Orientador: Ernesto Ruppert Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-19T04:10:37Z (GMT). No. of bitstreams: 1 Nogueira_ViniciusdeFreitasGomes_M.pdf: 1151425 bytes, checksum: 25421deb7c7d0073c31744365ccb6e53 (MD5) Previous issue date: 2011 / Resumo: Os geradores síncronos trifásicos são atualmente os mais utilizados em geração de energia elétrica em grande escala no mundo todo. Na geração de energia elétrica em pequena escala, geralmente como geração distribuída, ligada à rede de distribuição em média tensão ou até mesmo em baixa tensão, eles tem sido muito usados devido à sua principal qualidade que é a de operar em velocidade constante. Entre as suas aplicações em geração distribuída destacam-se aquelas que usam energias renováveis como em médios e pequenos aproveitamentos hidráulicos, em aproveitamentos da biomassa e nos aproveitamentos eólicos. Neste trabalho estuda-se a modelagem do gerador síncrono, estabilidade transitória utilizando os diferentes modelos de representação do gerador síncrono e o seu desempenho dinâmico em algumas situações de operação em geração distribuída com cargas lineares e com cargas não lineares, com e sem o uso de filtragem ativa / Abstract: The three-phase synchronous generators are currently the most used in generating electricity on a large scale worldwide. In generating electricity on a small scale, usually as distributed generation, connected to the distribution network or even medium voltage low voltage, they have been widely used due to its main quality is to operate at constant speed. Among its applications in distributed generation to include those using renewable energy as in medium and small hydroelectric plants, biomass and hydroelectric in the Windmill. This paper studies the modeling of the synchronous generator, transient stability using different models of representation of the synchronous generator and its dynamic performance in some situations of operation distributed generation with linear loads and nonlinear loads, with and without the use of filtering active / Mestrado / Energia Eletrica / Mestre em Engenharia Elétrica

<p>Worldwide concern on fossil fuels depletion and adverse impact on environment pushed researchers to find an alternative energy source. Among various potential systems, electrochemical energy storage devices have attracted significant attraction due to short charge/discharge time, easy relocation, and relatively cheap cost compared to large storage systems. Much research has been reported to suggest a material for electrochemical storage systems. Carbon is a key part of human life in terms of energy source, building materials, daily clothing and foods. The extraordinary characteristics of carbon materials, including good conductivity, good structure stability, relatively low cost, and sustainability, draw interest to carbon application in energy storage systems. </p> <p>The introduction of lithium ion batteries (LIB), using graphite as an anode material, fulfilled the need of alternative energy source and elevated the technologies into next level high-performance applications such as portable devices. While the technology advancement in high performance electronics fosters the development of advanced lithium ion batteries, the introduction of electric vehicles and large intermittent systems seeks energy storage devices with high capacity, sustainability, and low cost. In this thesis, the impact of the characteristics of carbon material on energy storage system performance is studied. The work presented in this thesis not only suggests a cost-effective carbon synthesis for advanced LIB, but also addresses how the carbon structure impact and resolves the systematic issue associated with next generation energy storage systems.</p> <p>Chapter 3 describes a facile, one-step, solvent-free ‘dry autoclaving’ synthesis method utilizing coffee oil as the carbon precursor to obtain micrometer diameter spheroidal carbon particles for lithium ion battery anodes. The spheroidal morphology resulted from the evaporation of liquid oil into a liquid/gas phase interphase at elevated temperature (700 ^oC), followed by solid/gas sublimation interactions during cooling (below 350 ^oC) in a closed autoclave. A mechanism of spheroidal carbon formation is proposed considering the precursor’s composition and chemical interactions during autoclaving. The prepared carbon from dry autoclave has shown successful LIB performance and structure stability after 250 cycles.</p> <p>Chapter 4 illustrates the temperature effect on the structure of biomass derived carbon. In this study, due to its abundance and high porosity, pistachio shells were selected as the primary carbon source and carbonized at a range from 700 to 1500 °C. The temperature effect on carbon structure was analyzed by XRD, Raman, BET, and electron microscopy. To propose an advanced lithium ion battery, pistachio shell-derived carbon was applied as an anode material for a sodium ion battery (SIB). The correlation of carbon structure and SIB electrochemical performance is presented. Pistachio shell carbonized at 1000 °C resulted in highly amorphous structure with specific surface area (760.9 m²/g) and stable cycle performance (225 mAh g^-1 at 10 mA g^-1). With support from Raman, XRD, and BET, the storage mechanism has been studied as well.</p> <p> Chapter 5 describes the impact of carbon structure on resolving the polysulfide shuttling effect in lithium sulfur (Li-S) batteries. Lithium sulfur batteries have received tremendous attention due to its high theoretical capacity (1672 mAh g^-1), sulfur abundance, and low cost. However, main systemic issues, associated with polysulfide shuttling and low Coulombic efficiency, hinder the practical use of sulfur electrodes in commercial batteries. The work in this thesis demonstrated an effective strategy of decorating nano-MnO₂ (less than 10 wt. %) onto a sulfur reservoir in order to further capture the out-diffused polysulfides via chemical interaction, and thereby improve the electrochemical performance of sulfur electrodes without increasing the mass burden of the total battery configuration. Pistachio shell-derived sustainable carbon (PC) was employed as an effective sulfur container due to its structural characteristics (interconnected macro channels and micropores). With the aids of the structural benefits of PC scaffold and the uniform decoration of nano-MnO₂, the polysulfide shuttling effect was significantly suppressed and cycling performance of a sulfur cathode was dramatically improved over 250 cycles.</p> This thesis offers a new prospect in the study of carbon materials applications in various energy storage systems. This concept can be further extended to other applications, such as lithium metal batteries. The intercalation property of carbon structure can reduce the local current density, reducing the risk of lithium dendrite growth, which is the most critical issue of lithium metal battery.

