Power Control Optimization of an Underwater Piezoelectric Energy Harvester

Over the past few years, it has been established that vibration energy harvesters with intentionally designed components can be used for frequency bandwidth enhancement under excitation for sufficiently high vibration amplitudes. Pipelines are often necessary means of transporting important resources such as water, gas, and oil. A self-powered wireless sensor network could be a sustainable alternative for in-pipe monitoring applications. A new control algorithm has been developed and implemented into an underwater energy harvester. Firstly, a computational study of a piezoelectric energy harvester for underwater applications has been studied for using the kinetic energy of water flow at four different Reynolds numbers Re = 3000, 6000, 9000, and 12,000. The device consists of a piezoelectric beam assembled to an oscillating cylinder inside the water of pipes from 2 to 5 inches in diameter. Therefore, unsteady simulations have been performed to study the dynamic forces under different water speeds. Secondly, a new control law strategy based on the computational results has been developed to extract as much energy as possible from the energy harvester. The results show that the harvester can efficiently extract the power from the kinetic energy of the fluid. The maximum power output is 996.25 mu W and corresponds to the case with Re = 12,000.The funding from the Government of the Basque Country and the University of the Basque Country UPV/EHU through the SAIOTEK (S-PE11UN112) and EHU12/26 research programs, respectively, is gratefully acknowledged. The authors are very grateful to SGIker of UPV/EHU and European funding (ERDF and ESF) for providing technical and human

Vibrational energy harvesting for sensors in vehicles

The miniaturization of semiconductor technology and reduction in power requirements have begun to enable wireless self-sufficient devices, powered by ambient energy. To date the primary application lies in generating and transmitting sensory data. The number of sensors and their applications in automotive vehicles has grown drastically in the last decade, a trend that seems to continue still. Wireless self-powered sensors can facilitate current sensor systems by removing the need for cabling and may enable additional applications. These systems have the potential to provide new avenues of optimization in safety and performance.This thesis delves into the topic of vibrations as ambient energy source, primarily for sensors in automotive vehicles. The transduction of small amounts of vibrational, or kinetic, energy to electrical power, also known as vibrational energy harvesting, is an extensive field of research with a plethora of inventions. A short review is given for energy harvesters, in an automotive context, utilizing transduction through either the piezoelectric effect or magnetic induction. Two practical examples, for ambient vibration harvesting in vehicles, are described in more detail. The first is a piezoelectric beam for powering a strain sensor on the engines rotating flexplate. It makes combined use of centrifugal force, gravitational pull and random vibrations to enhance performance and reduce required system size. The simulated power output is 370 \ub5W at a rotation frequency of 10.5 Hz, with a bandwidth of 2.44 Hz. The second example is an energy harvesting unit placed on a belt buckle. It implements magnetic induction by the novel concept of a spring balance air gap of a magnetic circuit, to efficiently harvest minute vibrations. Simulations show the potential to achieve 52 \ub5W under normal road conditions driving at 70 km/h. Theoretical modeling of these systems is also addressed. Fundamental descriptions of the lumped and distributed models are given. Based on the lumped models of the piezoelectric energy harvester (PEH) and the electromagnetic energy harvester (EMEH), a unified model is described and analyzed. New insights are gained regarding the pros and cons of the two types of energy harvester run at either resonance or anti-resonance. A numerical solution is given for the exact boundary of dimensionless quality factor and dimensionless intrinsic resistance, at which the system begins to exhibit anti-resonance. Regarding the maximum achievable power, the typical PEH is favored when running the system in anti-resonance and the typical EMEH is favored at resonance. The described modeling considers all parameters of the lumped model and thus provides a useful tool for developing vibrational energy harvester prototypes

Design and optimisation of constrained electromagnetic energy harvesting devices

This thesis investigates the design and optimisation of constrained electromagnetic energy harvesters. It provides optimal design guidelines for constrained electromagnetic energy harvesters under harmonic and random vibrations. To find the characteristics of the vibration source, for instance vertical motion of a boat, the spectrum of the excitation amplitude should be obtained. Two Kalman filter based methods are proposed to overcome the difficulties of calculating displacement from measured acceleration. Analytical models describing the dynamics of linear and rotational electromagnetic energy harvesters are developed. These models are used to formulate a set of design rules for constrained linear and rotational energy harvesters subjected to a given sinusoidal excitation. For the sake of comparison and based on the electromechanical coupling coefficient of the systems, the maximum output power and the corresponding efficiency of linear and rotational harvesters are derived in a unified form. It is shown that under certain condition, rotational systems have greater capabilities in transferring energy to the load resistance and hence obtaining higher efficiency than linear systems. Also, the performance of a designed rotational harvester in response to broadband and band-limited random vibrations is evaluated and an optimum design process is presented for maximizing the output power under these conditions. It is furthermore shown that the profile of the spectral density of the measured acceleration signal of a typical boat can be approximated by a Cauchy distribution which is used to calculate the extracted power extracted by the proposed energy harvester in real conditions. In order to increase the operational bandwidth of rotational energy harvesters, subjected to time-varying frequency vibrations, a variable moment of inertia mechanism is proposed to adaptively tune the resonance frequency of harvester to match the excitation frequency. Also, the effects of combining the variable moment of inertia mechanism and adjusting the load resistance to increase the operational bandwidth of the system for constrained and unconstrained applications are studied. Finally, a ball screw based prototype is manufactured and the experimental results of its testing are presented which confirm the validity of the design and the derived dynamic equations of the system

