Aeroelastic Harvester Research Articles

Stochastic stability of an aeroelastic harvester contaminated by wind turbulence and uncertain aeroelastic loads

The study describes the extension of a recently developed model that examines the stochastic stability of a torsional-flutter-based harvester. The new, extended model accounts for both uncertainty in the aeroelastic loads and wind turbulence effects. The first uncertainty source is a byproduct of the modelling simplifications of the aeroelastic loads, which are described by indicial function approach and ideally applicable to two-dimensional flow. The second source is the flow turbulence that operates by modifying the load through parametric, stochastic perturbations that are applied to the term describing the memory-effect of the load; stochastic perturbations simulate imperfections in the load assessment (e.g., measurement errors). Furthermore, since the “blade-airfoil” used for energy harvesting has finite dimensions, three-dimensional flow effect is simulated through a load reduction parameter applied to the static lift slope, dependent on the aspect ratio of the apparatus; this reduction parameter also leads to approximations and stochastic perturbations. Mean square stochastic flutter stability is examined. Post-critical states are discussed.

Coupled electro-aeroelastic energy harvester model based on piezoelectric transducers, VIV-galloping interaction and nonlinear switching circuits

Miniaturization, multi-functionality, and low power consumption are key features in the development of electronic devices today. These characteristics open up the possibility for the development of small, self-powered systems. Piezoelectric materials have emerged as a promising solution due to their ability to convert mechanical energy into electrical energy from the surrounding environment, such as wind. In this research work, we investigate an aeroelastic piezoelectric energy harvester based on the interaction between vortex-induced vibrations and galloping. The device, a bimorph cantilevered beam with a square-section bluff body attached to its tip, produces mechanical oscillations that are extracted by various electrical circuits, including a nonlinear switching interface. A numerical model, implemented in a Simulink environment, is developed to solve the coupled electro-aeroelastic problem for each electrical interface. The results are compared to experimental data collected from wind tunnel tests conducted at various wind velocities and load resistances, and a satisfactory correlation is observed. The validated model is finally used to carry out a parametric analysis aimed at optimizing the performance of the harvester in a low wind speed range. This investigation could contribute to a better understanding of an aeroelastic harvesting system and potentially assist in the optimization of design parameters and electrical interfaces for specific applications.

Finite wing effects on the energy harvesting from stall-induced oscillations

The modeling of aeroelastic harvesters usually employs methods for two-dimensional aerodynamics. Such convenient practice reflects the lack in the literature of efficient tools with low computational cost to assess unsteady and nonlinear aerodynamics loads accounting for three-dimensional wing effects. In this sense, the present work aims to fulfill this gap by developing a nonlinear unsteady lifting line to investigate finite wing effects on the power generation from stall-induced oscillations. The aerodynamic model links the Beddoes–Leishman dynamic stall method to a linear unsteady lifting line. The optimization of energy harvesters from stall-induced pitching oscillations is revisited considering the three-dimensional aerodynamic model. Results reveal that the three-dimensional harvester’s dynamic behavior may differ from the two-dimensional case, and the harvested power reduction is observed.

Parametric study of a novel magneto-electro-aeroelastic energy harvesting system

This paper investigates a parametric study on a novel type of flutter-based aeroelastic harvester by utilizing magneto-electro-elastic materials, which can be used as an alternative to piezoelectric materials in aeroelastic harvesters to enhance the output electric power. The considered model includes a deformable clamped beam attached to a rigid airfoil, covering with one or two magneto-electro-elastic layers. Connected electrodes to magneto-electro-elastic layers capture potential electric from the produced electric field. Furthermore, an extrinsic coil is wrapped around the vibrating beam to produce the magnetic-based electric energy in the applied magneto-electro-elastic layer. First, the harvesting system is modeled as a discrete model to derive the governing equations using Faraday and Gauss laws, and the constitutive equations of magneto-electro-elastic materials according to Hamilton's principle. Then, different configurations have been examined and compared. Afterward, the effect of various parameters on the chosen harvester characteristics is investigated through considering stability to determine the optimal parameters resulting in the highest electric power generation. Lastly, the efficiency of the magneto-electro-aeroelastic harvester is compared with a piezo-aeroelastic counterpart indicating the supremacy of the presented harvester.

Modeling and analysis of a coupled novel nonlinear magneto-electro-aeroelastic lumped model for a flutter based energy harvesting system

The present paper investigates the modeling and analysis of a novel aeroelastic energy harvesting system using magneto-electro-elastic (MEE) material considering the nonlinear elastic effects of the structure. The main aim of using this group of composite materials, as compared to common piezoelectric materials used in aeroelastic harvesters, is to increase the harvested electrical power. The proposed model to improve energy harvesting is composed of a rigid airfoil connected to an elastic beam, with the elastic beam covered by one or two layers of MEE material and two electrodes connected to the top and bottom of the MEE layers to harvest the electric potential from the generated electric field. An external coil was also provided around the oscillating beam to induce the electrical energy generated by the magnetic field established within the MEE layer. Firstly, simulating the harvesting system as a discrete model considering bending and torsional cubic nonlinear springs, the governing equations are extracted using the constitutive equations of MEE materials, Gauss’s law, and Faraday’s law of induction through Hamilton’s principle. Next, the effects of different design parameters are evaluated to find their optimal values to maximize the generated power as well as the harvester stability. Finally, a comparison is made between the considered MEE harvester and a piezo-aeroelastic (PA) energy harvester, indicating the superiority of the proposed MEE energy harvester.

