Power harvesting in a helicopter lag damper

In this paper a new power harvesting application is developed and simulated. Power harvesting is chosen within the European Clean Sky project as a solution to powering in-blade health monitoring systems as opposed to installing an elaborate electrical infrastructure to draw power from and transmit signals to the helicopter body. Local generation of power will allow for a ‘plug and play’ rotor blade and signals may be logged or transmitted wirelessly.\ud The lag damper is chosen to be modified as it provides a well defined loading due to the re-gressive damping characteristic. A piezo electric stack is installed inside the damper rod, effec-tively coupled in series with the damper. Due to the well defined peak force generated in the damper the stack geometry requires a very limited margin of safety. Typically the stack geometry must be chosen to prevent excessive voltage build-up as opposed to mechanical overload.\ud Development and simulation of the model is described starting with a simplified blade and piezo element model. Presuming specific flight conditions transient simulations are conducted using various power harvesting circuits and their performance is evaluated. The best performing circuit is further optimized to increase the specific power output. Optimization of the electrical and mechanical domains must be done simultaneously due to the high electro-mechanical cou-pling of the piezo stack. The non-linear electrical properties of the piezo material, most notably the capacitance which may have a large influence, are not yet considered in this study.\ud The power harvesting lag damper provides sufficient power for extensive health monitoring systems within the blade while retaining the functionality and safety of the standard component. For the 8.15m blade radius and 130 knots flight speed under consideration simulations show 7.5 watts of power is generated from a single damper

Piezoelectric energy harvesting from traffic-induced pavement vibrations

This paper focuses on the development and experimental testing of a potential clean energy source for powering the remote equipment used in transportation infrastructure. Traditional power sources (i.e., power cables and batteries) are excessively expensive or infeasible in this type of application. A compression-based roadway energy harvester has been developed that can be embedded into pavement to scavenge electrical energy from traffic-induced vibrations. The proposed roadway harvester employs a group of piezoelectric harvesting units to convert traffic-induced vibrations into electrical energy, and each single harvesting unit contains three piezoelectric multilayer stacks. According to the linear theory of piezoelasticity, a two-degree-of-freedom electromechanical model of the piezoelectric harvesting unit was developed to characterize its performance in generating electrical energy under external excitations. Experimental testing in the laboratory was conducted to investigate the output power properties of the harvesting unit and shows good agreement with the theoretical analysis. Based on the testing results of the harvesting unit, the capability of the proposed roadway harvester has been theoretically evaluated and demonstrated that it has the ability to generate sufficient energy for driving common electrical equipment used in transportation infrastructure. © 2014 AIP Publishing LLC

Piezoelectric Energy Harvesting Suspension System for a Half Car Model: Analytical and Experimental Study

One of the essential techniques for energy harvesting is the clean energy collection from ambient vibration. Recently, piezoelectric energy harvesting systems became a hot topic and attracted many researchers. This is due to their simple structure, relatively high output power among the other mechanisms (electromagnetic and electrostatic), compatibility with MEMS, and operation in a wide frequency range. The main objective of the current work is to develop a mathematical model to evaluate the potential of harvesting power from the car suspension system. Quarter and half car models with a built-in piezoelectric stack were modeled mathematically using Laplace transformation and simulated using MATLAB/Simulink. The piezoelectric stack was installed in series with the suspension spring to maintain the performance of the original suspension system in ride quality and comfortability. The harvested voltage and power were tested in both time and frequency domain approaches. The results from a quarter car model showed that, the maximum generated voltage and power under harmonic excitation with an acceleration amplitude of 0.5 g and frequency of 1.46 Hz were 19.11 V and 36.74 mW, respectively. By comparing the quarter car model with a half car model, the results illustrated that the output voltage and power of the half car models were increased to 33.56 V and 56.35 mW (75.6% and 53.4%), respectively. Furthermore, the quarter and half car models were subjected to random excitation and tested under three different road classes (A, C, and H). The findings confirmed that the harvested voltage and power were increased with the road roughness levels and car velocity. From very smooth to very rough road levels, the harvested power was increased by 434 mW for quarter car model and 537 mW for half car model. The influence of the different parameters of the piezoelectric stack (number of stack layers and area to thickness) and car suspension (sprung and unsprung stiffness, damping coefficients, and masses) were examined for half car model subjected to harmonic excitation. Also, the effect of road amplitude unevenness was considered. The analytical results of the quarter car model were verified with the experimental test under harmonic excitation. The results exhibited good agreement with the analytical results at different excitation frequencies (0 – 25 Hz). A significant contribution of this work is developing a half car model with a built-in piezoelectric stack. The findings of this work illustrated that there is a significant potential for harvesting energy from the car suspension system. This energy could be utilized in different ways. The study will encourage automobile manufacturers to develop and produce cars that are equipped with multiple energy harvesters to make the dissipated energy available for utilization. Such utilization of regenerated energy improves the fuel efficiency and the economy significantly

