ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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Description
This dissertation explores vulnerability to extreme heat hazards in the Maricopa County, Arizona metropolitan region. By engaging an interdisciplinary approach, I uncover the epidemiological, historical-geographical, and mitigation dimensions of human vulnerability to extreme heat in a rapidly urbanizing region characterized by an intense urban heat island and summertime heat waves. I first frame the overall research within global climate change and hazards vulnerability research literature, and then present three case studies. I conclude with a synthesis of the findings and lessons learned from my interdisciplinary approach using an urban political ecology framework. In the first case study I construct and map a predictive index of sensitivity to heat health risks for neighborhoods, compare predicted neighborhood sensitivity to heat-related hospitalization rates, and estimate relative risk of hospitalizations for neighborhoods. In the second case study, I unpack the history and geography of land use/land cover change, urban development and marginalization of minorities that created the metropolitan region's urban heat island and consequently, the present conditions of extreme heat exposure and vulnerability in the urban core. The third study uses computational microclimate modeling to evaluate the potential of a vegetation-based intervention for mitigating extreme heat in an urban core neighborhood. Several findings relevant to extreme heat vulnerability emerge from the case studies. First, two main socio-demographic groups are found to be at higher risk for heat illness: low-income minorities in sparsely-vegetated neighborhoods in the urban core, and the elderly and socially-isolated in the expansive suburban fringe of Maricopa County. The second case study reveals that current conditions of heat exposure in the region's urban heat island are the legacy of historical marginalization of minorities and large-scale land-use/land cover transformations of natural desert land covers into heat-retaining urban surfaces of the built environment. Third, summertime air temperature reductions in the range 0.9-1.9 °C and of up to 8.4 °C in surface temperatures in the urban core can be achieved through desert-adapted canopied vegetation, suggesting that, at the microscale, the urban heat island can be mitigated by creating vegetated park cool islands. A synthesis of the three case studies using the urban political ecology framework argues that climate changed-induced heat hazards in cities must be problematized within the socio-ecological transformations that produce and reproduce urban landscapes of risk. The interdisciplinary approach to heat hazards in this dissertation advances understanding of the social and ecological drivers of extreme heat by drawing on multiple theories and methods from sociology, urban and Marxist geography, microclimatology, spatial epidemiology, environmental history, political economy and urban political ecology.
ContributorsDeclet-Barreto, Juan (Author) / Harlan, Sharon L (Thesis advisor) / Bolin, Bob (Thesis advisor) / Hirt, Paul (Committee member) / Boone, Christopher (Committee member) / Arizona State University (Publisher)
Created2013
Description
Traditional approaches to modeling microgrids include the behavior of each inverter operating in a particular network configuration and at a particular operating point. Such models quickly become computationally intensive for large systems. Similarly, traditional approaches to control do not use advanced methodologies and suffer from poor performance and limited operating range. In this document a linear model is derived for an inverter connected to the Thevenin equivalent of a microgrid. This model is then compared to a nonlinear simulation model and analyzed using the open and closed loop systems in both the time and frequency domains. The modeling error is quantified with emphasis on its use for controller design purposes. Control design examples are given using a Glover McFarlane controller, gain sched- uled Glover McFarlane controller, and bumpless transfer controller which are compared to the standard droop control approach. These examples serve as a guide to illustrate the use of multi-variable modeling techniques in the context of robust controller design and show that gain scheduled MIMO control techniques can extend the operating range of a microgrid. A hardware implementation is used to compare constant gain droop controllers with Glover McFarlane controllers and shows a clear advantage of the Glover McFarlane approach.
ContributorsSteenis, Joel (Author) / Ayyanar, Raja (Thesis advisor) / Mittelmann, Hans (Committee member) / Tsakalis, Konstantinos (Committee member) / Tylavsky, Daniel (Committee member) / Arizona State University (Publisher)
Created2013
Description
This dissertation investigates spatial and temporal changes in land cover and plant species distributions on Cyprus in the past, present and future (1973-2070). Landsat image analysis supports inference of land cover changes following the political division of the island of Cyprus in 1974. Urban growth in Nicosia, Larnaka and Limasol, as well as increased development along the southern coastline, is clearly evident between 1973 and 2011. Forests of the Troodos and Kyrenia Ranges remain relatively stable, with transitions occurring most frequently between agricultural land covers and shrub/herbaceous land covers. Vegetation models were constructed for twenty-two plant species of Cyprus using Maxent to predict potentially suitable areas of occurrence. Modern vegetation models were constructed from presence-only data collected by field surveys conducted between 2008 and 2011. These models provide a baseline for the assessment of potential species distributions under two climate change scenarios (A1b and A2) for the years 2030, 2050, and 2070. Climate change in Cyprus is likely to influence habitat availability, particularly for high elevation species as the relatively low elevation mountain ranges and small latitudinal range prevent species from shifting to areas of suitable environmental conditions. The loss of suitable habitat for some species may allow the introduction of non-native plant species or the expansion of generalists currently excluded from these areas. Results from future projections indicate the loss of suitable areas for most species by the year 2030 under both climate regimes and all four endemic species (Cedrus brevifolia, Helianthemum obtusifolium, Pterocephalus multiflorus, and Quercus alnifolia) are predicted to lose all suitable environments as soon as 2030. As striking exceptions Prunus dulcis (almond), Ficus carica (fig), Punica granatum (pomegranate) and Olea europaea (olive), which occur as both wild varieties and orchard cultigens, will expand under both scenarios. Land cover and species distribution maps are evaluated in concert to create a more detailed interpretation of the Cypriot landscape and to discuss the potential implications of climate change for land cover and plant species distributions.
