In this research, an attempt is made to evaluate alternative model-predictive microgrid control approaches and to understand the trade-offs that emerge between model complexity and the ability to achieve real-time optimized system performance. Three alternative controllers are considered and their computational and optimization performance compared. In the first, nonlinearities of the generators are included within the optimization. Subsequently, an approach is considered wherein alternative (non-traditional) states and inputs of generators are used which enables one to leverage linear models with the model predictive control (MPC). Nonlinearities are represented outside the control in maps between MPC inputs and the physical inputs. Third, a recently proposed linearized trajectory (LTMPC) is considered. Finally, the performance of the controllers is examined utilizing alternative models of the synchronous machine that have been proposed for power system analysis.

<p> Integrating solar energy into the electric vehicle (EV) market alleviates the demand for</p> <p>fossil fuels used to generate the electricity used to power these vehicles. Integrated solar panels</p> <p>provide a new method of power generation for an electric vehicle, but researchers must consider</p> <p>new dependent variables such as drag in the figure of vehicle efficiency. For the solar array to be</p> <p>deemed a viable option for power generation, the solar array must generate enough energy to</p> <p>overcome the added weight and aerodynamic drag forces the solar system introduces. The thesis</p> <p>explores the application of photovoltaic modules for power generation in an EV system.</p> <p>Researchers installed an off-the-shelf solar module on the roof of an EV and investigated the</p> <p>system to explore the efficiency tradeoffs. The research sought to identify an optimized solar</p> <p>panel configuration for minimized drag based on maximized panel surface irradiance, cooling,</p> <p>and array output voltage parameters. The study utilized computational fluid dynamics modeling,</p> <p>wind tunnel testing, and full-scale track testing to analyze the system. The results of this study</p> <p>provide an optimized configuration for a Renogy RNG-100D atop a Chevrolet Bolt. The system</p> <p>was considered optimal at a tilt angle of zero degrees when in motion. The performance benefits</p> <p>due to the increased angle of the solar panel tilt were deemed insufficient in overcoming the</p> <p>aerodynamic drag forces introduced into the system while in motion.</p>

<p>As energy demands for the world increase, the necessity for alternate sources of energy are critical. Just in the United States alone, 92 quadrillion British thermal units (Btu) were used in 2020. As political and geographical pressures surrounding oil increase, along with the growing concern for climate, the drive to explore alternative and renewable means for harvesting energy is on the rise. Solar cells, also known as photovoltaics (PVs), are an attractive renewable source and have been developed as an alternative energy means for over 60 years. When considering losses due to atmospheric absorption and scattering, the Earth’s surface gets about 1000 W/m2 of energy from the sun, which is why there are research efforts around the world trying to maximize the efficiency of solar cells.</p> <p>Organic-inorganic halide perovskites provide for ideal absorbing layers that feature long carrier lifetime and diffusion lengths, strong photoluminescence, and promising tunability. Furthermore, the solution-processing methods used to make these perovskites ensure that the solar cells will remain low-cost and have easy scale-up possibilities. The main problem perovskites is that they degrade in the presence of water, thus leading to decreased device performance.</p> <p>In this work two approaches are investigated to increase moisture stability. The first investigates incorporation of thiols as pseudohalides into the 2D perovskite structure. Instead of the theorized perovskite, two novel 2D compounds were created, Pb₂X(S-C₆H₅)₃ (X= I, Br, Cl) and PbI_1.524(S-C₆H₅)_0.476. While not perovskites, this study gives insight into the effect that the thiol may have on determining structure when comparing –S-C₆H₅ with –SCN groups. Future work will explore more electronegative thiols that will be used to make moisture resistant, tunable 2D perovskites.</p> <p>The second approach is to incorporate longer organic ammonium cations into the perovskite structure to produce quasi-2D perovskite films fabricate them into devices. Adding in electronically insulating ligands leads to a stricter requirement for vertically aligned 2D films and special care must be taken to have efficient charge collection. The current field has successfully incorporated short ligands such as butylammonium (BA) into PVs, however the extension to larger and more beneficially hydrophobic ligands has been very scarce. In this work, a novel solvent engineering system is developed to create vertically aligned quasi-2D perovskite absorbing layers based off of a bithiophene ligand (2T). These absorbing layers are then characterized and incorporated into efficient PV devices. Generalizations to solvent conditions related to ligand choice is discussed herein, creating deep insights into incorporating more conjugated ligands into devices.</p>

