<p>Recycling valuable cathode material from end-of-life (EOL) Li-ion batteries (LIBs) is essential to preserve raw material depletion and environmental sustainability. Direct recycling reclaims the cathode material without jeopardizing its original functional structures and maximizing return values from spent LIBs compared to other regeneration processes. This work employed two chemically delithiated lithium cobalt oxide (LCO) cathodes at different states of health (SOH), which are analogous to the spent cathodes but free of any impurities, to investigate the effectiveness of cathode regeneration. The material and electrochemical properties of both delithiated SOHs were systematically examined and compared to pristine LCO cathode. Further, those model materials were regenerated by a hydrothermal-based approach. The direct cathode regeneration of both low and high SOH cathode samples restored their reversible capacity and cycle performance comparable to pristine LCO cathode. However, the inferior performance observed in higher current density (2C) rate was not comparable to pristine LCO. In addition, the higher resistance of regenerated cathodes is attributed to lower high-rate performance, which was pointed out as the key challenge of the cathode recycling process. This study provides valuable knowledge about the effectiveness of cathode regeneration by investigating how the disordered, lithium-deficient cathode at different SOH from spent EOL batteries are rejuvenated without changing any material and electrochemical functional properties.</p>

<p>This thesis proposes the design and documents analysis for a Modular River Current Energy Converter (MRCEC) to improve the efficiency of hydrokinetic turbine power systems. The MRCEC can produce electricity from low-velocity river flow with increased energy affordability and availability. The MRCEC, for the scope of this thesis, consists of the hydroturbine and maintenance systems. The turbine in the MRCEC system is a cross-flow cycloidal turbine that yields a high power coefficient (0.515) through a novel pitch variance mechanism involving a 3D cam that adapts to varying river flow conditions to maximize operational efficiencies. The cycloidal turbine is a four-section three-blade turbine that uses a unique hydrofoil profile designed for the MRCEC. The cycloidal turbine is housed in a frame supported by a flotation system to harness energy from near-surface currents. The flotation system, in turn, is connected to the service dock which houses the mooring, debris blockage, and maintenance systems. The mooring system allows the MRCEC to be fixed at the working site while allowing for self-adjustment with varying river depths. The debris blockage system prevents debris carried by the river from interfering with an operational hydroturbine. The maintenance system enables the installation, operation, and maintenance functions by integrating a flipping mechanism to invert the turbine for transportation and maintenance purposes. Mechanisms of these systems are designed to appropriate standards, then simulated to validate functionality at all stages of installation, operation, and maintenance.</p>

<p dir="ltr">Current mission plans for harvesting lunar resources require further investigation of technological and energy requirements to do so. This paper presents an analysis of the thermodynamics involved in hydrogen (H₂) evolution and liquefaction within this scope. It highlights the use of solar-powered systems for electrolysis and membrane separation as efficient means to produce H₂ on the lunar surface. The study compares energy requirements and logistical considerations of in-situ resource utilization (ISRU) against transporting precursors from Earth, where the energy penalty stands at 540 MJ/kg. It is argued that an ISRU solution stands to present the most energy efficient option, particularly with the use of an active magnetic regenerative refrigeration (AMRR) system for liquefaction. Furthermore, an AMRR system also makes the currently proposed plan of shipping methane (CH₄) from the Earth for H₂ production more favorable than implementing ISRU with the state-of-the-art (SOA) reverse turbo-Brayton cryocoolers (RTBC). This emphasizes the significance of an AMRR system for H₂ production and the need for further research in its development. Additionally, this study underscores the significance of regenerative technologies and advanced life support systems for sustainable off-planet human habitation, particularly in the context of lunar and Martian missions.</p>

