Engineering Commons^™

Dynamics Modeling Of Molten Salt Reactors, Visura Umesh Pathirana

Doctoral Dissertations

The abundance of energy is a necessity for the prosperity of humans. The rise in energy demand has created energy shortages and issues related to energy security. Nuclear energy can produce vast amounts of reliable energy without many of the negative externalities associated with other competing energy sources, such as coal and natural gas. As a result, public interest in nuclear power has increased in the past decade. Many new types of nuclear reactor are proposed. These nuclear reactor designs feature many passive technologies that can operate without external influence. Reactors that feature advanced passive safety features are catagorized as …

Additively Manufactured Nature Inspired Morphology For Redesign: Advancing Next Generation Energy Systems, Vanshika Singh

Doctoral Dissertations

To meet cleaner energy goals and increasing demand, energy systems such as gas turbines and power plants are required to be operated under harsh loading conditions like higher temperatures and pressures, fluctuating loads, and corrosive environments. Advanced manufacturing techniques such as additive manufacturing (AM) have put us on the trajectory for next-generation system designs, allowing complex geometries and high-temperature alloys with tailored material properties. We need new and systematic design philosophies to use AM's unique characteristics prudently. For a given functionality, nature tends to provide similar solutions in animate and inanimate structures. We propose to take inspiration from nature's repetitive …

Heat Pump Integrated Thermal Storage For Building Demand Response And Decarbonization, Sara Sultan

Doctoral Dissertations

This work presents a novel thermal energy storage (TES) integrated with existing residential heat pump (HP). The research focuses on controls and configuration for energy, demand, cost and carbon emissions savings for residential buildings’ energy consumption. This work will be significant in developing a framework especially for reduced energy demand and carbon emissions associated with space heating and cooling in residential buildings. Since buildings account for about 40% primary energy consumption in U.S. and half of that is associated with HP.

An existing air source HP in integrated with a phase change material (PCM) based TES via active configuration where …

Investigating The Electrochemical Performance Of Biphenyl-Sodium Polysulfide Organic Redox Flow Batteries, Mohammad Bahzad

Doctoral Dissertations

With the increased utilization of renewable energy sources, demand for long-duration energy storage systems has increased to moderate the intermittent power generation problem of these sources. Among the various energy storage technologies, those based on electrochemical conversion have received tremendous attention in recent decades. Organic redox flow batteries (ORFBs) are promising candidates for large-scale energy storage. The advantages of ORFBs are flexibility, wide voltage window, high energy density, and low cost. Although recent developments in ORFBs are promising, their future implementation requires further development, especially to understand their electrochemical performance and alleviate system inefficiencies. Most of ORFBs' performance loss comes …

Heat Transfer Characteristics Of Latent Heat Thermal Energy Storage, Kedar Prashant Shete

Doctoral Dissertations

Latent heat thermal energy storage (LHTES) systems can be used to reduce electric demand when used in conjunction with Combined Heat and Power Plants or HVAC(Heating, Ventilation, Refrigeration and Air-Conditioning), as they can regulate the demand and supply of thermal energy. They can also be used to integrate renewable energy sources with the grid. A design procedure and performance modeling is required for designing and using thermal energy storage systems effectively. We propose hypotheses about the performance of an LHTES device with different operating conditions and material properties, for devices that are governed by different modes of heat transfer. We …

Multiscale Investigation Of Freeze Cast Process And Ion Transport For Graphene Aerogel Electrodes, Yu-Kai Weng

Doctoral Dissertations

Effective use of renewable energy resources has been regarded as the most promising solution to climate emergency and energy crisis. However, the fluctuating and intermittent nature of renewable resources causes stability issues in the electric grid. High-capacity electrical energy storage is essential to stabilize the electric power supply using renewable resources. Among various types of energy storage systems, organic redox flow battery (ORFB) has attracted attentions due to their high stability, flexibility, low cost, and environmental compatibility, but the performance of the ORFB still needs a significant improvement due to their low energy or current density. Specifically, even though the …

