Abstract
Frequency up-conversion is a promising technique for energy harvesting in low frequency environments. In this approach, abundantly available environmental motion energy is absorbed by a Low Frequency Resonator (LFR) which transfers it to a high frequency Piezoelectric Vibration Energy Harvester (PVEH) via impact or magnetic coupling. As a result, a decaying alternating output signal is produced, that can later be collected using a battery or be transferred directly to the electric load. The paper reports an impact-coupled frequency up-converting tandem setup with different LFR to PVEH natural frequency ratios and varying contact point location along the length of the harvester. RMS power output of different frequency up-converting tandems with optimal resistive values was found from the transient analysis revealing a strong relation between power output and LFR-PVEH natural frequency ratio as well as impact point location. Simulations revealed that higher power output is obtained from a higher natural frequency ratio between LFR and PVEH, an increase of power output by one order of magnitude for a doubled natural frequency ratio and up to 150% difference in power output from different impact point locations. The theoretical results were experimentally verified.
Highlights
In recent decades smart gadgets, various micro electro-mechanic devices, and other MEMs have become popular
−mass of Low Frequency Resonator (LFR) while the geometry of Piezoelectric Vibration Energy Harvester (PVEH) was were achieved by varying the geometry and proof cantilever and a proof mass attached to its tip
Experimental and modelling results are in a good agreement, and the experimental results show the model underpredicted the power output by ~8%
Summary
In recent decades smart gadgets, various micro electro-mechanic devices, and other MEMs have become popular. It can be seen that the impact-driven vibration energy harvesters have the highest potential in the systems with low or uneven base excitation frequencies since the power is generated not by a low frequency resonator, which can as well be a free mass, but by a piezoelectric harvester, in which the vibrations are induced via impact or magnetic coupling. Such low frequency and high acceleration environments can be found in human motion. It is intended to investigate the influence of excitation to the first natural frequency of the PVEH ratio on the power output of the harvester
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