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Balagurunathan, JayakishanInvestigation of Ignition Delay Times of Conventional (JP-8) and Synthetic (S-8) Jet Fuels: A Shock Tube Study
Master of Science (M.S.), University of Dayton, 2012, Mechanical Engineering
The global depletion of petroleum-based fuels has led the world to more closely examine alternate fuels. Therefore, alternate fuels produced from feedstocks such as coal, soybeans, palm oil or switch grass through methods such as coal liquefaction, biomass gasification, and Fischer-Tropsch synthesis have been tested. Among these techniques, fuels generated using Fischer-Tropsch technologies are of interest because they produce clean burning hydrocarbons similar to those found in commercial fuels. Therefore, in this study the Fischer-Tropsch derived S-8 fuel was evaluated as a drop-in replacement for the jet fuel JP-8. The jet fuel JP-8 is comprised of n-, iso- and cyclo- alkanes as well as aromatics while the S-8 fuel is primarily comprised of n- and iso- alkanes. The composition of the fuel affects its ignition characteristics chemically and physically by either advancement or delay of time to ignition. Since this study focused on the chemical effects, the fuels were completely pre-vaporized and pre-mixed. A high pressure, high temperature heated single pulse shock tube was used for this study. The shock tube is an established experimental tool used to obtain ignition delay data behind reflected shock waves under operating conditions relevant to modern engines. The experiments were conducted over a temperature range of 1000-1600 K, a pressure of 19±2 atm, equivalence ratios of 0.5, 1 and 3, within a dwell time of 7.6±0.2 ms and an argon dilution of 93% (v/v). Ignition delay times were measured using the signal from the pressure transducer on the end plate with guidance from the optical diagnostic signal. Along with JP-8 and S-8, the ignition delay of n-heptane was also studied. N-heptane was chosen to represent the n-alkanes in the fuels for this study since it was present in both fuels and also to prove the fact that the n-alkanes were rate controlling. The results indicate that both S-8 and JP-8 fuels have similar ignition delays at corresponding equivalence ratios. The fuel-rich mixtures ignited faster at lower temperatures (<1150 K) and the fuel-lean mixtures ignited faster at higher temperatures (>1150 K). In the transition period between lower to higher temperatures (~1100-1200 K), the equivalence ratio had no significant effect on the ignition delay time. The results also show that the ignition delay time measurements of S-8 and JP-8 fuels are similar to the ignition delay of n-heptane at the equivalence ratio of Φ=0.5 and thereby indicate that the n-alkanes present in these fuels controlled the ignition under these conditions. The ignition delay results of S-8 and JP-8 at Φ=3.0 from this study were also compared to prior work (Kahandawala et al., 2008) on 2-methylheptane and n-heptane/toluene (80/20 liquid vol.%), respectively and found to be indistinguishable. This data serves to extend the gas phase ignition delay database for both JP-8 and S-8 and is the first known data taken for both these fuels at higher temperatures (>1000 K) for an equivalence ratio of 3.0 with argon as the diluent gas.

Committee:

Sukh Sidhu, Dr (Committee Chair); Philip Taylor, Dr (Committee Member); Moshan Kahandawala, Dr (Committee Member)

Subjects:

Aerospace Engineering; Aerospace Materials; Alternative Energy; Automotive Engineering; Automotive Materials; Chemical Engineering; Chemistry; Energy; Engineering; Environmental Engineering; Mechanical Engineering; Petroleum Engineering; Technology

Keywords:

Ignition delay; shock tube; S-8; JP-8; Jet fuels; Fuel characteristics; heated shock tube; Fischer-Tropsch; Alternate fuels; alkanes; synthetic fuel; fuel; iso-alkanes; jayakishan balagurunathan

von Deak, Dieter G.Heteroatom-containing Carbon Nanostructures as Oxygen Reduction Electrocatalysts for PEM and Direct Methanol Fuel Cells
Doctor of Philosophy, The Ohio State University, 2011, Chemical and Biomolecular Engineering
The main goal of this work was to undertake a fundamental investigation of precious metal-free carbon catalysts nano-structure modification to enable their use as oxygen reduction reaction (ORR) catalysts in proton exchange membrane (PEM) fuel cells. The sluggish ORR is accelerated by fiscally prohibitive loadings of Pt catalyst. The expense and availability of platinum motivate the development of non-precious metal carbon-nitroge-based ORR catalysts (CNx). The project targets the nature of oxygen reduction reaction active sites and exploring ways to create these sites by molecular tailoring of carbon nano-structures. CNx grown with phosphorous had a significant increase in the ORR active site density. CNx catalyst growth media was prepared by acetonitrile deposition over a Fe and P impregnated MgO. Rotating Ring Disk Electrode (RRDE) Activity and selectivity showed a significant increase in oxygen reduction current with CNx grown with less than a 1:1 molar ratio of P:Fe. Selectivity for the full reduction of dioxygen to water trended with increasing ORR activity for phosphorous grown CNx catalysts. Phosphorus growth altered the morphology of carbon-nitride graphite formed during pyrolysis. The role of the transition metal used to form non-noble metal electrochemical oxygen reduction CNx catalysts was investigated through sulfur and carbon monoxide treatments of the CNx and Pt/carbon electrocatalysts. The intent of poisoning was to show the existence of a non-iron containing electrocatalytic active site in CNx. The sulfur treatment increased the overpotential on a platinum catalyst, but enhanced the current density of the CNx catalyst while leaving the CNx iron phase unchanged. CO in the present of oxygen was found to strongly adsorb to platinum and completely eliminate all oxygen reduction. Under identical conditions, CNx showed a displacement of oxygen due to CO and no oxygen reduction poisoning effect. This suggests that either iron-based active site is sulfur and CO tolerant or that this active site does not participate in the electrocatalytic reduction of oxygen in CNx catalysts. Density functional theory (DFT) calculations of small polycyclic aromatic hydrocarbons (PAHs) that have a similar electronic structure to carbon-nitride catalyst materials were preformed. A strong correlation between B3LYP method N 1s energies and experimental N 1s energies was established for the PAHs studied. Additionally, experimental ionization potentials that would correspond to electron donation trended strongly with the DFT adiabatic and vertical ionization potentials. The testing and setup of fuel cell test station was accomplished. Bench scale membrane electrode assemblies (MEAs) were fabricated cell and achieved comparable performance to a commercial MEA constructed from similar materials. A MEA was constructed with a CNx cathode and was found to have fuel cell performance of the same order of magnitude as other graphitic carbon-nitrogen catalysts heat-treated in the presence of a transition metal. Vulcan carbon and CNx catalysts were compared in accelerated carbon corrosion by examining the current of the electrochemically active surface species hydroquinone/quione with cyclic voltammetry after extended potential holds. CNx was found to be more corrosion resistant than Vulcan carbon that is the most commonly used support in fuel cell electrodes.

Committee:

Umit Ozkan, S (Advisor); David Wood, W (Committee Member); James Rathman, F (Committee Member)

Subjects:

Alternative Energy; Analytical Chemistry; Chemical Engineering; Chemistry; Energy; Engineering; Experiments

Keywords:

catalyst; PEM; fuel cell; oxygen reduction; carbon nitride; graphite; XPS; XAS; corrosion; TEM; phosphorus; sulfur; electrochemistry; RRDE

Amin, Majdi TalalDynamic Modeling and Verification of an Energy-Efficient Greenhouse With an Aquaponic System Using TRNSYS
Doctor of Philosophy (Ph.D.), University of Dayton, 2015, Engineering
Currently, there is no integrated dynamic simulation program for an energy efficient greenhouse coupled with an aquaponic system. This research is intended to promote the thermal management of greenhouses in order to provide sustainable food production with the lowest possible energy use and material waste. A brief introduction of greenhouses, passive houses, energy efficiency, renewable energy systems, and their applications are included for ready reference. An experimental working scaled-down energy-efficient greenhouse was built to verify and calibrate the results of a dynamic simulation model made using TRNSYS software. However, TRNSYS requires the aid of Google SketchUp to develop 3D building geometry. The simulation model was built following the passive house standard as closely as possible. The new simulation model was then utilized to design an actual greenhouse with Aquaponics. It was demonstrated that the passive house standard can be applied to improve upon conventional greenhouse performance, and that it is adaptable to different climates. The energy-efficient greenhouse provides the required thermal environment for fish and plant growth, while eliminating the need for conventional cooling and heating systems.

