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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- All Subjects: Alternative Energy
Description
With a recent shift to a more environmentally conscious society, low-carbon and non-carbon producing energy production methods are being investigated and applied all over the world. Of these methods, fuel cells show great potential for clean energy production. A fuel cell is an electrochemical energy conversion device which directly converts chemical energy into electrical energy. Proton exchange membrane fuel cells (PEMFCs) are a highly researched energy source for automotive and stationary power applications. In order to produce the power required to meet Department of Energy requirements, platinum (Pt) must be used as a catalyst material in PEMFCs. Platinum, however, is very expensive and extensive research is being conducted to develop ways to reduce the amount of platinum used in PEMFCs. In the current study, three catalyst synthesis techniques were investigated and evaluated on their effectiveness to produce platinum-on copper (Pt@Cu) core-shell nanocatalyst on multi-walled carbon nanotube (MWCNT) support material. These three methods were direct deposition method, two-phase surfactant method, and single-phase surfactant method, in which direct deposition did not use a surfactant for particle size control and the surfactant methods did. The catalyst materials synthesized were evaluated by visual inspection and fuel cell performance. Samples which produced high fuel cell power output were evaluated using transmission electron microscopy (TEM) imaging. After evaluation, it was concluded that the direct deposition technique was effective in synthesizing Pt@Cu core-shell nanocatalyst on MWCNTs support when a rinsing process was used before adding platinum. The peak power density achieved by the rinsed core-shell catalyst was 618 mW.cm-2 , 13 percent greater than that of commercial platinum-carbon (Pt/C) catalyst. Transmission electron microscopy imaging revealed the core-shell catalyst contained Pt shells and platinum-copper alloy cores. Rinsing with deionized (DI) water was shown to be a crucial step in core-shell catalyst deposition as it reduced the number of platinum colloids on the carbon nanotube surface. After evaluation, it was concluded that the two-phase surfactant and single-phase surfactant synthesis methods were not effective at producing core-shell nanocatalyst with the parameters investigated.
ContributorsAdame, Anthony (Author) / Madakannan, Arunachalanadar (Thesis advisor) / Peng, Xihong (Committee member) / Tamizhmani, Govindasamy (Committee member) / Arizona State University (Publisher)
Created2012
Description
Alternative energy technologies must become more cost effective to achieve grid parity with fossil fuels. Dye sensitized solar cells (DSSCs) are an innovative third generation photovoltaic technology, which is demonstrating tremendous potential to become a revolutionary technology due to recent breakthroughs in cost of fabrication. The study here focused on quality improvement measures undertaken to improve fabrication of DSSCs and enhance process efficiency and effectiveness. Several quality improvement methods were implemented to optimize the seven step individual DSSC fabrication processes. Lean Manufacturing's 5S method successfully increased efficiency in all of the processes. Six Sigma's DMAIC methodology was used to identify and eliminate each of the root causes of defects in the critical titanium dioxide deposition process. These optimizations resulted with the following significant improvements in the production process: 1. fabrication time of the DSSCs was reduced by 54 %; 2. fabrication procedures were improved to the extent that all critical defects in the process were eliminated; 3. the quantity of functioning DSSCs fabricated was increased from 17 % to 90 %.
