Browsing by Author "Bandhauer, Todd, committee member"
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Item Open Access Cationic-doping of mayenite electride: synthesis, processing, and effect on thermal stability(Colorado State University. Libraries, 2021) DeBoer, Brodderic, author; Ma, Kaka, advisor; Weinberger, Chris, committee member; Bailey, Travis, committee member; Bandhauer, Todd, committee memberMayenite electride is an electrically conductive ceramic developed from its parent phase, oxy-mayenite (12CaO•7Al2O3, commonly referred to as C12A7). C12A7 has a unique unit cell that consists of a positively charged [Ca24Al28O64]4+ framework containing twelve cages and two extra-framework O2- ions located inside two cages. The extra-framework O2- ions can be replaced with electrons when C12A7 is heated in a reducing environment, and those extra-framework electrons act like anions, forming the mayenite electride phase, denoted as C12A7:e- hereafter. The anionic electrons enable peculiar properties of C12A7:e- such as high electrical conductivity and low work function, making it a promising material for field emission devices, thermionic-cooling, and as a hallow cathode for electrical propulsion. Compared to other electride materials such as Ca2N, which barely sustain their electride properties even at ambient conditions, C12A7:e- has been reported to be stable up to 400 °C. This temperature is yet not high enough to enable its applications in the technologies mentioned above. Doped derivatives of C12A7:e- emerged in recent years to improve its electronic properties, mainly electron density and electrical conductivity. However, the effects of doping on the oxidation resistance and thermal stability of C12A7:e- remained unclear. Experimental effort on cationic doping of C12A7:e- was particularly lacking in the literature. Therefore, the goal of this study is two-fold: (1) to develop processing routes for successful cationic doping of C12A7:e-, and (2) to test if cationic doping can improve the thermal stability of C12A7:e-. Copper (Cu) and niobium (Nb) were selected as cationic dopants in this study to elucidate how cationic doping affects the thermal stability of the mayenite electride. First, effort was focused on developing synthesis and processing methods to effectively dope Cu and Nb into C12A7:e-. Three different methods were investigated, including diffusion doping; in conventional furnace or via spark plasma sintering (SPS), single-step in-situ formation via SPS, and a solid-state reaction (SSR) synthesis followed by reduction. The phase constitutions, lattice parameters, and microstructure of the various C12A7:e- samples fabricated via the aforementioned methods were characterized to verify if cationic doping was successfully achieved. Electrical conductivity was measured to verify the electride phase is sustained after the doping. Thermal analysis was performed to determine the thermal stability of the cation-doped C12A7:e- compared to undoped counterparts, including onset temperature and peak temperature of oxidation, oxidation rate, mass gain percentage resulted from oxidation, and any decomposition reaction. The key findings of this study include: (1) both Cu-doping and Nb-doping improved the thermal stability of the C12A7:e- by increasing the onset temperatures of oxidation; (2) Cu-doping was effectively and efficiently achieved via the novel SPS diffusion doping method. SPS diffusion doping of Cu at 800 °C gave rise to a minimum lattice parameter (a = 11.942 Å) of C12A7:e-, the lowest oxidation rate, and the smallest mass gain percent at 1050 °C; (3) Using oxy-mayenite and Nb2O5 as precursor for reaction sintering and in-situ reduction in SPS led to successful Nb-doping into the C12A7:e-. Despite the increased onset oxidation temperature resulted from Nb addition, pest oxidation occurred in Nb-doped C12A7:e- samples, leading to high oxidation rate, high total mass gain percentage, and fracture of the solid samples at temperature above 700 °C. In conclusion, Cu-doping was experimentally proved to be an effective approach to improve the thermal stability of C12A7:e- and meanwhile increase the electrical conductivity.Item Open Access Effect of endothermic reactions on the global extinction strain rate of large hydrocarbon fuels(Colorado State University. Libraries, 2018) Jadhav, Anish, author; Windom, Bret C., advisor; Bandhauer, Todd, committee member; Hussam, Mahmoud, committee memberWhen a hydrocarbon fuel is used as a coolant, the extreme environment can have a significant impact on the fuel composition. Heat exchange occurs through phase change, sensible heat extraction, and endothermic reactions experienced by the liquid fuel. From previous studies it has been demonstrated that the fuel composition changes significantly as well as the fuel properties as a result of the endothermic reactions. To investigate the effect of endothermic reactions on the fundamental flame behavior we have developed a counterflow flame burner that can measure the flame extinction strain rate of a thermally stressed fuel. The counterflow flame burner is coupled with a high-pressure reactor, capable of exposing the fuel to extreme conditions of 170 atm and 650 °C. Flame robustness is quantified by measuring the flame extinction strain rate. n-heptane is studied as a