Committee:

John Kissock (Advisor)

Subjects:

Agricultural Engineering; Agriculture; Alternative Energy; Energy; Engineering; Environmental Science; Mechanical Engineering

Keywords:

Energy-Efficiency, Renewable Energy, Greenhouse, Aquaponics, Efficient-Building, Dynamic Simulation

Triplett, Angela LynnVibration-Based Energy Harvesting with Essential Non-Linearities
Doctor of Philosophy, University of Akron, 2011, Mechanical Engineering

The dependence on electrical power and the advancement of new technology devices has driven new research in the area of alternative energy sources. As electronic devices become smaller and more portable, the use of conventional batteries have become less practical. This has lead to an increase in the study of vibration-based energy harvesting and its use as an alternative source of energy. Previously, linear systems have been developed to harvest energy efficiently when the mechanical oscillator is tuned to the appropriate excitation frequency. This tuning requirement limits the application to a narrow bandwidth of frequencies and puts significant demand on properly designing the system to match a specific excitation. By incorporating non-linearities in the design and analysis of energy harvesting devices, an increase in the performance of the harvester and versatilely of application can be achieved.

This work investigates the role of non-linearities in the mechanical component on the performance of energy harvesting systems, and their advantages compared to a typical linear harvesting system. In particular, an energy harvester that incorporates a piezoelectric element as the attachment and exhibits strong non-linear behavior is analyzed through numerical and analytical simulations, as well as an experimental validation of the simulations. The harvester is subjected to an excitation of ambient vibrations of either a periodic impulsive or harmonic manner. Strong non-linearities are obtained by either the geometric design of the system or by attaching non-linear springs to the primary mass of a spring-mass-damper system. Under certain operating conditions, the resulting unique dynamic behavior of the non-linear system increases the efficiency in comparison to a single degree-of-freedom linear energy harvester.

The use of strongly non-linear energy harvesters as vibration absorbers was also investigated. Vibration absorbers have been shown to be efficient over a wide bandwidth of frequencies when multiple non-linear masses are attached to the primary mass of a linear oscillator. In this work, the conventional vibration absorber described by [21], is enhanced by the insertion of an energy harvester in series with with the non-linear spring. The results indicate an increase in the efficiency of the vibration absorber, while simultaneously creating a proficient energy harvester.

Committee:

D. Dane Quinn, Dr. (Advisor); Tom Hartley, Dr. (Committee Member); Curtis Clemons, Dr. (Committee Member); Jiang Zhe, Dr. (Committee Member); Ernie Pan, Dr. (Committee Member)

Subjects:

Alternative Energy; Applied Mathematics; Energy; Engineering; Mechanical Engineering; Technology

Keywords:

energy harvesting; NES; non-linear; elliptic functions; method of averaging; impulse; piezoelectrics

Niechayev, Nicholas AlexanderThe Environmental Productivity and Photosynthetic Light Response of Agave americana: A Potential Semi-Arid Biofuel Feedstock
Master of Science (MS), Ohio University, 2016, Environmental Studies (Voinovich)
The potential for the desert succulent species Agave americana (L.) as an advanced biofuel crop in water limited regions has recently been recognized. However, the potential productivity of A. americana in the United States is not yet fully understood. This study developed an environmental productivity index (EPI) model that can be used to estimate the actual growth of A. americana based on the seasonal patterns of water, temperature, and photosynthetically active radiation (PAR) on a monthly time scale for any given region. Previously published research was used to construct indices that predict growth responses of A. americana to water and temperature. Light responses, however, have not previously been determined for this species, and this study is the first to experimentally resolve the physiological response of A. americana to varying intensities of PAR. The photosynthetic response to light was determined by measuring gas exchange over 24 hours in plants that were acclimated to varied light levels over 10 days. Results were used to derive a predictive index of the growth response to light. Maximum CO2 fixation rates were observed at a light intensity of 1250 µmol photons m-2 s-1. A monthly EPI was calculated as the product of the water, temperature, and light indices appropriate for the monthly environmental conditions in Maricopa, AZ, where the first trial of A. americana was recently completed. Growth predicted using the EPI was compared to actual production. The summed EPI values were highly correlated (R2 = 0.99) with the average total biomass of healthy 2 and 3 year old plants. Quantitative relationships derived here between environmental conditions and production of A. americana provide a simple tool to estimate and compare potential productivity across regions where this species has not yet been grown, and to determine potential geographic ranges in the future as climate changes.

Committee:

Sarah Davis, Dr. (Advisor); David Rosenthal, Dr. (Advisor); Ahmed Faik, Dr. (Advisor)

Subjects:

Agriculture; Agronomy; Alternative Energy; Biochemistry; Biology; Botany; Cellular Biology; Energy; Environmental Science; Environmental Studies; Horticulture; Plant Biology; Plant Sciences

Keywords:

crassulacean acid metabolism; light response; Li-Cor 6400; environmental productivity index; abiotic responses; agave americana; CAM; arid; semi-arid; bioenergy; climate change; PEPC; phosphoenolpyruvate carboxylase; scyphophorus acupunctatus; range; GIS

Briggs, Maxwell H.Improving Free-Piston Stirling Engine Power Density
Doctor of Philosophy, Case Western Reserve University, 2015, EMC - Mechanical Engineering
Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

Committee:

Joseph Prahl (Advisor)

Subjects:

Aerospace Engineering; Alternative Energy; Applied Mathematics; Conservation; Design; Electrical Engineering; Energy; Engineering; Mechanical Engineering; Mechanics; Naval Engineering; Nuclear Engineering; Technology

Keywords:

Stirling, Engine, Power Density, Energy, Free-Piston, Nodal Analysis, Isothermal Analysis, Analysis, Experimental Validation,

Mahabaduge, Hasitha PadmikaInfluence of a Front Buffer Layer on the Performance of Flexible CdS/CdTe Solar Cells
Doctor of Philosophy, University of Toledo, 2013, Physics
Cadmium telluride (CdTe) solar cells have been developing as a promising candidate for large-scale application of photovoltaic energy conversion and have become the most commercially successful polycrystalline thin-film solar module material. In scaling up from small cells to large-area modules, inevitably non-uniformities across the large area will limit the performance of the large cell or module. The effects of these non-uniformities can be reduced by introducing a thin, high-resistivity transparent buffer layer between the conductive electrodes and the semiconductor diode. ZnO is explored in this dissertation as a high-resistivity transparent buffer layer for sputtered CdTe solar cells and efficiencies over 15% have been achieved on commercially available Pilkington TEC15M glass substrates. The highest open-circuit voltage of 0.858V achieved using the optimized ZnO buffer layer is among the best reported in the literature. The properties of ZnO:Al as a buffer are also investigated. We have shown that ZnO:Al can serve both as a transparent conducting oxide layer as well as a high-resistivity transparent layer for CdTe solar cells. ZnO:Al reactively sputtered with oxygen can give the necessary resistivities that allow it to be used as a high-resistivity transparent layer. Glass is the most common choice as the substrate for solar cells fabricated in the superstrate configuration due to its transparency and mechanical rigidity. However flexible substrates offer the advantages of light weight, high flexibility, ease of integrability and higher throughput through roll-to-roll processing over glass. This dissertation presents significant improvements made to flexible CdTe solar cells reporting an efficiency of 14% on clear Kapton® flexible polyimide substrates. Our efficiency of 14% is, to our knowledge, the best for any flexible CdTe cell reported in literature.

