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Climate Change Impacts on Snowpack Heterogeneity: Spatial and Temporal Variability at Multiple Scales
No full textThroughout the western United States, seasonal snowpack is critical for water resources timing and availability and ecosystem function. Warming temperatures associated with climate change reduce snow accumulation and advance melt timing, with serious consequences for snow-dependent social and ecological systems. While many impacts of climate change on snowpack are well established, this dissertation investigates several elements of changing snowpack that have not been previously assessed. In particular, each chapter contributes to an improved understanding of the changing heterogeneity of snow under climate change. The first chapter tests the sensitivity of snow drifting to altered climate, using a physically-based hydrologic model and thirty years of hydroclimatological data at a site where aspen stands are subsidized by a wind-driven snow drift. We find a warming-induced reduction in snow drifting, increase in ecohydrologic homogeneity across the landscape, and altered interannual variability of hydrologic metrics. The second chapter assesses changes in interannual variability of snowpack magnitude and timing across the western United States, using downscaled global climate model data as forcing to the Variable Infiltration Capacity (VIC) model. We find that changes in interannual variability are spatially heterogeneous across the western U.S., but that interannual variability of annual maximum snow water equivalent (SWEmax) decreases in regions transitioning from snow- to rain-dominated precipitation regimes. Changes in the date of SWEmax are less spatially coherent, but agreement between general circulation models (GCMs) is most reliably found at relatively warm sites where the date of SWEmax variability increases. The third chapter assesses another element of snow heterogeneity by testing the effect of snowfall intensity on winter ablation. Using a statistical modeling approach with observational snow data, we find that higher snowfall intensity is associated with reduced winter ablation; projected changes in snowfall intensity will likely exacerbate warming-induced increases in winter ablation in the maritime mountains of the western U.S. and mitigate it in the cooler continental regions. Finally, a fourth interdisciplinary, collaborative chapter synthesizes research on climate change in the mountainous headwaters of the Columbia River Basin. Findings show that research in this basin is focused on climate change impacts, rather than adaptation or mitigation, that social and biophysical sciences are not well integrated, and that research priorities differ across an international boundary. Cumulatively, this set of studies advances knowledge of how the spatial and temporal heterogeneity of snowpack will respond to climate change in the western United States, with implications for snow-dependent social and ecological systems.doctoral, Ph.D., Water Resources -- University of Idaho - College of Graduate Studies, 2019-0
Spatio-temporal Variability of Wildfires and Their Climate Drivers from Continental to Global Scale
No full textFire is a natural component of most ecosystems, and it has effects on vegetation, soil, water, atmospheric composition, and human well-being. Despite increasing interest in interdisciplinary approaches to analyzing global fire activity and the growing body of wildfire research, there are still many gaps and uncertainties in our knowledge. Some come from the lack of understanding of the complex relationships between fire and climate, which is additionally entangled by the strong influence of human activity. This dissertation evaluates the role of environmental context in determining the spatial patterns of fire activity on a large scale. First, the fire-climate relationship was analyzed in terms of the most studied and understood fire metric – the amount of burned area – which was shown to have changed significantly in the last two decades. Most of the recent changes were attributed to the decrease in fire activity in Africa, where the amount of burned area declined by 18.5% between 2002 and 2016. Although humans have a long history of modifying fire activity in Africa, climate factors directly related to biomass productivity and aridity explained about 70% of the changes in burned area in natural land covers, providing evidence that increased terrestrial moisture during 2002-2016 facilitated declines in fire activity in Africa. These results illustrate the strong influence of climate on fire activity and in particular proxy for fuel productivity and fuel dryness. Based on these findings, a framework was proposed for defining and classifying fire regimes (a range of characteristics that describe the fire events in the space-time window). This framework was based on the assumption that fuel productivity and desiccation are the two fundamental processes that limit fire activity, and their combination sets important boundary conditions for key fire regime metrics on a large scale. By testing this approach in Africa and Australia, it was evident that while the amount of rainfall is an important driver of fire through controlling fuel productivity, a variation of rainfall within and between years drives fuel dryness and fire activity especially in Australia, a continent with a strong precipitation gradient. Additionally, among continents, fire metrics vary substantially even within the same biome. These results informed an additional global analysis, where 26 distinct fire regions were identified, not including areas where fire activity is highly modified by human activity. This approach did not only discriminate between regions with significantly different fire activity across a number of biomes but also identified how fire attributes vary under different conditions and what factors constrain modern fire regimes. These findings should help to improve our understanding of fire complexity and its interaction and feedbacks with climate which is essential to assess the potential effect of global climate change on fire regimes.doctoral, Ph.D., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-1