Environmental Design And Optimization Of Modular Hydropower Plants, Colin Sasthav

Doctoral Dissertations

This research aimed to understand the pathways to cost-effective and sustainable low-head hydropower. Designing viable hydropower projects requires optimization across many economic, environmental, and social outcomes. However, existing run-of-river hydropower design models often focus on economic performance and customizing technologies for high-head diversion schemes. Standard modular hydropower is a new design approach that uses standardized rather than custom-designed technologies to achieve economies of scale. Oak Ridge National Laboratory established a conceptual outline for module classes based on functions, such as generation modules and fish passage modules, but further research was needed to identify how modules should be selected and operated …

Computational Study Of Internal Flow, Near Nozzle And External Spray Of A Gdi Injector Under Flash-Boiling Conditions, Chinmoy Krushna Mohapatra

Doctoral Dissertations

The early and late portions of transient fuel injection have proven to be a rich area
of research, especially since the end of injection can cause a disproportionate amount
of emissions in direct injection internal combustion engines. While simulating the
internal flow of fuel injectors, valve opening and closing events are the perennial
challenges. A typical adaptive-mesh CFD simulation is extremely computationally
expensive, as the small gap between the needle valve and the seat requires very
small cells to be resolved properly. Capturing complete closure usually involves a
topological change in the computational domain. Furthermore, Internal Combustion
Engines(ICE) operating with …

Modeling Portfolios Of Low Carbon Energy Generation Under Deep Uncertainty, Franklyn Kanyako

Doctoral Dissertations

In the 2015 Paris Agreement, nearly every country pledge through the Nationally Determined Contributions (NDCs) increased adoption of low carbon energy technologies in their energy system. However, allocating investments to different low carbon energy technologies under rising demand for energy and budget constraints, uncertain technical change in these technologies involves maneuvering significant uncertainties among experts, models, and decision-makers. We examine the interactions of low carbon energy sources (LCES) under the condition of deep uncertainty. Deep uncertainty directly impacts the understanding of the role of low carbon energy technologies in climate change mitigation and how much R&D investment should be allocated …

Numerical Modeling Of Advanced Propulsion Systems, Peetak P. Mitra

Doctoral Dissertations

Numerical modeling of advanced propulsion systems such as the Internal Combustion Engine (ICE) is of great interest to the community due to the magnitude of compute/algorithmic challenges. Fuel spray atomization, which determines the rate of fuel-air mixing, is a critical limiting process for the phenomena of combustion within ICEs. Fuel spray atomization has proven to be a formidable challenge for the state-of-the-art numerical models due to its highly transient, multi-scale, and multi-phase nature. Current models for primary atomization employ a high degree of empiricism in the form of model constants. This level of empiricism often reduces the art of predictive …

Experimental And Computational Study Of Determining Mass Transport Parameters In Vanadium Redox Flow Batteries, Tugrul Y. Ertugrul

Doctoral Dissertations

Vanadium redox flow batteries are a promising large-scale energy storage technology, but a number of challenges must be overcome for commercial implementation. At the cell level, mass transport contributes significantly to performance losses, limiting VRFB performance. Therefore, understanding mass transport mechanisms in the electrode is a critical step to mitigating such losses and optimizing VRFBs.

In this study, mass transport mechanisms (e.g. convection, diffusion) are investigated in a VRFB test bed using a strip cell architecture, having 1 cm² active area. It is found that diffusion-dominated cells have large current gradients; convection-dominated cells have relatively uniform current distribution from …

Utility Scale Building Energy Modeling And Climate Impacts, Brett C. Bass

Doctoral Dissertations

Energy consumption is steadily increasing year over year in the United States (US). Climate change and anthropogenically forced shifts in weather have a significant impact on energy use as well as the resilience of the built environment and the electric grid. With buildings accounting for about 40% of total energy use in the US, building energy modeling (BEM) at a large scale is critical. This work advances that effort in a number of ways. First, current BEM approaches, their ability to scale to large geographical areas, and global climate models are reviewed. Next, a methodology for large-scale BEM is illustrated, …

