Design and Evaluation of Double-Stage Energy Harvesting Floor Tile

Isarakorn Isarakorn,Hamamoto Hamamoto,Panthongsy Panthongsy,Jayasvasti Jayasvasti,Janphuang Janphuang

doi:10.3390/su11205582

Abstract

This paper introduces the design and characterization of a double-stage energy harvesting floor tile that uses a piezoelectric cantilever to generate electricity from human footsteps. A frequency up-conversion principle, in the form of an overshooting piezoelectric cantilever, plucked with a proof mass is utilized to increase energy conversion efficiency. The overshoot of the proof mass is implemented by a mechanical impact between a moving cover plate and a stopper to prevent damage to the plucked piezoelectric element. In an experiment, the piezoelectric cantilever of a floor tile prototype was excited by a pneumatic actuator that simulated human footsteps. The key parameters affecting the electrical power and energy outputs were investigated by actuating the prototype with a few kinds of excitation input. It was found that, when actuated by a single simulated footstep, the prototype was able to produce electrical power and energy in two stages. The cantilever resonated at a frequency of 14.08 Hz. The output electricity was directly proportional to the acceleration of the moving cover plate and the gap between the cover plate and the stopper. An average power of 0.82 mW and a total energy of 2.40 mJ were obtained at an acceleration of 0.93 g and a gap of 4 mm. The prototype had a simple structure and was able to operate over a wide range of frequencies.

Highlights

With the recent miniaturization and low-power consumption trends in electronic technology, the realization of autonomous energy devices, especially self-powered wireless sensors for the industry, agriculture, and healthcare, has attracted a lot of interest and considerably increased over the last decade
Sustainable electrical energy is commonly extracted from several kinds of ambient environment energies through a particular transduction mechanism known as energy harvesting [1,2,3,4,5,6,7,8,9,10,11,12,13]
Many piezoelectric energy harvesters must face the challenge of low and variable frequency vibration, especially of human movement, i.e., the frequency of a vibration source usually does not match with the resonant frequency of a harvester, resulting in low energy conversion efficiency

Summary

Introduction

With the recent miniaturization and low-power consumption trends in electronic technology, the realization of autonomous energy devices, especially self-powered wireless sensors for the industry, agriculture, and healthcare, has attracted a lot of interest and considerably increased over the last decade. Several researchers have recently attempted to address this problem in several piezoelectric frequency up-converting energy harvesters [16,17,18,19,20,21,22,23,24], which always oscillated at their resonant frequency no matter what the frequency of the vibration source was Their basic structure can be divided into two main parts: a frequency up-converting mechanism and a piezoelectric cantilever or disc. The teeth of a rotating gear driven by an oscillating mass were able to pluck a piezoelectric cantilever in both clockwise and counterclockwise directions Both energy harvesting devices were based on a contact frequency up-conversion mechanism that could pluck a piezoelectric cantilever effectively. It was able to make the bimorph last longer, but the generated energy significantly dropped at a high speed of magnetic plucking

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Conclusion