Theses and Dissertations from UMD
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Item THE ROLES AND IMPLICATIONS OF AGRICULTURAL AND ENERGY RESOURCES TRADE IN A CLIMATE CHANGE-MITIGATING WORLD(2024) Yarlagadda, Brinda; Hultman, Nathan E.; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Global dependence on agricultural and energy resources trade has grown significantly in the past several decades. In the coming decades, the roles and implications of international trade of various commodities will change, influenced by and important for achieving climate mitigation goals. As globalization increases, new energy technologies emerge, and new climate-oriented trade policies are enacted, there is a need to understand the resulting implications (opportunities and vulnerabilities) on exporters and importers. I present three essays that use the Global Change Analysis Model (GCAM) to evaluate future, inter-regional trade dynamics in a climate-mitigating world. Essay 1 focuses on Latin America and the Caribbean (LAC), a key agricultural exporting region. I show that agricultural market integration (i.e., the reduction of trade barriers) and climate mitigation policies could increase agricultural production and trade opportunities for many LAC economies (particularly in southern South America). Total net export revenue across LAC could reach $110-$270 billion annually by 2050. However, these opportunities could also pose significant economic and environmental trade-offs, including emissions reduction challenges, potential loss of livestock production, increased consumer expenditures, and deforestation and water scarcity pressures. Essay 2 explores the role of liquefied natural gas (LNG) trade as a rapidly emerging technology compared to pipeline natural gas. I analyze how advances in LNG technology, limitations on trade, and climate mitigation policies could affect global and regional vulnerabilities in energy supply. Globally, new additions in LNG and pipeline export infrastructure, range from 330-1330 and 130-440 million tons per annum (MTPA), respectively, by 2050 across scenarios, with the lower end of this range achieved through a transition to a net-zero energy system and limited trade. The results also highlight diverging risks for different gas exporters. For example, Russia, which produces gas largely for pipeline exports, may face larger underutilization due to advances in LNG technology and geopolitical shifts than regions oriented towards domestic and LNG markets, such as the USA and Middle East. Essay 3 evaluates whether import-restrictions on deforestation linked oil crops (i.e., oil palm and soybean) can be effective in reducing deforestation and land use change (LUC) emissions as well as their broader economic implications. I find that current EU restrictions will likely have minimal impact. If extended beyond the EU, import restrictions could drive reductions in cumulative LUC emissions in key oil-crop exporting regions— up to 0.9% in Indonesia, 1.5% in the rest of Southeast Asia, 3.8% in Argentina and 6.7% in Brazil, relative to a scenario with no import restrictions. However, these key exporters could also face losses ranging $4.1-$61 billion in cumulative agricultural production revenue by 2050.Item THE WATER-ENERGY-LAND NEXUS OF BIOENERGY PRODUCTION IN BRAZIL(2020) Munoz Castillo, Raul; Sun, Laixiang; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biofuels play a critical role in the Paris Agreement to help achieve climate change mitigation targets. However, a significant increase in production of biofuels might potentially be realized at the expense of overusing natural resources, particularly land and water. Understanding the tradeoffs between the development of biofuels and its impacts on land and water is a critical issue for sustainable development. This energy-water-land nexus might be particularly important for Brazil, given its position as top exporter and second top producer of bioenergy. Furthermore, Brazil itself has set up its own Intended Nationally Determined Contribution agenda with a significant growth of biofuel production by 2030. The aim of this research is to quantitatively characterize the nexus of biofuels production with the overall appropriation of land and water resources at the subnational level in Brazil by answering the following questions: (i) How will the implementation of international climate mitigation commitments adopted by Brazil impact water and land use and therefore water and land stress in Brazil?; (ii) what will be the geographical distribution of such impacts at subnational level? ; (iii) will increase competition among economic sectors aggravate such impacts?; and (iv) how will other socio-economic and physical drivers of change affect those impacts combined with INDC related policies implementation?. To answer these questions, I developed a set of socio-economic, policy and climate scenarios through an environmentally extended input-output approach that represents socio-economic activities in the 27 Brazilian states, allowing comparison of the resulting water and land demands among main competitive users under different scenarios. I also introduced the use of water scarcity and land stress as environmental impact indicators. My study confirms that to properly understand the impacts of biofuel production in Brazil on land and water and its “nexus”, the consideration of resource scarcity and its spatial variability are key to ensure sustainable planning of biofuel production. Moreover, I found that the mitigation policies committed by Brazil and its role as top global provider of biofuel will take a significant toll in both water and land consumption in the country, leading to increasing competition among food production, energy generation and human consumption, especially in the most vulnerable and already environmentally stressed states.Item