Characterization Of Near Isothermal Compression And Expansion For Energy Storage, Saiid Kassaee

Doctoral Dissertations

As the global share of electricity generation from intermittent renewable energy sources increases, developing efficient and scalable electricity storage technologies becomes critical to modernizing the grid, matching the supply and demand, and raising the capacity factor of renewable generation. The Ground-Level Integrated Diverse Energy Storage (GLIDES) is an efficient energy storage technology invented at Oak Ridge National Laboratory (ORNL). GLIDES stores energy by compressing gas using a liquid piston in pressure vessels benefiting from employing hydraulic turbomachinery which are more efficient than gas turbomachinery. Therefore, GLIDES has higher round-trip efficiency (RTE) than Compressed Air Energy Storage (CAES). Since GLIDES employs …

Enhanced Kinetics And Modeling Of Pan-Based Carbon Felt Anodes In Vanadium Redox Flow Batteries, Michael Cyrus Daugherty

Doctoral Dissertations

All-vanadium redox flow batteries (VRFBs) are a promising technology for grid-level energy storage, however, there are still several limitations in the forms of durability, efficiency, and overall costs, which are barriers to its commercial viability. With both bulk electrolyte flowing through its porous matrix and species flux at the solid-electrolyte interface, electrodes are the component of VRFB systems which host electrochemical reactions and facilitate contact between the liquid phase electrolyte and the electronically conductive solid phase. While the more limiting electrode in VRFB systems is dependent on the material, for polyacrylonitrile (PAN)-based carbon felts, the anode constitutes a larger portion …

Robust And Sustainable Energy Pathways To Reach Mexico’S Climate Goals, Rodrigo Mercado Fernandez

Doctoral Dissertations

As countries set climate change goals for adaptation and mitigation efforts, there are many questions regarding to how to reach these targets. These efforts will necessitate the transition of our electricity infrastructure from relying on conventional electricity generation technologies including natural gas, coal and oil, to clean energy generation with renewables. Through the three essays presented in this dissertation, we explore various pathways of development for the electricity system to reach long term climate change goals. We are interested in identifying: Is there a unique optimal development option or are there various? How do different mixes of electricity generation technologies …

Structural Control Of Offshore Wind Turbines Using Passive And Semi-Active Control, Semyung Park

Doctoral Dissertations

Offshore wind energy has the potential to generate substantial electricity production compared to onshore locations, due to the high-quality wind resource. Offshore wind turbines must endure severe offshore environmental conditions and be cost effective, in order to be sustainable. As a result, load mitigation becomes crucial in successfully enabling deployment of offshore wind turbines. A direct approach to reduce loads in offshore wind turbines is the application of structural control techniques. So far, the application of structural control techniques to offshore wind turbines has shown to be effective in reducing fatigue and extreme loads of turbine structures. However, the majority …

Thermodynamic And Economic Analysis Of Several Hybrid Multigeneration Cycles And Waste Heat Recovery Systems Driven By Concentrated Solar Tower, Kasra Mohammadi

Doctoral Dissertations

In recent decades, growth in the world population, economic and living standards have been responsible for substantial increases in global energy consumption. Moreover, exploitation of fossil fuels to supply energy demands has led to global climate change, which is expected to have far-reaching and long-lasting consequences on the planet. These factors have motivated the importance and necessity of developing more efficient ways for energy conservation and generation that avoid the production of greenhouse gases that contribute to climate change. One method to address these issues is to develop combined production such as multigeneration for simultaneous production of electricity, cooling, fresh …

Deep Understanding Of Degradation In Lithium Ion Batteries Through Experimental And First-Principles Study, Yufang He

Doctoral Dissertations

"The growing interests in Lithium-ion Batteries (LIBs) have significantly accelerated the development of active materials. However, the key challenge is that electrode materials suffer from degradation, which include transition metal dissolution, solid electrolyte interphase (SEI) layer formation, and mechanical fracture. To address these issues, applying an ultrathin coating onto active materials via Atomic Layer Deposition (ALD) is an efficient way. Although numerious works have been done for active material performance improvement via ALD technology, the fundamental enhancement mechanisms of ALD coating on battery performance improvement are not yet known. Therefore, this dissertation consists of four papers, which focused on the …