ContributorsRidder, Elizabeth (Author) / Fall, Patricia L. (Thesis advisor) / Myint, Soe W (Committee member) / Hirt, Paul W (Committee member) / Arizona State University (Publisher)
Created2013
Description
Global climate change (GCC) is among the most important issues of the 21st century. Adaptation to and mitigation of climate change are some of the salient local and regional challenges scientists, decision makers, and the general public face today and will be in the near future. However, designed adaptation and mitigation strategies do not guarantee success in coping with global climate change. Despite the robust and convincing body for anthropogenic global climate change research and science there is still a significant gap between the recommendations provided by the scientific community and the actual actions by the public and policy makers. In order to design, implement, and generate sufficient public support for policies and planning interventions at the national and international level, it is necessary to have a good understanding of the public's perceptions regarding GCC. Based on survey research in nine countries, the purpose of this study is two-fold: First, to understand the nature of public perceptions of global climate change in different countries; and secondly to identi-fy perception factors which have a significant impact on the public's willingness to sup-port GCC policies or commit to behavioral changes to reduce GHG emissions. Factors such as trust in GCC information which need to be considered in future climate change communication efforts are also dealt with in this dissertation. This study has identified several aspects that need to be considered in future communication programs. GCC is characterized by high uncertainties, unfamiliar risks, and other characteristics of hazards which make personal connections, responsibility and engagement difficult. Communication efforts need to acknowledge these obstacles, build up trust and motivate the public to be more engaged in reducing GCC by emphasizing the multiple benefits of many policies outside of just reducing GCC. Levels of skepticism among the public towards the reality of GCC as well as the trustworthiness and sufficien-cy of the scientific findings varies by country. Thus, communicators need to be aware of their audience in order to decide how educational their program needs to be.
ContributorsHagen, Bjoern (Author) / Pijawka, David (Thesis advisor) / Brazel, Anthony (Committee member) / Chhetri, Netra (Committee member) / Guhathakurta, Subhrajit (Committee member) / Arizona State University (Publisher)
Created2013
Description
The United Nation's Framework Convention on Climate Change (UNFCCC) recognizes development as a priority for carbon dioxide (CO2) allocation, under its principle of "common but differentiated responsibilities". This was codified in the Kyoto Protocol, which exempt developing nations from binding emission reduction targets. Additionally, they could be the recipients of financed sustainable development projects in exchange for emission reduction credits that the developed nations could use to comply with emission targets. Due to ineffective results, post-Kyoto policy discussions indicate a transition towards mitigation commitments from major developed and developing emitters, likely supplemented by market-based mechanisms to reduce mitigation costs. Although the likelihood of achieving substantial emission reductions is increased by the new plan, there is a paucity of consideration to how an ethic of development might be advanced. Therefore, this research empirically investigates the role that CO2 plays in advancing human development (in terms of the Human Development Index or HDI) over the 1990 to 2010 time period. Based on empirical evidence, a theoretical CO2-development framework is established, which provides a basis for designing a novel policy proposal that integrates mitigation efforts with human development objectives. Empirical evidence confirms that CO2 and HDI are highly correlated, but that there are diminishing returns to HDI as per capita CO2 emissions increase. An examination of development pathways reveals that as nations develop, their trajectories generally become less coupled with CO2. Moreover, the developing countries with the greatest gains in HDI are also nations that have, or are in the process of moving toward, outward-oriented trade policies that involve increased domestic capabilities for product manufacture and export. With these findings in mind, future emission targets should reduce current emissions in developed nations and allow room for HDI growth in developing countries as well as in the least developed nations of the world. Emission trading should also be limited to nations with similar HDI levels to protect less-developed nations from unfair competition for capacity building resources. Lastly, developed countries should be incentivized to invest in joint production ventures within the LDCs to build capacity for self-reliant and sustainable development over the long-term.
