Energy Harvesters", Journal of Applied Mechanics | Volume 80 | Issue 6, 2013 -- Paper No: JAM-12-1470; doi: 10.1115/1.4023961 -- for the published version of this articl

Increased Bandwidth of Mechanical Energy Harvester

This paper presents a new approach for enlarging the relative movement of a base excited cantilevered system at off-resonance. The aim is to broaden the peak resonance of resonators without compromising the quality factor. The idea is to gather the resonance phenomenon conditions at off resonance. We do so by using a rebound system to block the seismic mass of the cantilever with support of vibration, when the speed of this one is maximum. The present study shows that using this technique will amplify the movement of the seismic mass and hence, the transferred mechanical energy from the source to the cantilever. This approach is useful for vibration harvesters operating in environments presenting a variable frequency or even for random vibrations. In this work we detail the approach; we also show how to optimize the efficiency of the present structure. Finally we present the experimental results that validate the approach. We show that a gain six times greater than simple resonator was obtained over more than one octave