Committee:

Alvin Compaan (Committee Co-Chair); Dean Giolando (Committee Co-Chair); Robert Deck (Committee Member); Michael Heben (Committee Member); Upali Jayamaha (Committee Member)

Subjects:

Alternative Energy; Energy; Materials Science; Optics; Physics

Keywords:

CdTe; HRT; TCO

Baktiono, SuryaA Study of Field-Oriented Control of a Permanent Magnet Synchronous Generator and Hysteresis Current Control for Wind Turbine Application
Master of Science, The Ohio State University, 2012, Electrical and Computer Engineering
Wind turbine has been popular in the area of renewable energy source. Wind turbine has shown the biggest growth in the past 10 years compared to other renewable sources. Permanent Magnet Synchronous Generator (PMSG) used as wind turbine generator. PMSG is suitable for the application due to its high efficiency, high torque-to-size ratio, and low maintenance requirement. The intermittent characteristic of wind requires a wind turbine to have good control system. This thesis discusses the Field Oriented Control (FOC) and Hysteresis Current Control (HCC) technique used to control the generator-side and grid-side respectively. In order to perform these controls, good understanding of the PMSG and electrical grid are required. In addition, reference frame theory and Space Vector Modulation are explained as supplement theories used for the Field Oriented Control. A MATLAB/Simulink simulation has been developed to simulate the control algorithms.

Committee:

Ali Keyhani, PhD (Advisor); Mahesh Illindala, PhD (Committee Member)

Subjects:

Alternative Energy; Energy; Engineering

Keywords:

Wind Energy; Wind Turbine; PMSG: FOC; HCC; Field oriented control; Hysteresis current control; Permanent magnet synchronous generator

Yarlagadda, SriramA Battery Management System Using an Active Charge Equalization Yechnique Based on DC-DC Converter Topology
Master of Science in Engineering, University of Akron, 2011, Electrical Engineering

Several alternative approaches are presently being considered to replace gasoline for portable energy. The efficient utilization, storage and management of energy are extremely important with regard to portable energy supply. The most abundant commodity available in the market for portable energy storage is the battery. Series strings of storage batteries are used in portable electrical appliances, electric vehicles, space vehicles, telephone industry, power system industries and military applications. Each battery when operating in series has a slightly different capacity due to manufacturing tolerances and environmental conditions. After several charge/discharge cycles, the battery strings tend to go out of balance. This is the motivation to develop a Battery Management system (BMS) to increase the capacity and efficiency of batteries. In this work, a BMS is developed for lead-acid batteries in series which monitors the state of all the batteries in the stack by keeping track of battery operational parameters such as voltage, charge during charging/discharging, idle periods and ensures proper operational conditions to safeguard the battery pack from degrading its useful life.

A novel active charge equalization technique is proposed to achieve the balancing of batteries in a stack in terms of both voltage and charge as the battery is being charged/discharged, and in idle periods in order to maximize the energy of stack. In the proposed scheme, the energy is transferred to the battery with lowest voltage from a battery with highest voltage. An overvoltage and over-discharge protection circuit has also been developed to reduce the degradation of battery life. The proposed scheme comprises of the following: • Dissipative schemes of charge equalization where extra energy is somehow dissipated across passive elements. • Bidirectional DC/DC converters which are expensive and tough to implement. • Switching capacitive schemes of equalization where energy is transferred to the neighboring cells.

Committee:

Tom T. Hartley, PhD (Advisor); Iqbal Husain, PhD (Advisor); Yilmaz Sozer, PhD (Committee Member)

Subjects:

Alternative Energy; Automotive Engineering; Computer Engineering; Electrical Engineering; Energy; Technology

Keywords:

Active charge equalization technique; Battery Management System; DC DC converters; Matlab Simulink models for Electric vehicle; Power Electronics; Battery

Chettiyar, ThanigasalamExamination of Power Quality Control within a Cost-based Microgrid Architecture
Master of Science (M.S.), University of Dayton, 2013, Electrical Engineering
Microgrids (MGs) are important because of their ability to provide a "greener" solution to obtain reliable, secure and sustainable electricity from renewable sources of energy. As a MG can be islanded (i.e. disconnected from the main grid), the power quality issues observed are very different when compared to the traditional centralized grid. These issues are of significant importance because the reliability of the grid is impacted by the MG operation. Currently, the typical power quality issues such as total harmonic content and transient stability have been studied only for an ideal voltage source of constant magnitude - assumed to be the distributed generator (DG) connected to a grid. However, under practical conditions, a MG might have more than one DG (Example: solar, wind, diesel generators, and CHP, among others) connected to it and some of these DGs would be subject to varying output throughout the day based on changes in intensity of solar radiation, wind speed, and other environmental factors. The current research takes this into account and examines the efficacy of an existing power quality control strategy for a MG consisting of a stochastically modeled renewable energy source i.e. a solar PV array. A Robust Servomechanism Controller in conjunction with a Discrete Sliding Mode Controller is employed to achieve voltage and current regulation in the MG. Stochastic model of a solar PV array along with a supplemental DC voltage source model have been presented in this research. The solar PV array utilizes actual TMY3 irradiance data for Dayton, Ohio. The supplemental DC voltage source is connected in series with the solar PV output and helps to compensate for the intermittent nature of energy produced by the solar PV array. A cost-based approach to connecting and disconnecting the MG from the utility supply whilst ensuring the maximum use of incident solar energy is also presented in this research. The MG model developed in Matlab Simulink® follows the Consortium for Electric Reliability Technology Solutions (CERTS) architecture for modeling MGs. The examination of the efficacy of an existing control strategy in a MG topology capable of making real-time cost-based decisions is expected to help the practical implementation of MGs.

Committee:

Malcolm Daniels, Ph.D. (Advisor); Raúl Ordóñez, Ph.D. (Committee Member); Kevin Hallinan, Ph.D. (Committee Member)

Subjects:

Alternative Energy; Electrical Engineering; Energy

Keywords:

microgrid; power quality control; cost-based microgrid architecture; simulink microgrid model; solar PV; transient performance assessment;

Haile, YohannesSustainable Value And Eco-Communal Management: Systemic Measures For The Outcome Of Renewable Energy Businesses In Developing, Emerging, And Developed Economies
Doctor of Philosophy, Case Western Reserve University, 2016, Management
The International Energy Agency (IEA) forecast of 2014 indicates a 37% energy demand increase in the next 25 years. To meet the forecasted energy demand increase and ameliorate ecological stress associated with meeting the demand, the increased deployment and effective operations of renewable energy projects and businesses are of paramount importance. This study sought to understand the factors impacting renewable energy businesses and identifies an integrative measure for the performance of these businesses in the context of developing, emerging, and developed economies. Our research data have revealed that the performance of renewable energy (RE) systems cannot be viewed or determined in isolation (contextual reduction) from the social system of the host community. Hence, the best way to understand its implications is using integrative approaches. Our research suggests well-developed and deployed eco-communal management practices, a type of innovative management, is the best way to create value proposition of RE businesses/projects into sustainable value. For developed economies the primary value path is from knowledge creation => eco-communal management => sustainable value, whereas, it is from connectedness => eco-communal management => sustainable value for emerging economies. In the context of emerging economies, the impact of knowledge creation on sustainable value is primarily indirect through hastening and affecting transformational changes, hence deploying effective transition engagements and instituting accurate methods to measure the efficacy of knowledge creation are imperative. In the context of developing economies knowledge creation and integrated vision frame the outcome of the RE business or project mediated by both eco-communal management and market creation. Our research further suggests the level of managerial authority bifurcates the translation of strategic objectives of businesses, and the relatedness of the key decision maker into sustainable value through its strategic management practices in emerging economies, while it does not have significance in developed economies. Our research makes theoretical, and practical contribution to the theory of innovation by discovering a novel type of management strategy, which is effective and instrumental in creating sustainable value from the initial conditions of integrated vision, knowledge creation, and connectedness.