Bistable energy harvesting backpack:Design, modeling, and experiments

Inspired by the dynamics of the noninertial systems, a novel bistable energy harvesting backpack is proposed that improves biomechanical energy harvesting performance. In contrast to traditional bistable energy harvesters that use an oblique compressed spring, a new bistable backpack is developed that uses the change of a spring torque direction located on a pinion. A detailed nondimensionalized model of the novel bistable energy harvesting backpack is developed and analyzed. Based on the dynamic bistable model, the influence of the carried backpack mass on the symmetry and the bifurcation frequency and amplitude of oscillation is examined to determine the ideal design parameters of the bistable backpack for experimental analysis and prototype manufacture. A comparison is made between the new bistable backpack and a traditional linear backpack under both harmonic and human walking excitation. The new bistable backpack design exhibits an improved frequency bandwidth from 1 Hz to 1.65 Hz at the base harmonic excitation of 2 m/s2 and the harvesting performance is enhanced from 2.34 W to 3.32 W when the walking speed is 5.6 km/h. The bench and treadmill tests verify the theoretical analysis and demonstrate the ability of the bistable energy harvesting backpack for broadband and performance enhancement.</p

Piezoelectric energy harvesting from low frequency and random excitation using frequency up-conversion

The field of energy harvesting comprises all methods to produce energy locally and from surrounding sources, e.g. solar illumination, thermal gradients, vibration, radio frequency, etc. The focus of this thesis is on inertial power generation from host motion, in particular for low frequency and random excitation sources such as the human body. Under such excitation, the kinetic energy available to be converted into electrical energy is small and conversion efficiency is of utmost importance. Broadband harvesting based on frequency tuning or on non-linear vibrations is a possible strategy to overcome this challenge. The technique of frequency up-conversion, where the low frequency excitation is converted to a higher frequency that is optimal for the operation of the transducer is especially promising. Regardless of the source excitation, energy is converted more efficiently. After a general introduction to the research area, two different prototypes based on this latter principle and using piezoelectric bending beams as transducers are presented, one linear design and one rotational. Especially for human motion, the advantages of rotational designs are discussed. Furthermore, magnetic coupling is used to prevent impact on the brittle piezoceramic material when actuating. A mathematical model, combining the magnetic interaction forces and the constitutive mechanical and electrical equations for the piezoelectric bending beam is introduced and the results are provided. Theoretical findings are supported by experimental measurements and the calculation model is validated. The outcome is the successful demonstration of a rotational energy harvester, tested on a custom made shaking set-up and in the real world when worn on the upper arm during running.Open Acces

Study of the effects of magneto-mechanical coupling in the performance of electromagnetic vibration energy harvesters