first attempt to understand the role of the endothermic reactions on the combustion and flame behavior of a liquid rocket propellant fuel. Modeling of the reactor and the counterflow flame is carried out using CHEMKIN. The flame extinction strain rate of the reacted n-heptane is compared with the unreacted n-heptane flame, thus allowing us to determine and extrapolate the role of endothermic reactions on the combustion behavior of jet and rocket fuels.Item Open Access Elucidating the performance and mechanisms of membrane separation: the use of artificial intelligence and a case study of produced water treatment(Colorado State University. Libraries, 2023) Jeong, Nohyeong, author; Tong, Tiezheng, advisor; Carlson, Kenneth, committee member; Sharvelle, Sybil, committee member; Bandhauer, Todd, committee memberPressure-driven membrane technologies such as nanofiltration (NF) and reverse osmosis (RO) have been widely used in water and wastewater treatment because of their effective removal of contaminants and exceptional energy efficiencies. The performance of NF and RO membranes is regulated by the well-documented permeability-selectivity tradeoff, in which an increase of membrane permeability typically occurs at the expense of membrane selectivity and vice versa. To break the upper bound of this tradeoff and further enhance the efficiency of NF and RO treatment, a mechanistic understanding of the solute transport across membranes with pore sizes at the nanometer- or angstrom-scale is required. Current theoretical models relating to solute transport across membranes are limited as the models require precise acquisition of multiple parameters. Machine learning (ML) models, a data-driven approach, have been applied to predict membrane performance and elucidate the membrane separation mechanisms. However, whether the ML models possess appropriate knowledge on membrane separation mechanisms has not yet been studied. Probing knowledge of ML models on membrane separation mechanisms can enhance the reliability of the ML model, which is of great importance to the implementation of ML models for decision-making processes, such as membrane design and selection. Moreover, contrary to the well-controlled experiments for studying the mechanisms or models associated with solute transport, where a limited number of defined solutes are present, membrane treatment has been used to treat wastewater containing diverse organic and inorganic compounds. Thus, along with fundamental research on predictive ML models for membrane performance, investigating the performance of membranes for treating wastewater with complex compositions is also valuable to provide knowledge of solute transport across membranes in practical applications. In this thesis, I present both a fundamental study of probing solute transport across NF and RO membranes using ML models and an applied study that explores membrane treatment of unconventional oil and gas (UOG) produced water. First, the reliability of the ML model as a tool to predict membrane performance was investigated. Specifically, the influence of data leakage on the ML model performance, as well as the solution to prevent this issue, was explored to evaluate the prediction capability of the ML model objectively. I discovered that data leakage can lead to falsely high prediction accuracy of the ML model, and appropriate data splitting for the training, validation, and testing dataset is necessary to avoid data leakage. Second, the underlying knowledge of ML models for organic and inorganic solute transport across polyamide membranes was investigated by using a model interpretation method (i.e., Shapley additive explanation, SHAP). I not only tested whether ML models are able to possess adequate knowledge on solute transport, but also utilized the SHAP method to reveal solute transport mechanisms that are typically obtained using tedious, well-controlled experiments. For the ML model applied to predicting the rejection of organic constituents by NF and RO membranes, I found that the ML model had proper knowledge of size exclusion, but its understanding of electrostatic interaction and adsorption remains rudimentary. By using ML to predict the rejection of inorganic constituents, I elucidated that explainable artificial intelligence (XAI) can capture the major governing mechanisms of ion/salt transport across polyamide membranes (i.e., size exclusion and electrostatic interaction), which have different importance for the transport of single salt, cation, anion transport in mixture salt solution. Lastly, the performance of RO/NF membranes for the treatment of UOG produced water was explored as a case study, which comprehensively investigated the chemical composition and toxicity level of the treated water. NF permeates, which still had high salinities and high boron concentrations, were found to be inappropriate for irrigation and livestock drinking water, while RO membranes effectively removed most pollutants and met most water quality standards for beneficial reuse (i.e., irrigation and livestock drinking water). However, the chloride concentrations and sodium adsorption ratio (SAR) values of RO permeates were still higher than the recommended thresholds for irrigation. Also, surfactants with molecular weights higher than the molecular weight cut-off of RO/NF