The Analysis and Design of a High Efficiency Piezoelectric Harvesting Floor with Impacting Force Mechanism

Sheng-He Wang,Mi-Ching Tsai,Tsung-His Wu

doi:10.3390/cryst11040380

Sheng-He Wang, Mi-Ching Tsai + Show 1 more

Open Access

https://doi.org/10.3390/cryst11040380

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Abstract

In renewable energy technology development, piezoelectric material has electro-mechanical converted capability and the advantages of simple construction and compact size, it has potential development since the environment vibration can be transferred into an electrical energy in daily harvesting applications. To improve the electro-mechanical converted efficiency of a piezoelectric harvester at low-frequency environment, a free vibration type of piezoelectric cantilever harvesting structure was proposed, which can generate a resonant oscillation by releasing an initial deformed displacement, and was uninfluenced from the effects of external environment. To analyze the harvesting behaviors, an equivalent circuit with voltage source was provided, and the parameters in theoretical model can be determined by the dimensions of the piezoelectric unimorph plate and its initial deformation. From the comparison of measurement and simulation, it reveals a significant efficient theoretical model where 8% error occurrence for storage energy was found. Finally, the proposed free-vibration generation method was developed in a piezoelectric harvesting floor design, which can transfer human walking motion into electric energy, and store in an external storage capacitor. From the testing result, one time of footstep motion can cause the charging energy in a 33 μF of storage capacitor achieve to 0.278 mJ, which was larger than the driven power of the wireless transmitter module, and then the wireless transmitter can be driven to send a RF signal without external power supply. Therefore, the designed piezoelectric harvesting floor has potential development to locate the user’s current position, which can provide users with future appropriate service for intelligent building application.

Highlights

In the recent years, depending on the tendency of miniaturization and low-power consumption in electronic product development, a self-powered electric device with autonomous energy has attracted a lot of interest, especially for wireless-sensor network technologies in intelligent living and industrial applications, such as public stations, commercial buildings, and manufacturing factories [1]
In order to obtain the best harvesting efficiency, a cantilever beam construction was developed for its capacity of large deformation in the most piezoelectric harvester, and its structure resonance frequency should be appropriated to the exciting frequency from the external environment [8]
The oscillation produced from the ambient environment is unstable, and the frequency is lower than the resonance frequency of the piezoelectric harvester, which results in the decreasing electro-mechanical conversion efficiency

Summary

Introduction

In the recent years, depending on the tendency of miniaturization and low-power consumption in electronic product development, a self-powered electric device with autonomous energy has attracted a lot of interest, especially for wireless-sensor network technologies in intelligent living and industrial applications, such as public stations, commercial buildings, and manufacturing factories [1]. In order to obtain the best harvesting efficiency, a cantilever beam construction was developed for its capacity of large deformation in the most piezoelectric harvester, and its structure resonance frequency should be appropriated to the exciting frequency from the external environment [8]. Different from most literature in which the plucking process was modeled as a stable force applied to the beam, and the characteristics of plucking piezoelectric energy harvesters would be hard to investigate due to experimentally validation of impact force difficulty, this paper used the Euler-Bernoulli governing equations to estimate the deformed distribution of the unimorph cantilever excited by an initial plucking displacement. An equivalent impact force by releasing an initial deformed displacement was utilized to generate a free vibration motion on the piezoelectric cantilever beam. Combined with Equation (5), the internal axial stress applied in the piezoelectric unimorph plate can be estimated as: T1(xb, z, t)

Electric Generating Analysis

Discussion

Conclusions