Power and Energy Commons^™

Deposition Of Silicon Thin Films By Ion Beam Assisted Deposition, Tejaswini Miryala

Electrical & Computer Engineering Theses & Dissertations

With the depletion of non-renewable energy sources owing to increasing demands, we need to develop renewable energy sources, which can replace them with cleaner energy sources. The solar industry is one of these renewable energies. In spite of having very high potential, harvesting solar energy has been a challenge due to the cost of solar cells. Silicon dominates the photovoltaic industry, but even this technology can accommodate great improvements. This can be done notably by finding low cost deposition techniques for the silicon. The main aim of this thesis is to form high-quality nanocrystalline silicon thin films with the help …

Modification Of Deposition Process Parameters For Uniform Indium Layer Deposition, Isaac Butt

Electrical & Computer Engineering Theses & Dissertations

The need for more efficient light to energy converting cells has long been a subject of research and development. With abundant availability of solar energy that the earth receives, the photovoltaic industry has sought materials that could serve the purpose of great energy conversion. The photovoltaic industry is mainly dominated by Silicon owing to its abundant availability, reliability and economic cost. However, due to limitations on efficiency improvements, some focus has shifted toward III-V based solar cells with a great potential for attaining higher efficiency and multi-junction applications. However, the cost of the III-V materials is extremely high due to …

A Study Of The Sensitivity Of Energy Conversion Efficiency To Load Variation In Class-E Resonant Power Inverter, Richard Samuel Jennings

Electrical & Computer Engineering Theses & Dissertations

In this thesis the sensitivity of energy conversion efficiency (ECE) and output power of a class-E resonant inverter under variable resistive and inductive load assignments is examined for wireless power transfer (WPT) applications. By performing simulation and mathematical analysis, it was found that the on-resistance of the switching device has minor effect on the design’s efficiency. Additional comparisons between the simulation and mathematical analysis show reasonable output power and ECE load variation performance for the design, but with unique load impedances where zero voltage switching (ZVS) and zero derivative switching (ZDS) are achieved. These comparisons also expose inaccurate mathematical assumptions. …

Study Of A High-Efficient Wide-Bandgap Dc-Dc Power Converter For Solar Power Integration, Yashwanth Bezawada

Electrical & Computer Engineering Theses & Dissertations

This research focuses on the design and analysis of a Boost cascaded Buck-Boost (BoCBB) power converter with super high efficiency in electric power conversion. The BoCBB power converter is based on emerging wide-bandgap silicon-carbide (SiC) MOSFETs and Schottky diodes, which have only 1/6 times of power loss in traditional silicon power semiconductor devices. The BoCBB power converter can be widely applied in solar harvesting for the National Aeronautics and Space Administration (NASA), military bases and electric utilities, as well as high-power DC motor drives for the electric vehicles, robotics, and manufacturing and product lines.

This research analyzed the topology and …

Investigation Of Low Cost Substrate Approaches For Iii-V Solar Cells, Marlene Lydia Lichty

Electrical & Computer Engineering Theses & Dissertations

With the need for cleaner energy sources, which can displace fossil fuel, the solar cell industry is of particular interest due to the abundancy of the Sun. Silicon currently dominates terrestrial applications, but efficiency improvements have saturated. III-V based solar cells have reported the highest efficiencies, however, high costs due to substrates and fabrication processes have limited these devices to specialty applications, such as space. In order to reduce the cost associated with fabricating III-V semiconductor substrate material, two different approaches were taken in this work with a particular focus on making III-Vs more applicable outside of specialty applications, including …

Design Of Electrical Layout Of Offshore Wind Farms, Shirshak K. Dhali, Mahidhar Nandigam

Electrical & Computer Engineering Faculty Publications

The cost and efficiency of offshore wind farms are determined by a variety of factors which include the type of electrical system (AC or DC), transmission length, transmission voltage, rated power, wind turbine type, farm topology, and wind speed. Since the design variable space is large for such problems, computational optimization is necessary to find an optimal solution. This paper discusses a design methodology to determine the optimal values of components to minimize the cost of an offshore wind farm. The cost, loss, reliability models, and the application of geometric programing for optimization of the layout and configuration of an …

A New Formulation Of Time Boundary Integral Equation For Acoustic Wave Scattering In The Presence Of A Uniform Mean Flow, Fang Q. Hu, Michelle E. Pizzo, Douglas M. Nark