membranes were able to traverse through the membrane, indicating that NF and RO are not complete barriers against organic contaminants. The toxicity test results of NF and RO permeates demonstrated that NF permeates were still toxic to Daphnia, while RO permeates showed less toxicity than NF permeates or no toxicity. The toxicity level of NF and RO permeates showed a correlation with salinity in the permeates, which might be the main driver of the toxicity. I envision that my thesis provides a framework to evaluate the knowledge and reliability of ML model predictions, while presenting a comprehensive investigation on membrane performance and the potential risks associated with membrane treatment of UOG produced water for beneficial reuse. The knowledge gained in this thesis improves our capability for rational membrane material design and selection, which has the potential to lead to more efficient NF and RO technologies for sustainable water and wastewater treatment.Item Open Access Evaluating the sustainability performance of U.S. biofuel in 2017 with an integrated techno-economic and life cycle assessment framework(Colorado State University. Libraries, 2022) Smith, Jack Philip, author; Quinn, Jason, advisor; Simske, Steve, committee member; Bandhauer, Todd, committee memberThe United States produced more than 66.2 million m3 of biofuel for the transportation industry in 2017. Most of that volume (60.6 million m3) was produced in the form of corn ethanol and the majority of the remaining volume (4.2 million m3) was produced in the form of soybean-based biodiesel. Numerous works have assessed the economic and environmental performance of these two biofuel types. However, no work exists which evaluates both the economic and environmental outcomes of these two fuels with adequate geospatial resolution and national scope. In this study, a model framework is constructed that performs concurrent Techno-Economic Analysis (TEA) and Life Cycle Assessment (LCA) using high-resolution input datasets to provide a granular estimation of sustainability performance of every county in the United States. This work presents results that include sector wide estimates and highlights the importance of capturing geographic heterogeneity. Results show a total emission volume of 55 MMT CO2-eq produced by the 2017 US biofuel industry, with 7 MMT CO2-eq of that amount resulting from Land Use Change effects. Nationwide weighted mean Global Warming Potential results are 38 gCO2-eq/MJ and 37 gCO2-eq/MJ for corn ethanol and soybean biodiesel, respectively, when Land Use Change emissions are included. Minimum Fuel Selling Price results are $0.0208/MJ ($2.52/GGE) and $0.0225/MJ ($2.72/GGE) for corn ethanol and soybean biodiesel, respectively. A Zero-Emissions Cost (ZEC) metric is applied, which combines the economic and environmental performance of a fuel into its analysis. Specifically, the cost associated with offsetting all fuel production and use emissions through Direct Air Capture (DAC) is added to the standard price of the fuel. Mean ZEC results are $0.037/MJ ($4.53/GGE) for corn ethanol and $0.039/MJ ($4.69/GGE) for soybean biodiesel which are lower than the ZEC of conventional gasoline of $0.062/MJ ($7.45/GGE). Finally, the cost of Direct Air Capture which results in ZEC parity between each biofuel and its petroleum-based counterpart is assessed to be $49/MT CO2-eq.Item Open Access Evaluation of ethanol substitution in a compression ignition engine(Colorado State University. Libraries, 2017) Van Roekel, Chris, author; Olsen, Daniel B., advisor; Bandhauer, Todd, committee member; Reardon, Ken, committee memberHeavy duty compression ignition engines rely on advanced emission control strategies to mitigate regulated emissions in compliance with requirements set by the Environmental Protection Agency. These strategies add significant cost and complexity to engine design. Previous work identified that a diesel-ethanol dual fuel combustion technique may be able to reduce diesel fuel consumption and supplement current emission control methods. The substitution of diesel fuel with a renewable, U.S. based fuel such as corn ethanol would also improve US energy security. A review of diesel-ethanol dual fuel combustion identified five possible methods of diesel-ethanol dual fuel combustion. They were ethanol-diesel emulsions, ethanol-diesel-additive blending, twin direct injection of ethanol and diesel, ethanol fumigation of intake air with standard diesel fuel injection, and full substitution of diesel with ethanol. Analysis of ethanol-diesel emulsions and ethanol-diesel-additive blending concluded that only low volumes of ethanol (<10%) could be blended in diesel fuel before the two fuels were immiscible. However, analysis using ternary phase diagrams showed that additives such as B100 biodiesel could be used to extend the substitution limit significantly such that at 25°C mixtures of 80% 200 proof ethanol, 10% B100 biodiesel, and 10% off-road diesel were visibly miscible. Miscible mixtures containing high volumes of ethanol underwent further analysis, which showed that these fuels were not suitable drop in replacements for diesel fuel due to poor cold flow properties. Based on fuel blending analysis and previously published literature ethanol fumigation of intake air was selected for an on-engine