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Surface roughness has a negative impact on several failures of materials medium. It can accelerate the pitting corrosion, increase effective heat transfer and increase the rate of effective charge loss. However, the controlled surface roughness may be desirable in many situations. The automotive lead-acid battery is very sensitive to such

Surface roughness has a negative impact on several failures of materials medium. It can accelerate the pitting corrosion, increase effective heat transfer and increase the rate of effective charge loss. However, the controlled surface roughness may be desirable in many situations. The automotive lead-acid battery is very sensitive to such effects. The cast-on-strap machine has the largest effect on the surface roughness of the lead-antimony alloy in our case study. The two-point correlation function is an efficient characterization tool for two-phase heterogeneous materials. Considering the nature that the two-point correlation function is a spatial statistical function, it cannot distinguish between a two-phase material or materials with surfaces containing protrusion of distinct heights. A case study to examine its capability in quantifying surface roughness isintroduced. The possibility of applying a simulated annealing procedure to optimize using information obtained from the two-point correlation function is investigated. Outcomes show a successful surface representation, as well as optimization, that agrees with the initially proposed hypothesis.
ContributorsBasyoni, Mohamed Nasser (Author) / Jiao, Yang Prof. (Thesis advisor) / Yang, Sui Dr. (Committee member) / Zhuang, Houlong Dr. (Committee member) / Arizona State University (Publisher)
Created2022
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Description
Siloxane, a common contaminant present in biogas, is known for adverse effects on cogeneration prime movers. In this work, the solid oxide fuel cell (SOFC) nickel-yttria stabilized zirconia (Ni-YSZ) anode degradation due to poisoning by siloxane was investigated. For this purpose, experiments with different fuels, different deposition substrate materials, different

Siloxane, a common contaminant present in biogas, is known for adverse effects on cogeneration prime movers. In this work, the solid oxide fuel cell (SOFC) nickel-yttria stabilized zirconia (Ni-YSZ) anode degradation due to poisoning by siloxane was investigated. For this purpose, experiments with different fuels, different deposition substrate materials, different structure of contamination siloxane (cyclic and linear) and entire failure process are conducted in this study. The electrochemical and material characterization methods, such as Electrochemical Impedance Spectroscopy (EIS), Scanning Electron Microscope- Wavelength Dispersive Spectrometers (SEM-WDS), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Raman spectroscopy, were applied to investigate the anode degradation behavior. The electrochemical characterization results show that the SOFCs performance degradation caused by siloxane contamination is irreversible under bio-syngas condition. An equivalent circuit model (ECM) is developed based on electrochemical characterization results. Based on the Distribution of Relaxation Time (DRT) method, the detailed microstructure parameter changes are evaluated corresponding to the ECM results. The results contradict the previously proposed siloxane degradation mechanism as the experimental results show that water can inhibit anode deactivation. For anode materials, Ni is considered a major factor in siloxane deposition reactions in Ni-YSZ anode. Based on the results of XPS, XRD and WDS analysis, an initial layer of carbon deposition develops and is considered a critical process for the siloxane deposition reaction. Based on the experimental results in this study and previous studies about siloxane deposition on metal oxides, the proposed siloxane deposition process occurs in stages consisting of the siloxane adsorption, initial carbon deposition, siloxane polymerization and amorphous silicon dioxide deposition.
ContributorsTian, Jiashen (Author) / Milcarek, Ryan J. (Thesis advisor) / Muhich, Christopher (Committee member) / Wang, Liping (Committee member) / Phelan, Patrick (Committee member) / Nian, Qiong (Committee member) / Arizona State University (Publisher)
Created2022
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Description
Global decarbonization requires a large-scale shift to sustainable energy sources. Innovation will be a key enabler of this global energy transition. Although the energy transition and innovation literatures overwhelmingly focus on the Global North, energy innovation is arguably even more important for the Global South because it can enable them