Thermoacoustic-Piezoelectric Systems with Dynamic Magnifiers

Thermoacoustic energy conversion is an emergent technology with considerable potential for research, development, and innovation. In thermoacoustic resonators, self-excited acoustic oscillations are induced in a working gas by means of a temperature gradient across a porous body and vice versa with no need of moving parts. In the first part of this dissertation, thermoacoustic resonators are integrated with piezoelectric membranes to create a new class of energy harvesters. The incident acoustic waves impinge on a piezo-diaphragm located at one end of the thermoacoustic-piezoelectric (TAP) resonator to generate an electrical power output. The TAP design is enhanced by appending the resonator with an elastic structure aimed at enhancing the strain experienced by the piezo-element to magnify the electric energy produced for the same input acoustic power. An analytical approach to model the thermal, acoustical, mechanical and electrical domains of the developed harvester is introduced and optimized. The performance of the harvesters is compared with experimental data obtained from an in-house built prototype with similar dimensions. In an attempt to further understand the dynamics and transient behavior of the excited waves in the presence of piezoelectric coupling, a novel approach to compute and accurately predict critical temperature gradients that onset the acoustic waves is discussed. The developed model encompasses tools from electric circuit analogy of the lumped acoustical and mechanical components to unify the modeling domain. In the second part of the dissertation, piezo-driven thermoacoustic refrigerators (PDTARs) are presented. The PDTARs rely on the inverse thermoacoustic effect for their operation. A high amplitude pressure wave in a working medium is used to create a temperature gradient across the ends of a porous body located in an acoustic resonator. Finally, PDTARs with dynamic magnifiers are introduced. The developed design is shown, theoretically and experimentally, as capable of potentially enhancing the cooling effect of PDTARs by increasing the temperature gradient created across the porous body

Performance Enhancement of Cantilever Beam Piezoelectric Energy Harvesters

During the last decade, driven by the need, energy harvesting has drawn considerable attention due to the cost-effectiveness and simplicity of the structure. The most important feature or advantage of energy harvesters is their energy sources which are coming from the energy that would be wasted otherwise to the ambient surroundings. Among the three types of energy conversion methodologies, piezoelectric energy harvesters (PEHs) have been highlighted as a self-power source of energy for small wireless sensors with low required power input due to their simple converting structure. While conventional piezoelectric materials possess ideal sensing properties, the microfabrication of these structures typically requires access to the sophisticated equipment and cleanroom facilities. Moreover, the fabrication process is time-consuming and expensive, researchers found it interesting to resort to micro-electromechanical system (MEMS) designs with inexpensive, simple and green-based materials and simple fabrication techniques such as paper. Generally, the paper-based devices have offered significant benefits but their recorded performance is significantly below that of the ones of the commercial smart structures. Their development is still in the early stage of growth and they need to be properly designed to satisfy the general requirements of the commercial products. Geometry optimization, sizing and functionalizing are among the strategies which can be adopted to boost the performance of all types of piezoelectric energy harvesters including the paper-based piezoelectric energy harvesters (PPEH). Therefore, the major contributions of this work are improvement of the performance of piezoelectric energy harvesters using the geometry modification, sizing analysis and functionalizing. In this work, the governing equations of piezoelectric cantilevers based on both Euler-Bernoulli and Timoshenko beam theories are developed and solved using one type of element with a great rate of convergence called superconvergent element (SCE). The theoretical analysis was validated against results published in the open literature and the results indicate that the proposed method yields higher accurate results. Further, the effect of non-uniformity on the electrical output and efficiency of Piezoelectric Energy Harvesters (PEH) are studied. Then, the influence of sizing and application of a series of piezoelectric cantilever energy harvesters on the performance of structure are studied. The effect of the shape of the piezoelectric elements is also investigated below. Eventually, development of functionally graded piezoelectric materials (FGPMs) for non-uniform beams are presented to evaluate the effect of functionalizing

Enhanced bandwidth nonlinear resonance electromagnetic human motion energy harvester using magnetic-springs and ferrofluid

An enhanced bandwidth nonlinear resonant electromagnetic energy harvester has been designed to harness low frequency energy from basic human motion. Some vertical stacked cylindrical permanent magnets (PMs) constitute the inertial mass of the proposed harvester, which is suspended axially by two magnetic-springs and circumferentially by ferrofluid within a carbon fiber tube. In order to widen the frequency band and improve harvesting efficiency, two PMs are respectively fixed on the two end caps of the carbon fiber tube, so as to form two magnetic-springs with variable stiffness by cooperating with the PM stack. The self-assembled ferrofluid around the PM stack acts as its bearing system to minimize any friction during its movement. Copper wire are wrapped outside the tube to form the armature winding. The stiffness characteristic of the magnetic-springs and the optimum equilibrium position and number of windings have been determined by finite element method (FEM) analysis. As a proof of concept, a portable prototype of the proposed energy harvester that weighs 110g and with a volume of only 37.7cm $^3$ is fabricated. A series of experiments are carried out and the results show that the frequency band of the harvester becomes wider as the external vibration intensity increases. In addition, the effectiveness of ferrofluid in reducing friction is demonstrated under walking and running conditions. Without ferrofluid, the maximum average outputs are 10.15 mW and 32.53 mW respectively for walking and running. With ferrofluid, the maximum outputs are 17.72 mW and 54.61 mW, representing an increase of 74.58% and 67.88%, respectively. Furthermore, the prototype exhibits an average power density of 1.45 mW/cm $^3$ during running motions, which compares favorably with existing harvesters used in low power wearable devices