<p>Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials. </p> <p>In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂(NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications. </p>

<p>This dissertation describes the design and characterization of a lightweight hydrogen reactor coupled to a proton exchange membrane fuel cell for portable power delivery. The system is intended to recharge portable batteries in the absence of an established electrical power supply. The presented work can be divided into two endeavors; the first being an investigation of various hydrogen generation pathways and the second being the design, fabrication, and testing of a system to house hydrogen generation and deliver electrical power.</p> <p>Two hydrogen storage materials are considered for this work: ammonia borane and sodium borohydride. Organic acids are investigated for their ability to accelerate the hydrolysis of either material and generate hydrogen on-demand. In the case of ammonia borane, organic acids are investigated for a secondary role beyond reaction acceleration, serving also to purify the gas stream by capturing the ammonia that is produced during hydrolysis. Organic acids are found to accelerate the hydrolysis of ammonia borane and sodium borohydride with relative indifference towards the purity of water being used. This is advantageous as it allows the user to collect water at the point of use rather than transport highly pure water for use as a reactant. Collecting water at the point of use increases system energy density as only ammonia borane or sodium borohydride and an organic acid are transported with the system hardware.</p> <p>A custom hydrogen reactor is developed to facilitate hydrolysis of ammonia borane or sodium borohydride. The reactor is paired with a fuel cell to generate electrical power. The rate of hydrogen being generated by the system is modulated to match the fuel cell’s consumption rate and maintain a relatively constant pressure inside the reactor. This allows the system to satisfy a wide range of hydrogen consumption rates without risking over pressurization. The system is shown to produce up to 0.5 sLpm of hydrogen without exceeding 30 psia of hydrogen pressure or a temperature rise greater than 35°C.</p><p>The envisioned use for this system is portable battery charging for expeditionary forces within the United States military. This application informed several design choices and is considered when evaluating technological maturation. It is also used to compare the designed system to existing energy storage technologies.</p>