ContributorsFauss, Brian (Author) / Munukutla, Lakshmi V. (Thesis advisor) / Polesky, Gerald (Committee member) / Madakannan, Arunachalanadar (Committee member) / Arizona State University (Publisher)
Created2012
Description
Emergent environmental issues, ever-shrinking petroleum reserves, and rising fossil fuel costs continue to spur interest in the development of sustainable biofuels from renewable feed-stocks. Meanwhile, however, the development and viability of biofuel fermentations remain limited by numerous factors such as feedback inhibition and inefficient and generally energy intensive product recovery processes. To circumvent both feedback inhibition and recovery issues, researchers have turned their attention to incorporating energy efficient separation techniques such as adsorption in in situ product recovery (ISPR) approaches. This thesis focused on the characterization of two novel adsorbents for the recovery of alcohol biofuels from model aqueous solutions. First, a hydrophobic silica aerogel was evaluated as a biofuel adsorbent through characterization of equilibrium behavior for conventional second generation biofuels (e.g., ethanol and n-butanol). Longer chain and accordingly more hydrophobic alcohols (i.e., n-butanol and 2-pentanol) were more effectively adsorbed than shorter chain alcohols (i.e., ethanol and i-propanol), suggesting a mechanism of hydrophobic adsorption. Still, the adsorbed alcohol capacity at biologically relevant conditions were low relative to other `model' biofuel adsorbents as a result of poor interfacial contact between the aqueous and sorbent. However, sorbent wettability and adsorption is greatly enhanced at high concentrations of alcohol in the aqueous. Consequently, the sorbent exhibits Type IV adsorption isotherms for all biofuels studied, which results from significant multilayer adsorption at elevated alcohol concentrations in the aqueous. Additionally, sorbent wettability significantly affects the dynamic binding efficiency within a packed adsorption column. Second, mesoporous carbons were evaluated as biofuel adsorbents through characterization of equilibrium and kinetic behavior. Variations in synthetic conditions enabled tuning of specific surface area and pore morphology of adsorbents. The adsorbed alcohol capacity increased with elevated specific surface area of the adsorbents. While their adsorption capacity is comparable to polymeric adsorbents of similar surface area, pore morphology and structure of mesoporous carbons greatly influenced adsorption rates. Multiple cycles of adsorbent regeneration rendered no impact on adsorption equilibrium or kinetics. The high chemical and thermal stability of mesoporous carbons provide potential significant advantages over other commonly examined biofuel adsorbents. Correspondingly, mesoporous carbons should be further studied for biofuel ISPR applications.
ContributorsLevario, Thomas (Author) / Nielsen, David R (Thesis advisor) / Vogt, Bryan D (Committee member) / Lind, Mary L (Committee member) / Arizona State University (Publisher)
Created2011
Description
This is a two part thesis:
Part – I
This part of the thesis involves automation of statistical risk analysis of photovoltaic (PV) power plants. Statistical risk analysis on the field observed defects/failures in the PV power plants is usually carried out using a combination of several manual methods which are often laborious, time consuming and prone to human errors. In order to mitigate these issues, an automated statistical risk analysis (FMECA) is necessary. The automation developed and presented in this project generates about 20 different reliability risk plots in about 3-4 minutes without the need of several manual labor hours traditionally spent for these analyses. The primary focus of this project is to automatically generate Risk Priority Number (RPN) for each defect/failure based on two Excel spreadsheets: Defect spreadsheet; Degradation rate spreadsheet. Automation involves two major programs – one to calculate Global RPN (Sum of Performance RPN and Safety RPN) and the other to find the correlation of defects with I-V parameters’ degradations. Based on the generated RPN and other reliability plots, warranty claims for material defect and degradation rate may be made by the system owners.
Part – II
This part of the thesis involves the evaluation of Module Level Power Electronics (MLPE) which are commercially available and used by the industry. Reliability evaluations of any product typically involve pre-characterizations, many different accelerated stress tests and post-characterizations. Due to time constraints, this part of the project was limited to only pre-characterizations of about 100 MLPE units commercially available from 5 different manufacturers. Pre-characterizations involve testing MLPE units for rated efficiency, CEC efficiency, power factor and Harmonics (Vthd (%) and Ithd (%)). The pre-characterization test results can be used to validate manufacturer claims and to evaluate the product for compliance certification test standards. Pre-characterization results were compared for all MLPE units individually for all tested parameters listed above. The accelerated stress tests are ongoing and are not presented in this thesis. Based on the pre-characterizations presented in this report and post-characterizations performed after the stress tests, the pass/fail and time-to-failure analyses can be carried out by future researchers.
