•The metasurface is employed for harvesting energy from vortex-induced vibration.•The effects of different metasurfaces on the aerodynamics of bluff bodies are investigated.•Wind tunnel tests are ...conducted to evaluate the performance of the proposed systems.•3D CFD simulation is performed to illustrate the flow fields around the bluff bodies.
This paper explores the use of metasurface in designing an aerodynamic system for potential vortex-induced vibration (VIV) suppression or energy harvesting. Four kinds of metasurface patterns are designed to decorate an ordinary cylinder bluff body for modifying its aerodynamic characteristics. A theoretical model is developed for the VIV system by describing the wake as a van der Pol oscillator. The aerodynamic parameters, i.e., the lift and drag coefficients, used in the theoretical model, are determined from three-dimensional CFD simulations. A wind tunnel experiment is conducted to validate the theoretical model and investigate the aerodynamic behaviors of the VIV systems with different bluff bodies. It is found that the metasurface pattern has a significant influence on the aerodynamic characteristics of the bluff body. Using different metasurface patterns to decorate the bluff body, the vortex-induced vibration of the system could be either enhanced or suppressed, compared with the baseline reference using an ordinary bluff body with a smooth surface. Furthermore, the vortex shedding processes are simulated to give further insights into the wake oscillating motions. The roles of the metasurface in suppressing or enhancing the vortex-induced vibration are reasonably explained: the existence of metasurfaces could alter the flow field around the bluff bodies and consequently the aerodynamic force. In addition, based on the validated theoretical model, it is learned from a parametric study that the power output reaches saturation when the electromechanical coupling strength is increased to a certain level. Therefore, piezoelectric transducers with moderate coupling coefficients are recommended for practical applications from the cost-effective perspective.
The dramatic reduction in power consumption of current integrated circuits has evoked great research interests in harvesting ambient energy, such as vibrations, as a potential power supply for ...electronic devices to avoid battery replacement. Currently, most vibration-based energy harvesters are designed as linear resonators to achieve optimal performance by matching their resonance frequencies with the ambient excitation frequencies a priori. However, a slight shift of the excitation frequency will cause a dramatic reduction in performance. Unfortunately, in the vast majority of practical cases, the ambient vibrations are frequency-varying or totally random with energy distributed over a wide frequency spectrum. Hence, developing techniques to increase the bandwidth of vibration-based energy harvesters has become the next important problem in energy harvesting. This article reviews the advances made in the past few years on this issue. The broadband vibration-based energy harvesting solutions, covering resonance tuning, multimodal energy harvesting, frequency up-conversion, and techniques exploiting non-linear oscillations, are summarized in detail with regard to their merits and applicability in different circumstances.
Conventional vibration energy harvesters have been usually studied as single-degree-of-freedom models. The fact that such harvesters are only efficient near sole resonance limits their applicability ...in frequency-variant or random vibration scenarios. In this article, a novel multiple-degree-of-freedom piezoelectric energy harvesting model is presented. First, a two-degree-of-freedom model is analyzed, and its two configurations are characterized. In the first configuration, the piezoelectric element is placed between one mass and the base, and in the second configuration, it is placed between the two masses. It is shown that the former is advantageous over the latter since with a slight increase of overall weight to the single-degree-of-freedom model, we can achieve two close and effective peaks in power response or one effective peak with significantly enhanced magnitude. The first configuration is then generalized to an n-degree-of-freedom model, and its analytical solution is derived. This solution provides a convenient tool for parametric study and design of a multiple-degree-of-freedom piezoelectric energy harvesting model. Finally, the equivalent circuit model of the proposed n-degree-of-freedom piezoelectric energy harvesting model is developed via the analogy between the mechanical and electric domains. With the equivalent circuit model, system-level electric simulation can be performed to evaluate the system performance when sophisticated interface circuits are attached.