Program at the WI&M Railway Depot freight room
No full textPhotograph of a program in the freight room of the WI&M Railway Depot
ENHANCED MODULAR MULTILEVEL CONVERTER-BASED STATCOM WITH HYBRID ENERGY STORAGE
No full textWith the advent of power electronic converter-based generation technology in the power utility industry, there is an increasing need for sources of dynamically controllable real and reactive power to maintain stability of electric power systems. Static Synchronous Compensators (STATCOMs) improve the stability of electric power systems by dynamically controlling reactive power supply to the system. However, they cannot provide dynamic real power control. In this dissertation, a device capable of both dynamic real power and reactive power control is presented. The device consists of a modular multilevel converter (MMC) -based STATCOM combined with a hybrid energy storage system that combines a battery energy storage with a supercapacitor energy storage system. Matlab/Simulink is utilized to examine the stability of the response of an electric transmission system under fault conditions without compensation, with a STATCOM alone and with the enhanced energy storage system. Simulation plots show that the system stability improves significantly when the hybrid energy storage system is combined with the STATCOM for dynamic real and reactive power compensation.doctoral, Ph.D., Electrical and Computer Engineering -- University of Idaho - College of Graduate Studies, 2019-1
Evaluation of Skid Resistance at Different Speeds in Idaho
No full textAdequate skid resistance is essential for road safety. Many transportation agencies measure the skid number using a locked-wheel skid trailer at a reference speed (e.g., 40 mph). Due to some limitations (e.g., speed limit, road geometry), the skid number is often measured at lower speeds. In addition, some interstate highways have a speed limit up to 80 mph, yet the skid numbers are collected at lower speeds (e.g., 40 mph) which could impose hazard to motorists. This study developed a statistical model to describe the change in skid number with speed. This model can be used to predict the skid number at a reference speed (e.g., 40 mph) based on measurements of skid number at any operation and safe speed between 20 mph to 60 mph and mean profile depth of pavement surface. The results demonstrated good correlation between measured and predicted skid numbers. The developed model can be used to convert skid numbers measured at any operation and safe speeds between 20 mph and 60 mph to a skid number at a reference speed. In addition, this study developed a simple software to facilitate the calculations of skid number at any the desired speed. The software imports the texture and skid data collected using the pavement friction tester and calculates the skid number at a reference speed specified by the user using the developed model. The outcome of this study will improve the safety of the skid crew and motorists, in addition, it will expedite the skid data collection. Keywords: Skid resistance, skid number, pavements, microtexture, macrotexture, skid truck, mean profile depthmasters, M.S., Civil Engineering -- University of Idaho - College of Graduate Studies, 2019-0
Composition-structure-property Relationship in Cs-based halide Perovskites using Electronic Structure Calculations
No full textThe last three decades have witnessed significant progress in electronic materials due to the constant discovery of new materials for various applications. ABX3 (A = Cs; B = Ca, Sr, Ba; X =I, Br, Cl, or F) s-block halide perovskites are widely considered as a scintillator material and a replacement of lead-based solar device due to their excellent electronic properties. The performance of the device is linked to the atomic and electronic structure of the halide perovskites. Using ab-initio calculations, we studied the effect of chemical composition, atomic structure on the electronic properties (bandgap) of s-block halide perovskite for both bulk and surfaces. We found that the bulk and the surface bandgaps of the perovskites are closely related to the intrinsic properties such as atomic or ionic size, electronegativity, bond-dissociation energy of B and X. The bandgap changes on the surfaces compare to the bulk are explained in terms of the structural changes such as bond-distance and bond-angle. Defects are produced inevitably during the synthesis of these compounds and largely depends on the synthesis condition. It has been reported that the point defects such as antisite defects are detrimental to carrier transport as they create localized electronic (deep trap) defects on the band gap. Using ab-initio calculations, we also investigated the impact of antisite defect, XB on the electronic properties of ABX3 (A = Cs; B = Ca, Sr, or Ba; X =I, Br, Cl, or F) bulk perovskites. Our results