Global decarbonization requires a large-scale shift to sustainable energy sources. Innovation will be a key enabler of this global energy transition. Although the energy transition and innovation literatures overwhelmingly focus on the Global North, energy innovation is arguably even more important for the Global South because it can enable them to grow their energy demand and power their development with sustainable resources. This dissertation examines three aspects of energy innovation, focusing on Mexico, to advance the understanding of innovation systems and identify policy levers for accelerating energy innovation in emerging economies. The first project utilizes econometric models to assess patenting drivers for renewable energy (wind and solar) and enabling technologies (energy storage, high voltage direct current technologies, hydrogen technologies, and fuel cells) across 34 countries, including Mexico. The examination of enabling technologies is a particular contribution, since most research on energy innovation focuses on renewable generation technologies. This research finds that policies have differential effects on renewable technologies versus enabling technology, with innovation in enabling technologies lagging behind the deployment of renewable energy. Although renewable energy policies have some spillover effects on enabling technologies, this research suggests that targeted policy instruments for enabling technologies may be needed for global decarbonization. The second and third projects apply the innovation systems framework to understand energy innovation in Mexico. The second project analyzes the sectoral innovation system (SIS) for wind and solar technologies, using expert interviews to evaluate SIS structure and functions systemically. It finds that this innovation system is susceptible to changes in its structure, specifically institutional modifications, and encounters cultural and social aspects that reduce its performance. Further, it finds that non-government organizations and local governments are trying to support the SIS, but their efforts are hampered by low participation from the federal government. The third project studies the technology innovation system (TIS) for green hydrogen, an emerging industrial opportunity for Latin America. It evaluates this TIS's functionality and identifies 22 initiatives to improve its performance by interviewing green hydrogen experts in Mexico. The most important initiatives for strengthening the green hydrogen TIS are information campaigns, policy and regulation (taxes, subsidies, standards, and industrial policies), pilot or demonstration projects, and professional training. Overall, this dissertation contributes to the nexus of energy transition and innovation studies by advancing the understanding of energy innovation in an emerging economy.
ContributorsAguiar Hernandez, Carlos Gabriel (Author) / Breetz, Hanna (Thesis advisor) / Parker, Nathan (Committee member) / Solis, Dario (Committee member) / Arizona State University (Publisher)
Created2022
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Description
Interdigitated back contact (IBC) solar cells have achieved the highest single junction silicon wafer-based solar cell power conversion efficiencies reported to date. This thesis is about the fabrication of a high-efficiency silicon heterojunction IBC solar cell for potential use as the bottom cell for a 3-terminal lattice-matched dilute-nitride Ga (In)NP(As)/Si

Interdigitated back contact (IBC) solar cells have achieved the highest single junction silicon wafer-based solar cell power conversion efficiencies reported to date. This thesis is about the fabrication of a high-efficiency silicon heterojunction IBC solar cell for potential use as the bottom cell for a 3-terminal lattice-matched dilute-nitride Ga (In)NP(As)/Si monolithic tandem solar cell. An effective fabrication process has been developed and the process challenges related to open circuit voltage (Voc), series resistance (Rs), and fill factor (FF) are experimentally analyzed. While wet etching, the sample lost the initial passivation, and by changing the etchant solution and passivation process, the voltage at maximum power recovered to an initial value of over 710 mV before metallization. The factors reducing the series resistance loss in IBC cells were also studied. One of these factors was the Indium Tin Oxide (ITO) sputtering parameters, which impact the conductivity of the ITO layer and transport across the a-Si:H/ITO interface. For the standard recipe, the chamber pressure was 3.5 mTorr with no oxygen partial pressure, and the thickness of the ITO layer in contact with the a-Si:H layers, was optimized to 150 nm. The patterning method for the metal contacts and final annealing also change the contact resistance of the base and emitter stack layers. The final annealing step is necessary to recover the sputtering damage; however, the higher the annealing time the higher the final IBC series resistance. The best efficiency achieved was 19.3% (Jsc = 37 mA/cm2, Voc = 691 mV, FF = 71.7%) on 200 µm thick 1-15 Ω-cm n-type CZ C-Si with a designated area of 4 cm2.
ContributorsMoeini Rizi, Mansoure (Author) / Goodnick, Stephen (Thesis advisor) / Honsberg, Christina (Committee member) / Goryll, Michael (Committee member) / Smith, David (Committee member) / Bowden, Stuart (Committee member) / Arizona State University (Publisher)
Created2022
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Description
The colloidal solutions of nanoparticles have been seen as promising solutions forheat transfer enhancement. Additionally, there has been an accelerated study on the effects of ultrasound on heat transfer enhancement in recent years. A few authors have studied the combined impact of Al2O3 nanofluids and ultrasound on mini channels. This study focused on