Essays in Personal Transportation Demand and Consumer Finance(2016) Evans, Jaclyn; Williams, Roberton C; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation is composed of three essays covering two areas of interest. The first topic is personal transportation demand with a focus on price and fuel efficiency elasticities of mileage demand, challenging assumptions common in the rebound effect literature. The second topic is consumer finance with a focus on small loans. The first chapter creates separate variables for fuel prices during periods of increasing and decreasing prices as well as an observed fuel economy measure to empirically test the equivalence of these elasticities. Using a panel from Germany from 1997 to 2009 I find a fuel economy elasticity of mileage of 53.3%, which is significantly different from the gas price elasticity of mileage during periods of decreasing gas prices, 4.8%. I reject the null hypothesis or price symmetry, with the elasticity of mileage during period of increasing gas prices ranging from 26.2% and 28.9%. The second chapter explores the potential for the rebound effect to vary with income. Panel data from U.S. households from 1997 to 2003 is used to estimate the rebound effect in a median regression. The estimated rebound effect independent of income ranges from 17.8% to 23.6%. An interaction of income and fuel economy is negative and significant, indicating that the rebound effect may be much higher for low income individuals and decreases with income; the rebound effect for low income households ranged from 80.3% to 105.0%, indicating that such households may increase gasoline consumption given an improvement in fuel economy. The final chapter documents the costs of credit instruments found in major mail order catalogs throughout the 20th century. This study constructs a new dataset and finds that the cost of credit increased and became stickier as mail order retailers switched from an installment-style closed-end loan to a revolving-style credit card. This study argues that revolving credit's ability to decrease salience of credit costs in the price of goods is the best explanation for rate stickiness in the mail order industry as well as for the preference of revolving credit among retailers.Item SOVLENT REACTIVITY AND INTERFACE EVOLUTION AT MODEL ELECTRODES FOR ENERGY APPLICATIONS(2016) Song, Wentao; Reutt-Robey, Janice E; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Li-ion rechargeable battery (LIB) is widely used as an energy storage device, but has significant limitations in battery cycle life and safety. During initial charging, decomposition of the ethylene carbonate (EC)-based electrolytes of the LIB leads to the formation of a passivating layer on the anode known as the solid electrolyte interphase (SEI). The formation of an SEI has great impact on the cycle life and safety of LIB, yet mechanistic aspects of SEI formation are not fully understood. In this dissertation, two surface science model systems have been created under ultra-high vacuum (UHV) to probe the very initial stage of SEI formation at the model carbon anode surfaces of LIB. The first model system, Model System I, is an lithium-carbonate electrolyte/graphite C(0001) system. I have developed a temperature programmed desorption/temperature programmed reaction spectroscopy (TPD/TPRS) instrument as part of my dissertation to study Model System I in quantitative detail. The binding strengths and film growth mechanisms of key electrolyte molecules on model carbon anode surfaces with varying extents of lithiation were measured by TPD. TPRS was further used to track the gases evolved from different reduction products in the early-stage SEI formation. The branching ratio of multiple reaction pathways was quantified for the first time and determined to be 70.% organolithium products vs. 30% inorganic lithium product. The obtained branching ratio provides important information on the distribution of lithium salts that form at the very onset of SEI formation. One of the key reduction products formed from EC in early-stage SEI formation is lithium ethylene dicarbonate (LEDC). Despite intensive studies, the LEDC structure in either the bulk or thin-film (SEI) form is unknown. To enable structural study, pure LEDC was synthesized and subject to synchrotron X-ray diffraction measurements (bulk material) and STM measurements (deposited films). To enable studies of LEDC thin films, Model System II, a lithium ethylene dicarbonate (LEDC)-dimethylformamide (DMF)/Ag(111) system was created by a solution microaerosol deposition technique. Produced films were then imaged by ultra-high vacuum scanning tunneling microscopy (UHV-STM). As a control, the dimethylformamide (DMF)-Ag(111) system was first prepared and its complex 2D phase behavior was mapped out as a function of coverage. The evolution of three distinct monolayer phases of DMF was observed with increasing surface pressure — a 2D gas phase, an ordered DMF phase, and an ordered Ag(DMF)2 complex phase. The addition of LEDC to this mixture, seeded the nucleation of the ordered DMF islands at lower surface pressures (DMF coverages), and was interpreted through nucleation theory. A structural model of the nucleation seed was proposed, and the implication of ionic SEI products, such as LEDC, in early-stage SEI formation was discussed.Item Effects of Information and Time of Use Pricing on Irish Electricity Demand and Supply(2016) Pon, Shirley; Alberini, Anna; Agricultural and Resource Economics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation I quantify residential behavior response to interventions designed to reduce electricity demand at different periods of the day. In the first chapter, I examine the effect of information provision coupled with bimonthly billing, monthly billing, and in-home displays, as well as a time-of-use (TOU) pricing scheme