Analysis and design of levitation based vibration energy harvesters

A computational approach for the evaluation of the electro-mechanical response of levitation based vibration energy harvesters is presented in this paper. The key aspects of the design of levitation based energy harvesters, such as the existence of the resonance phenomenon, the influence of damping in the system response, the magnetic force nonlinearity and the calculation of the magnetic flux derivative for multi-magnet configurations are addressed. The evolution in time of the electromechanical variables is investigated through a hybrid numericalanalytical approach. The evaluation of the levitational force and the magnetic flux derivative is done through a nonlinear model based on the finite element method. A performance assessment is done by comparing the results obtained with the present formulation against measurements; a physical prototype of a multi-pole-multi-coil harvester is built ad hoc. An excellent agreement between the mathematical model and the experiments was found.Publicado en: Mecánica Computacional vol. XXXV, no. 26Facultad de Ingenierí

Structural vibration energy harvesting via bistable nonlinear attachments

A vibration-based bistable electromagnetic energy harvester coupled to a directly excited host structure is theoretically and experimentally examined. The primary goal of the study is to investigate the potential benet of the bistable element for harvesting broadband and low-amplitude vibration energy. The considered system consists of a grounded, weakly damped, linear oscillator (LO) coupled to a lightweight, damped oscillator by means of an element which provides for both cubic nonlinear and negative linear stiness components and electromechanical coupling elements. Single and repeated impulses with varying amplitude applied to the LO are the vibration energy sources considered. A thorough sensitivity analysis of the system's key parameters provides design insights for a bistable nonlinear energy harvesting (BNEH) device able to attain robust harvesting efficiency. Energy localization into the bistable attachment is achieved through the exploitation of three BNEH main dynamical regimes; namely, periodic cross-well, aperiodic (chaotic) cross-well, and in-well oscillations. For the experimental investigation on the performance of the bistable device, nonlinear and negative linear terms in the mechanical coupling are physically realized by exploiting the transverse displacement of a buckled slender steel beam; the electromechanical coupling is accomplished by an electromagnetic transducer

MULTI‐PHYSICAL MODELLING AND PROTOTYPING OF AN ENERGY HARVESTING SYSTEM INTEGRATED IN A RAILWAY PNEUMATIC SUSPENSION

The aim of this PhD thesis is the investigation of an energy harvesting system to be integrated in a railway pneumatic spring to recovery otherwise wasted energy source from suspension vibration. Exploiting the piezoelectric effect to convert the mechanical energy into an electrical one, the final scope consists on the use of this system to power supply one or more sensors that can give useful information for the monitoring and the diagnostics of vehicle or its subsystems. Starting from the analysis of the energy sources, a multi‐physical approach to the study of an energy harvesting system is proposed to take into account all physics involved in the phenomenon, to make the most of the otherwise wasted energy and to develop a suitable and affordable tool for the design. The project of the energy harvesting device embedded in a railway pneumatic spring has been carried out by means of using a finite element technique and multi‐physics modelling activity. The possibility to combine two energy extraction processes was investigated with the purpose of making the most of the characteristics of the system and maximize the energy recovering. Exploiting commercial piezoelectric transducers, an experimental activity was conducted in two steps. A first mock‐up was built and tested on a shaker to develop the device and to tune the numerical model against experimental evidence. In the second step a fullscale prototype of an air spring for metro application with the EH system was realized. In order to test the full‐scale component, the design of a new test bench was carried out. Finally, the Air spring integrated with the EH device was tested and models validated

Energy Harvesters and Self-powered Sensors for Smart Electronics

This book is a printed edition of the Special Issue “Energy Harvesters and Self-Powered Sensors for Smart Electronics” that was published in Micromachines, which showcases the rapid development of various energy harvesting technologies and novel devices. In the current 5G and Internet of Things (IoT) era, energy demand for numerous and widely distributed IoT nodes has greatly driven the innovation of various energy harvesting technologies, providing key functionalities as energy harvesters (i.e., sustainable power supplies) and/or self-powered sensors for diverse IoT systems. Accordingly, this book includes one editorial and nine research articles to explore different aspects of energy harvesting technologies such as electromagnetic energy harvesters, piezoelectric energy harvesters, and hybrid energy harvesters. The mechanism design, structural optimization, performance improvement, and a wide range of energy harvesting and self-powered monitoring applications have been involved. This book can serve as a guidance for researchers and students who would like to know more about the device design, optimization, and applications of different energy harvesting technologies