<p dir="ltr">Investigating clearance flows and blockage generation in axial compressors represents a longstanding area of research for enhancing aerodynamic performance and operational stability in turbomachinery. With advancements in computational fluid dynamics (CFD), opportunities to explore these phenomena have expanded, allowing a deeper understanding of the turbomachine's inherently complex and highly unsteady flow fields. This work delves into these topics, focusing on the Purdue 3-Stage (P3S) compressor, an engine-representative, multistage, high-speed compressor.</p><p dir="ltr">The primary objective of this research is to compare the performance and stability characteristics of two distinct stator configurations: a shrouded baseline configuration and a cantilevered stator configuration. This comparison reveals the impacts of clearance flows and blockage generation on compressor operation. Through a series of experimental investigations, this study aims to identify the differences in performance and stability traits between these configurations and the flow structures responsible.</p><p dir="ltr">Experimental characterization has a central role in this study, involving the analysis of leakage flow structures, corner separations, wake structures, and resulting endwall blockage generation. This research seeks to provide detailed insights into the flow phenomena within the compressor by utilizing detailed measurement techniques, such as circumferential interrogation of the flow field using 7-element Kiel-head rakes. Pressure deficits associated with leakage flows, corner separations, and wakes are quantified to assess their impact on compressor performance.</p><p dir="ltr">In conjunction with experimental investigations, this work outlines the development and validation of the supporting high-fidelity CFD models. These models, employing scale-adaptive turbulence model simulations, aim to simulate the flow field within the compressor with accuracy and reliability. Validation of these models against experimental data ensures their fidelity in capturing the complex flow phenomena observed experimentally. Furthermore, a detailed exploration of convergence aspects, including iterative convergence, grid convergence, and periodic-unsteady signals, lays the foundations for building confidence in the model predictions.</p><p dir="ltr">The computational models complement experimental findings, allowing for a comprehensive flow field analysis focusing on endwall flow structures. Visualization of vortex core and three-dimensional blockage regions provides valuable insights into the flow physics governing compressor performance. Moreover, the comparative nature of computational simulations facilitates systematic exploration of geometric changes and their effects on compressor operation. This study leverages complementary methodologies of experimental measurements and high-fidelity computational models to advance the understanding of clearance flows and blockage generation in axial compressors.</p><p dir="ltr">The experimental analysis concludes that the cantilevered configuration achieves better performance and stability than the shrouded stator configuration. However, this conclusion is not apparent when the machine is considered holistically. The cantilevered stages show significant performance improvements, with increases in total pressure ratio of up to 1% and an increase in isentropic efficiency of as much as 2%. However, the common Stage 3 shrouded Stator 3 shows a corresponding deficit of as much as 2% loss in efficiency relative to the fully shrouded stator configuration baseline. These contrasting benefits in the cantilevered stator compressor show that Stage 3 seems to cancel the overall benefits gained by the cantilevered stator. Similar studies have been done on low-speed multistage compressors, but this shows the value of the study in a high-speed research compressor with appreciable stagewise temperature and density increase.</p>

<p dir="ltr">The demand for sustainable and renewable energy sources has prompted significant research and development efforts in the field of biomass gasification. Biomass gasification technology holds significant promise for sustainable energy production, offering a renewable alternative to fossil fuels while mitigating environmental impact. This thesis presents a detailed study on the design, development, and implementation of a Plug-Flow Reactor Biomass Gasifier integrated with an Automated Auger Jam Detection System and a Blower Algorithm to maintain constant reactor pressure by varying blower speed with respect to changes in reactor pressure. The system is based on indirectly- heated pyrolytic gasification technology and is developed using Simulink™.</p><p dir="ltr">The proposed gasification system use the principles of pyrolysis and gasification to convert biomass feedstock into syngas efficiently. An innovative plug-flow reactor configuration ensures uniform heat distribution and residence time, optimizing gasification performance and product quality. Additionally, the system incorporates an automated auger jam detection system, which utilizes sensor data to detect and mitigate auger jams in real-time, thereby enhancing operational reliability and efficiency. By monitoring these parameters, the system detects deviations from normal operating conditions indicative of auger jams and initiates corrective actions automatically. The detection algorithm is trained using test cases and validated through detailed testing to ensure accurate and reliable performance.</p><p dir="ltr">The MATLAB™-based implementation offers flexibility, scalability, and ease of integration with existing gasifier control systems. The graphical user interface (GUI) provides operators with real-time monitoring and visualization of system status, auger performance, and detected jam events. Additionally, the system generates alerts and notifications to inform operators of detected jams, enabling timely intervention and preventive maintenance. </p><p dir="ltr">To maintain consistent gasification conditions, a blower algorithm is developed to regulate airflow and maintain constant reactor pressure within the gasifier. The blower algorithm dynamically adjusts blower speed based on feedback from differential pressure sensors, ensuring optimal gasification performance under varying operating conditions. The integration of the blower algorithm into the gasification system contributes to stable syngas production and improved process control. The development of the Plug-Flow Reactor Biomass Gasifier, Automated Auger Jam Detection System, and Blower Algorithm is accompanied by rigorous simulation studies and experimental validation.</p><p dir="ltr">Overall, this thesis contributes to the advancement of biomass gasification technology by presenting a detailed study on a plug flow reactor biomass gasifier with indirectly- heated pyrolytic gasification technology with an Automated Auger Jam Detection System and Blower Algorithm. The findings offer valuable insights for researchers, engineers, policymakers, and industry stakeholders supporting the transition towards cleaner and more renewable energy systems.</p>