Supercapacitors are an emerging energy storage device that have gained attention because of the large specific power, at a reasonable specific energy, that they exhibit. These energy storage devices could be used alongside of or in the place of traditional electrochemical battery technologies to power reliable electrical devices. The performance of supercapacitorsis largely determined by electrode properties including the surface area to volume ratio, the electrical conductivity, and the ion diffusivity. Nanomaterial synthesis has been proposed as a method of enhancing the performance of many macroscopic supercapacitor electrodes due to the high surface area to volume ratio and unique tunable properties that are often size or thickness dependent for many materials. Specifically, carbon materials (such as carbon nanotubes), metal organic frameworks, (such as ZIF-8), and transition metal dichalcogenides (such as molybdenum disulfide) have been of interest due to their conductivity, large surface area, and ion diffusivity that they exhibit when one or more of their characteristic lengths is on the order of several nanometers.<div><br></div><div>For the experiments, a carbon nanotube-/ZIF-8-/MoS2framework was synthesized into an electrode material. This process involved first dispersing the carbon nanotubes in DMF using ultrasonication and then modifying the structure with polydopamine to create a binding site for the ZIF-8 to attach to the carbon nanotubes. The ZIF-8 was synthesized by combining 1,2,4-Triazole-3-thiol and ZnCl under 120 degrees Celsius. Afterwards, the MoS2was associated with the carbon nanotube and ZIF-8 framework by a disulfide bond with the sulfur vacancy of the MoS2andthe sulfide group of the ZIF-8. Finally, the sample solution was filtered by vacuum filtration and then annealed at 110 degrees Celsius before being deposited on a nickel foam substrate and tested in a 3-electrode electrochemical cyclic voltammetry study.<br></div><div><br></div><div>The resulting materials were found to have a capacitance of 262.15 F/g with corresponding specific energy and specific power values of 52.4Whr/kg and 1572W/kg. Compared to other supercapacitor research materials, this electrode shows a much larger capacitance than other exclusively carbon materials, and comparable capacitance values to the ZIF-8 and MoS2materialswith the added benefits of an easier and faster manufacturing process. Overall, the electrodes developed in this study, could potentially reduce the cost per farad of the supercapacitor to be more competitive energy storage devices<br></div>

<p>Smart textiles, characterized by their ability to sense and react to various environmental stimuli, represent an evolution beyond conventional textiles, with wide-ranging applications across healthcare, sports, fashion, and defense sectors. However, the prevalent use of synthetic, petroleum-based fibers in the production of these textiles presents significant environmental and sustainability challenges. This thesis addresses this concern by exploring the functionalization of cellulose fibers—a biodegradable and renewable resource—for use in smart textiles.</p><p>The central objective of this research is to develop methodologies for the functionalization of cellulose fibers that can impart them with the requisite properties. We have developed a smart textile with integrated sensor networks and self-powering units, which features excellent stretchability, bendability, washability, and comfort, without additional uncomfortable, bulky, and rigid power sources. Via a facile infiltration process, an active polymer-based semiconductor is incorporated into the primary thread and textile towards the realization of a high-performance, self-powered biaxial motion detection, and sensing network.</p><p>The results demonstrate that, through strategic functionalization, cellulose fibers can indeed be transformed into smart materials, effectively integrating the benefits of interactive textiles with the sustainability of cellulose. By bridging the gap between sustainability and functionality, this thesis points towards a future where the textile industry can thrive on the intersection of ecological responsibility and technological innovation.</p>

<p>  </p> <p>As consumer adoption and total energy consumption of electric vehicles continues to rapidly increase, it is important to develop comprehensive system modeling frameworks that consider the complex interactions of their mechanical, electrical, and thermal subsystems to guide component technology development. This thesis studies the influence of cabin glass properties on the performance of an electric vehicle thermal system and overall cabin design considerations. The work first builds a generic long-range electric vehicle dynamic thermal system model while considering the system architecture, component sizing, control scheme, and glass properties. This comprehensive system model is used to assess the influence of cabin glass radiative properties on vehicle performance. The system model incorporates simplified models for all salient components in the electric traction drive, cabin HVAC, and battery subsystems, and uses a higher fidelity cabin thermal model that is able to capture the individual properties of the cabin glass used in the vehicle. To study the cabin model in isolation, a heat-up scenario is used to find that a cabin air temperature reduction of 8 °C through the use of different glass properties alone. Additionally, the cabin model is run repeatedly to produce a large data set that is trained using a machine learning regression model. This surrogate regression model that is used to reduce the computational time allowing for fast studies of glass properties and build an application engineering tool. The overall system performance is then evaluated under a dynamic NEDC drive cycle which is repeated until battery depletion to determine a vehicle range. A system validation is done on the HVAC subsystem by using steady-state thermodynamic analysis and comparing to the dynamic system model. This results in good agreement between four different subsystem modeling approaches. The system model is used to study five different glazing design cases, each corresponding to different transmission and reflection properties of the glass, by predicting their impact on the vehicle range. The cases span all theoretically possible glass properties while also enabling inspection of practical glass technologies that are available or under development to be adopted in modern electric vehicles. The influence of glass on vehicle range is then further compared at various locations across the United States to understand and illustrate the effects of ambient conditions and solar load. The system model predicts a vehicle range of 188.5 miles under a high solar loading scenario typical for Phoenix, AZ using traditional glass properties, which increases to a range of 221.6 miles using high-performance glass properties, representing a significant potential gain of 33.1 miles using technologies available on the market today. Under this same loading scenario, the glass properties at their extreme physical limits could theoretically affect the vehicle range by up to 92.5 miles. The influence of the glass properties is location-specific, and the model predicts that using the same glass at different locations can affect the range of vehicle by up to 100.8 miles for traditional glass properties and 73.4 miles for high-performance glass properties. </p>

