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

Small-Signal Modelling and Analysis of Doubly-Fed Induction Generators in Wind Power Applications

The worldwide demand for more diverse and greener energy supply has had a significant impact on the development of wind energy in the last decades. From 2 GW in 1990, the global installed capacity has now reached about 100 GW and is estimated to grow to 1000 GW by 2025. As wind power penetration increases, it is important to investigate its effect on the power system. Among the various technologies available for wind energy conversion, the doubly-fed induction generator (DFIG) is one of the preferred solutions because it offers the advantages of reduced mechanical stress and optimised power capture thanks to variable speed operation. This work presents the small-signal modelling and analysis of the DFIG for power system stability studies. This thesis starts by reviewing the mathematical models of wind turbines with DFIG convenient for power system studies. Different approaches proposed in the literature for the modelling of the turbine, drive-train, generator, rotor converter and external power system are discussed. It is shown that the flexibility of the drive train should be represented by a two-mass model in the presence of a gearbox. In the analysis part, the steady-state behaviour of the DFIG is examined. Comparison is made with the conventional synchronous generators (SG) and squirrel-cage induction generators to highlight the differences between the machines. The initialisation of the DFIG dynamic variables and other operating quantities is then discussed. Various methods are briefly reviewed and a step-by-step procedure is suggested to avoid the iterative computations in initial condition mentioned in the literature. The dynamical behaviour of the DFIG is studied with eigenvalue analysis. Modal analysis is performed for both open-loop and closed-loop situations. The effect of parameters and operating point variations on small signal stability is observed. For the open-loop DFIG, conditions on machine parameters are obtained to ensure stability of the system. For the closed-loop DFIG, it is shown that the generator electrical transients may be neglected once the converter controls are properly tuned. A tuning procedure is proposed and conditions on proportional gains are obtained for stable electrical dynamics. Finally, small-signal analysis of a multi-machine system with both SG and DFIG is performed. It is shown that there is no common mode to the two types of generators. The result confirms that the DFIG does not introduce negative damping to the system, however it is also shown that the overall effect of the DFIG on the power system stability depends on several structural factors and a general statement as to whether it improves or detriorates the oscillatory stability of a system can not be made