demonstration using a Cummins 6.7L QSB Tier 4 Final engine. Three ethanol based fuels were selected for this dual fuel combustion work: 200 proof ethanol, 190 proof ethanol, and a blend of 15% E0 gasoline and 85% 200 proof ethanol. Pre and post aftertreatment emission data and high speed combustion data were collected while operating the engine at ISO 8178 test points C1-7, C1-3, and C2-4. The maximum diesel substitution at each test point was similar among the three test fuels. and at moderate to high engine loads diesel substitution was limited to 25% and 39%, respectively due to engine knock . At low engine loads substitution was limited to 25% by exhaust emission requirements. Premixed ethanol combustion increased brake specific efficiency at moderate and high engine loads by 3% and 3.2%, respectively, but reduced efficiency at low engine loads by 1.4%. Finally, although the complete ISO 8178 test map was not completed the Tier 4 Final after treatment system was able to reduce ethanol premixed combustion emissions to at or below the diesel baseline emissions at nearly every test point.Item Open Access Investigation of indirect (secondary loop) refrigeration systems in commercial food service buildings(Colorado State University. Libraries, 2016) Anderson, Chris, author; Bradley, Thomas, advisor; Bandhauer, Todd, committee member; Cross, Jennifer, committee memberIndirect (secondary loop) refrigeration systems have recently received increased attention due to their well-known effects on reducing refrigerant losses, particularly in commercial food sales buildings. Although their effects on operating costs, particularly in terms of energy efficiency, are less definitive, there is potential that indirect refrigeration systems might offer significant energy efficiency improvements in food service buildings. The aim of this thesis was to determine the feasibility of an indirect (secondary loop) refrigeration system for a food service building, specifically a Starbucks coffee shop. Six commercial refrigeration units were installed in a laboratory setting. The units were first tested with their air-cooled condensers to establish a baseline. Then, each unit was retrofitted with a water-cooled condenser, and all six water-cooled condensers were connected in series to form a secondary loop system and tested again. The results of this laboratory testing were used to create a predictive model to estimate the payback period for installing the system in different Starbucks coffee shop locations around the country. The model predicted the major requirements for a two year payback period to be high energy costs (>$0.22/kWh), a warm to hot climate (AC runtime > 20 hours per day), and a sufficiently large store (containing multiple large food cases or ice machines).Item Open Access Multi-objective optimization of the economic feasibility for mobile on-site oil and gas produced water treatment and reuse(Colorado State University. Libraries, 2021) Cole, Garrett M., author; Quinn, Jason C., advisor; Bandhauer, Todd, committee member; Tong, Tiezheng, committee memberDevelopment of unconventional oil and gas wells has resulted in large volumes of produced and flowback water that require careful handling to minimize environmental and human health risks due to high concentrations of salt and other contaminants. Common practice is to truck the wastewater from well sites to Environmental Protection Agency (EPA) Class II underground injection control (UIC) wells. The cost of transportation often accounts for much of the handling costs. As an alternative, on-site desalination followed by surface water discharge of the water product for downstream reuse has the potential to lower handling cost by reducing the volume of water requiring transport to UIC wells while additionally alleviating strain on water supplies in arid regions. In contrast to centralized FP water treatment, capacity factor for on-site desalination is highly dependent on management strategy and shale bed characteristics. Therefore, this work studies how accounting for capacity factor might determine the attributes of an optimal management strategy and the cost of produced water treatment. The volume of wastewater to be treated by desalination, the method for desalination unit deployment, desalination unit capacity, and desalination technology (membrane distillation, mechanical vapor compression, and reverse osmosis) are decision variables defining a management strategy. This work explores different produced and flowback water management strategies in Weld County, Colorado, to determine a set of Pareto optimal produced water management strategies from a techno-economic and environmental perspective optimizing economics and water reclamation. Results show that as the desired level of water reclamation increases there is an increase in the marginal cost of water reclamation. Ultimately, the optimal volume of wastewater to be reused was determined to be between 50% and 88% of the total produced costing between $5.82 and $9.79 per m3, respectively, in Weld County, CO where business as usual operation (injection) cost is $7.68 per m3. Generally, optimal management strategies, when accounting for capacity factors, utilized packaged desalination units of 100 m3/d capacity with deployment location reevaluated on a 1-6 month planning