The investigation on structural health monitoring of aerospace structures via piezoelectric aeroelastic energy harvesting

From the past few decades, the aerospace industry is using composite materials having low weight to strength ratio, and the aerospace vehicles are subjected to adverse and harsh conditions, during the operational time. Furthermore, they require a continuous power supply to operate the wireless sensors. So, in the aerospace industry, energy harvesting and structural health monitoring (SHM) are the critical tasks. Piezoelectric (PZT) materials can play a vital role in the field of energy harvesting and structural health monitoring of the structures at the same time, which makes them more convenient to use in aerospace applications. In this research paper, the fluid-structure interaction (FSI) based system is analyzed, the PZT harvester is subjected to the axial airflow for energy harvesting. The campaign is carried out to predict the energy harvesting capability of the aeroelastic harvester via PZT transduction. The parameters influencing the energy harvesting mechanism i.e., airflow and external resistance are analyzed. The numerical bifurcation diagram is also constructed to understand the plunge amplitude of the harvester at the different values of airflow. Moreover, the SHM of the host structure (aeroelastic harvester) is also analyzed via the admittance method at the same time. The results showed that the magnitude of energy harvesting and quality of SHM for the harvester attached with the rectangular PZT patch is better than with the circular PZT patch.

Characterisation of aeroelastic harvester efficiency by measuring transient growth of oscillations

With growing demand for small autonomous electrical devices, such as those in wireless sensor networks, energy harvesting has attracted interest with the promise of low maintenance and sustainable power sources. Galloping energy harvesters utilise the fluid-structure interaction to transform kinetic energy in fluid flow into electrical energy. The performance of galloping energy harvesters depends on the geometry of the tip, with the structure of the flow around the tip defining the nature of fluid-structure interaction and hence the potential efficiency of the device.In this work the curved blade tip geometry is investigated. To experimentally characterise the performance of the harvester, a method utilising the free oscillation transient is developed. The method avoids implementation of a transduction mechanism and hence optimisation of the associated parameters. The developed method is generic and can be applied to other energy generators.The power coefficient of curved blades of different curvatures is measured and the optimal range identified. The maximum coefficient of performance of the curved blade harvester occurs at tip speed ratios from 0.32 to 0.74 and reaches 0.08, which is 3 to 4 times lower than Savonius turbines, the best performing devices at similar Reynolds numbers. The square prism geometry is used as a comparator and found to have a coefficient of performance 10 times less than the curved blade. Flow visualisations confirm the curved blade to act as an airfoil in the highest performing cases, hence future tip shapes should be developed to promote flow attachment.

Overview of micro/nano-wind energy harvesters and sensors.

Wind energy is a kind of renewable and widely distributed energy and has attracted more and more attention from researchers in both energy harvesting and sensing fields. Here, micro/nano-wind energy harvesters and sensors have been systematically reviewed. Based on the fundamental wind energy harvesting principle, the windmill-based and aeroelastic harvesters are analyzed at first. On this basis, four kinds of energy harvesters for converting wind energy of different regions and scales have been compared and summarized. An electromagnetic energy harvester is exploited to scavenge macro-scale wind energy, while piezoelectric, electrostatic and triboelectric energy harvesters are applied to collect micro-scale wind energy. In addition, several micro/nano-wind sensors have also been surveyed. Passive wind sensors are exploited and improved to realize high precision and multi-functionality, while active wind sensors and self-powered sensing systems are used for wireless and intelligent wind information monitoring. Finally, the existing challenges and future perspectives in both micro/nano-wind energy harvesters and sensors have been discussed.

Design and performance evaluation of a piezoelectric aeroelastic energy harvester based on the limit cycle oscillation phenomenon

In the present era, the demand for self-powered electronic instruments is increasing and their energy consumption is decreasing. The ability to extract energy from the operating environment is of great importance in advanced industrial applications particularly in the field of aerospace. In this research, a nonlinear piezoelectric aeroelastic energy harvester (PAEH) is modeled based on fluid-structure interaction (FSI) that represents an important area of research for the development of innovative energy harvesting solution. This PAEH operates on post critical aeroelastic behavior i.e., Limit Cycle Oscillations (LCOs) that arise after the flutter velocity. Moreover, it is emphasized that the determination of aerodynamic model is necessary for correct prediction of PAEH performance. The design of an aeroelastic harvester based on the use of two different types of piezoelectric materials is presented. The designed model is suitable for energy harvesting and can be utilized to drive nano and microelectronics. Maximum output power obtained for the designed PAEH is found to be 0.55 mW.

Equivalent electrical circuits for advanced energy harvesting

Energy harvesting is now an established field, and the linear equivalent circuit models for single- and multiple-degree-of-freedom systems are being routinely used to assess the energy harvesting efficiency of various interface and electronic circuits. However, as the field of energy harvesting moves toward more complex systems such as nonlinear energy harvesting and fluidic energy harvesting, modified equivalent circuits are required to effectively capture the behavior of these devices. This article presents two general methods (a system-level approach and a dependent source equivalent approach) that can adequately model the behavior of more advanced harvesters. These approaches can also be easily used to model single- and multiple-degree-of-freedom linear harvesters. Equivalent circuits for both piezoelectric and electromagnetic harvesters are discussed. Four case studies are presented to illustrate the application of these equivalent circuit approaches including the following: (1) a piezoelectric Duffing harvester, (2) an electromagnetic Duffing harvester, (3) a simplified aeroelastic harvester, and (4) a piezoelectric Duffing harvester with a rectifier circuit.