Cantilever-based Piezoelectric Energy Harvesters Research Articles

Performance Evaluation of Novel Piezoelectric Cantilever Beam Structure for Energy Harvesting

This study proposes an elastic compact Piezoelectric energy harvester (PEH) in multiple configurations, including a single cantilever beam, a single cantilever beam with a hole, two cantilever beams with a hole contributing towards a wider operating bandwidth. The cantilever beams are designed in multiple structural forms and section shapes, including symmetrical uniform section rectangle frames. Natural frequencies, vibration modes, and output voltages of PEH are estimated using Finite element software, with the frame acting as a rigid body and the cantilever plate acting as a deformed structure. A PEH with a rectangular cantilever plate surrounded by a rigid frame is designed and attached to the vibration platform with a customized fixture in the simulation software. The design meets the requirements of natural frequency and high output voltage in the low-frequency band. The PEH structure is simulated using a variety of piezoelectric materials, primarily PZT4 and PZT5H, barium titanate, lithium niobate, zinc oxide, and polyvinylidene difluoride (PVDF) using the finite element method. In the structural configuration of two cantilever beams with holes, PEH exhibited the maximum output voltage of 32.832 V for Zinc oxide compared to other materials. So, it can be concluded that insertion of hole and variation in the geometry of cantilever structure along with frame plays a vital role in achieving a large voltage from the vibrations in PEH. HIGHLIGHTS The finite element approach was used to develop and simulate the cantilever-based piezoelectric energy harvesting structure Multiple elastic compact Piezoelectric energy harvester (PEH) designs, including a single cantilever plate, a single cantilever plate with a hole, and two cantilever plates with a hole, are simulated using different materials The frame, hole insertion, and geometry modification of the cantilever structure all play important roles in generating a substantial voltage from the vibrations in PEH This study presents an Eigen frequency analysis of different PEH structures GRAPHICAL ABSTRACT

Topological optimization of a variable cross-section cantilever-based piezoelectric wind energy harvester

Wind energy is a typical foreseeable renewable energy source. This study constructs and optimizes a variable cross-section cantilever-based piezoelectric energy harvester for low-speed wind energy harvesting. The Galerkin approach is usually used to discretize the continuum model and then get the ordinary differential equations. However, this method is more suitable for calculating uniformity than the variable cross-sectional beam model. To solve this problem, we proposed an improved piecewise Galerkin approach for discretizing the continuum model with a variable cross section. By modifying the boundary expressions and modal functions between segments, it can improve both computation speed and accuracy. COMSOL simulations demonstrate that natural frequencies calculated via the improved method are more accurate than those of the traditional Galerkin method. The method of multiple scales is applied to determine the output power and critical wind velocity. A distinctive numerical approach is presented for shape optimization by combining the analytical calculation method with the particle swarm optimization (PSO) technique for low-speed wind energy harvesting. Additionally, the logic function is chosen to produce the optimal shape’s fitting expression for engineering applications. With all the improvements, the output power of a variable cross-section beam-based harvester reaches as much as 3.668 times that of a uniform beam model, demonstrating the importance of structural optimization for this type of energy harvesters. Finally, experiments are set up to verify the optimization procedure. Actually, it builds an analytical framework for the adaptive selection of variable-section piezoelectric cantilever wind-induced vibration energy harvesters.

Design, modeling, and experiment of a multi-bifurcated cantilever piezoelectric energy harvester

A multi-bifurcated cantilever piezoelectric energy harvester (BCPEH) is designed and verified to achieve a wide and adjustable response frequency band. The theoretical model is derived based on the Euler-Bernoulli beam theory and continuity boundary conditions to investigate the dynamic response of the BCPEH. The displacement frequency response function and the voltage frequency response function of the BCPEH are deduced based on the Galerkin method, and the theoretical results of a typical multi-bifurcated cantilever piezoelectric energy harvester, the Y-shaped BCPEH, are verified by the finite element method (FEM) and experiments. In addition, by comparing experimental output power of the Y-shaped BCPEH with that of the traditional cantilever-based piezoelectric energy harvester with the same mass of the bifurcated part at the beam-tip, it demonstrates that the Y-shaped BCPEH has a wider operational frequency band. Moreover, it is found that the Y-shaped BCPEH can be designed with an asymmetric configuration to adjust its response frequency distribution. The number of resonant frequencies and the output power of the asymmetric Y-shaped BCPEH are higher than that of the symmetric Y-shaped BCPEH. And the Y-shaped BCPEH has even better performance than L-shaped BCPEH. This study provides a new design concept for enhanced energy harvester.