horizon.Item Open Access Performance of steel structures subjected to fire following earthquake(Colorado State University. Libraries, 2016) Memari, Mehrdad, author; Mehmoud, Hussam, advisor; Ellingwood, Bruce, committee member; van de Lindt, John, committee member; Heyliger, Paul, committee member; Bandhauer, Todd, committee memberFires following earthquakes are considered sequential hazards that may occur in metropolitans with moderate-to-highly seismicity. The potential for fire ignition is elevated by various factors including damage to active and passive fire protections following a strong ground motion. In addition, damage imposed by an earthquake to transportation networks, water supply, and communication systems, could hinder the response of fire departments to the post-earthquake fire events. In addition, the simultaneous ignitions – caused by strong earthquake – might turn to mass conflagrations in the shaken area, which could lead to catastrophic scenarios including structural collapse, hazardous materials release, loss of life, and the inability to provide the emergency medical need. This has been demonstrated through various historical events including the fires following the 1906 San Francisco earthquake and the 1995 Kobe earthquakes, among others, making fire following earthquake the most dominant contributor to earthquake-induced losses in properties and lives in the United States and Japan in the last century. From a design perspective, current performance-based earthquake design philosophy allows certain degrees of damage in the structural and non-structural members of steel-framed buildings during the earthquake. The cumulative structural damages, caused by the earthquake, can reduce the load-bearing capacity of structural members in a typical steel building. In addition, potential damage to active and passive fire protections following an earthquake leaves the steel material exposed to elevated temperatures in the case of post-earthquake fire events. The combined damage to steel members and components following an earthquake combined with damage to fire protection systems can increase the vulnerability of steel buildings to withstand fire following seismic events. Therefore, there is a pressing need to quantify the performance of steel structures under fire following earthquake in moderate-to-high seismic regions. The aim of the study is to assess the performance of steel structural members and systems under the cascading hazards of earthquake and fire. The research commences with evaluation of the stability of hot-rolled W-shape steel columns subjected to the earthquake-induced lateral deformations followed by fire loads. Based on the stability analyses, equations are proposed to predict the elastic and inelastic buckling stresses in steel columns exposed to the fire following earthquake, considering a wide variety of variables. The performance of three steel moment-resisting frames – with 3, 9, and 20 stories – with reduced beam section connections is assessed under multi-story fires following a suite of earthquake records. The response of structural components – beams, columns, and critical connection details – is investigated to evaluate the demand and system-level instability under fire following earthquake. Next, a performance-based framework is established for probabilistic assessment of steel structural members and systems under the combined events of earthquake and fire. A stochastic model of the effective random variables is utilized for conducting the probabilistic performance-based analysis. This framework allows structural engineers to generate fragility of steel columns and frames under multiple-hazard of earthquake and fire. The results demonstrate that instability can be a major concern in steel structures, both on the member and system levels, under the sequential events and highlights the need to develop provisions for the design of steel structures subjected to fire following earthquake. Furthermore, a suite of recommendations is proposed for future studies based on findings in this dissertation.Item Open Access Systematic analysis of beneficial reuse in unconventional oil and gas wastewater management(Colorado State University. Libraries, 2021) Robbins, Cristian A., author; Tong, Tiezheng, advisor; Carlson, Kenneth, advisor; Sharvelle, Sybil, committee member; Bandhauer, Todd, committee memberWastewater management within the unconventional oil and gas (UOG) sector has continued to grow in importance in correlation with the rising water footprint of hydraulic fracturing (HF). The predominant UOG wastewater management method in the U.S. is to dispose of the wastewater deep underground in geologically stable formations by deep-well injection (DWI). However, this method has been plagued with concerns such as induced seismicity and decreasing capacity for DWI in various UOG regions. Further, when the wastewater is disposed of via DWI this potential resource is no longer available for beneficial purposes. An alternative method to DWI is UOG wastewater treatment for beneficial reuse which repurposes the treated wastewater for end uses such as surface discharge. The main objective of this dissertation is to analyze key aspects of UOG wastewater management to include topics within technology, logistics, regulations, and economics