IPMC materjali hp-FEM mudel

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Ioonjuhtivaid polümeer-metall komposiitmaterjale (edaspidi lühendatud IPMC ehk ionic polymer-metal composite) on uuritud juba vähemalt kaks aastakümmet nende huvipakkuvate omaduste tõttu. Võimalikeks kasutusaladeks on vaiksed aktuaatorid või sensorid. IPMC eelised teiste elektroaktiivsete polümeeride ees on töötamine madalal pingel (1...5V), suur paindeulatus, ja toimimine veekeskkonnas. Kuigi põhiliselt on uuritud materjalide omadusi aktuaatoritena, on hiljuti materjalide sensor-omadused rohkem tähelepanu saanud. Et materjali toimimisest aru saada ning seda kirjeldada erinevate rakenduste tarbeks, on vajalik füüsikal baseeruvat mudelit. Sellest lähtuvalt on välja töötatud Poisson-Nernst-Planck-Navier võrranditel baseeruva IPMC mudel. See baseerub füüsikalistel printsiipidest, ehk et saab kasutada võimalikult palju mõõdetavaid suurusi ääretingimustena (nagu materjali paindumine, rakendatud pinge jne). Lisaks on oluline, et meetod millel mudel baseerub, oleks efektiivne ning võimaldaks arvutusi väikese või vähemalt teadaoleva maksimaalse arvutusveaga. Käesoleva töö keskendub peamiselt just arvutusmeetodil ja annab ülevaate uudsest hp-FEM (finite element method) ehk hp lõplike elementide meetodist ja sellel baseeruvast IPMC mudelist. Kõigepealt on täielikult tuletatud võrrandid ja nende integraalne esitus Newtoni meetodi jaoks. Seejärel antakse lühike ülevaade hp-FEM meetodist adaptiivse väljapõhise võrguga ning kogu süsteemi Jakobiaani tuletus hp-FEM tarkvara Hermes jaoks. On näidatud kuidas automaatne adaptiivne hp-FEM võimaldab probleemi suuruse hoida väiksena (süsteemi vabadusastmeid ja kasutatud mälu silmas pidades). Kõige pealt on lahendatud Poisson-Nernst-Plancki võrrandisüsteem ja on käsitletud erinevaid adaptiivusalgoritme. Üks huvitav tulemus on, et adaptiivsed algoritmid võimaldavad lahendada probleemi tingimustel, kus Debye pikkus jääb nanomeetri suurusjärku – seda süsteemis mille mõõtmed on millimeetri skaalas. Nendest tulemustest lähtuvalt esitatakse lahendus terve Poisson-Nernst-Planck-Navier võrrandite süsteemile IPMC paindumise arvutustes. Taaskord on lõplikud võrrandid koos tuletuskäiguga esitatud. Lisaks on analüüsitud suur hulk simulatsiooni tulemusi arvutusprobleemi suurust ja kulutatud arvutusaega silmas pidades ja sellest lähtuvalt leitud parim adaptiivuse algoritm seda liiki probleemide jaoks. On ka näidatud kuidas meetod võimaldab arvutusdomeeni geomeetriat arvesse võtta – domeeni pikkuse ja laiuse suhtest tulenevad ääreefektid on automaatselt arvutustes käsitletud. Kokkuvõtteks, käesolevas töös on detailselt kirjeldatud kuidas kasutades uudne hp-FEM meetod koos adaptiivsete algoritmide ja väljapõhise võrguga võimaldab Nernst-Planck-Poisson-Navier probleemi lahendada efektiivselt, samal ajal hoides lahenduse arvutusvea etteseatud piirides.Ionic polymer-metal composites (IPMC) have been studied during the past two decades for their potential to serve as noiseless mechanoelectrical and electromechanical transducers. The advantages of IPMC over other electroactive polymer actuators are low voltage bending, high strains (>1%), and an ability to work in wet environments. The main focus has been on the electromechanical transduction property – the material’s ability to exhibit large bending deformation in response to a low (typically 1...5 V) applied voltage. However, lately research on the mechanoelectrical transduction properties of the material has gained more attention. In order to describe both deformation in response to applied voltage (electromechanical transduction) and induced voltage in response to applied deformation (mechanoelectrical transduction) properties of IPMC, an advanced physics based model of the material is necessary. Ongoing research has been focused on creating such model where real measurable quantities can be imposed as boundary conditions in order to reduce the number of unknown parameters required for calculations. In this dissertation, a physics based model that is based on novel hp-FEM (finite element method) is proposed. From the fundamental aspect, previously proposed and validated physics based model consisting of a system of Poisson-Nernst-Planck-Navier’s equations is described in detail and used in IPMC deformation calculations. From the mathematical aspect, a novel hp-FEM method was researched to model the equations efficiently. The main focus of this disseration is on the mathematical aspect. Full derivation of the equations with an in-depth study of the benefits of using higher order FEM with automatic adaptivity is presented. The explicit weak form of the Poisson-Nernst-Planck system for Newton’s method is presented. Thereafter, a brief overview of the adaptive multi-mesh hp-FEM is introduced and the residual vector and Jacobian matrix of the system is derived and implemented using hp-FEM library Hermes. It is shown how such problem benefits from using individual meshes with mutually independent adaptivity mechanisms. To begin with, a model consisting of only the Poisson-Nernst-Planck system is solved using different adaptivity algorithms. For instance, it is demonstrated that the problem with set of constants that results Debye’s length in the nanometer scale can be successfully solved. What makes it even more remarkable is the fact that the calculation domain size is in the millimeter scale. Based on those results, the complete Poisson-Nernst-Planck-Navier’s system of equations is studied for IPMC electromechanical transduction calculations. Again, the entire mathematical derivation including weak forms, the residual vector and Jacobian matrix are presented. Thereafter, a number of simulations are analyzed in terms of problem size and consumed CPU time. The best automatic adaptivity mode for such problem is determined. It is also shown how hp-FEM helps to keep the problem geometrically scalable. Additionally, it is demonstrated how employing a PID controller based time step adaptivity helps to reduce the total calculation time. Overall, by using hp-FEM with adaptive multi-mesh configuration the Nernst-Planck-Poisson-Navier’s problem size in IPMC deformation calculations is reduced significantly while a prescribed precision of the solution is maintained