ContributorsClark, Susan Spierre (Author) / Seager, Thomas P. (Thesis advisor) / Allenby, Braden (Committee member) / Klinsky, Sonja (Committee member) / Arizona State University (Publisher)
Created2013
Description
The object of this study was a 26 year old residential Photovoltaic (PV) monocrystalline silicon (c-Si) power plant, called Solar One, built by developer John F. Long in Phoenix, Arizona (a hot-dry field condition). The task for Arizona State University Photovoltaic Reliability Laboratory (ASU-PRL) graduate students was to evaluate the power plant through visual inspection, electrical performance, and infrared thermography. The purpose of this evaluation was to measure and understand the extent of degradation to the system along with the identification of the failure modes in this hot-dry climatic condition. This 4000 module bipolar system was originally installed with a 200 kW DC output of PV array (17 degree fixed tilt) and an AC output of 175 kVA. The system was shown to degrade approximately at a rate of 2.3% per year with no apparent potential induced degradation (PID) effect. The power plant is made of two arrays, the north array and the south array. Due to a limited time frame to execute this large project, this work was performed by two masters students (Jonathan Belmont and Kolapo Olakonu) and the test results are presented in two masters theses. This thesis presents the results obtained on the north array and the other thesis presents the results obtained on the south array. The resulting study showed that PV module design, array configuration, vandalism, installation methods and Arizona environmental conditions have had an effect on this system's longevity and reliability. Ultimately, encapsulation browning, higher series resistance (potentially due to solder bond fatigue) and non-cell interconnect ribbon breakages outside the modules were determined to be the primary causes for the power loss.
ContributorsBelmont, Jonathan (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Henderson, Mark (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2013
Description
The implications of a changing climate have a profound impact on human life, society, and policy making. The need for accurate climate prediction becomes increasingly important as we better understand these implications. Currently, the most widely used climate prediction relies on the synthesis of climate model simulations organized by the Coupled Model Intercomparison Project (CMIP); these simulations are ensemble-averaged to construct projections for the 21st century climate. However, a significant degree of bias and variability in the model simulations for the 20th century climate is well-known at both global and regional scales. Based on that insight, this study provides an alternative approach for constructing climate projections that incorporates knowledge of model bias. This approach is demonstrated to be a viable alternative which can be easily implemented by water resource managers for potentially more accurate projections. Tests of the new approach are provided on a global scale with an emphasis on semiarid regional studies for their particular vulnerability to water resource changes, using both the former CMIP Phase 3 (CMIP3) and current Phase 5 (CMIP5) model archives. This investigation is accompanied by a detailed analysis of the dynamical processes and water budget to understand the behaviors and sources of model biases. Sensitivity studies of selected CMIP5 models are also performed with an atmospheric component model by testing the relationship between climate change forcings and model simulated response. The information derived from each study is used to determine the progressive quality of coupled climate models in simulating the global water cycle by rigorously investigating sources of model bias related to the moisture budget. As such, the conclusions of this project are highly relevant to model development and potentially may be used to further improve climate projections.
ContributorsBaker, Noel C (Author) / Huang, Huei-Ping (Thesis advisor) / Trimble, Steve (Committee member) / Anderson, James (Committee member) / Clarke, Amanda (Committee member) / Calhoun, Ronald (Committee member) / Arizona State University (Publisher)
Created2013
Description
Dye sensitized solar cells (DSSCs) are currently being explored as a cheaper alternative to the more common silicon (Si) solar cell technology. In addition to the cost advantages, DSSCs show good performance in low light conditions and are not sensitive to varying angles of incident light like traditional Si cells. One of the major challenges facing DSSCs is loss of the liquid electrolyte, through evaporation or leakage, which lowers stability and leads to increased degradation. Current research with solid-state and quasi-solid DSSCs has shown success regarding a reduction of electrolyte loss, but at a cost of lower conversion efficiency output. The research work presented in this paper focuses on the effects of using nanoclay material as a gelator in the electrolyte of the DSSC. The data showed that the quasi-solid cells are more stable than their liquid electrolyte counterparts, and achieved equal or better I-V characteristics. The quasi-solid cells were fabricated with a gel electrolyte that was prepared by adding 7 wt% of Nanoclay, Nanomer® (1.31PS, montmorillonite clay surface modified with 15-35% octadecylamine and 0.5-5 wt% aminopropyltriethoxysilane, Aldrich) to the iodide/triiodide liquid electrolyte, (Iodolyte AN-50, Solaronix). Various gel concentrations were tested in order to find the optimal ratio of nanoclay to liquid. The gel electrolyte made with 7 wt% nanoclay was more viscous, but still thin enough to allow injection with a standard syringe. Batches of cells were fabricated with both liquid and gel electrolyte and were evaluated at STC conditions (25°C, 100 mW/cm2) over time. The gel cells achieved efficiencies as high as 9.18% compared to 9.65% achieved by the liquid cells. After 10 days, the liquid cell decreased to 1.75%, less than 20% of its maximum efficiency. By contrast, the gel cell's efficiency increased for two weeks, and did not decrease to 20% of maximum efficiency until 45 days. After several measurements, the liquid cells showed visible signs of leakage through the sealant, whereas the gel cells did not. This resistance to leakage likely contributed to the improved performance of the quasi-solid cells over time, and is a significant advantage over liquid electrolyte DSSCs.