<p>This thesis addresses the development and implementation of an experimental methodology for turbine rotors which enables experiments to be performed in the stationary frame. This method enables measurements with increased spatial resolution and reduced probe blockage effects while also reducing the cost and complexity of the experimental apparatus. Adding this experimental method to the turbine designer’s toolbox will enable more rapid design evaluation and iteration, resulting in faster and less expensive development cycles for new turbine designs. To demonstrate the viability of this new methodology it has been used to evaluate a family of high-lift, high-diffusion turbine geometries in a rainbow ring in the Big Rig for Aerothermal Stationary Turbine Analysis (BRASTA) facility at Purdue University.</p>

<p>A novel two-loop estimation and control strategy is proposed to reduce the natural gas (NG) spark-ignition (SI) engine tail pipe emissions, with focus on the outer loop development. In the outer loop, an fractional oxidation state (FOS) estimator consisting of a three-way catalyst (TWC) model and an extended Kalman-filter is used to estimate the real-time TWC's FOS, and a robust controller is used to control the first-half TWC's FOS by manipulating the desired engine lambda (i.e., air–fuel equivalence ratio; lambda=1 at stoichiometry). The outer loop estimator and controller are combined with an industry-production baseline inner loop controller, which controls the engine $\lambda$ based on the desired lambda value. This novel two-loop control strategy reduces more CH4 and NOx emissions over no-outer-loop control strategy and the conventional two-loop control strategies through simulation. </p> <p><br></p> <p>Engine with and without fuel cut-off are both investigated. Although fuel cut-off brings better fuel economy, it also over-oxidizes the TWC during fuel cut events, which makes the FOS-based controller's competence in NOx reduction over non-FOS-based controllers less significant. By comparing simulation results with and without fuel cut-off, it shows huge potential for much better emission result if fuel cut-off's side effect can be alleviated. Considering that fuel cut-off generally being cutting engine fueling during zero load periods and introducing unreacted oxygen into the after-treatment system, the best way of dealing with the issue is to cut off or reduce the oxygen input to the TWC during those events. Several advanced engine technologies such as cylinder deactivation and exhaust gas re-circulation are good candidates to approach this issue. </p> <p><br></p> <p>An industry-production Cummins B6.7N natural gas SI engine was installed in the Ray W. Herrick Laboratories for study of variable valve actuation (VVA) technology, for the purpose of evaluating/improving SI engine's fuel efficiency, emission reduction, and engine knock resistance. A one-dimensional, physics-based natural gas SI engine model was investigated and calibrated in GT-Power software. To calculate the burn rates in the cylinder, three different pressure analysis methods were investigated and implemented. It is observed that all six cylinders' pressure curves are different, which in turn render different burn rates cylinder-to-cylinder. Cylinder with a higher peak cylinder pressure has a faster burn rate. Each operating condition has its unique pressure curve, and their burn rates are different under different operating conditions. Considering that the burn rate profile can vary cylinder-to-cylinder and operation-to-operation, to make the GT combustion model work for a larger range of loads, a fixed burn rate model may help in the preliminary research phase, but a predictive combustion model is more preferable.</p> <p><br></p> <p>The GT-Power model's VVA capability is investigated, where intake valve closure (IVC) modulation and cylinder de-activation (CDA) are built and analyzed. To mitigate TWC's over-oxidation issue during engine's fuel cut-off events, the CDA is implemented and simulated to demonstrate its benefit on further emission and fuel consumption reductions.</p>

<p dir="ltr">An EGR Pump and High-Efficiency turbo were installed on a 13.6 L John Deere diesel engine. The main objective of this study was to examine how a high-efficiency turbocharger and an electric EGR pump can work together to improve fuel efficiency in engines without increasing the emission of NOx. The focus is on finding a balance, between enhancing efficiency and controlling emissions which will ultimately contribute to making vehicles eco-friendly and fuel-efficient.</p>