Els recol·lectors electromagnètics d’energia de vibracions converteixen energia mecànica, en forma de vibracions, a electricitat. Són per tant, dispositius amb un gran potencial però també amb grans desavantatges pel que fa a adaptabilitat, eficiència i cost. El seu comportament és complex de caracteritzar, especialment quan hi ha una interacció magnètica significativa entre el propi dispositiu i components magnètics o electromagnètics externs, fet que podria derivar en un comportament no-lineal i afectar considerablement al seu rendiment. L’objectiu principal d’aquest projecte és el d’entendre millor la influencia d’aquestes forces magnètiques al rendiment mecànic d’aquest tipus de dispositius desenvolupant una eina de simulació que permeti predir el comportament d’un recol·lector sota diferents escenaris d’interès. El model que es proposa és el d’un sistema massa-esmorteïdor-molla d’un grau de llibertat amb forces magnètiques aplicades. La resposta del sistema és calculada per a una excitació d’entrada sinusoidal i a través de dos mètodes diferents. El primer és un mètode d’integració temporal mentre que el segon, conegut com a harmonic balance method, es calcula en l’espai freqüencial. Per unir la part magnètica amb la mecànica s’empra un acoblament dèbil; calculant en primer lloc les forces magnètiques que rep el dispositiu per posteriorment introduir-les en l’equació de moviment del sistema. Diferents tests experimentals representatius dels diversos escenaris a estudiar es duen a terme per tal de validar l’eina de simulació. Tant experimentalment com numèricament, en aquells casos en que hi ha forces magnètiques aplicades, s’observa un canvi substancial en la freqüència de ressonància del sistema, és a dir, un canvi en la seva rigidesa. Aquest canvi implica una reducció en la rigidesa del sistema quan l’imant del recol·lector està subjecte a forces d’atracció i un augment quan les forces són de repulsió.Electromagnetic vibration energy harvesters convert mechanical energy, in the form of vibrations, into electricity. They are, therefore, devices with huge potential but also with major drawbacks regarding adaptability, efficiency and return of investment. Their behaviour is complex to characterize, especially when there is a significant magnetic interaction between the device and external ferromagnetic or magnetic components, which could result in strong non-linear behaviours that might affect the performance of the device. The aim of this project is to understand better the influence of these magnetic forces on the mechanical system response by developing a simulation tool which can predict the behaviour of a harvester under different scenarios of interest. The proposed model is a one-degree-of-freedom spring-damper-mass system with applied magnetic forces. Its system response is computed for a sinusoidal excitation input and through two different methods. The former being a time domain integration method and the latter known as harmonic balance method, which is performed in the frequency domain. A weak coupling between magnetic and mechanical phenomena is assumed by performing the electromagnetic simulation independently and later inputting the results in the equation of motion of the system. Several experimental tests representing the different case scenarios are carried out in order to validate the simulation tool. Both experimentally and numerically, when magnetic forces are being applied, the harvester is seen to experience a significant shift in its resonant frequency, i.e., a change in its stiffness. This shift results in a softening effect if the oscillation magnet is subjected to attraction forces and in a hardening effect if, on the contrary, it is subjected to repulsion forces

Performance Analysis of Piezoelectric Energy Harvesting System.

[EN] This paper analyzes a piezoelectric system made of a smart lead zirconate material. The system is composed of a monolithic PZT (piezoelectric ceramic) plate made of a ceramic-based piezoelectric material. The experiment was conducted on a test stand with a GUNT HM170 wind tunnel and a special measurement system. The developed bluff-body shape mounted on an elastic beam with a piezoelectric was mounted on a mast with arms. Springs were fixed on the arms to limit the movement of the test object. Air flow velocity in the wind tunnel and forced vibration frequencies were changed during the tests. The recorded parameters were an output voltage signal from the piezoelectric element and linear accelerations at selected points of the test object. The highest energy efficiency of the tested system was specified from mechanical vibrations and air flow. The results of the tests are a resonance curve for the tested system and a correlation of RMS voltage and acceleration as a function of the velocity of air flow for the excitation frequency f ranging from 1 to 6 Hz. The tests specified the area where the highest output voltage under the given excitation conditions is generated.Publication was supported by the program of the Polish Ministry of Science and Higher Education under the project DIALOG 0019/DLG/2019/10 in the years 2019¿2021.Ambrozkiewicz, B.; Czyz, Z.; Staczek, P.; Tiseira, A.; Garcia Tiscar, J. (2022). Performance Analysis of Piezoelectric Energy Harvesting System. Advances in Science and Technology Research Journal. 16:179-185. https://doi.org/10.12913/22998624/1562151791851

Human Powered Energy Harvester based on Autowinder Mechanism: Analysis, Build and Test

Experts estimate that approximately one third of the worldwide population currently owns a smartphone, and subscriptions continue to grow. Compared to mobile devices of the past decade, smartphones provide desktop computer-level processing power in a palm-sized package. However, the high computing power and 24 hours - 7 days a week connectivity results in a shorter battery life, often forcing the user to rely on portable battery packs. Worldwide energy consumption statistics show that the electric power grid depends primarily on fossil fuels. Thus, a renewable power source based on human motion energy harvesting offers a potential solution to power portable communication devices and may help reduce dependence on the power grid. A novel wrist-worn energy-harvester, based on an automatic winding mechanism, was designed, fabricated and experimentally tested. The mechanism frequently employed in wrist and pocket watches dates back to the 18th century, and is one of the oldest examples of mobile human energy harvesting. In this project, the prototype device contains a rotary pendulum connected to a DC generator through a planetary gear train. An electronics module consisting of a rectifier and boost converter filters the generator output, supplying regulated DC output to charge a battery, and/or power an electrical load. An onboard microcontroller broadcasts the voltage, current, and power data wirelessly for data collection during testing. Numerical and experimental validations were conducted for the energy harvester. A mathematical model for human arm swing dynamics was developed based on a triple pendulum system, and the device’s behavior was studied for both walking and running activities. The mechanical energy output from the rotary harvester pendulum was predicted to be 0.42 mJ and 2.06 mJ for simulated walking and running sequences over a period of 5 seconds (without load). A subsequent mathematical model was developed incorporating the electromechanical behavior of the generator and attached electronics module. A simulated running sequence with a representative electrical load yielded 1.72 mJ of electrical energy output over 5 seconds. The prototype was experimentally validated over the same conditions, resulting in an unregulated energy output of 1.39 mJ and a regulated energy output at 5 VDC of 1.16mJ for 5 seconds. Experimental testing successfully demonstrated the harvester’s potential as a mobile energy source for portable consumer electronics. Future steps shall focus on implementing efficient components for increased power output and designing for improved ergonomics