Part – I
This part of the thesis involves automation of statistical risk analysis of photovoltaic (PV) power plants. Statistical risk analysis on the field observed defects/failures in the PV power plants is usually carried out using a combination of several manual methods which are often laborious, time consuming and prone to human errors. In order to mitigate these issues, an automated statistical risk analysis (FMECA) is necessary. The automation developed and presented in this project generates about 20 different reliability risk plots in about 3-4 minutes without the need of several manual labor hours traditionally spent for these analyses. The primary focus of this project is to automatically generate Risk Priority Number (RPN) for each defect/failure based on two Excel spreadsheets: Defect spreadsheet; Degradation rate spreadsheet. Automation involves two major programs – one to calculate Global RPN (Sum of Performance RPN and Safety RPN) and the other to find the correlation of defects with I-V parameters’ degradations. Based on the generated RPN and other reliability plots, warranty claims for material defect and degradation rate may be made by the system owners.
Part – II
This part of the thesis involves the evaluation of Module Level Power Electronics (MLPE) which are commercially available and used by the industry. Reliability evaluations of any product typically involve pre-characterizations, many different accelerated stress tests and post-characterizations. Due to time constraints, this part of the project was limited to only pre-characterizations of about 100 MLPE units commercially available from 5 different manufacturers. Pre-characterizations involve testing MLPE units for rated efficiency, CEC efficiency, power factor and Harmonics (Vthd (%) and Ithd (%)). The pre-characterization test results can be used to validate manufacturer claims and to evaluate the product for compliance certification test standards. Pre-characterization results were compared for all MLPE units individually for all tested parameters listed above. The accelerated stress tests are ongoing and are not presented in this thesis. Based on the pre-characterizations presented in this report and post-characterizations performed after the stress tests, the pass/fail and time-to-failure analyses can be carried out by future researchers.
ContributorsMoorthy, Mathan Kumar (Author) / Govindasamy, Tamizhmani (Thesis advisor) / Devarajan, Srinivasan (Committee member) / Bradley, Rogers (Committee member) / Arizona State University (Publisher)
Created2015
Description
It is well known that the overall performance of a solar cell is limited by the worst performing areas of the device. These areas are usually micro and nano-scale defects inhomogenously distributed throughout the material. Mitigating and/or engineering these effects is necessary to provide a path towards increasing the efficiency of state-of-the-art solar cells. The first big challenge is to identify the nature, origin and impact of such defects across length scales that span multiple orders of magnitude, and dimensions (time, temperature etc.). In this work, I present a framework based on correlative X-ray microscopy and big data analytics to identify micro and nanoscale defects and their impact on material properties in CuIn1-xGaxSe2 (CIGS) solar cells.
Synchrotron based X-ray Fluorescence (XRF) and X-ray Beam Induced Current (XBIC) are used to study the effect that compositional variations, between grains and at grain boundaries, have on CIGS device properties. An experimental approach is presented to correcting XRF and XBIC quantification of CIGS thin film solar cells. When applying XRF and XBIC to study low and high gallium CIGS devices, it was determined that increased copper and gallium at grain boundaries leads to increased collection efficiency at grain boundaries in low gallium absorbers. However, composition variations were not correlated with changes in collection efficiency in high gallium absorbers, despite the decreased collection efficiency observed at grain boundaries.
Understanding the nature and impact of these defects is only half the battle; controlling or mitigating their impact is the next challenge. This requires a thorough understanding of the origin of these defects and their kinetics. For such a study, a temperature and atmosphere controlled in situ stage was developed. The stage was utilized to study CIGS films during a rapid thermal growth process. Comparing composition variations across different acquisition times and growth temperatures required the implementation of machine learning techniques, including clustering and classification algorithms. From the analysis, copper was determined to segregate the faster than indium and gallium, and clustering techniques showed consistent elemental segregation into copper rich and copper poor regions. Ways to improve the current framework and new applications are also discussed.