Sensitivity Analysis and Parametric Optimization of Micro-Plasma Actuators: A Mini Review

The Dielectric Barrier Discharge (DBD) micro-plasma actuator stands out as a highly promising tool for active fluid flow control. Researchers specializing in flow control have taken a keen interest in this actuator due to its economical manufacturing, low energy consumption, compact size, lightweight nature, straightforward implementation, and absence of movable components or pneumatic/hydraulic systems. Given its extensive application, achieving the best design for plasma actuators necessitates a more profound grasp of how diverse physical factors (like electrode thickness, electrode length, dielectric thickness, and dielectric materials) and operational variables (such as applied voltage, frequency, and waveform) impact its performance. Within this article, we delve into a comprehensive assessment of both numerical and experimental investigations focused on optimizing actuator parameters. These studies can be categorized into two main groups. The initial group involves fundamental test cases conducted on flat plates, while the subsequent group pertains to modeling controlled flow in real-world scenarios, including curved surfaces

Comparative performance analysis of an electric actuator for control valves

This article deals with the analysis of performances of electric actuators for control valves in industrial control loops. The objective of the recent collaboration between University of Pisa and CLUI AS is to assess potentials and benefits of control valve electric actuators, by testing and comparing devices of different typologies and manufacturers. As a premise, it should be noted that pneumatic actuators still represent the most commonly used actuation devices in the process industry, mainly because of high performance and fast response. In recent years, electric actuators, as a result of their enhanced features, are finding increasing applications in the area of process control. Anyway, some practical aspects, such as the degradation of the valve seat, an excessive tightening of the seal, and an expansion of metallic components due to high temperature operation, can cause malfunctions, and in particular, phenomena of wear and friction within a control valve regardless of the type of actuator. In fact, pneumatic and electric valves differ only in the actuation system; while the valve body, subject to most of the friction forces, is absolutely the same. In detail, the present work has been focused on the analysis of a recent electric actuator installed on an rotary control valve, and tested in the last biennium in an pilot plant, owned by ENEL in Livorno (Italy). Specific experimental tests were carried out, by collecting operating data in open-loop and closed-loop mode. The validity and effectiveness of the performance was verified in nominal and faulty conditions, in particular, by introducing a dead-band. Furthermore, performances of this electric actuator was compared with that of a conventional pneumatic actuator with positioner, coupled to the same valve, installed on the same plant line, and tested in equivalent experimental conditions. In general terms, it has been confirmed that the electric actuator for control valve is a promising technology, and its performance are fully comparable - if not superior - to those of the pneumatic actuator. In particular, some simple performance indices assume similar numerical values, and also the time trends of the positional error and the limit cycles registered on polar diagram between valve input and output signals are similar

An Experimental Study of Synthetic Jet Actuators with Application in Airfoil LCO Control

An experimental study on the development and implementation of Synthetic Jet Actuators (SJAs) is conducted for eliminating aeroelastic phenomenon such as Limit Cycle Oscillations (LCO). One of the biggest challenges involved in the design of UAVs operating in unsteady atmosphere conditions is the susceptibility of the airframe to aeroelastic instabilities, such as flutter or LCO. Suppression of such instabilities can be achieved through the implementation of Active Flow Control (AFC) techniques, however to this day, a limited amount of experimental studies exist. Thus, the focus of this work is to develop a new AFC method consisting of an actuator that is directly instrumented in the internal volume of the airfoil. Due to the complex geometry of airfoil/actuator integration, advanced manufacturing technique has been employed for rapid manufacturing of these complex parts. In addition, a newly designed experimental test facility is fabricated to study the effect of the developed actuator on aerodynamic performance. Parametric analysis are conducted to investigate the effect of actuator along the airfoil surface, Reynolds number, and angle of attack. Results of this study demonstrated the actuator effectiveness on overall aerodynamic performance and show consistent trends with high-order Computational Fluid Dynamics (CFD)