to measure consumption over each month of the Irish Consumer Behavior Trial. I find that time-of-use pricing with real time usage information reduces electricity usage up to 8.7 percent during peak times at the start of the trial but the effect decays over the first three months and after three months the in-home display group is indistinguishable from the monthly treatment group. Monthly and bi-monthly billing treatments are not found to be statistically different from another. These findings suggest that increasing billing reports to the monthly level may be more cost effective for electricity generators who wish to decrease expenses and consumption, rather than providing in-home displays. In the following chapter, I examine the response of residential households after exposure to time of use tariffs at different hours of the day. I find that these treatments reduce electricity consumption during peak hours by almost four percent, significantly lowering demand. Within the model, I find evidence of overall conservation in electricity used. In addition, weekday peak reductions appear to carry over to the weekend when peak pricing is not present, suggesting changes in consumer habit. The final chapter of my dissertation imposes a system wide time of use plan to analyze the potential reduction in carbon emissions from load shifting based on the Ireland and Northern Single Electricity Market. I find that CO2 emissions savings are highest during the winter months when load demand is highest and dirtier power plants are scheduled to meet peak demand. TOU pricing allows for shifting in usage from peak usage to off peak usage and this shift in load can be met with cleaner and cheaper generated electricity from imports, high efficiency gas units, and hydro units.Item Electricity Generation Using Sediment Microbial Fuel Cells with a Manganese Dioxide Cathode Catalyst(2014) Tatinclaux, Maia; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Wastewater treatment plants employ an energetically costly aerobic unit process to remove organic matter from municipal wastewater; this process is known as activated sludge. Microbial fuel cells (MFCs) present an anaerobic, energy-saving approach to wastewater treatment that results in electricity generation. However, MFCs are often limited by internal resistance from membrane fouling and slow cathodic oxygen reduction. This work examined an option to overcome these limitations-- adapting membrane-less sediment microbial fuel cells (SMFCs) for use with wastewater as an organic substrate by using floating carbon cloth air cathodes coated with an oxygen reduction reaction (ORR) catalyst. The performance of a platinum ORR catalyst at the cathode was compared to a manganese dioxide ORR catalyst and several additional cathode materials and reactor configurations were tested to optimize SMFC performance. The MnO2 catalyst, though significantly cheaper than platinum, was unable to sustain consistent high cathode potentials in wastewater over time.Item ISOTOPE EFFECTS IN THE STATE-RESOLVED COLLISION DYNAMICS OF HIGHLY EXCITED MOLECULES(2014) Echebiri, Geraldine Onyinyechi; Mullin, Amy S; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The importance of highly excited molecules in the fields of combustion and atmospheric chemistry makes it essential to study pathways by which energy is lost from the excited molecule. One such pathway is by inelastic collisions with a bath molecule. In this dissertation, the collisional relaxation of highly excited pyrazine-h4 (Evib = 37900 cm-1) and pyrazine-d4 (Evib = 37900 cm-1) with HCl (300 K) is studied. The outcomes of the inelastic collision studies reveal quantum state-energy gaps of molecules and their intermolecular interactions affect the mechanism and dynamics of collisional energy transfer. The results from collisional relaxation of pyrazine-h4 (Evib = 37900 cm-1) with HCl were compared to those from collisional relaxation of pyrazine-h4 (Evib) with DCl in order to deduce the effects of quantum state-energy gaps on the dynamics of collisional energy transfer. The comparison shows the dynamics for collisional deactivation of pyrazine-h4 (Evib) with HCl and DCl are different, and are possibly due to their intermolecular interactions with pyrazine-h4 (Evib. The data for collisional relaxation of pyrazine-d4 (Evib = 37900 cm-1) with HCl were compared to those for pyrazine-h4 (Evib) + HCl collisions in order to determine the contributions of near-resonant vibrational energies of the collision partners on the collision dynamics. The comparison shows the energy transfer dynamics for collisional quenching of pyrazine-h4 (Evib) and pyrazine-d4 (Evib) with HCl are similar. The similarity in their energy transfer dynamics suggests near-resonance effects are not contributing significantly to the collision dynamics.Item Interdisciplinary Reasoning about Energy in an Introductory Physics Course for the Life Sciences(2014) Dreyfus, Benjamin William; Redish, Edward F; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Energy is a unifying concept that cuts across physics, chemistry, and biology. However, students who study all three disciplines can end up with a fragmented understanding of energy. This dissertation sits at the intersection of two active areas of current research: the teaching and learning of energy, and interdisciplinary science education (particularly the intersection of physics and biology). The context for this research is an introductory physics course for undergraduate life sciences majors that is reformed to build stronger interdisciplinary connections between physics, biology, and chemistry. An approach to energy that incorporates chemical bonds and chemical reactions is better equipped to meet the needs of life sciences students than a traditional introductory physics approach that focuses primarily on mechanical energy, and so