Synchrotron based X-ray Fluorescence (XRF) and X-ray Beam Induced Current (XBIC) are used to study the effect that compositional variations, between grains and at grain boundaries, have on CIGS device properties. An experimental approach is presented to correcting XRF and XBIC quantification of CIGS thin film solar cells. When applying XRF and XBIC to study low and high gallium CIGS devices, it was determined that increased copper and gallium at grain boundaries leads to increased collection efficiency at grain boundaries in low gallium absorbers. However, composition variations were not correlated with changes in collection efficiency in high gallium absorbers, despite the decreased collection efficiency observed at grain boundaries.
Understanding the nature and impact of these defects is only half the battle; controlling or mitigating their impact is the next challenge. This requires a thorough understanding of the origin of these defects and their kinetics. For such a study, a temperature and atmosphere controlled in situ stage was developed. The stage was utilized to study CIGS films during a rapid thermal growth process. Comparing composition variations across different acquisition times and growth temperatures required the implementation of machine learning techniques, including clustering and classification algorithms. From the analysis, copper was determined to segregate the faster than indium and gallium, and clustering techniques showed consistent elemental segregation into copper rich and copper poor regions. Ways to improve the current framework and new applications are also discussed.
ContributorsWest, Bradley (Author) / Bertoni, Mariana I (Thesis advisor) / Verebelyi, Darren (Committee member) / Holman, Zachary (Committee member) / Rose, Volker (Committee member) / Arizona State University (Publisher)
Created2018
Description
The Energiewende aims to drastically reduce Germany’s greenhouse gas emissions, without relying on nuclear power, while maintaining a secure and affordable energy supply. Since 2000 the country’s renewable-energy share has increased exponentially, accounting in 2017 for over a third of Germany's gross electricity consumption. This unprecedented achievement is the result of policies, tools, and institutional arrangements intended to steer society to a low-carbon economy. Despite its resounding success in renewable-energy deployment, the Energiewende is not on track to meet its decarbonization goals. Energiewende rules and regulations have generated numerous undesired consequences, and have cost much more than anticipated, a burden borne primarily by energy consumers. Why has the Energiewende not only made energy more expensive, but also failed to bring Germany closer to its decarbonization goals? I analyzed the Energiewende as a complex socio-technical system, examining its legal framework and analyzing the consequences of successive regulations; identifying major political and energy players and the factors that motivated them to pursue socio-technical change; and documenting the political trends and events in which the Energiewende is rooted and which continue to shape it. I analyzed the dynamics and the loopholes that created barriers to transition, pushed the utility sector to the brink of dissolution, and led to such undesirable outcomes as negative wholesale prices and forced exports of electricity to Germany’s European neighbors. Thirty high-level energy experts and stakeholders were interviewed to find out how the best-informed members of German society perceive the Energiewende. Surprisingly, although they were highly critical of the way the transition has unfolded, most were convinced that the transition would eventually succeed. But their definitions of success did not always depend on achieving carbon-mitigation targets. Indeed, Germany jeopardizes the achievement of these targets by changing too many policy and institutional variables at too fast a pace. Good intentions and commitment are not enough to create economies based on intermittent energy sources: they will also require intensive grid expansion and breakthroughs in storage technology. The Energiewende demonstrates starkly that collective action driven by robust political consensus is not sufficient for steering complex socio-technical systems in desired directions.
ContributorsSturm, Christine (Author) / Sarewitz, Daniel (Thesis advisor) / Miller, Clark (Committee member) / Anderies, John (Committee member) / Hirt, Paul (Committee member) / Arizona State University (Publisher)
Created2018
Description
Organic reactions in natural hydrothermal settings have relevance toward the deep carbon cycle, petroleum formation, the ecology of deep microbial communities, and potentially the origin of life. Many reaction pathways involving organic compounds under geochemically relevant hydrothermal conditions have now been characterized, but their mechanisms, in particular those involving mineral surface catalysis, are largely unknown. The overall goal of this work is to describe these mechanisms so that predictive models of reactivity can be developed and so that applications of these reactions beyond geochemistry can be explored. The focus of this dissertation is the mechanisms of hydrothermal dehydration and catalytic hydrogenation reactions. Kinetic and structure/activity relationships show that elimination occurs mainly by the E1 mechanism for simple alcohols via homogeneous catalysis. Stereochemical probes show that hydrogenation on nickel occurs on the metal surface. By combining dehydration with and catalytic reduction, effective deoxygenation of organic structures with various functional groups such as alkenes, polyols, ketones, and carboxylic acids can be accomplished under hydrothermal conditions, using either nickel or copper-zinc alloy. These geomimetic reactions can potentially be used in biomass reduction to generate useful fuels and other high value chemicals. Through the use of earth-abundant metal catalysts, and water as the solvent, the reactions presented in this dissertation are a green alternative to current biomass deoxygenation/reduction methods, which often use exotic, rare-metal catalysts, and organic solvents.