Mathematics & Statistics Faculty Publications

It has been well-known that under the assumption of a constant uniform mean flow, the acoustic wave propagation equation can be formulated as a boundary integral equation, in both the time domain and the frequency domain. Compared with solving partial differential equations, numerical methods based on the boundary integral equation have the advantage of a reduced spatial dimension and, hence, requiring only a surface mesh. However, the constant uniform mean flow assumption, while convenient for formulating the integral equation, does not satisfy the solid wall boundary condition wherever the body surface is not aligned with the uniform mean flow. In …

Simulation, Measurement, And Emulation Of Photovoltaic Modules Using High Frequency And High Power Density Power Electronic Circuits, Yunas Erkaya

Electrical & Computer Engineering Theses & Dissertations

The number of solar photovoltaic (PV) installations is growing exponentially, and to improve the energy yield and the efficiency of PV systems, it is necessary to have correct methods for simulation, measurement, and emulation. PV systems can be simulated using PV models for different configurations and technologies of PV modules. Additionally, different environmental conditions of solar irradiance, temperature, and partial shading can be incorporated in the model to accurately simulate PV systems for any given condition.

The electrical measurement of PV systems both prior to and after making electrical connections is important for attaining high efficiency and reliability. Measuring PV …

Thin Film Studies Toward Improving The Performance Of Accelerator Electron Sources, Md Abdullah Al Mamun

Mechanical & Aerospace Engineering Theses & Dissertations

Future electron accelerators require DC high voltage photoguns to operate beyond the present state of the art to conduct new experiments that require ultra-bright electron beams with high average current and higher bunch charge. To meet these demands, the accelerators must demonstrate improvements in a number of photogun areas including vacuum, field emission elimination in high voltage electrodes, and photocathodes. This dissertation illustrates how these improvements can be achieved by the application of suitable thin-films to the photogun structure for producing ultra-bright electron beams.

This work is composed of three complementary studies. First, the outgassing rates of three nominally identical …

Romania's Participation To The European Assessment Project Titled Hyunder, Multi-Criterial Analyses Of Salt Cavern Locations, Ioan Iordache, Dorin Schitea, Adriana Marinoiu, Mihaela Buga, Mihai Balan, Ioan Stefanescu, Adrian Gheorghe, Mihaela Iordache, Viviana Cigolotti (Ed.), Chiara Barchiesi (Ed.), Michela Chianella (Ed.)

Engineering Management & Systems Engineering Faculty Publications

The scope of the work is to assess the potential, the actors and relevant business cases for large scale storage of renewable electricity by hydrogen underground storage in Romania. This presentation intends to provide a picture of the multi-criterial analyses of salt cavern locations in Romania.

The energy sector is facing with the necessity to store large energy quantities for short to long term in order to adapt to the increasingly intermittent renewable energy. The results of this presentation have originated from an ongoing European assessment project by the name of HyUnder (FCH JU, grant 303417) regarding utilization of salt …

Temporary Bonding With Polydimethylglutarimide Based Lift Off Resist As A Layer Transfer Platform, T. Matsumae, A. D. Koehler, J. D. Greenlee, T. J. Anderson, H. Baumgart, G. G. Jernigan, K. D. Hobart, F. J. Kub

Electrical & Computer Engineering Faculty Publications

Bonding of lift off resist (LOR) was performed to realize temporary wafer bonding without residue. Bonding process conditions such as spin speed, pre-bake temperature, and bonding temperature were optimized to obtain a large bonded area with high bond strength. Under optimized process conditions, a bonded area covering over 98% of the wafer surface, with a room temperature bond strength of nearly 5 J/m² is achieved. During razor blade testing, fracture often occurs at the Si wafer. Moreover, debonding using an N-Methyl-2-pyrrolidone (NMP)-based solvent left the wafer surface extremely small amount of residue. Thus, the optimized bonding processed developed in …

Emergency Diesel-Electric Generator Set Maintenance And Test Periodicity, Stephen John Fehr

Engineering Management & Systems Engineering Theses & Dissertations

Manufacturer and industry recommendations vary considerably for maintenance and tests of emergency diesel-electric generator sets supporting critical operations power systems facilities. There is little consistency among sets of similar technology, and manufacturers and their representatives often provide contradictory guidance. As a result, periodicity of emergency diesel-electric generator set maintenance and tests varies considerably in practice. This work proposes and tests a research and analysis framework to develop parametric regression survival models of modern diesel-electric generator sets in emergency standby duty as a function of maintenance periodicity, test periodicity, and other predictors. Within this framework, predictors are developed from common maintenance …