The point absorber, one of the most popular types of ocean wave energy converter (WEC), usually consists of a rigid body buoy that can be efficiently modeled using existing WEC simulation tools. However, new wave energy technologies have looked to utilize flexible buoy structures to decrease costs, improve power generation, and increase portability. In addition to replacing rigid body designs, the combination of multiple renewable energy sources is another area that shows promising potential for increasing WEC power generation. With these concepts in mind, this work considers a new WEC design that features a flexible-inflatable buoy, an ocean current harvesting turbine, and a buoy shape that has been optimized for simultaneous wave and current energy harvesting. For this device, conventional modeling techniques cannot be used due to the highly nonlinear hydrodynamic interactions that result between the flexible buoy and the ocean waves. As a result, a Fluid-Structure Interaction (FSI) model must be used to determine how the flexibility of the buoy will influence the device's power generation. Currently, high-fidelity FSI modeling approaches are computationally expensive and unsuitable for early design decisions. As a result, this thesis utilizes a mid-fidelity method, the generalized modes modeling approach, to accurately and efficiently model the FSI of a WEC's flexible buoy. The resulting flexible buoy model was then compared to a rigid design to determine the performance differences between a rigid and flexible buoy, with a complex, optimized shape. / Master of Science / The ocean is a vast potential energy resource with a variety of different sources of renewable energy. Of these sources, ocean waves and ocean currents are two potentially massive power reserves present in many coastal areas. To capture energy from these sources, this work discusses the development of a device that can harvest energy from ocean waves and ocean currents simultaneously. In addition to harvesting energy from multiple sources, this device also features a flexible-inflatable buoy, with a shape that has been optimized for this unique application. However, since this device utilizes flexible materials, traditional modeling techniques used for rigid body designs would not be applicable. As a result, this work looks to model the interaction between the flexible buoy and the ocean waves to accurately predict the power generation of this device's wave energy converter.

A utilização da energia eólica é ainda recente no setor elétrico e, por isso, apresenta inúmeros desafios na operação e integração dessa nova tecnologia com o sistema elétrico. Desta forma, este trabalho aborda o impacto da injeção de correntes harmônicas que as Centrais de Geração Eólica geram no Sistema Interligado Nacional. Inicialmente, aborda-se a fundamentação teórica e o conceito básico da energia eólica, principalmente em relação ao panorama desta fonte renovável no Brasil e no mundo e, de uma forma sucinta, aborda-se também sobre o aspecto tecnológico dos aerogeradores. Outro aspecto relevante deste trabalho, é o levantamento do estado da arte sobre os conceitos e cálculos das distorções harmônicas, bem como sobre o processo de integração das novas Centrais de Geração Eólica à rede básica. O principal resultado obtido neste trabalho, é o estudo de sensibilidade da distorção harmônica de tensão, no ponto de acoplamento da Central à rede básica de transmissão, frente à variação topológica da rede coletora da Central de Geração Eólica. Para tal estudo, foi modelada uma Central de Geração Eólica e aplicadas as metodologias estudadas no estado da arte. Os resultados obtidos do estudo de sensibilidade, é de grande interesse para os operadores da rede e transmissão de energia elétrica, bem como às geradoras de energia eólica. / The use of wind energy is still recent in the electric sector and, therefore, presents numerous challenges in the operation and integration of this new technology with the electric system. In this way, this work approaches the impact of the injection of harmonic currents generated by the Wind Generation Plants in the National Interconnected System. Initially, it addresses the theoretical basis and the basic concept of wind energy, mainly in relation to the panorama of this renewable source in Brazil and in the world and, briefly, it also addresses the technological aspect of wind turbines. Another relevant aspect of this work is the state of the art survey on the concepts and calculations of harmonic distortions, as well as on the integration process of the new Wind Generation Plants into the basic grid. The main result obtained in this work is the sensitivity study of the harmonic distortion of voltage at the coupling point of the Central to the basic transmission network, in front of the topological variation of the collecting network of the Wind Generation Plant. For such study, a Wind Generation Plant was modeled and the methodologies studied in the state of the art were applied. The results obtained from the sensitivity study, is of great interest to the network operators and transmission of electricity, as well as to wind power generators.