ContributorsBockisch, Christiana (Author) / Gould, Ian R (Thesis advisor) / Hartnett, Hilairy E (Committee member) / Shock, Everett L (Committee member) / Arizona State University (Publisher)
Created2018
Description
Just for a moment! Imagine you live in Arizona without air-conditioning systems!
Air-conditioning and refrigeration systems are one of the most crucial systems in anyone’s house and car these days. Energy resources are becoming more scarce and expensive. Most of the currently used refrigerants have brought an international concern about global warming. The search for more efficient cooling/refrigeration systems with environmental friendly refrigerants has become more and more important so as to reduce greenhouse gas emissions and ensure sustainable and affordable energy systems. The most widely used air-conditioning and refrigeration system, based on the vapor compression cycle, is driven by converting electricity into mechanical work which is a high quality type of energy. However, these systems can instead be possibly driven by heat, be made solid-state (i.e., thermoelectric cooling), consist entirely of a gaseous working fluid (i.e., reverse Brayton cycle), etc. This research explores several thermally driven cooling systems in order to understand and further overcome some of the major drawbacks associated with their performance as well as their high capital costs. In the second chapter, we investigate the opportunities for integrating single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) via cascade of rejected heat for large-scale plants. Similarly, in the third chapter, we explore a new polygeneration cooling-power cycle’s performance based on Rankine, reverse Brayton, ejector, and liquid desiccant cycles to produce power, cooling, and possibly fresh water for various configurations. Different configurations are considered from an energy perspective and are compared to stand-alone systems. In the last chapter, a new simple, inexpensive, scalable, environmentally friendly cooling system based on an adsorption heat pump system and evacuated tube solar collector is experimentally and theoretically studied. The system is destined as a small-scale system to harness solar radiation to provide a cooling effect directly in one system.
Air-conditioning and refrigeration systems are one of the most crucial systems in anyone’s house and car these days. Energy resources are becoming more scarce and expensive. Most of the currently used refrigerants have brought an international concern about global warming. The search for more efficient cooling/refrigeration systems with environmental friendly refrigerants has become more and more important so as to reduce greenhouse gas emissions and ensure sustainable and affordable energy systems. The most widely used air-conditioning and refrigeration system, based on the vapor compression cycle, is driven by converting electricity into mechanical work which is a high quality type of energy. However, these systems can instead be possibly driven by heat, be made solid-state (i.e., thermoelectric cooling), consist entirely of a gaseous working fluid (i.e., reverse Brayton cycle), etc. This research explores several thermally driven cooling systems in order to understand and further overcome some of the major drawbacks associated with their performance as well as their high capital costs. In the second chapter, we investigate the opportunities for integrating single- and double-stage ammonia-water (NH3–H2O) absorption refrigeration systems with multi-effect distillation (MED) via cascade of rejected heat for large-scale plants. Similarly, in the third chapter, we explore a new polygeneration cooling-power cycle’s performance based on Rankine, reverse Brayton, ejector, and liquid desiccant cycles to produce power, cooling, and possibly fresh water for various configurations. Different configurations are considered from an energy perspective and are compared to stand-alone systems. In the last chapter, a new simple, inexpensive, scalable, environmentally friendly cooling system based on an adsorption heat pump system and evacuated tube solar collector is experimentally and theoretically studied. The system is destined as a small-scale system to harness solar radiation to provide a cooling effect directly in one system.