<p>Lithium-Ion Batteries (Li-ion batteries or LIBs) have been extensively used in a wide variety of industrial applications and consumer electronics. Additive Manufacturing (AM) or 3D printing (3DP) techniques have evolved to allow the fabrication of complex structures of various compositions in a wide range of applications. </p> <p><br></p> <p>The objective of the thesis is to investigate the application of 3DP to fabricate a LIB, using a modified process from the literature [1]. The ultimate goal is to improve the electrochemical performances of LIBs while maintaining design flexibility with a 3D printed 3D architecture. </p> <p><br></p> <p>In this research, both the cathode and anode in the form of specifically formulated slurry were extruded into filaments using a high-temperature pellet-based extruder. Specifically, filament composites made of graphite and Polylactic Acid (PLA) were fabricated and tested to produce anodes. Investigations on two other types of PLA-based filament composites respectively made of Lithium Manganese Oxide (LMO) and Lithium Nickel Manganese Cobalt Oxide (NMC) were also conducted to produce cathodes. Several filaments with various materials ratios were formulated in order to optimize printability and battery capacities. Finally, flat battery electrode disks similar to conventional electrodes were fabricated using the fused deposition modeling (FDM) process and assembled in half-cells and full cells. Finally, the electrochemical properties of half cells and full cells were characterized. Additionally, in parallel to the experiment, a 1-D finite element (FE) model was developed to understand the electrochemical performance of the anode half-cells made of graphite. Moreover, a simplified machine learning (ML) model through the Gaussian Process Regression was used to predict the voltage of a certain half-cell based on input parameters such as charge and discharge capacity. </p> <p><br></p> <p>The results of this research showed that 3D printing technology is capable to fabricate LIBs. For the 3D printed LIB, cells have improved electrochemical properties by increasing the material content of active materials (i.e., graphite, LMO, and NMC) within the PLA matrix, along with incorporating a plasticizer material. The FE model of graphite anode showed a similar trend of discharge curve as the experiment. Finally, the ML model demonstrated a reasonably good prediction of charge and discharge voltages. </p>

<p dir="ltr">Improving environmental sustainability in energy production and waste management are of critical importance. Anaerobic digestion (AD) uses microbes to biologically decompose organic waste and produce biogas, which can be used for various forms of sustainable energy. It can be particularly valuable for livestock facilities considering AD of their manure, and potentially other feedstocks as well, a process known as co-digestion. Improved understanding of co-digestion of agro-industrial feedstocks is critical for these facilities. Understanding the macromolecular composition (carbohydrate, protein, and lipid portions) of potential AD feedstocks has the potential to provide important information for predicting important parameters of AD behavior. However, the stability of these macromolecules in AD samples during long-term storage must be confirmed. Furthermore, synergistic and antagonistic impacts of co-digestion on methane production and digestate composition need to be more thoroughly explored.</p><p dir="ltr">This dissertation investigates the impact of storage at refrigeration temperatures (4°C) for up to one-year on the macromolecular composition of various agro-industrial feedstocks (beef manure, starch, slaughterhouse waste, soap stock, and filter press slurry) and anaerobic co-digestion samples. These same feedstocks were co-digested with manure in batch digesters at different proportions, using two or three feedstocks to determine possible synergistic effects.</p><p dir="ltr">The findings show that minimal macromolecular degradation occurred in AD samples during storage at refrigeration temperatures for up to one-year. A major exception was samples containing high concentrations of readily biodegradable starches, which did experience >50% carbohydrate degradation. This indicates a need for methodological rigor during sample storage and reporting experimental design.</p><p dir="ltr">Furthermore, the co-digestion experiments demonstrated frequent improvements or synergy in specific methane yield, methane production rate, and a wide variety of physical and chemical parameters in the digester effluent. Specific methane yield was shown to be at least additive, with improvement ranging from 3-168%. Some improvements in kinetic performance were also observed and quantified. Statistical results suggest that influent characteristics could be useful as predictors for methane production. This research could catalyze additional work needed to optimize co-digestion feeding strategies for full-scale digesters.</p>