in order to further facilitate increased wastewater treatment and beneficial reuse. At the core of UOG wastewater treatment and beneficial reuse is an advanced treatment technology that can effectively treat hypersaline and complex UOG wastewater. For my work, I focused on membrane distillation (MD), a hybrid thermal-membrane desalination process well-suited to treat UOG wastewater. An advantage of using MD is its inherent ability to use low grade waste heat as an energy source to power treatment. I investigated the availability and sufficiency of waste heat at the well-pad to power MD for on-site UOG wastewater treatment in Weld County, Colorado. Additionally, I also investigate the availability and sufficiency of natural gas at the well-pad to power MD. The analysis showed that well-pad waste heat is insufficient while natural gas is sufficient for long term on-site MD treatment. Next, the impact of logistics, specifically transportation distance and costs, was researched for DWI and centralized wastewater treatment (CWT) powered by natural gas compressor station (NGCS) waste heat. Unlike on-site treatment, wastewater needs to be transported for DWI or CWT and thus incurs a transportation cost. Using ArcGIS software, transportation distances and associated costs were analyzed for Weld County, Colorado at various scales. At the county scale, DWI was economically favored based on transportation, however, when the scale of operation was reduced for certain areas (i.e., county to local) the economic advantage shifted towards CWT. Additionally, NGCS waste heat for Weld County was quantified and the MD treatment demand was correlated to MD treatment capacity provided by NGCS waste heat for CWT. This analysis emphasized the importance of matching treatment demand with capacity provided by waste heat. Further, MD treatment of UOG wastewater has been constrained by surfactant-induced membrane pore wetting. Surfactants, commonly found in HF fluid, reduce the surface tension of membranes inducing wetting. We investigated two mitigation strategies, pretreatment via coagulation-adsorption and fabrication of omniphobic membranes. UOG wastewater sourced from the Denver-Julesburg Basin that induced exceptional wetting of a hydrophobic polyvinylidene fluoride membrane during MD treatment was used. Both strategies proved effective at mitigating surfactant-induced wetting, however, flux decline with the use of omniphobic membrane was unacceptable due to the effects of fouling thus hindering its viability. To better understand the surfactant composition in the UOG wastewater, ultrahigh pressure liquid chromatography (UHPLC) coupled with quadrupole time-of-flight mass spectrometry (QToF/MS) was implemented to identify surfactants in the UOG wastewater and qualify the effect of pretreatment in reducing surfactants. In the UOG wastewater, 192 surfactants were identified with 91 being reduced by full pretreatment. Finally, an in-depth perspective on the motivations and barriers to increased future treatment and beneficial reuse of UOG wastewater was provided. This analysis moved beyond technology, which receives the majority of research interest, to explore and better understand other non-treatment aspects. Four major barriers to beneficial reuse were identified which are technology, economics, regulations, and social. These barriers were clearly elucidated providing insight into ways to overcome them to facilitate increased beneficial reuse. A systems-level approach requiring broad collaborations across multiple disciplines pertaining to technology, policy, legislation, economics, and social science to shift UOG wastewater management towards treatment and beneficial reuse was proposed.Item Open Access Techno-economic analysis of advanced small modular nuclear reactors(Colorado State University. Libraries, 2022) Asuega-Souza, Anthony, author; Quinn, Jason, advisor; Simske, Steve, committee member; Bandhauer, Todd, committee memberSmall modular nuclear reactors (SMRs) represent a robust opportunity to develop low-carbon and reliable power with the potential to meet cost parity with conventional power systems. This study presents a detailed, bottom-up economic evaluation of a 12x77 MWe (924 MWe total) light-water SMR (LW-SMR) plant, a 4x262 MWe (1,048 MWe) gas-cooled SMR (GC-SMR) plant, and a 5x200 MWe (1,000 MWe total) molten salt SMR (MS-SMR) plant. Cost estimates are derived from equipment costs, labor hours, material inputs, and process-engineering models. The advanced SMRs are compared to natural gas combined cycle plants and a conventional large reactor. Overnight capital cost (OCC) and levelized cost of energy (LCOE) estimates are developed. The OCC of the LW-SMR, GC-SMR, and MS-SMR are found to be $4,844/kW, $4,355/kW, and $3,985/kW respectively. The LCOE of the LW-SMR, GC-SMR, and MS-SMR are found to be $89.6/MWh, $81.5/MWh, and $80.6/MWh respectively. A Monte Carlo analysis is performed, for which the OCC and construction time of the LW-SMR is found to have a lower mean and standard deviation than a conventional large reactor. The LW-SMR OCC is found to have a mean of $5,233/kW with a standard deviation of $658/kW and a 90% probability of remaining between $4,254/kW and $6,399/kW, while the construction duration is found to have a mean of 4.5 years with a standard deviation of 0.8 