• Smart Structures and Systems
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• 제16권4호
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• pp.623-640
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• 2015

This paper presents techniques to harvest higher voltage from piezoelectric cantilever energy harvester by structural alteration. Three different energy harvesting structures are considered namely, stepped cantilever beam, stepped cantilever beam with rectangular and trapezoidal cavity. The analytical model of three energy harvesting structures are developed using Euler-Bernoulli beam theory. The thickness, position of the rectangular cavity and the taper angle of the trapezoidal cavity is found to shift the neutral axis away from the surface of the piezoelectric element which in turn increases the generated voltage. The performance of the energy harvesters is evaluated experimentally and is compared with regular piezoelectric cantilever energy harvester. The analytical and experimental investigations reveal that, the proposed energy harvesting structures generate higher output voltage as compared to the regular piezoelectric cantilever energy harvesting structure. This work suggests that through simple structural modifications higher energy can be harvested from the widely reported piezoelectric cantilever energy harvester.

• 한국전기전자재료학회논문지
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• 제24권5호
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• pp.416-421
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• 2011

Nowadays, the increasing demands upon mobile devices such as wireless sensor networks and the recent advent of low power electrical devices such as MEMS make such renewable power sources attractive. A vibration-driven MEMS lead zirconate titanate $Pb(Zr,Ti)O_3$ (PZT) cantilever device is developed for energy harvesting application. This paper presents a piezoelectric based energy harvester which is suitable for power generating from conventional vibration and has in providing energy for low power electron ic devices. The PZT cantilever is used d33 mode to get the electrical power. The PZT cantilever based energy harvester with the dimension of 7 mm${\times}$3 mm${\times}$0.03 mm is fabricated using micromachining technologies. This PZT cantilever has the mechanical resonance frequency with a 900 Hz. With these conditions, we get experimentally the 37 uW output power from this device with the application of 1g acceleration using the 900 Hz vibration. From this study, we show the feasibility of one of energy harvesting candidates using PZT based structure. This PZT energy harvester could be used for various applications such a batteryless micro sensors and micro power generators.

• Smart Structures and Systems
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• 제19권5호
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• pp.567-576
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• 2017

Design of piezoelectric energy harvester for a wide operating frequency range is a challenging problem and is currently being investigated by many researchers. Widening the operating frequency is required, as the energy is harvested from ambient source of vibration which consists of spectrum of frequency. This paper presents a new technique to increase the operating frequency range which is achieved by designing a harvester featured by a propped cantilever beam with variable over hang length. The proposed piezoelectric energy harvester is modeled analytically using Euler Bernoulli beam theory and the effectiveness of the harvester is demonstrated through experimentation. The results from analytical model and from experimentation reveal that the proposed energy harvester generates an open circuit output voltage ranging from 36.43 V to 11.94 V for the frequency range of 27.24 Hz to 48.47 Hz. The proposed harvester produces continuously varying output voltage and power in the broadened operating frequency range.

• Smart Structures and Systems
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• 제16권4호
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• pp.579-591
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• 2015

This paper investigates a magnetoelectric (ME) vibration energy harvester that can scavenge energy in arbitrary directions in a plane as well as wide working bandwidth. In this harvester, a circular cross-section cantilever rod is adopted to extract the external vibration energy due to the capability of it's free end oscillating in arbitrary in-plane directions. And permanent magnets are fixed to the free end of the cantilever rod, causing it to experience a non-linear force as it moves with respect to stationary ME transducers and magnets. The magnetically coupled cantilever rod exhibits a nonlinear and two-mode motion, and responds to vibration over a much broader frequency range than a standard cantilever. The effects of the magnetic field distribution and the magnetic force on the harvester's voltage response are investigated with the aim to obtain the optimal vibration energy harvesting performances. A prototype harvester was fabricated and experimentally tested, and the experimental results verified that the harvester can extract energy from arbitrary in-plane directions, and had maximum bandwidth of 5.5 Hz, and output power of 0.13 mW at an acceleration of 0.6 g (with $g=9.8ms^{-2}$).

• Smart Structures and Systems
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• 제9권6호
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• pp.549-563
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• 2012

Theoretical analysis is performed on a multi-mode energy harvester design with focus on the first two vibration modes. Based on the analysis, a modification is proposed for designing a novel adaptive multi-mode energy harvester. The device comprises a simply supported beam with distributed mass and piezoelectric elements, and an adaptive damper that provides a 180 degree phase shift for the motions of two supports only at the second vibration mode. Theoretical analysis and numerical simulations show that the new design can efficiently scavenge energy at the first two vibration modes. The energy harvesting capability of the multi-mode energy harvester is also compared with that of a cantilever-based energy harvester for single-mode vibration. The results show that the energy harvesting capacity is affected by the damping ratios of different designs. For fixed damping ratio and design dimensions, the multi-mode design has higher energy harvesting capacity than the cantilever-based design.