Idpal – A Partially-Adiabatic Energy-Efficient Logic Family: Theory And Applications To Secure Computing, Mihail T. Cutitaru

Electrical & Computer Engineering Theses & Dissertations

Low-power circuits and issues associated with them have gained a significant amount of attention in recent years due to the boom in portable electronic devices. Historically, low-power operation relied heavily on technology scaling and reduced operating voltage, however this trend has been slowing down recently due to the increased power density on chips. This dissertation introduces a new very-low power partially-adiabatic logic family called Input-Decoupled Partially-Adiabatic Logic (IDPAL) with applications in low-power circuits. Experimental results show that IDPAL reduces energy usage by 79% compared to equivalent CMOS implementations and by 25% when compared to the best adiabatic implementation. Experiments ranging …

Generation Of Bipolar Nanosecond Pulses, Sambasiva Rao Rajulapati

Electrical & Computer Engineering Theses & Dissertations

Bipolar pulse generation has been studied using transmission line technology, which was mainly used for monopolar pulse generation. In this thesis, low impedance, high current, nanosecond pulse generators were designed, constructed and tested. Five transmission lines were connected in parallel, so the impedance was 10 n. The transmission lines were switched by a spark gap switch operated in air. The closing of the switch creates a matched condition on one side of the transmission lines and a short circuit on the other side of the transmission lines. When the transmission lines are precharged, one of the two waves in opposite …

Hydrothermal Processing Of Biomass For Biofuels, Sandeep Kumar

Civil & Environmental Engineering Faculty Publications

[First paragraph] In recent years, significant research interests have been placed on the conversion of non-food biomass resources such as lignocellulosic biomass (terrestrial) and algae (aquatic) to biofuels. Among all the alternative or renewable energy options, biomass is the only resource which is carbon neutral and can potentially replace part of fossil fuels use as liquid transportation fuels as well as contribute to electricity generation. Therefore, it can play a significant role in partially replacing oil, natural gas, and coal utilization for heat and energy generation. However, high moisture content of fresh biomass or algae is one of the major …

Photovoltaic Tracker Optimization With Unique Fault Detection And Enhanced Combiner System, Caitlin Nicole Conway

Electrical & Computer Engineering Theses & Dissertations

Renewable energy resources are rapidly becoming extremely important as the world's energy consumption continues to rise. The most popular of these resources is solar energy and more specifically photovoltaic energy. Currently, solar modules on the market are still not highly efficient. In order to increase the productivity of solar energy systems, larger fixed-panel photovoltaic systems or tracking photovoltaic systems are utilized. The major disadvantage of larger photovoltaic systems is the increased space requirements. Therefore, tracking photovoltaic systems are the best alternative to achieve higher solar energy yields.

To date, the only method of monitoring tracking photovoltaic systems is with the …

Improving The Efficiency Of P3ht:Icba Organic Solar Cells By Modifying The Photoactive Solution Preparation Step, Matthew Blaine Samson

Electrical & Computer Engineering Theses & Dissertations

Organic solar cells (OSCs) are a promising alternative to conventional silicon solar cells. These organic devices offer the promise of facile low cost large scale solution based processing on lightweight, flexible, plastic substrates. At the present state of the technology, however, OSCs exhibit relatively low power conversion efficiencies. To improve these efficiencies, new materials are constantly being developed.

One such material is the fullerene indene-C₆₀ bisadduct (ICBA). When implemented in a poly(3-hexylthiophene-2, 5-diyl) (P3HT) : ICBA bulk heterojunction solar cell, these devices exhibit open circuit voltages exceeding 0.8 V, a value much higher than the devices made implementing phenyl-C …

Optimization Of Solar Cell Arrays Using The Fibonacci Search Algorithm, Felicia Tyyan Farrow

Electrical & Computer Engineering Theses & Dissertations

In our energy hungry world, there is a growing demand to develop creative mechanisms to extract, conserve, and use energy from different resources. The use of solar cells to extract and convert solar energy into electrical energy is a growing and popular field of study because solar energy is clean, free, and renewable. One limitation for photovoltaic (PU) or solar technology is its loss in efficiency and availability as a result of shading or partial shading. Shading or partial shading decreases the total capable output power that the PV system can produce because the array is receiving irradiation from the …