<p dir="ltr">This thesis presents a comprehensive dynamic modeling and model calibration framework and experimental validations for air-source heat pumps under cycling of frosting and reverse-cycle defrosting operations. </p>

<p>  </p> <p>With the surge of interest in the electrification of transportation driven by global climate change, the need for powertrains using non-carbon energy sources has become more urgent than ever. The fuel cell electric vehicles (FCEVs) using polymer electrolyte membrane fuel cells (PEMFCs) have many advantages over the internal combustion engine (ICE) and other renewable energy vehicles such as high efficiency, zero-emission, fast fueling, unique power, and energy scalability (without heavy penalty from the increased mass). After three decades of intensive development, there are only several thousand FCEVs on the road, in contrast to the millions of battery electric vehicles (BEV) in use today. The biggest challenge of the widespread implantation of the PEMFCs is the cost, primarily due to the use of platinum catalysts. The high intrinsic catalyst activity exhibited using a rotating disc electrode (RDE) is rarely realized in the membrane electrode assembly (MEA), which is the core of PEMFC, due to the difference on the electrolyte(ionomer)/catalyst interfaces. Much of my Ph. D research effort is concentrated on how to reduce the Pt usage and improve the stability of catalyst to reduce the operation cost of fuel cells. Several approaches were practiced improving the performance of MEA in a fuel cell, such as optimizing the ink formulation and MEA fabrication method, enhancing proton conductivity of carbon support for catalysts, engineering the ionomer and catalyst interface via surface functionalization. Such studies unraveled the relationship between property, structure, and performance of MEA, and significantly improved the performance of MEA. Further, to reduce the cost of fuel cell operation, approaches that is to improve the stability of catalysts either in reducing Oswald ripening or limiting surface migration were practiced on developing novel catalysts. Such as doping anion into Pt and Ni alloy crystal structure, introducing PANI on catalyst surface. These approaches significantly improve the stability of catalyst and MEA. Finally, same as platinum group metal (PGM) catalysts, PGM-free catalysts as well as their MEAs were studied. A novel method of PGM-free MEA fabrication was developed which significantly reduced the thickness of catalyst layer, thus greatly reduced the mass transfer resistance. Also, a highly stable and active PGM-free catalyst was developed and can be considered as a strong competitor to replace the traditional PGM catalysts in MEA.</p>

<p dir="ltr">Li-ion batteries are ubiquitous in today’s world with portable electronics, EVs making inroads into daily lives, and electric aircraft at the cusp of becoming reality. These and many more applications revolutionize the world with improvements in batteries at scales from materials, manufacturing, electrode architectures, cell design, and protocols. The various challenges associated with the current generation of batteries include the fast-charging capabilities, economic return of the longevity of the battery, and thermal safety characteristics. The aging and degradation of LIBs appears to be a key pain point particularly when exposed to harsh operating temperature and fast charging conditions. LIBs undergo aging due to numerous chemical and physical degradation processes throughout their lifetime owing to their operation. These challenges are exacerbated by the presence of stringent operating conditions including extreme fast charging, and sub-zero temperature resulting in severe degradation and short cycle life. The LIBs also face challenges in their thermal stability characteristics, failing catastrophically when exposed to high temperature or mechanical abuse conditions. The onset and intensity of these thermal runaway behaviors are further modified when batteries undergo varied aging leading to increased heat and gas generation potentially causing fire or explosions. Overall, a comprehensive characterization to delineate the interconnected role and implications of operating extremes and electrode design on electrochemical performance, cell aging, and thermal runaway behavior is critical for better batteries. </p><p dir="ltr">To this end, the role of electrode microstructure in mitigating lithium plating behavior under various operating conditions, including extreme fast charging has been examined. Further, these multi-length scale characteristics of the electrode microstructure are explored via data-driven approaches to study the complex interaction of transport and kinetic limitations on the microstructure designs. A third study is undertaken for in-operando characterization of the LIB degradation, probing the multi-length scale degradation using pulse voltammetry. Here an accurate degradation descriptors dataset is identified and accurately parametrized, throughout its cycling lifespan. These aging behaviors are translated to physio-chemical degradation mechanisms via a reduced-order coupled electrochemical-thermal-aging interactions model. Lastly, the implication of aging behavior on thermal-safety interactions is delineated. Overall the dissertation is focused on developing a fundamental understanding of the LIB performance, degradation, and safety interactions.</p>

