• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.11
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• pp.696-701
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• 2016

In this study, to increase output of road piezoelectric energy harvester, it was made into rack type in which many piezoelectric materials can be installed and load transfer device of the leverage type to transfer vehicle load was made. By paving it in the road, the output characteristics depending on vehicle load and speed were evaluated. Changing vehicle load, harvester output characteristics depending on speed changes were evaluated at the interval of 10 km/h from 10 km/h to 100 km/h. Also, by making a wireless switch and sending wireless signal with output of rack type harvester, whether to receive it was evaluated by distance. It was checked that all switches work up to front-to-back 100 m from harvester.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.1
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• pp.62-67
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• 2012

Owing to the rapid growth of mobile and electronic equipment miniaturization technology, the supply of micro mobile computing machine has been fast raised. Accordingly they have performed many researches on energy harvesting technology to provide promising power supply equipment to substitute existing batteries. In this paper, in order to have low resonance frequency for piezoelectric energy harvester, we have tried to make it larger than before by adopting nickel that has much higher density than silicon. We have applied it for our energy harvesting actuator instead of the existing silicon based actuator. Through such new concept and approach, we have designed energy harvesting device and made it personally by making with micromachining process. The energy harvester structure has a cantilever type and has a dimension of $10{\times}2.5{\times}0.1\;mm^3$ for length, width and thickness respectively. Its electrode type is formed by using Au/Ti of interdigitate d33 mode. The pattern size and gap size is 50 ${\mu}m$. Based on the measurement of the nickel-based piezoelectric energy harvester, it is found to have 778 Hz for a resonant frequency with no proof mass. In that resonance frequency we could get a maximum output power of 76 ${\mu}W$ at 4.8 $M{\Omega}$ being applied with 1 g acceleration.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.805-812
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• 2011

In this study, a cantilevered energy harvester comprising piezoelectric fiber and epoxy composites was designed and analyzed electro-mechanically. In order to maximize the power of the cantilevered energy harvester, its exciting frequency was tuned to the first natural frequency of the beam. An efficient analysis method for predicting the output voltage of the beam was developed by using the finite element method coupled with piezoelectric behavior. By using this method, the effects of geometric parameters and various piezoelectric materials on power generation were investigated and the electric characteristics were evaluated. Design optimization of the beam geometries was performed for a base model. The optimum MFC design generated a maximum electric output of 40.1 V at a first natural frequency of 24.5 Hz.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.7
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• pp.1059-1065
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• 2017

In this paper, the energy harvester with a piezoelectric materials is modeled as the electric equivalent circuit, and performances of a standard DC method and a Parallel-SSHI method are verified through experiment under variable force and load conditions. Piezoelectric generator consists of mass, damper and spring constant, and it is modeled by electrical equivalent circuit with RLC components. Standard DC and Parallel-SSHI are used as power conversion methods, and standard DC consists of full-bridge rectifier and smoothing capacitor. Parallel-SSHI method is composed of L-C resonant circuit, zero-crossing detector and full-bridge rectifier. In case of simulation under $100k{\Omega}$ load condition, the harvested power is $500{\mu}W$ in Standard DC and $670{\mu}W$ in Parallel-SSHI, respectively. In experiment, the harvested power under $100k{\Omega}$ load condition is $420{\mu}W$ in standard DC and $602{\mu}W$ in Parallel-SSHI. Harvested power of Parallel-SSHI is improved by approximately 40% more than that of standard DC method.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.371-377
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• 2019

A flexible piezoelectric energy harvester(f-PEH) that converts tiny mechanical and vibrational energy resources into electric signals without any restraints is drawing attention as a self-powered source to operate flexible electronic systems. In particular, the nanocomposites-based f-PEHs fabricated by a simple and low-cost spin-coating method show a mechanically stable and high output performance compared to only piezoelectric polymers or perovskite thin films. Here, the non-piezoelectric polymer matrix of the nanocomposite-based f-PEH is replaced by a P(VDF-TrFE) piezoelectric polymer to improve the output performance generated from the f-PEH. The piezoelectric hybrid nanocomposite is produced by distributing the perovskite PZT nanoparticles inside the piezoelectric elastomer; subsequently, the piezoelectric hybrid material is spin-coated onto a thin metal substrate to achieve a nanocomposite-based f-PEH. A fabricated energy device after a two-step poling process shows a maximum output voltage of 9.4 V and a current of 160 nA under repeated mechanical bending. Finite element analysis(FEA) simulation results support the experimental results.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.5
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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.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.489.2-489.2
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• 2014