Committee:

Roger Saillant, PhD (Committee Chair); Kathleen Buse, PhD (Committee Member); James Gaskin, PhD (Committee Member); Christopher Laszlo, PhD (Committee Member); Hokey Min, PhD (Committee Member)

Subjects:

Alternative Energy; Area Planning and Development; Asian Studies; Atmosphere; Behavioral Psychology; Behavioral Sciences; Business Administration; Business Education; Climate Change; Cognitive Psychology; Communication; Comparative; Conservation; Demographics; Design; Ecology; Economic History; Economic Theory; Economics; Education; Electrical Engineering; Energy; Engineering; Entrepreneurship; Environmental Economics; Environmental Education; Environmental Engineering; Environmental Health; Environmental Justice; Environmental Management; Environmental Philosophy; Environmental Science; Environmental Studies; European Studies; Experiments; Finance; Geography; Health; Health Sciences; Higher Education; History; Hydrologic Sciences; Information Science; Information Systems; Information Technology; International Relations; Labor Economics; Labor Relations; Latin American Studies; Management; Marketing; Mass Communications; Mathematics; Mechanical Engineering; Meteorology; Natural Resource Management; Occupational Psychology; Organizational Behavior; Personal Relationships; Personality; Political Science; Public Policy; Regional Studies; Religion; Social Structure; Spirituality; Statistics; Sub Saharan Africa Studies; Sustainability; Systematic; Systems Design; Systems Science; Technology

Keywords:

Performance, nested complexity, connectedness, eco-communal management, transition engagement, technology and business model innovations, entrepreneurship, and sustainable value

Gassama, EdrissaA Model of the Dye-Sensitized Solar Cell: Solution Via Matched Asymptotic Expansion
Master of Science, University of Akron, 2014, Applied Mathematics
The distribution of the components in the dye-sensitized titanium dioxide solar cell (DSC) is investigated in the thesis. The transport and drift of the ions (iodide, triiodide and cathion) in the electrolyte and the electrons in the nanocrystalline titanium dioxide semiconductor were modeled in the operation of the cell. Homogenization is used to reduce the three dimensional solar cell into a one dimensional system along the thickness of the cell. The model includes both the porous semiconductor and the bulk electrolyte layer between the semiconductor and the cathode. The influence of the parameters of the cell on electron concentration profile is investigated. In particular, the influence of the electron lifetime and the thickness of the nanocrytalline semiconductor are investigated. We applied boundary layer techniques in the solution of the resulting system.

Committee:

Dmitry Golovaty, Dr. (Advisor); Gerald Young, Dr. (Committee Member); Curtis Clemens, Dr. (Committee Member)

Subjects:

Alternative Energy; Applied Mathematics; Energy

Keywords:

solar cell ; dye sensitized titanium dioxide; solar cell ; semiconductor; boundary layer techniques; matched asymptotic expansion;

Deal, Michael WilliamNet Primary Production in Three Bioenergy Crop Systems Following Land Conversion
Master of Science, University of Toledo, 2011, Biology (Ecology)
Many factors influence net primary production (NPP) and the distribution of fixed carbon (C) within an agro-ecosystem which includes, but is not limited to, management activities, microclimate variables, the amount of carbon available from photsynthate, soil structure, soil texture, nutrient availability, plant phenology and crop species. The objectives of this study were to: (1) determine the differences in aboveground net primary production (ANPP), belowground net primary production (BNPP), shoot to root ratio (S:R), and leaf area index (LAI) in three bioenergy crop systems, (2) evaluate the production of these three systems in two different land-use conversions, and (3) identify the key biophysical drivers of NPP in the first year after conversion. This investigation included three agriculture sites converted from conservation reserve program (CRP) management to bioenergy crop production (corn, switchgrass with oat cover crop, and prairie-mix with oat cover crop), three sites converted from traditional agriculture production to bioenergy crop production, and one site left as a reference grassland. The site converted from conventional agriculture produced smaller ANPP in corn (19.03 ± 1.90 Mg ha-1 yr-1) than the site converted from the CRP to corn (24.54 ± 1.43 Mg ha-1 yr-1). The two land conversions were similar in terms of ANPP for switchgrass (4.88 ± 0.43 for CRP and 2.04 ± 0.23 Mg ha-1 yr-1 for agriculture) and ANPP for prairie-mix (4.70 ± 0.50 for CRP and 3.38 ± 0.33 Mg ha-1 yr-1 for agriculture). The BNPP at the end of the growing season in all the bioenergy crop systems was not significantly different (p = 0.75, N = 8). SWC played the most important role in limiting ANPP, while S:R and SOC present before land conversion, had the strongest influence on BNPP. SWC represents an important regulation of photosynthesis in plants and therefore regulates aboveground production in the first year of planting. Belowground production was more closely linked to SOC present at the inception of the study. Understanding the variation in NPP within different scenarios of land-use change will improve the ability to predict the sustainability of bioenergy crop cultivation across the United States.

Committee:

Jiquan Chen, PhD (Committee Chair); Jonathon Bossenbroek, PhD (Committee Member); Christine Mayer, PhD (Committee Member)

Subjects:

Agronomy; Alternative Energy; Ecology; Energy; Environmental Science; Environmental Studies

Inoa, ErnestoA New High-Frequency Injection Method for Sensorless Control of Doubly-Fed Induction Machines
Doctor of Philosophy, The Ohio State University, 2012, Electrical and Computer Engineering

This research introduces a new method to solve the sensorless control problem for a grid-connected Doubly-Fed Induction Machine (DFIM). The proposed method is based on high-frequency signal injection and the fact that the rotor of a DFIM can be seen as a rotating secondary of an induction transformer.

The currently used sensorless techniques, besides being parameter sensitive, fail during fault ride-through conditions. This fact makes these techniques almost irrelevant for wind turbines applications since, due to new grid codes and regulations, wind turbines are required to stay connected during a fault. Hence, even if the machine in the wind turbine is equipped with a sensorless control algorithm, an encoder (or resolver) is still needed in order to be able to control the machine during fault ride-through conditions.

The proposed sensorless algorithm works by applying a high-frequency voltage to the rotor and measuring the produced high-frequency voltage on the stator. The high-frequency voltage applied to the rotor is independent of, and superimposed on, the control voltage applied to the rotor. It will be shown that the rotor position information is encoded in the phase of the space vector of the high-frequency voltage measured at the stator; hence, the proposed sensorless method is implemented by filtering out the high-frequency voltage at the stator, and determining the phase of its space vector. This results in a relatively easy implementation.

The proposed sensorless method, besides being parameter independent, remains fully functional during grid faults. Moreover, as opposed to other high frequency injection methods, the proposed method does not require rotor saliency; hence, it is not necessary to induce saturation in the machine.

The mathematical principle of the proposed technique and its implementation are presented. Computer simulations and experimental results are also included for verification.