<p>Sodium (Na)-ion battery displays many properties similar to Lithium (Li)-ion battery, such as operating principles and capacity, which noticeably compressed the Na-ion battery cathode exploration period. Having said that, anode materials of Na-ion battery is still underperforming as commercial graphite is inadequate in storing bulky Na ions. In the search for anode materials, both alloy-type and Na metal anode materials have gained popularity as these materials can absorb more charges and have higher storage capacity. It is essential to remember that such materials exhibit massive volume expansion upon sodiation and hence experience considerable mechanical stress upon cycling, leading to fractures and pulverization of the electrodes. In addition to electrode stability, ionic motions between the electrode and electrolyte are pivotal in determining the battery response. The decomposition of the electrolyte cocktails forms a passivation layer on the electrode surface, known as solid electrolyte interphase (SEI), which can rupture and regenerate in unstable cycles. Rickety SEI can cause the consumption of active Na and the formation of local hotspots for notorious dendrite growth, leading to short battery durability.</p> <p><br></p> <p>In the first part of the thesis, Tin (Sn) has been selected as an exemplar system to study the dynamic changes in a Na-ion battery. Higher ion-uptake capabilities of Sn electrode come with a price of large structural and morphological changes and can be controlled by careful charting of non-active phases such as binder and suitable electrolyte solution. This work comprehensively studies the technical challenges associated with Sn with different binder domains and in different liquid electrolyte environments. Parallelly, the sensitivity of the Na-Sn system towards the operating potential window and the crosstalk between the working electrode (alloying and de-alloying) and the counter electrode (plating and stripping) has been untied. Also, a fundamental understanding of the materials-transport-interface interactions during thermal abuse tests and their implication on the safety aspects of Na-ion batteries has been addressed. </p> <p><br></p> <p>Following that, the morphological stability of the Na metal anode is investigated based on the distinct electrochemical reactions arising from the composition of different liquid electrolytes. The role heterogeneity in the SEI layer of Na metal for the growth of dendritic patterns has been discussed. A unified framework incorporating a detailed electrochemical study of various electrolyte formulations, cognizant of the reactions and kinetics at the electrode-electrolyte interface, has been developed. To mechanistically counter the heterogeneity implications and synergistically leverage the electrolyte-additive-driven improvement in ionic transport, a flux-homogenizing separator has been introduced to extend the battery cycling. Based on this synergistic approach, the complex interplay between the homogeneity in SEI composition, electrodeposition/dissolution morphology, and cell performance in Na-metal-based batteries has been identified.</p> <p><br></p> <p>This work tried to offer fresh insights on fundamental mechanisms governing the evolution of the electrode-electrolyte interphases and their role in determining electro-chemo-mechano-thermal stability for future research endeavors in the Na-ion battery field. </p>

<p dir="ltr">The safe and reliable delivery of electricity is critical for the functioning of our modern society. However, high-impact, low-probability (HILP) catastrophic events (such as extreme weather caused by climate change, or cyber-physical attacks) pose an ever-growing threat to the power grid. At the same time, modern advancements in computational capabilities, communication infrastructure, and measurement technologies provide opportunities for new operation and control strategies that enhance the resilience of electric power systems to such HILP events. In this work, optimization-based operation and control approaches are proposed to improve resilience in two power systems applications. First, a real-time linearized-trajectory model-predictive controller (LTMPC) is developed for ensuring voltage, frequency, and transient (rotor angle) stability in systems engineered to operate as microgrids. Such microgrids are capable of seamlessly transitioning from grid-connected operation to an islanded mode and thus, enhance system resilience. The proposed LTMPC enables rapid deployment of such systems by reducing engineering costs and development time while maintaining stable operation. On the other hand, some power systems, such as distribution feeders, are not designed to operate as standalone microgrids. For these cases, a method is proposed for forming ad-hoc microgrids from intact sections of the damaged feeder in the aftermath of a HILP event. A feeder operating center-on-a-laptop (FOCAL) is introduced that coordinates the control of possibly hundreds of inverter-interfaced distributed energy resources (e.g., rooftop solar, battery storage) to improve system resilience. Theoretical analysis as well as numerical case studies and simulations of the proposed strategies are presented for both applications.</p>