The colloidal solutions of nanoparticles have been seen as promising solutions forheat transfer enhancement. Additionally, there has been an accelerated study on the effects of ultrasound on heat transfer enhancement in recent years. A few authors have studied the combined impact of Al2O3 nanofluids and ultrasound on mini channels. This study focused on the combined effects of Al2O3 nanofluids and ultrasound on heat transfer enhancement in a circular mini channel heat sink. Two concentrations of Al2O3-water nanofluids, i.e., 0.5% and 1%, were used for the experiments in addition to two heat input conditions, namely 40 W and 50 W providing a constant heat flux of 25000 W m-2 and 31250 W m-2 respectively. The effect on the nanofluids using 5 W ultrasound was analyzed. Experimental observations show that the usage of ultrasound increased the heat transfer coefficient. The heat transfer coefficient also increased with increasing nanoparticle concentration and high heat flux. The average heat transfer coefficient enhancement for 0.5% and 1% nanofluid due to increased heat flux in the absence of ultrasound was 12.4% and 9% respectively. At a constant heat input of 40 W, the induction of ultrasound enhanced the heat transfer coefficient by 22.8% and 23.9% for 0.5% and 1% nanofluid respectively. Similarly, for a constant heat input of 50 W, the usage of ultrasound enhanced the heat transfer coefficient by 19.8% and 22.9% for 0.5% and 1% nanofluid respectively Also, interesting findings are reported with low heat input with ultrasound vs. high heat input without ultrasound (i.e., 40 W with US vs. 50 W without US). The heat transfer coefficient and Nusselt number for 0.5% and 1% concentrations was enhanced by 9.2% and 13.6%, respectively. Furthermore, for fixed heat input powers of 40 W and 50 W, increasing the concentration from 0.5% to 1% along with ultrasound yielded an average enhancement in Nu of 38.3% and 32.4% respectively
ContributorsMastoi, Faisal Ali (Author) / Phelan, Patrick E (Thesis advisor) / Milcarek, Ryan (Committee member) / Kwon, Beomjin (Committee member) / Arizona State University (Publisher)
Created2022
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Description
This dissertation consists of three chapters that investigate the rapid adoption and complex implementation of city commitments to transition to 100% renewable energy (100RE). The first paper uses a two-stage, mixed methods approach to examine 100RE commitments across the US, combining a multivariate regression of demographic, institutional, and policy factors

This dissertation consists of three chapters that investigate the rapid adoption and complex implementation of city commitments to transition to 100% renewable energy (100RE). The first paper uses a two-stage, mixed methods approach to examine 100RE commitments across the US, combining a multivariate regression of demographic, institutional, and policy factors in adoption and six interview-based state case studies to discuss implementation. Adoption of this non-binding commitment progressed rapidly for city councils around the US. Results show that many cities passed 100RE commitments with no implementation plan and minimal understanding of implementation challenges. This analysis highlights that many cities will need new institutions and administrative capacities for successful implementation of these ambitious new policies. While many cities abandoned the commitment soon after adoption, collaboration allowed cities in a few states to break through and pursue implementation, examined further in the next two studies. The second paper is a qualitative case study examining policymaking for the Utah Community Renewable Energy Act. Process tracing methods are used to identify causal factors in enacting this legislation at the state level and complementary resolutions at the local level. This Act was passed through the leadership and financial backing of major cities and committed the investor-owned utility to fulfill any city 100RE resolutions passed through 2019. Finally, the third paper is a mixed-methods, descriptive case study of the benefits of Community Choice Aggregation (CCA) in California, which many cities are using to fulfill their 100RE commitments. Cities have adopted CCAs to increase their local voice in the energy process, while fulfilling climate and energy goals. Overall, this research shows that change in the investor-owned utility electricity system is in fact possible from the city scale, though many cities will need institutional innovation to implement these policies and achieve the change they desire. While cities with greater resources are better positioned to make an impact, smaller cities can collaborate to similarly influence the energy system. Communities are interested in lowering energy costs for customers where possible, but the central motivations in these cases were the pursuit of sustainability and increasing local voice in energy decision-making.
ContributorsKunkel, Leah Christine (Author) / Breetz, Hanna L (Thesis advisor) / Parker, Nathan (Committee member) / Salon, Deborah (Committee member) / Arizona State University (Publisher)
Created2022
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Description
This is an applied research paper, where a micro campus was designed for the San Carlos Apache Community with a goal of meeting requirements for at least three petals of Living Building Challenge. The end goal was to submit recommendations for attaining the petal certifications. The process of design not

