• Journal of Sensor Science and Technology
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• v.17 no.4
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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.

• Journal of Sensor Science and Technology
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• v.22 no.5
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• pp.364-368
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• 2013

Vibrational energy harvester based on piezoelectricity has been expected to be the dominant energy harvesting technology due to the advantages of high conversion efficiency, light weight and small size, night operation, etc. Its commercialization is just around the corner but the integration with power management electronics should be solved in advance. In this paper, therefore, fully-integrated design environment for piezoelectric energy harvesting systems is presented to assist co-design with the power management electronics. The proposed design environment is capable of analyzing the energy harvester including the package-induced damping effects and simulating the device and its power management electronics simultaneously. When the developed design environment was applied to the fabricated device, the simulated resonant frequency matched well with the experimental result with a difference of 2.97% only. Also, the complex transient response was completed in short simulation time of 3,001 seconds including the displacement distribution over the device geometry. Furthermore, a full-bridge power management circuit was modeled and simulated with the energy harvester simultaneously. Therefore the proposed, fully-integrated design environment is accurate and fast enough for the contribution on successful commercialization of piezoelectric energy harvester.

• Smart Structures and Systems
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• v.26 no.6
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• pp.681-692
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• 2020

Conventional Piezoelectric Energy Harvesters (CPEH) have been extensively studied for maximizing their electrical output through material selection, geometric and structural optimization, and adoption of efficient interface circuits. In this paper, the performance of Stepped Piezoelectric Energy Harvester (SPEH) under harmonic base excitation is studied analytically, numerically and experimentally. The motivation is to compare the energy harvesting performance of CPEH and SPEHs with the same characteristics (resonant frequency). The results of this study challenge the notion of achieving higher voltage and power output through incorporation of geometric discontinuities such as step sections in the harvester beams. A CPEH consists of substrate material with a patch of piezoelectric material bonded over it and a tip mass at the free end to tune the resonant frequency. A SPEH is designed by introducing a step section near the root of substrate beam to induce higher dynamic strain for maximizing the electrical output. The incorporation of step section reduces the stiffness and consequently, a lower tip mass is used with SPEH to match the resonant frequency to that of CPEH. Moreover, the electromechanical coupling coefficient, forcing function and damping are significantly influenced because of the inclusion of step section, which consequently affects harvester's output. Three different configurations of SPEHs characterized by the same resonant frequency as that of CPEH are designed and analyzed using linear electromechanical model and their performances are compared. The variation of strain on the harvester beams is obtained using finite element analysis. The prototypes of CPEH and SPEHs are fabricated and experimentally tested. It is shown that the power output from SPEHs is lower than the CPEH. When the prototypes with resonant frequencies in the range of 56-56.5 Hz are tested at 1 m/s2, three SPEHs generate power output of 482 μW, 424 μW and 228 μW when compared with 674 μW from CPEH. It is concluded that the advantage of increasing dynamic strain using step section is negated by increase in damping and decrease in forcing function. However, SPEHs show slightly better performance in terms of specific power and thus making them suitable for practical scenarios where the ratio of power to system mass is critical.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.5
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• pp.424-428
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• 2010

This paper describes the design and analysis of AlN piezoelectric micro energy harvester. The harvester was designed to convert ambient vibration energy to electrical power as a AlN piezoelectric material compatible with CMOS (complementary metal oxide semiconductor) process. To cut off the leakage current, AlN was used as the insulating layer. Also, Mo was used for the excellent c-axis crystal growth as the bottom electrode. The AlN harvester which it has the low operating frequency was designed by using the ANSYS FEA (finite element analysis). From the simulation results, the resonance frequency of designed model is about 360 Hz and analyzed the bending mode, displacement and expectation output.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.206-211
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• 2010

Piezoelectric energy harvesting uses piezoelectric, which is able to convert unused mechanical vibration energy to electrical energy, such as with motor and machinery. The piezoelectric energy harvester was constructed with a cantilever made of lead zirconate titanate with a metal plate. The primary material was soft lead zirconium titanate (PZT-5H) due to the large strain availability, acceptable mechanical strength and high piezoelectric constant. This technique's drawback is that the energy efficiency is lower than the other energy harvesting methods, but this study increases the output electric power efficiency by analyzing a finite element method for the structure of the piezoelectric energy harvester. We manufactured two cantilever types as follows: the L-60 and L-33 bimorph piezoelectric energy harvesters. Their resulting energy harvesters were able to obtain high voltage values as follows: 27.4 mV and 40.6 mV. Moreover, these results have a similar band of resonance frequency it comparison to the simulation. Consequently, this study was confirmed with validity. The output electric powers of the L-60 and L-33 types have 3.1 mW/s and 5.8 mW/s with 47 Hz and 148 Hz of resonance frequency and then, the load resistivities were $100k\Omega$ and $10k\Omega$, respectively.