Last decade has seen growing research interest in vibration energy harvesting using piezoelectric materials. When developing piezoelectric energy harvesting systems, it is advantageous to establish ...certain analytical or numerical model to predict the system performance. In the last few years, researchers from mechanical engineering established distributed models for energy harvester but simplified the energy harvesting circuit in the analytical derivation. While, researchers from electrical engineering concerned the modeling of practical energy harvesting circuit but tended to simplify the structural and mechanical conditions. The challenges for accurate modeling of such electromechanical coupling systems remain when complicated mechanical conditions and practical energy harvesting circuit are considered in system design. In this article, the aforementioned problem is addressed by employing an equivalent circuit model, which bridges structural modeling and electrical simulation. First, the parameters in the equivalent circuit model are identified from theoretical analysis and finite element analysis for simple and complex structures, respectively. Subsequently, the equivalent circuit model considering multiple modes of the system is established and simulated in the SPICE software. Two validation examples are given to verify the accuracy of the proposed method, and one further example illustrates its capability of dealing with complicated structures and non-linear circuits.
•Performances of four circuits for energy charging are evaluated and compared.•Optimal storage capacitor exists to maximize the accumulated energy.•The P-SSHI circuit is suitable for a PEH with weak ...coupling.•The SEH and S-SSHI circuits are suitable for a PEH with medium or strong coupling.
Four interface circuits have been widely studied in piezoelectric energy harvesting over the last two decades, namely, the standard energy harvesting (SEH) circuit, synchronized charge extraction (SCE) circuit, parallel synchronized switch harvesting on inductor (P-SSHI) circuit and series synchronized switch harvesting on inductor (S-SSHI) circuit. However, the abilities of these four circuits to charge storage capacitors are yet to be understood. This work focuses on the modeling and comparison of the charging process of these four circuits. First, the solutions of the voltage variations on the storage capacitors during charging process in each half-cycle are derived. Subsequently, the equivalent circuit model of the harvester interfaced with SEH and self-powered SCE, P-SSHI and S-SSHI circuits are implemented and simulated to validate the theoretical results. In the evaluation of the four circuits, different electromechanical coupling conditions of the PEH have been considered. The influence of the storage capacitance on charging performance are investigated. It is shown that for the SEH, P-SSHI or S-SSHI circuit, an optimal storage capacitor exists to maximize the accumulated energy and it varies with coupling condition. For a PEH with weak coupling, the P-SSHI circuits is suitable for energy charging. For the medium and strong coupling conditions, the SEH and S-SSHI circuits are more efficient as compared to the P-SSHI and SCE circuits.
•The effect of orientation of the piezoelectric beam is experimentally studied.•The theoretical model has been used to predict the voltage and power.•The best orientation of piezoelectric cantilever ...beam is proposed.
Harvesting energy from human body motion for powering small scale electronic devices is attracting research interest in recent years. Piezoelectric energy harvester (PEH) capable of harvesting energy from vibratory movement is a suitable candidate for this particular application. In this study, a cantilever beam with a piezoelectric patch attached at the end of the cantilever is evaluated for potential to harvest energy from human motion. Since the frequency of human walking motion is low, the frequency up conversion technique is adopted in this study to harvest the inertial energy. The effect of orientation of the cantilever beam with tip mass on the efficiency of the power generated is experimentally studied. A prototype is developed and attached onto the leg of a person walking on a treadmill at a constant speed. A theoretical lumped model is adopted to predict the voltage output using the experimentally measured acceleration as input data. Results show close agreement between the experiment and the model. Results also indicate that by varying the orientation of the PEH, the efficiency of the energy harvester can be significantly increased. Maximum power is found to be achieved when the PEH is orientated at 70° with reference to a coordinate system attached to the leg when walking on a treadmill.
Energy harvesting from ambient vibrations using piezoelectric effect is a promising alternative solution for powering small electronics such as wireless sensors. A conventional piezoelectric energy ...harvester usually consists of a cantilevered beam with a proof mass at its free end. For such a device, the second resonance of the piezoelectric energy harvester is usually ignored because of its high frequency as well as low response level compared to the first resonance. Hence, only the first mode has been frequently exploited for energy harvesting in the reported literature. In this article, a novel compact piezoelectric energy harvester using two vibration modes has been developed. The harvester comprises one main cantilever beam and an inner secondary cantilever beam, each of which is bonded with piezoelectric transducers. By varying the proof masses, the first two resonant frequencies of the harvester can be tuned close enough to achieve useful wide bandwidth. Meanwhile, this compact design efficiently utilizes the cantilever beam by generating significant power output from both the main and secondary beams. An experiment and simulation were carried out to validate the design concept. The results show that the proposed novel piezoelectric energy harvester is more adaptive and functional in practical vibrational circumstances.
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