• 센서학회지
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• 제17권4호
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• pp.267-272
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• 2008

Energy harvesting from the vibration through the piezoelectric effect has been studied for powering the small wireless sensor nodes. As piezoelectric uni-morph cantilever structure can transfer low vibration to large displacement, this structure was commonly deployed to harvest electric energy from vibrations. Through our previous results, when stress was applied on the cantilever, stress was concentrated on the certain point of the ceramic of the cantilever. In this study, for miniaturing the energy harvester, we investigated how the size of ceramics and the stress distribution in ceramic affects energy harvester characteristics. Even though the area of ceramic was 28.6 % decreased from $10{\times}35{\times}0.5mm^3$ to $10{\times}25{\times}0.5mm^3$, both samples showed almost same maximum power of 0.45 mW and the electro-mechanical coupling factor ($K_{31}$) of 14 % as well. This result indicated that should be preferentially considered to generate high power with small size energy harvester.

• 한국전기전자재료학회논문지
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• 제34권2호
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• pp.90-98
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• 2021

Piezoelectric ceramic fiber composite (PCFC) was fabricated using a planar electrode printed piezoelectric ceramic fiber driven in transverse mode for small-scale wind energy harvester applications. The PCFC consisted of an epoxy matrix material and piezoelectric ceramic fibers sandwiched by interdigitated electrode (IDE) patterned polyimide films. The PCFC showed an excellent mechanical performance under a continuous stress. For the fabrication of PCB cantilever harvester, five -PCFCs were vertically attached onto a flexible printed circuit board (PCB) substrate, and then PCFCs were serially connected through a printed Cu circuit. The energy harvesting performance was evaluated applying an inverted structure, which imples its free leading edge located at an open end but the trailing edge at a clamped end, to enhance strain energy in a wind tunnel. The output voltage of the PCB cantilever harvester was increased as the wind speed increased. The maximum output power was 17.2 ㎼ at a resistance load of 200 ㏀ and wind speed of 9 m/s. It is considered that the PCB cantilever energy harvester reveals a potential use for wind energy harvester applications.

• 한국음향학회지
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• 제43권2호
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• pp.168-177
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• 2024

수중 압전 에너지 하베스터(Piezoelectric Energy Harvester, PEH) 설계시 곡률변화를 통해 외팔보형 전체의 와류유기진동(Vortex Induced Vibration, VIV)을 생성시키고, VIV의 생성으로 곡면형 외팔보 PEH에 진동 변위가 증가한다는 것은 실제 전력을 증대 시키는 데 중요한 요소이다. 해석 모델인 곡면형 PEH의 재질은 Polyvinyline Di-Floride(PVDF) 압전 필름으로서 곡률이 다양한 50 mm, 130 mm, 210 mm 모델에 유속은 0.1 m/s ~ 0.50 m/s로 정하여 VIV에 의한 PEH의 스트레인 에너지 변화를 관찰하였다. 곡률 반경이 작을수록 큰 폭의 VIV가 나타났고, 유속이 증가할수록 VIV가 많이 나타났다. 작은 곡률로 인한 급격한 형상변환이 VIV의 생성에 효과적이었고 스트레인 에너지, 정규화 발생 전압, 평균 전력 등은 곡률이 증가할수록 감소하였다. PEH 자체의 전력량을 증대시키기 위해 급한경사의 곡률 개선뿐만 아니라 곡률형 PEH의 개수가 늘어남에 따라 평균 전력도 상승할 것으로 사료된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.3131-3135
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• 2008

This paper presents an energy harvester using piezoelectric elements that is a kind of generator which converts the mechanical power to the electric one using windmill system with many PZT actuators. In this study, low frequency characteristics of the cantilever-type piezoelectric actuator are experimentally investigated. Advantages of the cantilever use are to take a very large displacement and to improve the endurance of the PZT element. The material of cantilever is an aluminum and three kinds of cantilever of which size is $150[mm]{\times}20[mm]{\times}1.5[mm]$, $170[mm]{\times}20[mm]{\times}1.5[mm]$ and $190[mm]{\times}20[mm]{\times}1.5[mm]$ were experimented, respectively. The cantilever was fixed on the vibrator. The characteristics of frequency and mass variation of cantilever end part such as 0[g], 5[g], 10[g] are investigated. Maximum voltage was outputted at the condition of $150[mm]{\times}20[mm]{\times}1.5[mm]$ and 10[g] of mass. It was confirmed that the lower natural frequency at the larger length of cantilever and at the bigger of mass is gotten.

• 한국전기전자재료학회논문지
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• 제25권12호
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• pp.943-948
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• 2012

A new water energy harvester module, which is composed of piezoelectric bimorph cantilevers, harvesting circuit and a shaft with 16 impellers at a center axis, was fabricated for energy harvesting application. High energy density $Pb(Zr_{0.54}Ti_{0.46})O_3$ + 0.2 wt% $Cr_2O_3$ + 1.0 wt% $Nb_2O_5$ (PZT-CN) thick film obtained by tape casting method was used for the bimorph cantilever. The PZT-CN bimorph cantilever with a proof mass of 49 g exhibited extremely high output power of 22.5 mW (24 $mW//cm^3$) at resonance frequency of 11 Hz. In addition, the fabricated water energy harvester has a cylindrical structure with 48 bimorph cantilevers clamped at inner surface. A significantly high output power of 433 mW was obtained at a rotation speed of 120 rpm with a resistive load of $500{\Omega}$ for the water energy harvester.