reveal that the formation of defect state in the band gap due to antisite defect, XB strongly depends on the composition and the crystal structure. We observed that for a fixed composition of A and B the electronic defect forms at a higher energy level on the bandgap for bigger halogen atom compared to the halogen atom of smaller size. Further, the antisite defect creates localized states at two different locations in the band-gap for the orthorhombic structure. Whereas, for the same composition with the cubic crystal structure, the antisite defect creates a localized electronic state only at one location. Finally, we linked the location of these electronic defect states in the band gap to the intrinsic property of the constituent elements such as bond-dissociation energy and the atomic size, which can be a useful tool to understand and predict the position of localized electronic states produced by the point defects.masters, M.S., Chemical and Materials Science Engineering -- University of Idaho - College of Graduate Studies, 2019-0
The Power of a Forest: Informing Forest Bioenergy Policy Development through Facility Case Studies
No full textForest biomass is source of sustainable heat and electricity supplied through forest management activities. Sustainably utilizing forest biomass for energy provides a host of benefits including: supporting and diversifying the domestic energy industry, reducing the cost of hazardous fuel treatments, rural economic development, greenhouse gas (GHG) emissions reduction, and habitat improvements. Despite the aforementioned benefits the pace and scale of development has been slow and the role of policy intervention continues to be challenged. Numerous barriers to utilizing forest biomass are documented in the literature including unfavorable economics, supply chain deficiencies, and public opposition. Despite decades of industry innovations and prolific research, the bioenergy industry continues to lack policy intervention that effectively minimizes the barriers to biomass use. However, it is not just effective policy that is challenged, but also the role of government in shaping how forest resources are governed. This thesis focuses on two gaps of research pertaining to the use of forest biomass for energy purposes. First, despite being well documented in the literature, barriers are not understood in the context of necessary policy responses and there is little empirical data on biomass barriers from a forest bioenergy facility perspective. Specifically, unanswered questions include: How do the aforementioned barriers affect facility operations? And how do existing or proposed facility companies respond to changes in particular policies? Second, there are few empirical studies that explore the following questions: How do forest bioenergy networks influence policy intervention?masters, M.S., Natural Resources -- University of Idaho - College of Graduate Studies, 2019-0
Material Properties of Thermoelectric and Nuclear Energy Sources
No full textThermoelectric generators are a reliable solid-state energy conversion technology. Furthermore, flexible thermoelectric generators are especially of interest due to their potential to power flexible electronics and sensors using body heat or other ambient heat sources. This research focuses on developing flexible, bismuth telluride thin films utilizing a low-cost and scalable wet chemistry method. An overview of current alternative small energy sources demonstrates the need for flexible thermoelectric generators. Thin films fabricated from bismuth telluride nanocrystals exhibited a peak power factor of 0.35 mW/m∙K2 at 433 K, which is among the highest reported values for flexible thermoelectric films. In addition, the change in electrical resistance was 23% after 1000 bending cycles. Nuclear energy is a large scale energy alternative to fossil fuels which generate minimal environmental emissions. However, the thermal conductivity of nuclear fuel is necessary due to its impact on fuel temperature, the resulting reactor performance, and safety considerations. This research works to overcome this problem by utilizing an in-pile thermal conductivity measurement in order to determine the thermal conductivity under prototypic conditions over a range of burnup. A multilayer quadrupoles analytic model is developed to describe the transient thermal interactions between a line heat source and nuclear fuel for in-pile thermal conductivity measurements. The analytic model was verified using a finite element analysis. Ultimately, the analytic model was used to perform parameter and sensitivity studies to explore the viability of accurately measuring the sample thermal conductivity under various measurement conditions. The analytic model was then compared to experimental measurements of polytetrafluoroethylene and stainless steel 304, which showed good agreement. Using the analytic model, optimization of the needle probe was then performed in order to improve the accuracy of thermal conductivity measurements for UO2 related to the fuel diameters, various probe diameters, and thermal contact resistance. The standard equation for data reduction using the slope to determine the thermal conductivity is not capable of measuring samples with prototypic diameters. However, the validated analytic model provides the foundation to elucidate a better understanding of in-pile thermal conductivity measurements in samples with a diameter as low as 10 mm.doctoral, Ph.D., Mechanical Engineering -- University of Idaho - College of Graduate Studies, 2019-0