Performance And Economic Analysis Of Hybrid Microhydro Systems, Ram Poudel

Doctoral Dissertations

Microhydro (MHP) systems usually employ unregulated turbines and an electronic load controller, a demand-side control device. Existing analytical models for such systems are lacking details, especially supply-side flow control, for performance simulation at hourly or sub-hourly scales. This work developed stochastic models for downscaling of streamflow and an empirical model of MHP systems. We integrated these models within the framework of Hybrid2 tool to simulate the long-term performance of a tri-hybrid system consisting of hydropower, solar PV and wind turbine. Based on an additive model of time series decomposition, we develop a Multiple Input Single Output (MISO) model in order …

Aeroelastic Simulation Of Wind Turbines Using Free Vortex Methods And Strategies For Accelerating The Computation, Shujian Liu

Doctoral Dissertations

This dissertation integrated the free vortex method code Wake Induced Dynamics Simulator (WInDS), which was developed by Sebastian et al., into the open source and widely-used software FAST. A range of computational strategies including paral- lelization and Treecode algorithms are used to increase the computational efficiency of the software. Full aero-hydro-servo-elastic simulations with free vortex method are conducted, which focus on an in-depth study on the influence of the aeroelasticity of the wind turbine and platform motions on the unsteadiness of the aerodynamics, and the comparison of aeroelastic responses of two floating wind turbine concepts. This dissertation also applies long …

Correlating Long-Term Lithium Ion Battery Performance With Solid Electrolyte Interphase (Sei) Layer Properties, Seong Jin An

Doctoral Dissertations

This study was conducted to understand effects of some of key factors (i.e., anode surface properties, formation cycling conditions, and electrolyte conditions) on solid electrolyte interphase (SEI) formation in lithium ion batteries (LIBs) and the battery cycle life. The SEI layer passivates electrode surfaces and prevents electron transfer and electrolyte diffusion through it while allowing lithium ion diffusion, which is essential for stable reversible capacities. It also influences initial capacity loss, self-discharge, cycle life, rate capability and safety. Thus, SEI layer formation and electrochemical stability are primary topics in LIB development. This research involves experiments and discussions on key factors …

Value Of Flow Measurement Accuracy In Hydropower Plants With Short Converging Intakes, Mark Herbert Christian

Doctoral Dissertations

This report documents research undertaken to determine the value of flow measurement accuracy in hydropower plants with short converging intakes. The motivation was to provide a suite of tools and best practices to streamline flow measurement sensor modeling in any type of hydropower plant. The Lower Granite Lock and Dam hydroplant was leveraged in development of the analysis tool. Computational fluid dynamics (CFD) models of Lower Granite Unit 4 provided necessary information about the hydraulic structures distribution through the unit. Two different CFD models were created. The first was done using the as-built plans; the second was created through modifications …

Computational Thermal-Hydraulics Modeling Of Twisted Tape Enabled High Heat Flux Components, Emily Buckman Clark

Doctoral Dissertations

The goal of this work was to perform a computational investigation into the thermalhydraulic performance of water-cooled, twisted tape enabled high heat flux components at fusion relevant conditions. Fusion energy is a promising option for future clean energy generation, but the community must overcome significant scientific and engineering challenges before meeting the goal of electricity generation. One such challenge is the high heat flux thermal management of components in fusion and plasma physics experiments. Plasma facing components in the magnetic confinement devices, such as ITER or W7-X, will be subjected to extreme heat loads on the order of 10-20 MW/m …

Processing, Microstructure, And Mechanical Properties Of Zirconium Diboride-Molybdenum Disilicide Ceramics And Dual Composite Architectures, Ryan Joseph Grohsmeyer