Investigation on various beam geometries for piezoelectric energy harvester with two serially mounted piezoelectric materials

This paper presents the performance (frequency response, open-circuit voltage, optimum load, voltage and power under optimum load) of various designs of cantilever-based piezoelectric energy harvester with multiple piezoelectric materials, which is excited at the fixed end using the source of mechanical vibration and to compare the performance with single piezoelectric-mounted energy harvester. The performance of the energy harvester was determined using experimental and numerical methods. COMSOL Multiphysics 5.3a was used to obtain the numerical results of energy harvester. The results show that inverted taper in thick and width, inverted taper in thick and inverted taper in width piezoelectric energy harvesters produce 46.15%, 13.13% and 37.70% more power than the conventional rectangular piezoelectric energy harvester. The resonant frequency of inverted taper in thick and width, inverted taper in thick and inverted taper in width energy harvesters is 52.05%, 45.5% and 11.08% lower than the conventional rectangular energy harvester. It is observed that the different beam geometries with two piezoelectric material produce more power than the beams with single piezoelectric material.

Investigation of Electrical Properties for Cantilever-Based Piezoelectric Energy Harvester

Investigation of Electrical Properties for Cantilever-Based Piezoelectric Energy Harvester

Analysis of bimorph piezoelectric beam energy harvesters using superconvergent element

Cantilever-based piezoelectric energy harvesters have been utilized as structures to extract mechanical energy from the ambient mechanical vibrations and transfer it into the electrical output. In this article, the performance of bimorph piezoelectric beam energy harvesters is investigated. The cantilever beam is modeled by using both Timoshenko and Euler–Bernoulli beam theories. The equations are discretized using the conventional finite element method and superconvergent element. Besides the high rate of convergence, easy switching between the above beam theories is enabled by such type of element. The current model is presented for a Timoshenko beam model, but it could as well be used for a Euler–Bernoulli beam model. In addition, voltage, current, and power frequency response functions for different ranges of load resistance varying from the short-circuit to open-circuit conditions are determined to reach the maximum values. Effects of the slenderness ratio and the required beam model based on the geometric properties of the piezoelectric energy harvesters are discussed in the final part of this study. The results show that only for smaller values of the slenderness ratio (below 5), it is necessary to model the beam using the Timoshenko assumptions; otherwise both beam theories provide approximately the same responses.

Simulation Studies on Energy Harvesting Characterisitcs and Storage Analysis Through Microcantilever Vibration

Vibrations can be a good source of energy and can be harvested and utilized by simple design and fabrication using the MEMS technology. Energy harvesting provides unending sources of energy for low-power electronics devices where the use of batteries is not feasible. Piezoelectric energy harvesters are widely considered because of their compact design, compatibility to MEMS devices and ability to respond to a wide range of frequencies freely available in the environment. In this project, a rectangular model for cantilever-based piezoelectric energy harvester is proposed with different designs like two layer, two layer with proof mass, four layer and four layer with proof mass designed with dimensions as 50[Formula: see text][Formula: see text]m[Formula: see text][Formula: see text][Formula: see text]50[Formula: see text][Formula: see text]m[Formula: see text][Formula: see text][Formula: see text]1[Formula: see text][Formula: see text]m for each layer using COMSOL Multiphysics 5.0. Simulation results were obtained using silicon as substrate, aluminium as electrodes and PZT-5H and ZnO as piezoelectric materials and the respective stress and voltages were obtained by applying a force acting on foot, train, roller coaster and a general value of 10[Formula: see text]N/m2 on top of the cantilever. The effects of varying geometrical dimensions of the device were also investigated.

High-output piezoelectric energy harvester using tapered beam with cavity

Energy harvesting using cantilever-based piezoelectric structure is most popular for harvesting electrical energy from ambient vibrations. Efforts are also made to maximize the harvester power by means of tailoring the structural parameters of the cantilever beam. This article proposes a method to maximize the harvester voltage from the cantilever-based piezoelectric energy harvester by means of tailoring the structure of the cantilever, to have a tapering in width, thickness and in both width and thickness (double taper). It is also proposed to introduce rectangular and trapezoidal cavities in the tapered energy harvesters to further maximize the harvester voltage. The analytical model of the proposed harvesters is developed using Euler–Bernoulli beam theory, and its free vibration solution is analysed using Bessel functions. The energy harvesters are fabricated and experimentally evaluated for its performance. It is concluded from the results of analytical model and experimentation that width, thickness and double-tapered beam increases the harvester voltage by 35.6%, 84.8% and 126.6%, respectively, as compared to the energy harvester designed with uniform cantilever beam. Among all the energy harvesters proposed in this article, the maximum voltage is generated from the double-tapered beam with trapezoidal cavity. The experimental results are in close agreement with the results obtained from the analytical model.