The planar type flexible piezoelectric energy harvesters (PEH) based on PbZr0.52Ti0.48O3 (PZT) thin films on the flexible substrates are demonstrated to convert mechanical energy to electrical energy. The planar type energy harvesters have been realized, which have an electrode pair on the PZT thin films. The PZT thin films were deposited on double side polished sapphire substrates using conventional RF-magnetron sputtering. The PZT thin films on the sapphire substrates were transferred by PDMS stamp with laser lift-off (LLO) process. KrF excimer laser (wavelength: 248nm) were used for the LLO process. The PDMS stamp was attached to the top of the PZT thin films and the excimer laser induced onto back side of the sapphire substrate to detach the thin films. The detached thin films on the PDMS stamp transferred to adhesive layer coated on the flexible polyimide substrate. Structural properties of the PZT thin films were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). To measure piezoelectric power generation characteristics, Au/Cr inter digital electrode (IDE) was formed on the PZT thin films using the e-beam evaporation. The ferroelectric and piezoelectric properties were measured by a ferroelectric test system (Precision Premier-II) and piezoelectric force microscopy (PFM), respectively. The output signals of the flexible PEHs were evaluated by electrometer (6517A, Keithley). In the result, the transferred PZT thin films showed the ferroelectric and piezoelectric characteristics without electrical degradation and the fabricated flexible PEHs generated an AC-type output power electrical energy during periodically bending and releasing motion. We expect that the flexible PEHs based on laser transferred PZT thin film is able to be applied on self-powered electronic devices in wireless sensor networks technologies. Also, it has a lot of potential for high performance flexible piezoelectric energy harvester.

• Journal of Powder Materials
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• v.30 no.6
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• pp.521-527
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• 2023

Piezoelectric technology, which converts mechanical energy into electrical energy, has recently attracted drawn considerable attention in the industry. Among the many kinds of piezoelectric materials, BaTiO₃ nanotube arrays, which have outstanding uniformity and anisotropic orientation compared to nanowire-based arrays, can be fabricated using a simple synthesis process. In this study, we developed a flexible piezoelectric energy harvester (f-PEH) based on a composite film with PVDF-coated BaTiO₃ nanotube arrays through sequential anodization and hydrothermal synthesis processes. The f-PEH fabricated using the piezoelectric composite film exhibited excellent piezoelectric performance and high flexibility compared to the previously reported BaTiO₃ nanotube array-based energy harvester. These results demonstrate the possibility for widely application with high performance by our advanced f-PEH technique based on BaTiO₃ nanotube arrays.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.7
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• pp.511-515
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• 2012

A road energy harvester was designed and fabricated to convert mechanical energy from the vehicle load to electrical energy. The road energy harvester is composed of 24 piezoelectric cantilevers and a vehicle load transfer mechanism. Applying a vehicle load transfer mechanism rather than directly installing energy harvesters under roads decreases the area of road construction and allows more energy harvesters to be installed on the side of the road. The power generation amount with respect to the vehicular velocity change was assessed by installing the vehicle load transfer mechanism and the energy harvester in the form of speed bumps and underground. The energy harvester installed in a speed bump form generated power of 7.61 mW at the vehicular velocity of 20 km/h. Also, power generation of the energy harvester installed in the underground form was 63.9 mW at the vehicular velocity of 28 km/h. Although the number of piezoelectric cantilevers was reduced by 1/3 to 24 in comparison to the previous research results with 72 piezoelectric cantilevers, similar power generation characteristic value was obtained within the vehicular velocity of 20 km/h by altering the vehicle load transfer mechanism and cantilever vibration method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.637-644
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• 2010

A vibration-powered piezoelectric energy harvester yields the maximum power output when its resonant frequency is made equal to the excitation frequency; however, the power output is dramatically decreased when the energy harvester is operated at off-resonance frequency. It has been observed that the resonant frequency of a piezoelectric energy harvester may change with time and that the excitation frequency often varies when the energy harvester is used in real applications. Hence, in this study, we propose a piezoelectric energy-harvesting module that is suitable for excitations in a certain frequency range. The frequency characteristics of the electrical output of the module are studied through analysis and experiment. A simple frequency tuning method is also suggested for the proposed energy-harvesting module; in this method, frequency tuning is achieved by changing the electrical connections between the constituent energy-harvesting units of the module.