• International Journal of Highway Engineering
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• v.19 no.5
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• pp.107-115
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• 2017

PURPOSES : The piezoelectric energy road analysis technology using a three-dimensional finite element method was developed to investigate pavement behaviors when piezoelectric energy harvesters and a new polyurethane surface layer were installed in field conditions. The main purpose of this study is to predict the long-term performance of the piezoelectric energy road through the proposed analytical steps. METHODS : To predict the stresses and strains of the piezoelectric energy road, the developed energy harvesters were embedded into the polyurethane surface layer (50 mm from the top surface). The typical type of triaxial dump truck loading was applied to the top of each energy harvester. In this paper, a general purpose finite element analysis program called ABAQUS was used and it was assumed that a harvester is installed in the cross section of a typical asphalt pavement structure. RESULTS : The maximum tensile stress of the polyurethane surface layer in the initial fatigue model occurred up to 0.035 MPa in the transverse direction when the truck tire load was loaded on the top of each harvester. The maximum tensile stresses were 0.025 MPa in the intermediate fatigue model and 0.013 MPa in the final fatigue model, which were 72% and 37% lower than that of the initial stage model, respectively. CONCLUSIONS : The main critical damage locations can be estimated between the base layer and the surface layer. If the crack propagates, bottom-up cracking from the base layer is the main cracking pattern where the tensile stress is higher than in other locations. It is also considered that the possibility of cracking in the top-down direction at the edge of energy harvester is more likely to occur because the material strength of the energy harvester is much higher and plays a role in the supporting points. In terms of long-term performance, all tensile stresses in the energy harvester and polyurethane layer are less than 1% of the maximum tensile strength and the possibility of fatigue damage was very low. Since the harvester is embedded in the surface layer of the polyurethane, which has higher tensile strength and toughness, it can assure a good, long-term performance.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1240_1241
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• 2009

In this paper, sol-gel-spin coated $Pb(ZrTi)O_3$ thin film with $ZrO_2$ buffer-layer and $PbTiO_3$ seed-layer was investigated for vibration MEMS energy harvester to scavenge power from ambient vibration via d33 piezoelectric mode. Piezoelectric thin film deposition techniques on insulating layer is the important key for $d_{33}$ mode of piezoelectric vibration energy harvester. $ZrO_2$ buff-layer was utilized as an insulating layer. $PbTIO_3$ seed-layer was applied as an inter-layer between PZT and $ZrO_2$ layer to improve the crystalline of PZT thin film. The fabricated PZT thin film had a remanent polarization of 5.3uC/$cm^2$ and the coercive field of 60kV/cm. The fabricated energy harvester using PZT thin film with PTO seed-layer generated 1.1uW of electrical power to $2.2M{\Omega}$ of load with $4.4V_{pvp}$ from vibration of 0.39g at 528Hz.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.371-376
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• 2016

A self-powered piezoelectric energy harvester was developed for the application in wireless sensor node. The energy harvester was evaluated with power generation characteristics for the wireless sensor node for structural diagnosis of the electric power system. The self-powered wireless sensor node was set to measure temperature, vibration frequency of the electric power system. A piezoelectric harvester composed of 7 uni-morph cantilevers (functionalized as 6 generators and 1 vibration sensor) was connected to be an array and revealed to produce significantly high output power of approximately 10 mW at 120 Hz under 3.4 g((1 g = $9.8m/sec^2$). The wireless sensor node could work as the electric power generated by the developed piezoelectric harvester.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.301-302
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• 2007

Energy harvesting from the vibration through the piezoelectric effect has been studied for powering the wireless sensor node. For the driving wireless sensor node, the generated energy is required to store the capacitor or battery. For the rapid charging, higher voltage than battery's capacity voltage and a large current are necessitated. However, the piezoelectric energy harvester is generally featured as a high voltage and low current generator. As it is known that the generated current in the piezoelectric energy harvester is related to an area of electrode of piezoelectric ceramics, we fabricated the multilayer ceramics to increase effective area for the faster charging. The energy harvesting properties and charging characteristics of multilyaer ceramics were investigated and discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.863-865
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• 2014

Energy problem has been issued in worldwide because fossil fuel has being almost exhausted. A lot of renewable energy have been received attention to replace the energy from fossil fuel. Among them, piezoelectric energy harvester is one of excellent candidates. In general, micro scaled small sized energy harvesters were usually based on the lithography process. However, these lithography process require complicated process and high cost. In this paper, a new process has been proposed for micro-scaled piezoelectric energy harvester. $0.2Pb(Mg_{1/3}Nb_{2/3})O_3-0.8Pb(Zr_{0.52}Ti_{0.48})O_3$ composition was used as piezoelectric material due to excellent piezoelectric properties and also can be easily prepared by mixed oxide method.