O objetivo do trabalho é apresentar o funcionamento de um gerador a relutância chaveado monofásico. Para isso, foi desenvolvido um modelo computacional em ambiente Matlab Simulink, fazendo-se a comunicação entre diferentes partes do sistema. O comportamento da dinâmica de geração é apresentado para diferentes pontos do sistema, e testes experimentais realizados em um pequeno protótipo confirmam as características funcionais desta máquina. Ensaios realizados comprovam sua funcionalidade e simplicidade de operação, tendo estabilidade de geração para ampla faixa de velocidade de funcionamento, caracterizando uma máquina promissora, robusta e eficiente para aplicações especiais. / This work presents a single-phase switched reluctance machine operating as a generator. For that purpose, a computational model was developed in Matlab Simulink environment, wherein all the system components, such as voltage source, drive and machine model, and load were integrated. The current and voltage behavior for several points of operations are presented. Furthermore, experimental tests were also carried out in a simple prototype to validate its functionality and simplicity of operation, providing a stable power generation over a wide range of speed. The results showed that the single-phase switched reluctance generator can be robust, efficient, and promising for especial applications.

A utilização da energia eólica é ainda recente no setor elétrico e, por isso, apresenta inúmeros desafios na operação e integração dessa nova tecnologia com o sistema elétrico. Desta forma, este trabalho aborda o impacto da injeção de correntes harmônicas que as Centrais de Geração Eólica geram no Sistema Interligado Nacional. Inicialmente, aborda-se a fundamentação teórica e o conceito básico da energia eólica, principalmente em relação ao panorama desta fonte renovável no Brasil e no mundo e, de uma forma sucinta, aborda-se também sobre o aspecto tecnológico dos aerogeradores. Outro aspecto relevante deste trabalho, é o levantamento do estado da arte sobre os conceitos e cálculos das distorções harmônicas, bem como sobre o processo de integração das novas Centrais de Geração Eólica à rede básica. O principal resultado obtido neste trabalho, é o estudo de sensibilidade da distorção harmônica de tensão, no ponto de acoplamento da Central à rede básica de transmissão, frente à variação topológica da rede coletora da Central de Geração Eólica. Para tal estudo, foi modelada uma Central de Geração Eólica e aplicadas as metodologias estudadas no estado da arte. Os resultados obtidos do estudo de sensibilidade, é de grande interesse para os operadores da rede e transmissão de energia elétrica, bem como às geradoras de energia eólica. / The use of wind energy is still recent in the electric sector and, therefore, presents numerous challenges in the operation and integration of this new technology with the electric system. In this way, this work approaches the impact of the injection of harmonic currents generated by the Wind Generation Plants in the National Interconnected System. Initially, it addresses the theoretical basis and the basic concept of wind energy, mainly in relation to the panorama of this renewable source in Brazil and in the world and, briefly, it also addresses the technological aspect of wind turbines. Another relevant aspect of this work is the state of the art survey on the concepts and calculations of harmonic distortions, as well as on the integration process of the new Wind Generation Plants into the basic grid. The main result obtained in this work is the sensitivity study of the harmonic distortion of voltage at the coupling point of the Central to the basic transmission network, in front of the topological variation of the collecting network of the Wind Generation Plant. For such study, a Wind Generation Plant was modeled and the methodologies studied in the state of the art were applied. The results obtained from the sensitivity study, is of great interest to the network operators and transmission of electricity, as well as to wind power generators.

<p>The thesis covers the following topics:</p> <p>1. aggregation and size effect on metal-polymer nanocomposite thermal interface materials</p> <p>2. diffusion limited cluster aggregation lattice simulation on thermal conductivty</p> <p>3. thermal interfacial resistance reduction between metal and dielectric materials by inserting an intermediate metal layer</p> <p>4. absence of coupled thermal interfaces in al2o3/ni/al2o3 sandwich structure</p> <p>5. ultra-efficient low-cost radiative cooling paints</p>