we present a curricular thread for chemical energy in the physics course. Our first set of case studies examines student reasoning about ATP hydrolysis, a biochemically significant reaction that powers various processes in the cell. We observe students expressing both that an energy input is required to break a chemical bond (which they associate with physics) and that energy is released when the phosphate bond is broken in ATP (which they associate with biology). We use these case studies to articulate a model of interdisciplinary reconciliation: building coherent connections between concepts from different disciplines while understanding each concept in its own disciplinary context and justifying the modeling choices in deciding when to use each disciplinary model. Our second study looks at ontological metaphors for energy: metaphors about what kind of thing energy is. Two ontological metaphors for energy that have previously been documented include energy as a substance and energy as a location. We argue for the use of negative energy in modeling chemical energy in an interdisciplinary context, and for the use of a blended substance/location ontology in reasoning about negative energy. Our data show students and experts using the blended ontology productively when the two ontologies are combined in a coherent structure, as well as students getting confused when the ontologies are not coherently combined.Item The Impact of Cool Roofs in Different Climatic Regions: A Quantitative Empirical Analysis(2014) Petry, Kimberly Johanna; McIntosh, Marla S; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This research investigated regional climate differences and weather impacts on the effectiveness of cool roofs. In most US climate zones, cool roofs can reduce energy consumption because they reflect more sunlight and heat than standard roofs. Since temperatures are expected to increase in many regions, cool roofs may offer greater energy and cost savings than currently estimated. Energy consumption by Department of Energy (DOE) Research Laboratory buildings across the US with cool and standard roofs were assessed using metered energy datasets collected from 2003-2013. Statistical tests were conducted to compare differences in energy consumption of buildings between cool and standard roofs at sites in different climatic regions. In order to better understand the effectiveness of cool roof technologies in a future that is expected to become increasingly warmer, data collected from weather stations near each DOE site were used to interpret the potential influences of weather patterns on cool roof energy savings. This research confirmed that cool roofs do reduce energy consumption, especially at sites with warmer summers and milder winters. Regression analyses of energy consumption and temperature data were conducted to identify associations between air temperatures and heating and cooling degree-days with seasonal energy consumption. While the energy consumption of buildings with cool roofs was generally less than buildings with standard roofs, the differences in energy consumption varied depending on building use and building size.Item Algorithmic Approaches to Reducing Resource Costs in Data Centers(2013) Mukherjee, Koyel; Khuller, Samir; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A substantial portion of resource costs incurred by data centers relate to energy costs, with cooling energy and equipment powering energy accounting for a major fraction. Other major costs incurred by data centers, is due to huge data transmission volume and resultant network bandwidth consumption. In this dissertation, we study problems inspired by the needs to reduce energy consumption and network bandwidth billing costs in data centers. A significant amount of data center cooling energy is wasted due to thermal imbalance and hot spots. In order to prevent this, the workload should be scheduled in a thermally aware manner based on the overall thermal profile, since machine temperatures depend on local load as well as on neighboring machines' load. We define `effective load' that captures this spatial cross-interference and analyze different models for: 1) maximizing the profit of scheduled jobs under a cooling energy budget, for which we give 1/2 - O(epsilon) approximation algorithms; 2) minimizing the maximum temperature when all jobs have to be scheduled, for which we give a 2-approximation algorithm and a 3-competitive online algorithm for a single rack of machines, where the factors approach 4/3 and 2 respectively as the cross-interference decays. Servers consume energy while running; hence, shutting down some will reduce the costs. We consider two problems which study this in literature: active time and busy time, the goal being minimizing the total `on' time of machines. In active time, we have access to a single machine whereas in busy time, number of machines allowed is unlimited. Machines have bounded capacity and jobs have release times, deadlines and lengths. For active time, we show a minimal feasible solution is 3-approximate and give a 2-approximation algorithm via LP rounding. For busy time, we give a 3-approximation algorithm which improves the 4-approximation, and analyze the preemptive problem also. Data centers need to transmit a huge volume of data daily which results in high network bandwidth costs. Frequently, ISP's charge for Internet use either based on the peak bandwidth usage in any slot in the billing cycle, or according to some percentile cost. We provide an optimal offline algorithm for the percentile problem when jobs can have variable delay. For the online problem of minimizing peak bandwidth, we study small values of delay in a discrete time setting and give much better lower and upper bounds than the best known bound of e that holds when delay allowed is arbitrarily large and time is continuous.