Doctoral Dissertations

"This research had two objectives: characterization of processing-microstructure-mechanical property relationships of conventional ZrB₂-MoSi₂ ceramics at room temperature (RT) and 1500⁰C in air, and fabrication of ZrB₂-MoSi₂ dual composite architectures (DCAs) for use near 1500⁰C. Elastic moduli, fracture toughness, and flexure strength were measured at RT and 1500⁰C for 15 ZrB₂-MoSi₂ ceramics hot pressed using fine, medium, or coarse ZrB₂ starting powder with 5-70 vol.% MoSi₂, referred to as FX, MX, and CX respectively where X is the nominal MoSi₂ content. MoSi₂ decomposed during sintering, resulting in …

Impedance-Resolved Performance And Durability In Redox Flow Batteries, Alan Michael Pezeshki

Doctoral Dissertations

The realization of redox flow batteries (RFBs) as a grid-scale energy solution depends on improving the performance and lifetime of the technology to decrease the high capital costs. The electrodes are a key component in the RFB; performance enhancement is often achieved through chemical or thermal treatments of commercially available porous carbon materials.

This dissertation uses impedance spectroscopy-based methods to gain insight into performance and durability in RFBs, enabling intelligent cell design. Initial work focused on understanding the impact of improved electrode and membrane properties on system performance. An accelerated stress test was then developed that can be used to …

Fundamental Studies Of Electrochemical Reactions And Microfluidics In Proton Exchange Membrane Electrolyzer Cells, Jingke Mo

Doctoral Dissertations

In electrochemical energy devices, including fuel cells, electrolyzers and batteries, the electrochemical reactions occur only on triple phase boundaries (TPBs). The boundaries provide the conductors for electros and protons, the catalysts for electrochemical reactions and the effective pathways for transport of reactants and products. The interfaces have a critical impact on the overall performance and cost of the devices in which they are incorporated, and therefore could be a key feature to optimize in order to turn a prototype into a commercially viable product. For electrolysis of water, proton exchange membrane electrolyzer cells (PEMECs) have several advantages compared to other …

Investigation Of Localized Performance And Gas Evolution In All-Vanadium Redox Flow Batteries Via In-Situ Distributed Diagnostic Techniques, Jason Thomas Clement

Doctoral Dissertations

All-vanadium redox flow batteries (VRFBs) are an emerging grid-scale energy storage technology; however, enhancements in terms of performance, efficiency, durability, and cost are required before it can become commercially viable. These improvements are achievable through the development of advanced materials, superior architecture, and ultimately a deeper fundamental understanding of the influence of various phenomena and operational parameters on cell performance. There currently are a lack of in-situ experimental diagnostic techniques which can help in achieving this fundamental understanding.

Two separate distributed diagnostic techniques were developed in this work: in-plane current distribution, and neutron radiography. Localized current distribution measurements can identify …

Theoretical Modeling, Experimental Observation, And Reliability Analysis Of Flow-Induced Oscillations In Offshore Wind Turbine Blades, Pariya Pourazarm

Doctoral Dissertations

Offshore wind energy has been growing rapidly due to its capacity for utilizing much larger turbines and thus higher power generation compared to onshore. With the increasing size of offshore wind turbine rotors, the design criteria used for the blades may also evolve. Increased flexibility in blades causes them to be more susceptible to experiencing flow-induced instability. One of the destructive aero-elastic instabilities that can occur in flexible structures subjected to aerodynamic loading is coupled-mode flutter. Coupled-mode flutter instability has not been a design driver in the current wind turbine blades, however, considering the industry tendency in utilizing longer and …

Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem

Doctoral Dissertations

Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …

Wind Farm Wake Modeling And Analysis Of Wake Impacts In A Wind Farm, Yujia Hao

Doctoral Dissertations

More and more wind turbines have been grouped in the same location during the last decades to take the advantage of profitable wind resources and reduced maintenance cost. However wind turbines located in a wind farm are subject to a wind field that is substantially modified compared to the ambient wind field due to wake effects. The wake results in a reduced power production, increased load variation on the waked turbine, and reduced wake farm efficiency. Therefore the wake has long been an important concern for the wind farm installation, maintenance, and control. Thus a wake simulation tool is required. …