Committee:

Longya Xu, PhD (Advisor); Vadim Utkin, PhD (Committee Member); Donald Kasten, PhD (Committee Member); Mahesh Illindala, PhD (Committee Member); Herbert Ockerman, PhD (Committee Member)

Subjects:

Alternative Energy; Electrical Engineering; Energy

Keywords:

Wind power; Doubly-Fed Induction Machines; sensorless control; high-frequency injection method

Tulpule, Pinak J.Control and optimization of energy flow in hybrid large scale systems - A microgrid for photovoltaic based PEV charging station
Doctor of Philosophy, The Ohio State University, 2011, Electrical and Computer Engineering

This dissertation presents a hybrid large scale system model of a DC microgrid, its input to state stability analysis and an optimal control algorithm for load side energy management. The theoretical principles of hybrid large scale system modeling, stability, and optimal control for stochastic systems are applied to DC microgrid designed for a photovoltaic based charging station at a workplace parking garage. The example DC microgrid has two energy sources (renewable energy source and power grid) and many plug-in electric vehicle (PEV) charging stations. Stochastic inputs to the system are solar power and charging demand of the PEVs and the control inputs are the vehicle charging power and duration.

The hybrid large scale system model of the DC microgrid is developed in state space form to model the large number of DC-DC converters and discrete changes in the system configurations caused by actions of a supervisory controller and converter operating modes. Stability analysis of the model using the Gersgorin principle, an eigenvalue inclusion theorem and connective stability principles provide design guidelines and conditions on interconnection properties. Necessary conditions for the large scale system stability are provided using eigenvalue analysis. The input to state stability analysis is performed using Lyapunov theory for hybrid systems to provide constraints on the dwell time of the switching signal.

The optimization problem is structured as an inventory control problem and solved using dynamic programming with stochastic inputs to find the charging power of all the vehicles at each time step. A simple but realistic rule based algorithm is developed to distribute the total charging power among available vehicles. The control algorithm schedules PEV charging power to maximize the use of solar energy, reduce energy taken from the grid, and satisfy the charging demand of all vehicles within the switching constraints. Finally, this research is accompanied by the overall energy-economic analysis of the PV based PEV charging station to show the feasibility of the proposed method in real world applications. The economic analysis is based on one time charging during a day and considering bidirectional power flows with the grid using net metering.

Committee:

Stephen Yurkovich, PhD (Advisor); Giorgio Rizzoni, PhD (Committee Member); Jin Wang, PhD (Committee Member)

Subjects:

Alternative Energy; Economics; Electrical Engineering; Energy

Keywords:

Photovoltaic workplace charging; plug-in electric vehicles; DC microgrid; Hybrid Large Scale System Model; Economic analysis; solar power; Optimal load side energy management; Inventory control problem

Baughman, Jessi AlanSolid-State NMR Characterization of the Structure and Morphology of Bulk Heterojunction Solar Cells
Master of Science, University of Akron, 2012, Chemistry
A bulk heterojunction, organic solar cell, composed of a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was studied to determine the structure at the interface of the two compounds. Films of neat P3HT and the P3HT:PCBM composite where cast and annealed at elevated temperatures in order to determine the impact of sample annealing on the interface structure and interface volume of the blend. The films were characterized with 1D 13C solid-state NMR and 2D 1H-13C heteronuclear correlation (HETCOR) NMR. HETCOR NMR, with Lee-Goldburg cross polarization, was used to observe discrete intermolecular interactions between the alkyl side chain of P3HT and the C60, phenyl ring, and alkyl groups of PCBM. From these intermolecular interactions, a model of the structure at the P3HT:PCBM interface was constructed, which reveals the presence of stabilizing π- stacking between the thiophene ring of the P3HT and the phenyl ring of PCBM. Also, the C60 species interacts extensively with the alkyl groups of P3HT. The data indicates a phase separation after annealing that reduces the volume of the interface without disturbing the interface structure. A HETCOR NMR method using tangent cross polarization was used to confirm the phase separation of the P3HT and PCBM layers after thermal annealing.

Committee:

David Modarelli, Dr. (Advisor); Matthew Espe, Dr. (Committee Member); Kim Calvo, Dr. (Committee Chair)

Subjects:

Alternative Energy; Analytical Chemistry; Chemistry; Energy; Materials Science; Molecular Chemistry; Morphology; Polymer Chemistry; Polymers

Keywords:

bulk heterojunction; organic; solar cells; P3HT; PCBM; solid-state NMR; MAS; HETCOR; interface; electron transfer; power conversion efficiency; phase separation;

Alsharif, SameerWind Farm Cooperative Control Strategies for Optimal Power Generation and Frequency Control
Doctor of Philosophy, Case Western Reserve University, 2017, EECS - System and Control Engineering
As wind energy penetration increases, grid operators need more control capabilities of the wind farms. Typical wind farm control solutions currently used by wind turbine manufacturers and developers are based on simple look-up table algorithms for active and reactive power generation, and for the associated frequency and voltage control strategies. However, this approach does not consider power generation efficiency or mechanical fatigue issues at the wind farm level. To address these critical problems, we develop a new cooperative control strategy that provides power generation optimization for the frequency control case with de-rated wind turbines. The new methodology relies on finding the optimum rotational velocity of the wind turbines of the wind farm such that the sensitivity of power generation to the change in the wind velocity is minimized. The new strategy is validated at three complementary levels: (1) a multi-turbine simulator with 20 wind turbines with different rotors, sizes and wind speed, (2) a 2 machine wind farm based on the 5 MW NREL FAST simulator, and (3) real experiments of a small wind farm at the wind tunnel of the Control and Energy Systems Center, CWRU. The results increase the grid operator’s control capabilities and open the door to higher wind energy penetration levels.

Committee:

Mario Garcia-Sanz (Advisor); Mingguo Hong (Committee Member); Vira Chankong (Committee Member); Christos Papachristou (Committee Member)

Subjects:

Alternative Energy; Applied Mathematics; Automotive Engineering; Electrical Engineering; Energy; Engineering