Impact Of Primary User Activity On The Performance Of Energy-Based Spectrum Sensing In Cognitive Radio Systems, Sara L. Macdonald

Electrical & Computer Engineering Theses & Dissertations

Increasing numbers of wireless devices and mobile data requirements have led to a spectrum shortage. However spectrum utilization percentages are often low due to the current static spectrum allocation process where primary users (PUs) are given exclusive use to spectrum. Several mechanisms to increase spectrum utilization have been proposed including opportunistic spectrum access (OSA). Cognitive Radio (CR) is an emerging concept in wireless communication systems that aims to enable OSA in licensed frequencies by secondary users (SUs). CR systems are expected to sense the spectrum in order to determine if the PU is transmitting. Therefore OSA performance relies on the …

Resilience Governance Through Serious Energy Gaming, Adrian V. Gheorghe, Dan V. Vamanu

Engineering Management & Systems Engineering Faculty Publications

Physical analogies emphasizing cooperative behavior in systems are explored and integrated into so called 'serious energy games', to contribute in a better understanding, monitoring and good governance of some of the complex security issues confronting the evolvement of contemporary energy systems. It is believed that such exercises might be supportive in the necessary attempt, by the many stakeholders and actors / agents involved, to bring balance to prevailing policies of which seems to be “Go change yourself - in a resilient fashion!” An extrapolation of several findings to other than energy systems tempted to implement drastic changes based on substantial …

Fault Detection System For Solar Tracking Applications, Hareen Sekhar Illa

Electrical & Computer Engineering Theses & Dissertations

Oil, coal and natural gas reserves are being depleted faster than forecasted due to continued increase in demand for energy sources. We need, therefore, to develop renewable energy sources, such as solar, wind, biomass, geothermal, hydro power and tidal energy. In spite of having very high potential, harvesting solar energy has been a challenge because of the relatively low efficiency of solar cells. In the past few years different methods have been developed to increase the efficiency of the photovoltaic (PV) system: (I) improve the efficiency of solar cells (ill use a solar tracking system to increase the received solar …

Modeling Leakage Currents In Metal Insulator Metal Structures With High K Materials, Priyamvada Maleeswaran

Electrical & Computer Engineering Theses & Dissertations

Various products such as personal computers, cellular phones and mobile devices require high speed and low power consumption. Such improvements have been attained by minimizing physical dimensions of electronic devices, leading to high density integration of transistors and capacitors on integrated chips (]Cs). However, as a consequence of down-scaling device dimensions, tunneling of electrons through thin gate oxides (SiO₂) increases, leading to increased static power leakage. This constitutes wastage in power, and for the case of memory applications necessitates faster refresh cycles. In order to overcome such issues, high-k materials (such as HfO₂ and ZrO₂) …

Nonthermal Plasma Jet Efficacy On Candida Kefyr, Amber Marie Mattson Jackson

Electrical & Computer Engineering Theses & Dissertations

The inactivation abilities of a nonthermal plasma jet were investigated with the yeast C. kefyr, a pathogen with increasing importance in healthcare. The plasma is generated using a microhollow cathode discharge (MHCD) geometry operated with a DC voltage of 2 kV and a current of 30 mA using air as the operating gas at an airflow rate of 8 SLM. The plasma discharge approaches room temperature at a few mm away from the plasma jet allowing for the use on heat sensitive surfaces. Dry air and humid air were used as the operating gas to see if humidity plays …

Multi-Term Approximation To The Boltzmann Transport Equation For Electron Energy Distribution Functions In Nitrogen, Yue Feng

Electrical & Computer Engineering Theses & Dissertations

Plasma is currently a hot topic and it has many significant applications due to its composition of both positively and negatively charged particles. The energy distribution function is important in plasma science since it characterizes the ability of the plasma to affect chemical reactions, affect physical outcomes, and drive various applications. The Boltzmann Transport Equation is an important kinetic equation that provides an accurate basis for characterizing the distribution function—both in energy and space.