Improved energy harvesting from vibration by introducing cavity in a cantilever beam

This paper presents modeling and experimental evaluation of a cantilever-based piezoelectric energy harvester with cavity. The introduction of cavity in the beam shifts the neutral axis of the beam away from the surface of the piezoelectric element which in turn increases the strain and generated voltage. The generated voltage from the cantilever beam with cavity is higher when compared to the beam without cavity and is found to vary with its position and thickness. The analytical and experimental results are in close agreement. The cantilever beam with cavity generates 75% higher voltage than the voltage generated from the beam without cavity.

Investigation of folded spring structures for vibration-based piezoelectric energy harvesting

This paper presents a fixed-fixed folded spring as an alternative elastic element for beam-based piezoelectric energy harvesting. In order to harvest energy from low frequency vibration in an optimal manner, the natural/operational frequencies of harvesters must be reduced to match low frequency input vibrations. Therefore, natural frequency reduction of vibration-based energy harvesters is critical to maximize output power at low operational frequency. The mechanical optimization of cantilever-based piezoelectric energy harvesters is limited by residual stress-based beam curling that produced through microfabrication adding additional mechanical stiffness to the system. The fixed-fixed folded spring structure presented in this paper allows for increased effective beam length and residual stress relaxation, without out of plane beam curling to further reducing the natural frequency. Multiple designs of folded spring energy harvesters are presented to demonstrate the effect of important design parameters. It is shown that the folded spring harvesters were capable of harvesting electricity at low natural frequencies, ranging from 45 Hz to 3667 Hz. Additionally, the harvesters were shown to be insensitive to microfabrication-based residual stress beam curling. The maximum power output achieved by the folded spring harvesters was 690.5 nW at 226.3 Hz for a single harvesting element of an array, with a PZT layer thickness of 0.24 μm. The work presented in this paper demonstrates that the fixed-fixed folded spring can be used as a viable structural element for low frequency piezoelectric energy harvesting to take advantage of ambient vibrations found in low frequency applications.

Effect of shape of seismic mass on potential generated by MEMS-based cantilever-type piezoelectric energy harvester

A vibration-based piezoelectric energy harvester has received increasing attention as a potential power source for microelectronics because of its simplicity of design, operation, and fabrication of devices using microelectromechanical system (MEMS) technology. Energy harvesting provides unending sources of energy for low-power electronics such as wireless sensor nodes where replacement of batteries is not practically possible. Piezoelectric energy harvesters are widely considered because of their compact design, compatibility to MEMS devices, and ability to respond to a wide range of frequencies freely available in the environment. A model for cantilever-based piezoelectric energy harvester is designed and optimized by investigating the effect of seismic mass geometry on the potential generated. The effect of the shape geometry of the seismic mass on the resultant potential generated due to center of mass shift is calculated and compared. A seismic mass with a triangular-shaped geometry with fields concentrated at the tip of the triangle gives a resultant center of mass for a cantilever structure and the seismic mass at a higher point as compared with the rectangular or pyramidal shapes that were investigated. This shift in the center of mass of the combined geometry (cantilever beam and seismic mass) toward the applied pressure results in exerting a higher force and thus increasing the potential. This paper reports that an increased potential of 0.0533 V at a boundary load of 1 bar pressure (minimum feasible pressure) is generated by the energy harvester when a triangular-shaped seismic mass is used; this innovative shape is also compared with other geometries.

New output power estimation method for cantilever-based piezoelectric energy harvesters

In this report, we describe a new estimation method of output power for cantilever-based piezoelectric energy harvesters (CPEHs). To practically apply the energy harvester as an electronic component, on the basis of the vibration mode function, a design equation taking into account not only the output power but also the size and vibration conditions was newly proposed. Using the equation, an energy harvester was designed and fabricated to drive the communication chip based on IEEE 802.15.4. As a result, we succeeded in developing the energy harvester that had the output power of 730 nW at the resonant frequency of 1.5 kHz with the vibration acceleration of 9.8 m/s2. The size of the harvester was smaller than 1 mm3. The output power well agrees with the designed value and is sufficient to drive the communication chip with the intermittent mode.