He, RuixuanStudies on Ionic Conductivity and Electrochemical Stability of Plasticized Photopolymerized Polymer Electrolyte Membranes for Solid State Lithium Ion Batteries
Doctor of Philosophy, University of Akron, 2016, Polymer Engineering
In pursuit of safer and more flexible solid-state lithium ion batteries, solid polymer electrolytes have emerged as a promising candidate. The present dissertation entails exploration of solid plasticized, photopolymerized (i.e. ultraviolent-cured) polymer electrolyte membranes (PEM) for fulfilling the critical requirements of electrolytes, such as high ionic conductivity and good thermal and electrochemical stability, among others. Electrochemical performance of PEMs containing lithium ion half-cells was also investigated at different two temperatures. Phase diagram approach was adopted to guide the fabrication of two types of plasticized PEMs. Prepolymer poly (ethylene glycol) diacrylate (PEGDA) was used as a matrix for building an ionic conductive and mechanically sturdy network. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was incorporated as a source of lithium ions, while a solid plasticizer succinonitrile (SCN) and a liquid plasticizer tetraethylene glycol dimethyl ether (TEGDME) were incorporated in the respective systems. The important role of plasticizer on the enhancement of ionic conductivity (σ) to the superionic conductive level (10-3 S/cm) was revealed in both systems. It is worth noting that photopolymerization induced crystallization (PIC) occurred during UV-curing in the SCN-rich region of the ternary PEGDA/LiTFSI/SCN ternary mixtures. The PEM thus formed contained a plastic crystal phase, which showed lower σ relative to their amorphous PEGDA/LiTFSI/TEGDME counterpart. Comparisons on other thermal and electrochemical properties of the two types of PEMs are presented in Chapter IV. For the PEGDA/LiTFSI/SCN PEMs, fundamental study was carried out to clarify the relationship between σ and glass transition temperature (Tg). In lithium salt/polymer binary PEMs, increase in Tg and reduction in σ were observed; these may be attributed to ion-dipole complexation between dissociated lithium cations and ether oxygen upon salt addition. Notably, above the threshold salt concentration of 7 mol %, dual loss tangent peaks were observed in dynamic mechanical studies. These might be ascribed to segmental relaxations of ion-dipole complexed networks and that of polymer chains surrounding the undissociated lithium salt acting like “fillers”. Upon SCN incorporation, these two peaks merged into one that was further suppressed below the Tg of the pure network, whereas σ improved to the superionic conductor level. The role of SCN on the σ enhancement as both plasticizer for the polymer network and ionizer for the salt is discussed in Chapter V. In order to improve the mechanical toughness of the highly conductive PEGDA/LiTFSI/SCN PEM, effects of prepolymer molecular weight on mechanical and electrochemical properties of PEMs were further investigated. By increasing molecular weight of PEGDA from 700 to 6000 g/mol, toughness and elongation at break were enhanced as expected. Interestingly, improved ionic conductivity was achieved simultaneously. The dual improvement may be attributed to the less chemical crosslinked points and the more flexible chain motion in the looser network of PEGDA6000-PEM relative to its PEGDA700 counterpart. Subsequently, high thermal stability and electrochemical stability of both types of PEMs, as well as the satisfactory room temperature charge/discharge cycling performance of PEM containing lithium ion half-cells were observed. The pertinent information is documented in Chapter VI. Finally, the investigation of the charge/discharge cycling performance of solid-state LiFePO4 half-cells at an elevated temperature of 60 °C is discussed in Chapter VII. In the half-cells, particularly, SCN plasticized PEMs with and without electrolyte modifier lithium bis(oxalato)borate (LiBOB) were respectively employed. Rapid decline of capacity and increase of cell resistance were found in the unmodified PEM containing cell; however, these deteriorations were greatly suppressed upon LiBOB modification. Electrochemical and thermal compatibility of PEMs towards different electrodes were examined in several symmetric cells and half-cells. Detailed characterization on LiFePO4 electrodes and PEMs retrieved from these cells implied that the observed battery failure might be triggered by an amide-forming side reaction that took place at the interface of a SCN plasticized PEM and a lithium electrode at high temperature. Of particular importance is the fact that this detrimental side reaction was effectively suppressed upon LiBOB electrolyte modifier addition. Plausible mechanisms are discussed.

Committee:

Thein Kyu (Advisor); Xiong Gong (Committee Member); Younjin Min (Committee Member); Jie Zheng (Committee Member); Yu Zhu (Committee Member)

Subjects:

Alternative Energy; Energy; Materials Science; Physical Chemistry; Polymers

Keywords:

solid polymer electrolyte; lithium ion battery; ionic conductivity; plasticizer; phtopolymerization; glass transition temperature; high temperature; electrolyte additive

Kumin, Enid C.Ecosystem-Based Management and Refining Governance Of Wind Energy in the Massachusetts Coastal Zone: A Case Study Approach
Ph.D., Antioch University, 2015, Antioch New England: Environmental Studies
While there are as yet no wind energy facilities in New England coastal waters, a number of wind turbine projects are now operating on land adjacent to the coast. In the Gulf of Maine region (from Maine to Massachusetts), at least two such projects, one in Falmouth, Massachusetts, and another on the island of Vinalhaven, Maine, began operation with public backing only to face subsequent opposition from some who were initially project supporters. I investigate the reasons for this dynamic using content analysis of documents related to wind energy facility development in three case study communities. For comparison and contrast with the Vinalhaven and Falmouth case studies, I examine materials from Hull, Massachusetts, where wind turbine construction and operation has received steady public support and acceptance. My research addresses the central question: What does case study analysis of the siting and initial operation of three wind energy projects in the Gulf of Maine region reveal that can inform future governance of wind energy in Massachusetts state coastal waters? I consider the question with specific attention to governance of wind energy in Massachusetts, then explore ways in which the research results may be broadly transferable in the U.S. coastal context. I determine that the change in local response noted in Vinalhaven and Falmouth may have arisen from a failure of consistent inclusion of stakeholders throughout the entire scoping-to-siting process, especially around the reporting of environmental impact studies. I find that, consistent with the principles of ecosystem-based and adaptive management, design of governance systems may require on-going cycles of review and adjustment before the implementation of such systems as intended is achieved in practice. I conclude that evolving collaborative processes must underlie science and policy in our approach to complex environmental and wind energy projects; indeed, collaborative process is fundamental to the successful governance of such projects, including any that may involve development of wind energy in the Massachusetts coastal zone or beyond. Three supplemental files of coded data accompany this dissertation.

Committee:

James Jordan, Ph.D. (Committee Chair); Joy Ackerman, Ph.D. (Committee Member); Herman Karl, Ph.D. (Committee Member)

Subjects:

Alternative Energy; Energy; Environmental Management; Environmental Studies; Public Policy

Keywords:

alternative energy; case studies; coastal zone; collaborative management; content analysis; ecosystem-based management; environmental policy; environmental decision making; Massachusetts; renewable energy; siting; wind energy; wind power; wind turbines

Vance, William M.A Computational Study of a Photovoltaic Compound Parabolic Concentrator
Master of Science in Renewable and Clean Energy Engineering (MSRCE), Wright State University, 2015, Renewable and Clean Energy
Routines have been written and added to the Wright State developed solar system simulation program called Solar_PVHFC to model incident solar radiation for a compound parabolic concentrator (CPC) that uses solar panels (photovoltaic panels) to produce electrical energy. Solar_PVHFC is a program that models a solar energy system composed of solar panels to produce electricity from the sun, hydrogen storage tanks to chemically store the energy produced by the solar panels, and fuel cells to convert between electrical and chemical energy when required. Solar_PVHFC features several adjustable parameters to model a solar panel, hydrogen storage, and fuel cell system. Now Solar_PVHFC can model CPC solar panels. The CPC portion of this program allows for building and modifying CPCs based on three input variables: the concentration ratio, the degree of truncation, and the absorber width. Included in the program is a crude cost analysis that can be used as an economic means of comparing variations of CPCs and comparing CPCs against conventional solar panels. Solar_PVHFC models available solar radiation impinging on a solar panel using TMY3 data files. Inputs include the tilt and azimuthal angle of the panels, the geographical location of the panels, and the time period of the analysis. Because of this thesis work, Solar_PVHFC can now model panels that track the sun for any configuration of one or two axes of rotation and can even incorporate rotational limits. This thesis investigated panels using a fixed orientation, three different single axis tracking orientations, and two axis tracking. Any manufactured module with known specifications can be used as the solar panel, and the program calculates the current-voltage curve and maximum power point for that module on an hourly basis. This thesis investigated CPC and conventional solar panels with module efficiencies of 15.2%, 20.4%, 21.5%, and 28.3%. CPC solar panel simulations were run for concentration ratios of 2, 5, and 10. The degree of truncation ranged from no truncation with a truncated height ratio of 1, low truncation with a truncated height ratio of 0.75, moderate truncation with a truncated height ratio of 0.5, and high truncation with a truncated height ratio of 0.25. The absorbing width is the width of the solar cells at the bottom of the CPC and was scaled with the concentration ratio in an effort to maintain almost consistent total opening apertures. The absorbing width had values of 0.1657 m, 0.06627 m, and 0.03313 m with concentration ratios of 2, 5, and 10 respectively. Different mirror reflectivities and the use of cooling were also investigated. The standard of comparison between different configurations of CPCs and conventional panels was the LCE (levelized cost of energy). This was calculated based on inputs of solar cell price and reflector material price on a per unit area basis. The LCE analysis used in this work only accounts for the solar cell and reflector costs and does not include costs associated with framing, tracking, wiring, inverters, maximum power point tracking, etc. It was thought that these costs would be similar for both the conventional solar panel system and the CPC solar panel system. This thesis’ cost analysis only looks at the part of the system where the analysis used provides differences between the CPC and conventional solar system. The electric output per unit area was also used as a means of comparison between the two systems. Many results are shown and discussed in the main body of this thesis with an exhaustive collection of results found in the Appendix. East-west, north-south, and two axis tracking showed that CPCs could significantly reduce the LCE of higher priced conventional panels using the same solar cell module. Fixed and vertical axis tracking did not prove very effective for CPCs. The only CPC system to achieve a lower LCE than the low efficiency, low cost conventional panel was the low efficiency CPC, and this was conditional on two axis tracking and high reflectivity. The most effective CPCs generally utilized high degrees of truncation and low to moderate concentration ratios, with the exception of CPCs utilizing high concentration in combination with cell temperature control. All CPCs showed a drop in electric output per unit area compared to conventional panels; with north-south tracking showing the least drop. A decrease in reflector costs and in high efficiency solar cell costs could enhance the potential of CPC solar panels. A higher mirror reflectivity could also make CPCs more competitive with conventional panels. CPCs show promise when compared to expensive, high efficiency conventional panels, but cannot compete with inexpensive, lower efficiency conventional panels. A more thorough cost analysis may bring more clarity to the comparisons between CPC solar panels and conventional solar panels.