years and a 90% probability of remaining between 3.4 and 6.0 years. The economic impact of economies of scale, simplification, modularization, and construction time are evaluated for SMRs. Policy implications for direct capital subsidies and a carbon tax on natural gas emissions are additionally explored.Item Embargo Tuning antimony anodes through electrodeposition to inform on the reaction and degradation mechanisms in sodium-ion batteries(Colorado State University. Libraries, 2023) Nieto, Kelly, author; Prieto, Amy L., advisor; Sambur, Justin, committee member; Krummel, Amber, committee member; Bandhauer, Todd, committee memberElectrification of portable devices, transportation, and large grid-level storage necessitate a portfolio of energy storage devices tailored to specific applications. Sodium-ion batteries are a naturally abundant alternative to lithium, but high performing anodes must be developed in order to reach widespread commercialization. Alloy-based anodes such as antimony (Sb) are attractive targets for their high theoretical capacities. However, the electrochemical performance of Sb is poor, and the reaction mechanism is poorly understood. Herein, antimony-based anodes for sodium-ion batteries are explored to elucidate sodiation pathways and investigate the role of electrode fabrication, electrolyte composition, and architecture on the reaction and degradation mechanism. Chapter I describes our research methodology and consists of our synthetic method of electrodeposition, materials characterization, battery assembly, and electrochemical characterization. Through this process, we can develop a better understanding of the electrochemical performance of alloy-based anode materials. The tunability of electrodeposition as a synthetic technique for the fabrication of Sb-based anodes is exploited in Chapter II. The effects of solution additives in the electrodeposition of Sb anodes are investigated and provide insight into how the morphology and crystallinity of the deposited anodes can be tuned. It was revealed that CTAB and SPS could significantly tune the electrodeposition of Sb films by altering the deposition by causing structural changes that either improved cycle life or rate capabilities. In Chapter III, electrodeposited and slurry cast Sb anodes were compared through differential capacity analysis, and it was demonstrated that electrode fabrication can significantly impact the sodiation/desodiation reaction pathway. Additionally, electrodeposited Sb anodes provided valuable insight into the mechanism without having to deconvolute the influences of binders and additives necessary in slurry casting. Chapter IV describes preliminary studies on how electrolyte composition can influence sodiation/desodiation reactions during Sb anode cycling. Traditional battery electrolytes are composed of carbonate species and salts, which are reduced onto the anode surface to form the solid electrolyte interphase (SEI). Due to the inherent volume expansion of Sb anodes when sodiated/desodiated, the SEI is hypothesized to continuously form and affect the cyclability of these anodes. In this investigation, we have found that electrolyte composition can influence the cycle life and sodiation/desodiation pathway, and we describe additional studies to probe how the SEI could hinder sodium ion transport. Chapter V builds upon Chapter II and explores how electrodeposition can be employed to develop three-dimensional (3D) electrodes to enhance the energy and power density of Sb-based anodes. Although we show that experimental parameters can be tuned to obtain uniform coverage, significant challenges in achieving conformal coverage of the current collector while maintaining high active material loading remain. The final chapter, Chapter VI, concludes the dissertation by describing further directions required to deepen the understanding of the degradation mechanism for Sb. We have begun to develop a 3D-printed optical, electrochemical cell that can couple operando optical studies with electrochemical studies to understand how electrode composition, structure, and electrolyte composition affect mechanical stability and ionic/electronic diffusivity in these electrodes. Understanding these fundamental processes and developing tools and characterization techniques to study alloy-based anode materials will lay the foundation for creating earth-abundant energy storage systems with high energy densities and long cycle life.Item Open Access Two-stroke lean burn natural gas engine oxidation catalyst degradation and regeneration via washing(Colorado State University. Libraries, 2018) Hackleman, Bryan, author; Olsen, Daniel, advisor; Bandhauer, Todd, committee member; Carter, Ellison, committee memberLean burn two stroke engines are used extensively for stationary applications including power generation, cogeneration and compression. Natural gas is abundant, relatively inexpensive, and combustion produces less CO2, particulate matter, and SOx than gasoline and diesel. However, the Natural gas industry continues to be impacted by increasingly stricter emissions limits. One approach to comply with these emission limits is outfitting engines with an oxidation catalyst. Oxidation catalysts are proven to reduce hydrocarbon and carbon monoxide emissions, but surface poisoning due to lube