This is an applied research paper, where a micro campus was designed for the San Carlos Apache Community with a goal of meeting requirements for at least three petals of Living Building Challenge. The end goal was to submit recommendations for attaining the petal certifications. The process of design not only included following spatial requirements of designing the building, but also including a wider perspective of construction and energy management in it. The first step of the research was getting to know the community and their requirements and priorities. This was done in 1st semester as a part of an applied class Indigenous Project Delivery. The second part of the research was to design a micro campus for the community that is in sync with the main campus. The intent of design is to respect the community’s culture and help them pass it on to the next generation while abiding by the Living Building Challenge standards. The third step of this research was to back up the design with recommendations for petal certifications.
ContributorsSingaraju, Meghana (Author) / Costa, Wanda Dalla (Thesis advisor) / Coseo, Paul (Committee member) / Vekstein, Claudio (Committee member) / Parrish, Kristen (Committee member) / Arizona State University (Publisher)
Created2022
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Description
The welfare consequences of price versus quantity-based regulation are known to differ when information about marginal benefits or costs of abatement is imperfect. Does uncertainty about demand for the polluting good also matter for welfare of these two approaches to regulation? In chapter 1, I use plant-level survey data and

The welfare consequences of price versus quantity-based regulation are known to differ when information about marginal benefits or costs of abatement is imperfect. Does uncertainty about demand for the polluting good also matter for welfare of these two approaches to regulation? In chapter 1, I use plant-level survey data and high frequency variation in power consumption to assess the dynamic implications of uncertainty about future demand for the relative welfare consequences of carbon taxes and cap-and-trade regulation. I address this question in the context of the electricity sector where demand risk is particularly salient. I show that the choice between policy instruments depends on how firms and consumers balance unpredictable output volatility (higher with carbon taxes) vs. price volatility (higher with cap-and-trade regulation). Over a wide range of policy-relevant abatement targets, I find carbon taxes outperform cap-and-trade in terms of welfare. Financial incentives like the Production Tax Credit are central initiatives behind wind power as the leading renewable energy source in the U.S. But do institutional design features of energy markets matter for cost-effectiveness of subsidies to wind investments? In chapter 2, I answer this question by investigating how the design of procurement contracts that are typically used by wind developers affects their investment incentives. Using unit-level data from wind farm production and installed capacity, I find that structuring subsidies based on key features of the type of procurement contracts associated to wind projects leads to major reductions in public expenditures in terms of subsidy payments to wind developers without undermining their investment incentives. The U.S. federal government is known to have a history of heavily subsidizing the wind power industry. Subsidies either to output (Production Tax Credit) or investment goods (Investment Tax Credit) have been critical to replace emissions-intensive technologies with wind power. Which type of subsidy is best to incentivize wind investments at the least cost? In chapter 3, I use plant-level data of wind facilities from the Texas electricity market to develop and estimate a model of investment decisions that accounts for productivity shocks at the wind farm level and prudent behavior of developers. I find that subsidizing production can increase average yearly investment rates in wind capacity up to 2.5 percentage points over mean investment rates under alternative subsidies to capital. This is driven by precautionary savings that developers accumulate to smooth out potential future shocks to investment income when adverse weather conditions lead to low subsidy payments.
ContributorsGómez Trejos, Felipe Alberto (Author) / Silverman, Daniel (Thesis advisor) / Fried, Stephie (Committee member) / Ventura, Gustavo (Committee member) / Kuminoff, Nicolai (Committee member) / Arizona State University (Publisher)
Created2023
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Description
This work investigates the impact of wavelength-selective light trapping on photovoltaic efficiency and operating temperature, with a focus on GaAs and Si devices. A nanostructure array is designed to optimize the efficiency of a III-V narrow-band photonic power converter (PPC). Within finite-difference time-domain (FDTD) simulations, a nanotextured GaInP window layer