Committee:

James Menart, Ph.D. (Advisor); Hong Huang, Ph.D. (Committee Member); Amir Farajian, Ph.D. (Committee Member)

Subjects:

Alternative Energy; Energy; Engineering; Experiments; Sustainability

Keywords:

CPC; compound parabolic concentrator; PV; photovoltaic; computer model

Senevirathna, WasanaAzadipyrromethene-based Metal Complexes as 3D Conjugated Electron Acceptors for Organic Solar Cells
Doctor of Philosophy, Case Western Reserve University, 2014, Chemistry
Organic photovoltaic is a promising technology for solar energy harvesting. The power conversion efficiency (PCE) of solution-processed bulk heterojunction (BHJ) cells has reached over ~10%. Fullerene and its derivatives have been the most investigated acceptor. However, fullerene derivatives have disadvantages: (i) weak absorption in visible and near-IR range, (ii) limited energy tunability. Promising alternative non-fullerene acceptors are limited, and the best efficiency achieved so far is ~5%. In this study, we used azadipyrromethene (ADP) as the building block to synthesize a series of electron acceptors. ADP derivatives are strong chromophores with strong absorption around ~ 600 nm. They are electro-active materials with two reduction peaks. Their optoelectronic properties can be tuned upon structural modifications. In this work, we synthesized a series of 3-dimensional (3D) conjugated homoleptic Zn(II) complexes of ADP dyes. The degree of conjugation in ADP was extended by installing phenylacetylene, ethynylthiophene and thiophene groups at the pyrrolic positions of the ADP core using Stille coupling. 3D structures of these molecules were synthesized by chelating with Zn(II). These new molecules showed broad intense red to near-IR absorption with onsets around 800 nm. The estimated LUMO energy level of Zn(II) complexes ranged from -3.60 to -3.85 eV. Their strong acceptor properties were demonstrated by fluorescence quenching experiments using poly(3-hexylthiophene) as the donor. These metal complexes quenched the fluorescence efficiently in both solutions and film. DFT calculations showed that all the metal complexes have distorted tetrahedral structures, with additional conjugated `arms’ extending in 3 dimensions. A unique feature of these complexes is that the two ADP ligands are p-stacked with each other, with frontier molecular orbitals delocalized over the two ligands. These complexes can therefore easily accept electrons, delocalize the negative charge over a large conjugated structure and have the potential of transporting charges in 3D, making them alternatives to fullerene derivatives as acceptors in organic solar cells, photo-detectors and other optoelectronic applications. Small internal reorganization energy is very desirable for high-performance optoelectronic materials, as it facilitates both charge separation and charge transport. DFT calculations were performed for a series of model molecules to gain better understanding on the energy level tuning, electron affinity, and the internal reorganizations of the electron transfer process. ADP-based compounds were more stable in their anionic state than cationic or neutral states and had high electron affinity, indicating their potential as n-type electron accepting material. The internal reorganization energy of ADPs were relatively low due its conjugated structure, and decreased by extending the conjugation via phenylethylene and ethylenethiophene substitutions, or by coordinating with BF2+. The largest decrease in reorganization energy was obtained when coordinating two azadipyrromethenes with zinc(II) to form a three-dimensional homoleptic zinc(II) complex, with calculated internal reorganization energies below 0.1 eV. These low reorganization energies are mainly due to the large rigid conjugated ¿ system. This work suggests that Zn(II) complexation is a novel strategy for obtaining materials that combine low internal reorganization energy with high electron affinity for the development of novel n-type optoelectronic materials. To further demonstrate their potential as electron acceptor, we made solar cells by blending the ADP-based molecules with a common electron donor, poly(3-hexylthiophene). All solar cells using Zn(II) complexes showed a photovoltaic effect, with a power conversion efficiency as high as 4.1%. Structure-property studies suggest that the 3D nature of these Zn(II) complexes prevents crystallization and promotes a favorable nanoscale morphology. The acceptor also significantly contributed to photocurrent generation by harvesting light between 600 nm and 800 nm. These results demonstrate a new paradigm to designing acceptors with tunable properties that can overcome the limitations of fullerenes.

Committee:

Geneviève Sauvé (Advisor); Anna Samia (Committee Chair); Clemens Burda (Committee Member); Robert Dunbar (Committee Member)

Subjects:

Alternative Energy; Chemistry; Energy; Molecular Chemistry; Molecular Physics; Molecules; Morphology; Organic Chemistry; Physical Chemistry

Keywords:

Photovoltaic, organic solar cells, electron acceptors, non-fullerene acceptors, 3D molecules, organic semiconductors, n-type organic semiconductors, Inverted solar cells, azadipyrromethene, metal complexes, bulk hetero junction solar cells

Anwar, SaeedActive Power Compensation of Microgrid Connected Systems
Master of Science in Engineering, University of Akron, 2014, Electrical Engineering
The power quality of microgrids is one of the major issues in determining whether the microgrid is operating in grid connected (GC) mode or standalone (SA) mode. Power quality is degraded by harmonics, voltage unbalance, voltage sag and voltage swells. Harmonics cause performance degradation, aging, equipment heating and severe problems for critical loads that require very high power quality. In order to ensure the power quality of the grid and meet the standards, both active and passive power compensators are used. Due to the change in the coupling and inverter filter impedances in the microgrid, harmonics are not shared equally by the individual compensators. So, a particular inverter may be overstressed with the harmonic compensation operation. If the inverters in a decentralized microgrid structure are not adaptive, the system may be unstable due to inverter overloading. A novel adaptive harmonic compensation method for decentralized islanded microgrid structures is presented that incorporates the effect of line impedance parameter changes. The system can provide better harmonics sharing without any communication among the inverters or the central unit. For low harmonic current, the adaptive compensation system prioritizes voltage regulation at a Point of Common Coupling (PCC). For the GC mode of microgrid operation, the strategy to eliminate harmonics from the grid current as well as the PCC voltage for microgrid applications are presented in this dissertation. The position of the harmonics reduction unit is selected so that it can reduce the harmonic level of the grid current and PCC voltage harmonics irrespective of the distribution of the renewable energy sources in the microgrid. In the proposed control algorithm, the required amount of attenuation for the harmonics is determined to meet the THD requirement. A fast and efficient algorithm for phase detection irrespective of the presence of harmonics is used for the system. The effect of interharmonics and other disturbances on the phase detection system are presented. The role of a smart load in harmonic compensation is introduced through a dual boost PFC rectifier topology for input stage harmonic compensation. The effectiveness and performance of proposed methods are verified through simulations and experimental tests.