ContributorsAlelyani, Sami M (Author) / Phelan, Patrick E (Thesis advisor) / Wang, Liping (Committee member) / Stechel, Ellen B (Committee member) / Calhoun, Ronald J (Committee member) / Alalili, Ali R (Committee member) / Arizona State University (Publisher)
Created2018
Description
Learning from the anatomy of leaves, a new approach to bio-inspired passive evaporative cooling is presented that utilizes the temperature-responsive properties of PNIPAm hydrogels. Specifically, an experimental evaporation rate from the polymer, PNIPAm, is determined within an environmental chamber, which is programmed to simulate temperature and humidity conditions common in Phoenix, Arizona in the summer. This evaporation rate is then used to determine the theoretical heat transfer through a layer of PNIPAm that is attached to an exterior wall of a building within a ventilated cavity in Phoenix. The evaporation of water to the air gap from the polymer layer absorbs heat that could otherwise be conducted to the interior space of the building and then dispels it as a vapor away from the building. The results indicate that the addition of the PNIPAm layer removes all heat radiated from the exterior cladding, indicating that it could significantly reduce the demand for air conditioning at the interior side of the wall to which it is attached.
ContributorsBradford, Katherine (Author) / Reddy, T A (Thesis advisor) / Bryan, Harvey (Thesis advisor) / Ramalingam, Muthu (Committee member) / Arizona State University (Publisher)
Created2018
Description
With the increasing penetration of converter interfaced renewable generation into power systems, the structure and behavior of the power system is changing, catalyzing alterations and enhancements in modeling and simulation methods.
This work puts forth a Hybrid Electromagnetic Transient-Transient Stability simulation method implemented using MATLAB and Simulink, to study power electronic based power systems. Hybrid Simulation enables detailed, accurate modeling, along with fast, efficient simulation, on account of the Electromagnetic Transient (EMT) and Transient Stability (TS) simulations respectively. A critical component of hybrid simulation is the interaction between the EMT and TS simulators, established through a well-defined interface technique, which has been explored in detail.
This research focuses on the boundary conditions and interaction between the two simulation models for optimum accuracy and computational efficiency.
A case study has been carried out employing the proposed hybrid simulation method. The test case used is the IEEE 9-bus system, modified to integrate it with a solar PV plant. The validation of the hybrid model with the benchmark full EMT model, along with the analysis of the accuracy and efficiency, has been performed. The steady-state and transient analysis results demonstrate that the performance of the hybrid simulation method is competent. The hybrid simulation technique suitably captures accuracy of EMT simulation and efficiency of TS simulation, therefore adequately representing the behavior of power systems with high penetration of converter interfaced generation.
This work puts forth a Hybrid Electromagnetic Transient-Transient Stability simulation method implemented using MATLAB and Simulink, to study power electronic based power systems. Hybrid Simulation enables detailed, accurate modeling, along with fast, efficient simulation, on account of the Electromagnetic Transient (EMT) and Transient Stability (TS) simulations respectively. A critical component of hybrid simulation is the interaction between the EMT and TS simulators, established through a well-defined interface technique, which has been explored in detail.
This research focuses on the boundary conditions and interaction between the two simulation models for optimum accuracy and computational efficiency.
A case study has been carried out employing the proposed hybrid simulation method. The test case used is the IEEE 9-bus system, modified to integrate it with a solar PV plant. The validation of the hybrid model with the benchmark full EMT model, along with the analysis of the accuracy and efficiency, has been performed. The steady-state and transient analysis results demonstrate that the performance of the hybrid simulation method is competent. The hybrid simulation technique suitably captures accuracy of EMT simulation and efficiency of TS simulation, therefore adequately representing the behavior of power systems with high penetration of converter interfaced generation.
ContributorsAthaide, Denise Maria Christine (Author) / Qin, Jiangchao (Thesis advisor) / Ayyanar, Raja (Committee member) / Wu, Meng (Committee member) / Arizona State University (Publisher)
Created2018