oil carry over diminishes performance. Zinc, phosphorus, and sulfur found in oil additives poison the catalysts surface, and readily leach into an acidic environment. Two commercial catalyst modules were aged at a field site on a slipstream of a GMVH-12 engine until they no longer met the National Emissions Standards for Hazardous Air Pollutants (NESHAP) formaldehyde limit. The oxidation catalyst modules underwent a washing process of immersion into caustic soda, neutral water, and acetic acid baths. The surface chemistry of samples was analyzed on a scanning electron microscope (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Catalytic performance testing was carried out by a slipstream of a laboratory Cummins QSK-19G engine, five gas analyzer and Fourier transform infrared spectroscopy (FTIR). The washing process removed the majority of surface poisons and improved the catalytic performance. The modules were then aged again until non-compliance with emissions limits occurred. The modules were periodically tested for poison accumulation and catalytic performance to determine the rate of degradation post-washing. These results were used to compare with that of a new catalyst to estimate the increase in lifespan from washing. The results of the experiments reported here should encourage the use of washing as a low cost partial regeneration procedure for oxidation catalysts.Item Open Access Understanding the solid electrolyte interface (SEI) on alloying anodes: development of a methodology for SEI sample preparation and x-ray photoelectron spectroscopy characterization and studies of the SEI on electrodeposited thin film intermetallic anodes for Li-ion batteries(Colorado State University. Libraries, 2020) Kraynak, Leslie A., author; Prieto, Amy L., advisor; Shores, Matthew, committee member; Strauss, Steven, committee member; Bandhauer, Todd, committee memberThe solid electrolyte interface (SEI) is an important component of Li-ion rechargeable batteries that forms due to the potential stability limits of the organic electrolyte falling within the large operating potential window of the battery. It plays a crucial role in battery performance by passivating the electrode surface; it also affects the safety, Li-ion consumption/inventory, and Li-ion transport rates of the battery. Despite decades of study, there is still much that is unknown about the SEI, especially how to intentionally modify the composition and properties of the SEI in order to obtain better performance as measured by metrics that include reversible capacity and cycle lifetime. The gaps in understanding of the SEI are even more pronounced for alloying anode materials, and the mechanical and chemical instability of electrode surfaces and the SEI formed from conventional secondary battery electrolytes is one of the bottlenecks in the development of next generation battery technologies. The first chapter of this dissertation is an overview of studies from the past two decades concerning the SEI formed on metallic alloying anodes, examining SEI formation, the evolution of the SEI over long term cycling, and improvements to the SEI through the use of additives and novel electrolytes. Compared to the body of literature on the SEI on other anode materials such as graphite, Li metal, and silicon, there has been relatively little published about the SEI on metallic alloying anodes such as tin, antimony, and intermetallics, especially considering the scope of these types of anode materials. However, a comparison of the existing literature concerning the SEI on alloying anodes reveals interesting similarities and difference between the SEI formation and evolution on metallic alloying anodes and highlights some critical gaps in knowledge for the field. The second chapter concerns the development of a methodology to study the SEI formed on alloying anodes, and in particular binder- and additive-free thin film electrodes. The formation, composition, and properties of the SEI are dependent on a number of experimental variables, which makes it difficult understand the factors that affect SEI performance and limits progress towards the goal of more controlled or intentional SEI formation for better battery performance. One of the first steps towards this goal is to be able to make and characterize SEI samples in a reproducible manner. This chapter outlines some of the important considerations for SEI sample preparation that are not widely discussed in the battery community in addition to some of the important considerations for using X-ray photoelectron spectroscopy to characterize the SEI. The third and fourth chapters are about using the methodology described in Chapter 2 to characterize the SEI formed on intermetallic thin film anodes. The third chapter examines the role that vinylene carbonate, a conventional SEI-improving electrolyte additive, plays in passivating the surface and extending the cycle lifetime of Cu2Sb electrodes. The fourth chapter is concerned with understanding what role the SEI plays in the cycle performance of pure phase SnSb thin film electrodes. Studying changes in the SEI on SnSb over different stages of cycling can help elucidate whether the SEI plays a role in the capacity retention and long cycle lifetime of SnSb and whether it ultimately contributes to the failure of the electrode.