ContributorsMain, Laura (Author) / Munukutla, Lakshmi (Thesis advisor) / Madakannan, Arunachalanadar (Committee member) / Polesky, Gerald (Committee member) / Arizona State University (Publisher)
Created2012
Description
Potential induced degradation (PID) due to high system voltages is one of the major degradation mechanisms in photovoltaic (PV) modules, adversely affecting their performance due to the combined effects of the following factors: system voltage, superstrate/glass surface conductivity, encapsulant conductivity, silicon nitride anti-reflection coating property and interface property (glass/encapsulant; encapsulant/cell; encapsulant/backsheet). Previous studies carried out at ASU's Photovoltaic Reliability Laboratory (ASU-PRL) showed that only negative voltage bias (positive grounded systems) adversely affects the performance of commonly available crystalline silicon modules. In previous studies, the surface conductivity of the glass surface was obtained using either conductive carbon layer extending from the glass surface to the frame or humidity inside an environmental chamber. This thesis investigates the influence of glass surface conductivity disruption on PV modules. In this study, conductive carbon was applied only on the module's glass surface without extending to the frame and the surface conductivity was disrupted (no carbon layer) at 2cm distance from the periphery of frame inner edges. This study was carried out under dry heat at two different temperatures (60 °C and 85 °C) and three different negative bias voltages (-300V, -400V, and -600V). To replicate closeness to the field conditions, half of the selected modules were pre-stressed under damp heat for 1000 hours (DH 1000) and the remaining half under 200 hours of thermal cycling (TC 200). When the surface continuity was disrupted by maintaining a 2 cm gap from the frame to the edge of the conductive layer, as demonstrated in this study, the degradation was found to be absent or negligibly small even after 35 hours of negative bias at elevated temperatures. This preliminary study appears to indicate that the modules could become immune to PID losses if the continuity of the glass surface conductivity is disrupted at the inside boundary of the frame. The surface conductivity of the glass, due to water layer formation in a humid condition, close to the frame could be disrupted just by applying a water repelling (hydrophobic) but high transmittance surface coating (such as Teflon) or modifying the frame/glass edges with water repellent properties.
ContributorsTatapudi, Sai Ravi Vasista (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Srinivasan, Devarajan (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2012
Description
ABSTRACT As the use of photovoltaic (PV) modules in large power plants continues to increase globally, more studies on degradation, reliability, failure modes, and mechanisms of field aged modules are needed to predict module life expectancy based on accelerated lifetime testing of PV modules. In this work, a 26+ year old PV power plant in Phoenix, Arizona has been evaluated for performance, reliability, and durability. The PV power plant, called Solar One, is owned and operated by John F. Long's homeowners association. It is a 200 kWdc, standard test conditions (STC) rated power plant comprised of 4000 PV modules or frameless laminates, in 100 panel groups (rated at 175 kWac). The power plant is made of two center-tapped bipolar arrays, the north array and the south array. Due to a limited time frame to execute this large project, this work was performed by two masters students (Jonathan Belmont and Kolapo Olakonu) and the test results are presented in two masters theses. This thesis presents the results obtained on the south array and the other thesis presents the results obtained on the north array. Each of these two arrays is made of four sub arrays, the east sub arrays (positive and negative polarities) and the west sub arrays (positive and negative polarities), making up eight sub arrays. The evaluation and analyses of the power plant included in this thesis consists of: visual inspection, electrical performance measurements, and infrared thermography. A possible presence of potential induced degradation (PID) due to potential difference between ground and strings was also investigated. Some installation practices were also studied and found to contribute to the power loss observed in this investigation. The power output measured in 2011 for all eight sub arrays at STC is approximately 76 kWdc and represents a power loss of 62% (from 200 kW to 76 kW) over 26+ years. The 2011 measured power output for the four south sub arrays at STC is 39 kWdc and represents a power loss of 61% (from 100 kW to 39 kW) over 26+ years. Encapsulation browning and non-cell interconnect ribbon breakages were determined to be the primary causes for the power loss.
ContributorsOlakonu, Kolapo (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Srinivasan, Devarajan (Committee member) / Rogers, Bradley (Committee member) / Arizona State University (Publisher)
Created2012