A Study on Optimization of Piezoelectric Energy Harvesting Systems for Energy Source Type

Abstract

A Piezoelectric energy harvesting guideline was provided for ambient energy source type such as the constant, random vibration, rotatory and compressive moment types. There are many types of ambient energy sources, and the piezoelectric module needs to be modified for a specific condition of the energy source. Because there is no guideline for utilizing piezoelectric modules under the specific conditions of an input energy source, this paper proposes individual piezoelectric energy harvesting systems for different ambient energy source types. For example, the input energy source types known as the constant, random, rotatory and compressive moment types were considered in relation to Maglev vibration, KTX vibration, wind and fluid flows and human foot-steps respectively. First, for constant vibration of the Maglev, the effects of steel balls were optimized to convert the mechanism from the bending mode (d31) to the impact mode (d33). Both vertical and horizontal vibrations were considered for steel ball application. Secondly, for the random vibration of the KTX, the sensitivity was enhanced by optimizing tip mass and the dimensions of the piezoelectric module. The sensitivity of the piezoelectric module was enhanced by enlarging the piezoelectric ceramic area and by lowering the thickness of the piezoelectric ceramic and the substrate plate. Also, for the rotatory moment, such as application of the wind and fluid flow (higher than 1000 rpm), a fixed stick was used to damp any free vibration of the cantilever beam structured piezoelectric energy harvesting system. This fixed stick provided a multi-impact capability, which enables the saturation of the output power up to 132.25 mW, which is a relatively high output power compared to only regular vibration and the impact type of the piezoelectric energy harvesting system. Lastly, for the compressive moment from human foot-steps (less than 1 Hz), a piezoelectric module with urethane rubber was applied to delay the recovery time of the piezoelectric module with the cantilever beam shape. By applying a urethane rubber coating, the current generation time was increased by 50 times, from 0.05 sec to 2.5 sec. This effect was proved by inserting an LED, showing a longer time of voltage generation by the piezoelectric module. Overall, each piezoelectric model was investigated for a specific condition of the input energy source type, such as the constant, random vibration, rotatory moment and compressive moment types from Maglev vibration, KTX vibration, wind and fluid flow and human foot-steps respectively. A piezoelectric energy harvesting guideline for ambient energy source types was built to utilize piezoelectric module, acting as a guideline for piezoelectric module applications for specific conditions of input energy source types. Therefore, this piezoelectric energy harvesting guideline will be useful for future applications of piezoelectric modules for specific conditions of ambient energy sources.