Advanced Energy Harvesting Technologies

Energy harvesting is the conversion of unused or wasted energy in the ambient environment into useful electrical energy. It can be used to power small electronic systems such as wireless sensors and is beginning to enable the widespread and maintenance-free deployment of Internet of Things (IoT) technology. This Special Issue is a collection of the latest developments in both fundamental research and system-level integration. This Special Issue features two review papers, covering two of the hottest research topics in the area of energy harvesting: 3D-printed energy harvesting and triboelectric nanogenerators (TENGs). These papers provide a comprehensive survey of their respective research area, highlight the advantages of the technologies and point out challenges in future development. They are must-read papers for those who are active in these areas. This Special Issue also includes ten research papers covering a wide range of energy-harvesting techniques, including electromagnetic and piezoelectric wideband vibration, wind, current-carrying conductors, thermoelectric and solar energy harvesting, etc. Not only are the foundations of these novel energy-harvesting techniques investigated, but the numerical models, power-conditioning circuitry and real-world applications of these novel energy harvesting techniques are also presented

Energy harvesting from body motion using rotational micro-generation

Autonomous system applications are typically limited by the power supply operational lifetime when battery replacement is difficult or costly. A trade-off between battery size and battery life is usually calculated to determine the device capability and lifespan. As a result, energy harvesting research has gained importance as society searches for alternative energy sources for power generation. For instance, energy harvesting has been a proven alternative for powering solar-based calculators and self-winding wristwatches. Thus, the use of energy harvesting technology can make it possible to assist or replace batteries for portable, wearable, or surgically-implantable autonomous systems. Applications such as cardiac pacemakers or electrical stimulation applications can benefit from this approach since the number of surgeries for battery replacement can be reduced or eliminated. Research on energy scavenging from body motion has been investigated to evaluate the feasibility of powering wearable or implantable systems. Energy from walking has been previously extracted using generators placed on shoes, backpacks, and knee braces while producing power levels ranging from milliwatts to watts. The research presented in this paper examines the available power from walking and running at several body locations. The ankle, knee, hip, chest, wrist, elbow, upper arm, side of the head, and back of the head were the chosen target localizations. Joints were preferred since they experience the most drastic acceleration changes. For this, a motor-driven treadmill test was performed on 11 healthy individuals at several walking (1-4 mph) and running (2-5 mph) speeds. The treadmill test provided the acceleration magnitudes from the listed body locations. Power can be estimated from the treadmill evaluation since it is proportional to the acceleration and frequency of occurrence. Available power output from walking was determined to be greater than 1mW/cm³ for most body locations while being over 10mW/cm³ at the foot and ankle locations. Available power from running was found to be almost 10 times higher than that from walking. Most energy harvester topologies use linear generator approaches that are well suited to fixed-frequency vibrations with sub-millimeter amplitude oscillations. In contrast, body motion is characterized with a wide frequency spectrum and larger amplitudes. A generator prototype based on self-winding wristwatches is deemed to be appropriate for harvesting body motion since it is not limited to operate at fixed-frequencies or restricted displacements. Electromagnetic generation is typically favored because of its slightly higher power output per unit volume. Then, a nonharmonic oscillating rotational energy scavenger prototype is proposed to harness body motion. The electromagnetic generator follows the approach from small wind turbine designs that overcome the lack of a gearbox by using a larger number of coil and magnets arrangements. The device presented here is composed of a rotor with multiple-pole permanent magnets having an eccentric weight and a stator composed of stacked planar coils. The rotor oscillations induce a voltage on the planar coil due to the eccentric mass unbalance produced by body motion. A meso-scale prototype device was then built and evaluated for energy generation. The meso-scale casing and rotor were constructed on PMMA with the help of a CNC mill machine. Commercially available discrete magnets were encased in a 25mm rotor. Commercial copper-coated polyimide film was employed to manufacture the planar coils using MEMS fabrication processes. Jewel bearings were used to finalize the arrangement. The prototypes were also tested at the listed body locations. A meso-scale generator with a 2-layer coil was capable to extract up to 234 µW of power at the ankle while walking at 3mph with a 2cm³ prototype for a power density of 117 µW/cm³. This dissertation presents the analysis of available power from walking and running at different speeds and the development of an unobtrusive miniature energy harvesting generator for body motion. Power generation indicates the possibility of powering devices by extracting energy from body motion