Committee:

Yilmaz Sozer, Dr. (Advisor); Malik Elbuluk, Dr. (Committee Member); Tom T. Hartley, Dr. (Committee Member); Seungdeog Choi, Dr. (Committee Member)

Subjects:

Alternative Energy; Electrical Engineering; Energy

Cheekati, Sree LakshmiGRAPHENE BASED ANODE MATERIALS FOR LITHIUM-ION BATTERIES
Master of Science in Engineering (MSEgr), Wright State University, 2011, Materials Science and Engineering
Improvements of the anode performances in Li-ions batteries are in demand to satisfy applications in transportation. In comparison with graphitic carbons, transition metal oxides as well as graphene can store over twice amount of lithium per gram. Recently, graphene-based anodes for Li-ion batteries are under extensive development. In this research, lithium storage characteristics in graphene oxide (GO), GO/Manganese acetate (GO/MnAc), GO/manganese oxide (GO/MnOx) composites and Nano Graphene Platelets (NGP) were studied. The prepared GO delivered reversible capacities of 706mAh/g with an average columbic efficiency of 87%. Reversible capacities of 533 mAh/g were observed for GO/MnAc composite. GO/MnOx nanocomposite thermal annealed at 400°C in inert atmosphere exhibited high reversible charge capacity of 798 mAh/g with an average columbic efficiency of 95% and capacity fade per cycle of 1.8%. The EIS spectra of discharge and charge profiles of GO and GO/MnOx composites were analyzed to investigate the kinetics evolution of electrode process at different stages of lithium storage.

Committee:

Hong Huang, PhD (Advisor); Daniel Young, PhD (Committee Member); Chu Kuan-lun, PhD (Committee Member); George Huang, PhD (Other)

Subjects:

Alternative Energy; Automotive Materials; Chemistry; Energy; Engineering; Materials Science; Metallurgy; Nanotechnology

Keywords:

Lithium Ion Batteries; Anode Materials; Graphene; Graphene Oxide; Nano Graphene Platelets; Graphene Oxide Manganese Acetate Composite; Graphene Oxide Manganese Oxide Nano Composite; Electrochemical Impedance Spectroscopy; Graphene Based Anode Materials;

Shandilya, Kaushik K.Characterization, Speciation, and Source Apportionment of Particles inside and from the Exhaust of Public Transit Buses Fueled With Alternative Fuels
Doctor of Philosophy in Engineering, University of Toledo, 2012, College of Engineering

The practical issue of Scanning Electron Microscope/Energy Dispersive X-ray Spectrometry (SEM/EDX) instrumentation compatibility for particle analysis is addressed. The physical and chemical characterization of fine particles is carried out inside a public transit bus fueled with biodiesel (BD) and ultra low sulfur diesel (ULSD).

The three sorts of square surface patterns represented the morphological characteristics of single inhalable particles in the air inside the bus in Toledo. The size and shape distribution results are compared to those obtained for a bus using ULSD and BD respectively.

Only the reproducible results from repeated experiments on ESEM and size distribution obtained by the GRIMM dust monitor are used in this study. The collected filters are analyzed using a computer controlled SEM to obtain aerosol elemental compositions. Factor analysis suggested possible sources of indoor particle levels in public transit bus as motor vehicles, outdoor soil and secondary particle formation. The conclusion is that SEM methodology is a valuable tool for studying the distribution of particulates.

A part of this study examines the toxic nature of these engine exhausts under different idling conditions. The results of the PM emission analysis showed that the PM mean value of emission is dependent on the engine operation conditions and fuel type. It is found that lubricant oil, PM ash content, and storage tanks are the major sources of elemental concentrations in the PM.

Another part of this study looks at the change from ULSD to BD in different idling mode that is investigated with respect to organic carbon (OC) and elemental carbon (EC) for public transit buses in Toledo, Ohio. The carbon source profile for both alternative fuels for eight carbon fractions is developed through real time experiments. The results indicated that the use of BD instead of ULSD is environmentally sustainable for human health and climate change.

A new method for determining kinetic parameters of soot oxidation is applied for exhaust particles collected from public transit buses. The results indicate that the use of BD in public transit buses will result in lower particle formation from the engine. Particle morphology is clearly spherical carbon nano particles with chain-like agglomerates.

Committee:

Ashok Kumar, PhD (Advisor); Cyndee Gruden, PhD (Committee Member); Farhang Akbar, PhD (Committee Member); Defne Apul, PhD (Committee Member); Dong-Shik Kim, PhD (Committee Member)

Subjects:

Alternative Energy; Analytical Chemistry; Atmosphere; Atmospheric Chemistry; Atmospheric Sciences; Chemical Engineering; Chemistry; Civil Engineering; Climate Change; Energy; Environmental Engineering; Environmental Health; Environmental Science; Environmental Studies; Experiments; Health; Health Sciences; Inorganic Chemistry; Morphology; Nanoscience; Particle Physics; Physical Chemistry; Public Health

Keywords:

Public Transit buses; Alternative Fuel; Scanning Electron Microscope; Carbon Speciation; Heavy Metals and elements; Factor Analysis; Physical Characterization; Shape and Size Analysis; Kinetics

Petek, Tyler JosephEnhancing the Capacity of All-Iron Flow Batteries: Understanding Crossover and Slurry Electrodes
Doctor of Philosophy, Case Western Reserve University, 2015, Chemical Engineering
Flow batteries have been studied for grid-scale energy storage applications because their capacity and power delivery rate can be independently scaled. The all iron flow battery is particularly attractive because iron, the only active species, is low cost, abundant, and environmentally benign. With conventional electrodes, the capacity is severely limited and coupled to the power rating because the negative electrode involves iron metal. The available capacity is further reduced by ferric ions transferring across the separator from the positive to the negative electrode where they react with iron metal causing chemical self discharge of the battery. In order to enhance the capacity of the all iron flow battery, the use of slurry electrodes to decouple capacity from the power rating and the self discharge by active species crossover are both studied. Analytical models accounting for crossover estimate the iron concentrations during continuous cycling using microporous Daramic separators and cation-selective Nafion separators. With both, the model predicts a buildup of iron in the negative electrolyte and a depletion of iron in the positive electrolyte that limits the capacity. Decreasing the amount of negative electrolyte relative to the positive enhances the electrolyte utilization. Cost models were used to optimize the separator thickness for capacity retention, coulombic efficiency, and voltaic efficiency. Batteries using Nafion are found to be double the cost of those using Daramic. With the optimized separator, the capacity must be enhanced further to reach the full market potential. Slurry electrodes studied herein are flowing suspensions of electrically conductive particles in the electrolyte. The particles form a continuous conductive network that allows the iron metal to plate on the surface of the particles and are then carried out of the battery to be stored in the external reservoirs; decoupling the capacity from the power rate. Techniques for interpreting electrochemical impedance spectroscopy of different slurry configurations are developed. The performance of the all iron slurry electrode was enhanced as the amount of metal deposition increased, due to enhanced electronic conductivity and plating kinetics. After cycling, less than 5% of the charge was plated on the current collector indicating effective slurry operation.

Committee:

Robert Savinell (Advisor); Jesse Wainright (Advisor); Rohan Akolkar (Committee Member); Jaikrishnan Kadambi (Committee Member)

Subjects:

Alternative Energy; Chemical Engineering; Energy; Engineering

Keywords:

Flow Batteries; Slurry Electrodes; Energy Storage; Crossover

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