This work investigates the impact of wavelength-selective light trapping on photovoltaic efficiency and operating temperature, with a focus on GaAs and Si devices. A nanostructure array is designed to optimize the efficiency of a III-V narrow-band photonic power converter (PPC). Within finite-difference time-domain (FDTD) simulations, a nanotextured GaInP window layer yields a 25× path-length enhancement when integrated with a rear dielectric-metal reflector. Then, nanotexturing of GaInP is experimentally achieved with electron-beam lithography (EBL) and Cl2/Ar plasma etching. Time-resolved photoluminescence (TRPL) measurements show that the GaAs absorber lifetime does not drop due to the nanotexturing process, thus indicating a path to thinner, higher-efficiency PPCs. Next, wavelength-selective light management is examined for enhanced radiative cooling. It is shown that wavelength-selective optimizations of a module’s emissivity can yield 60-65% greater radiative cooling benefits compared to comparative changes across a broader wavelength range. State-of-the-art Si modules that utilize microtextured cover glass are shown to already achieve 99% of the radiative cooling gains that are possible for a photovoltaic device under full sunlight. In contrast, the sub-bandgap reflection (SBR) of Si modules is shown to be far below ideal. The low SBR of modules with textured Si cells (15%-26%) is shown to be the primary reason for their higher operating temperatures than modules with planar GaAs cells (SBR measured at 77%). For textured cells, typical of Si modules, light trapping amplifies parasitic absorption in the encapsulant and the rear mirror, yielding greater heat generation. Optimization of doping and the rear mirror of a Si module could increase the SBR to a maximum of 63%, with further increases available only if parasitic absorption in the encapsulation materials can be reduced. For thin films, increased heat generation may outweigh the photogeneration benefits that are possible with light trapping. These investigations motivate a wavelength-selective application of light trapping: light trapping for near- to above-bandgap photons to increase photogeneration; and out-coupling of light in mid- to far-infrared wavelengths to increase the emission of thermal radiation; but light trapping should ideally be avoided at sub-bandgap energies where there is substantial solar radiation to limit heat generation and material degradation.
ContributorsIrvin, Nicholas P. (Author) / Honsberg, Christiana B. (Thesis advisor) / King, Richard R. (Thesis advisor) / Nemanich, Robert J. (Committee member) / Smith, David J. (Committee member) / Arizona State University (Publisher)
Created2023
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Description
A photovoltaic (PV) module is a series and parallel connection of multiple PV cells; defects in any cell can cause module power to drop. Similarly, a photovoltaic system is a series and parallel connection of multiple modules, and any low-performing module in the PV system can decrease the system output

A photovoltaic (PV) module is a series and parallel connection of multiple PV cells; defects in any cell can cause module power to drop. Similarly, a photovoltaic system is a series and parallel connection of multiple modules, and any low-performing module in the PV system can decrease the system output power. Defects in a solar cell include, but not limited to, the presence of cracks, potential induced degradation (PID), delamination, corrosion, and solder bond degradation. State-of-the-art characterization techniques to identify the defective cells in a module and defective module in a string are i) Current-voltage (IV) curve tracing, ii) Electroluminescence (EL) imaging, and iii) Infrared (IR) imaging. Shortcomings of these techniques include i) unsafe connection and disconnection need to be made with high voltage electrical cables, and ii) labor and time intensive disconnection of the photovoltaic strings from the system.This work presents a non-contact characterization technique to address the above two shortcomings. This technique uses a non-contact electrostatic voltmeter (ESV) along with a probe sensor to measure the surface potential of individual solar cells in a commercial module and the modules in a string in both off-grid and grid-connected systems. Unlike the EL approach, the ESV setup directly measures the surface potential by sensing the electric field lines that are present on the surface of the solar cell. The off-grid testing of ESV on individual cells and multicells in crystalline silicon (c-Si) modules and on individual cells in cadmium telluride (CdTe) modules and individual modules in a CdTe string showed less than 2% difference in open circuit voltage compared to the voltmeter values. In addition, surface potential mapping of the defective cracked cells in a multicell module using ESV identified the dark, grey, and bright areas of EL images precisely at the exact locations shown by the EL characterization. The on-grid testing of ESV measured the individual module voltages at maximum power point (Vmpp) and quantitatively identified the exact PID-affected module in the entire system. In addition, the poor-performing non-PID modules of a grid-connected PV system were also identified using the ESV technique.
ContributorsRaza, Hamza Ahmad (Author) / Tamizhmani, Govindasamy (Thesis advisor) / Kiaei, Sayfe (Committee member) / Bakkaloglu, Bertan (Committee member) / Hacke, Peter (Committee member) / Arizona State University (Publisher)
Created2023