This dissertation research proposes a multi-term approximation to solve the Boltzmann Transport Equation by treating the relaxation process using an expansion of the electron distribution function …

Evaluation Of Ocean-Energy Conversion Based On Linear Generator Concepts, Michael Allen Stelzer

Electrical & Computer Engineering Theses & Dissertations

A turbine generator is a device that converts mechanical rotation into electrical energy. Unfortunately, the primary driving force that has been used to provide this rotation has, thus far, been fossil fuels. Although fossil fuels have proven to be a reliable resource to continually supply the growing demand for electrical power, they are not without their financial and environmental drawbacks. With the continuously increasing demand for energy, it is hypothesized that the world may, in time, exhaust this precious natural resource and/or inflict permanent environmental damage upon our planet.

However, motions that occur in nature, such as ocean waves, can …

On The Radius Of Convergence Of Interconnected Analytic Nonlinear Input-Output Systems, Makhin Thitsa, W. Steven Gray

Electrical & Computer Engineering Faculty Publications

A complete analysis is presented of the radii of convergence of the parallel, product, cascade and feedback interconnections of analytic nonlinear input-output systems represented as Fliess operators. Such operators are described by convergent functional series, which are indexed by words over a noncommutative alphabet. Their generating series are therefore specified in terms of noncommutative formal power series. Given growth conditions for the coefficients of the generating series for the subsystems, the radius of convergence of each interconnected system is computed assuming the subsystems are either all locally convergent or all globally convergent. In the process of deriving the radius of …

In Situ And Ex Situ Studies Of Molybdenum Thin Films Deposited By Rf And Dc Magnetron Sputtering As A Back Contact For Cigs Solar Cells, K. P. Aryal, H. Khatri, R. W. Collins, S. Marsillac

Electrical & Computer Engineering Faculty Publications

Molybdenum thin films were deposited by rf and dc magnetron sputtering and their properties analyzed with regards to their potential application as a back contact for CIGS solar cells. It is shown that both types of films tend to transition from tensile to compressive strain when the deposition pressure increases, while the conductivity and the grain size decreas. The nucleation of the films characterized by in situ and real time spectroscopic ellipsometry shows that both films follow a Volmer-Weber growth, with a higher surface roughness and lower deposition rate for the rf deposited films. The electronic relaxation time was then …

Improving The Efficiency Of Organic Solar Cells By Varying The Material Concentration In The Photoactive Layer, Kevin Anthony Latimer

Electrical & Computer Engineering Theses & Dissertations

Polymer-fullerene bulk heterojunction solar cells have been a rapidly improving technology over the past decade. To further improve the relatively low energy conversion efficiencies of these solar cells, several modifications need to be made to the overall device structure. Emerging technologies include cells that are fabricated with interfacial layers to facilitate charge transport, and tandem structures are being introduced to harness the absorption spectrum of polymers with varying bandgap energies.

When new structures are implemented, each layer of the cell must be optimized in order for the entire device to function efficiently. The most volatile layer of these devices is …

Long Term Surface Power Generator Design For Mars: Autonomously Deployable Photovoltaic Solar Arrays Along With Regenerative Fuel Cell Modules, Omer Demirok

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis studies the feasibility of incorporating a large autonomously deployed photovoltaic solar array power system as the primary power source for a large fixed Mars base. A mission duration of 10 Earth years has been assumed and the nominal power demands have been specified as a minimum of 40 kW, during daytime operation and a continuous 10 kW. demand for nighttime operation.

The overall system design developed in this thesis has an estimated total mass of 7,400 kg, when utilizing hydrogenated amorphous silicon thin film solar arrays and an estimated total mass of 5,100 kg when utilizing polycrystalline copper-indium-diselenide …

Coupled Photonic Crystal Micro-Cavities With Ultra-Low Threshold Power For Stiumulated Raman Scattering, Qiang Liu, Zhengbiao Ouyang, Sacharia Albin

Electrical & Computer Engineering Faculty Publications

We propose coupled cavities to realize a strong enhancement of the Raman scattering. Five sub cavities are embedded in the photonic crystals. Simulations through finite-difference time-domain (FDTD) method demonstrate that one cavity, which is used to propagate the pump beam at the optical-communication wavelength, has a Q factor as high as 1.254 × 10⁸ and modal volume as small as 0.03μm³ (0.3192(λ/n)³). These parameters result in ultra-small threshold lasing power ~17.7nW and 2.58nW for Stokes and anti-Stokes respectively. The cavities are designed to support the required Stokes and anti-Stokes modal spacing in silicon. The proposed structure …