La production d’électricité par des sources photovoltaïques joue un grand rôle dans les démarches qui visent à remplacer progressivement les combustibles fossiles par des sources d’énergie alternatives. La production énergétique photovoltaïque est en plein essor depuis l’introduction de systèmes photovoltaïques qui sont abordables pour des particuliers, une évolution à laquelle les subventions de l’Etat ont contribuée. C’est la raison pour l’installation de systèmes photovoltaïques dans des zones urbaines où les topologies conventionnelles de panneaux photovoltaïques en couplage série, qui sont appliquées dans les parc solaires, sont moins efficaces en raison des effets d’ombrage partiel par l’environnement urbain. Ce problème peut être réduit par l’application d’une topologie modulaire où chaque panneau est traité individuellement et indépendamment du reste des panneaux de couplage. Pour parvenir à cette modularité une topologie de convertisseur doit être développée qui peut être intégrée dans chaque module solaire. Dans le cadre de cette thèse un nouveau concept d'une installation solaire hybride modulaire a été étudié. Ce concept englobe le développement d'une topologie de convertisseur associé,qui peut être intégrée dans chaque module solaire du système solaire. Pour améliorer encore l’aspect de miniaturisation pour cette topologie de convertisseur et réduire ainsi le volume global du convertisseur, une augmentation de la fréquence de commutation accompagnée par l'utilisation de transistors à haute mobilité d'électrons (HEMT) a été fixée. Pour cette application,un HEMT sur la base de nitrure de gallium (GaN), qui est disponible dans le commerce auprès de la société EPC a été sélectionné. L'objectif de la thèse est le développement d’un nouveau concept d’un driver intégré avec une séparation galvanique qui est capable de contrôler les HEMT du convertisseur solaire avec une fréquence de commutation de l'ordre mégahertz.À cette fin, une technologie à haute température, fournie par X -Fab Semiconductors AG a été choisie et une bibliothèque de composants contenant toutes les cellules nécessaires à la conception du pilote ASIC a été développée. Pour le driver ASIC un circuit de tension de base a été développé qui génère une tension core stable qui est apte à supporter sans problèmes une large gamme de tensions d'alimentation (5V - 18V) qu’ainsi que les changements de température dans la gamme de température étendue (-40°C -175°C) de la nouvelle technologie ASIC haute température XA035 fourni par X-Fab. Pour réaliser la transmission du signal de commutation à travers l'isolation galvanique, plusieurs circuits ont été évalués et un nouvel algorithme de codage Manchester modifié a été élaboré pour réduire la complexité des éléments de couplage requis.Cela a permis la transmission différentielle de signaux de données et d'horloge sur seulement deux voies de signaux à séparation galvanique. En utilisant ce schéma de codage, une transmission de données à isolation galvanique a été développée, qui permet la transmission d’un signal codé PWM avec une fréquence allant jusqu'à 50 MHz. En outre, le circuit de driver lui même a été intégré ce qui permet de contrôler le nitrure de gallium (GaN) HEMT utilisé avec une fréquence de 5 MHz avec un minimum de retard entre les signaux d'entrée et de sortie.Ceci a permis l'augmentation susmentionnée de la fréquence de commutation du convertisseur et la réduction concomitante du volume global.Comme le concept de driver low-side qui a été développé utilise une isolation galvanique, il peut être utilisé aussi pour commander des transistors high-side, cette technologie n'est pas limitée à l'application dans un convertisseur photovoltaïque et il est envisageable qu’il puisse être réutilisé dans des types de conversion avec une topologie multi-level qui nécessite la commande du HEMT avec une fréquence de commutation élevée. / The generation of electricity through photovoltaic sources plays a great role in the transition from fossil fuel sources to alternate energy sources. It has been on the rise in the especially since the introduction of affordable photovoltaic systems for private customers accompanied by public subsidies. This leads to the application of photovoltaic systems in urban areas where conventional string topologies of photovoltaic arrays that are applied in solar parks are less efficient due to the effects of partial shading by the urban environment. This issue can be reduced by changing the photovoltaic array to a modular topology where each panel is treated individually and independently from the rest of the array. To achieve this modularity a converter topology needs to be developed that can be integrated into each solar module.In the frame of this work a novel concept of a hybrid modular solar array was researched and a converter topology supporting the solar modules was developed. To reinforce the miniaturization aspect of the converter topology the increase of switching frequency and the use of high-electron-mobility-transistors (HEMT) was decided. The focus of the thesis was to develop a novel integrated galvanically-isolated driver concept that is able to drive the HEMTs of the solar converter with a switching frequency in the MHz range. A high-temperature technology provided by X-Fab Semiconductors AG was chosen for this purpose and a component library containing all cells required for the design of the driver ASIC was developed. For the driver ASIC a core voltage circuit was developed that provides a stable core voltage of 3.3V while being able to tolerate a wide range of supply voltages (5V - 18V) as well as temperature changes in the complete extended temperature range (-40°C - 175°C) of the novel high-temperature ASIC technology XA035 provided by X-Fab. To achieve the transmission of the switching signal over the galvanic isolation several coupler circuits were evaluated and a novel modified Manchester coding algorithm was developed to reduce the complexity of the required coupling elements. This modified Manchester code enables the decoding and the rebuilding of the clock signal from just a single transmitted encoded signal and does not require the additional transmission of the original clock signal to for the decoding process usually necessary in a great part of conventional Manchester decoder circuits. Furthermore the driver circuit itself was developed that is able to drive the used GaN HEMT at a frequency of 5MHz with minimal delay between input and output signal of the driver.As the developed galvanically-isolated driver ASIC exhibits a low-side driver topology that can be also be applied for the high-side due to the galvanic isolation its use is not limited to the application in the presented modular photovoltaic system and it can be reused in any kind of multi-level converter topology that requires the driving of HEMTs with a high switching frequency. / Die Erzeugung elektrischer Energie durch Photovoltaik spielt angesichts des angestrebtenEnergiewechsels weg von fossilen Brennstoffen und hin zu erneuerbaren Energien eine bedeutendeRolle. Die photovoltaische Energieerzeugung befindet sich seit der Einführung erschwinglicherSolarmodule gepaart mit staatlichen Subventionen besonders im privaten Bereichim Aufschwung. Dies führte dazu, dass es auch im urbanen Bereich zum Aufbau vonPhotovoltaikanlagen kam, wo sich die herkömmlichen Reihenschaltungs-Topologien, die ingroßen Solarparks zur Anwendung kommen als nicht sehr effektiv erweisen, was besondersauf auftretende Teilverschattung durch die urbane Umgebung zurückzuführen ist. DiesesProblem kann durch die Verwendung von modularer Topologien verringert werden, da hier alleSolarpanels individuell und unabhängig voneinander behandelt werden können. Um diese Modularitätzu ermöglichen muss eine Wandlertopologie entwickelt werden, die in einzelne Solarmoduleintegriert werden kann.Im Rahmen dieser Arbeit wurde ein neuartiges Konzept einer hybriden, modularen Solaranlageuntersucht. Dieses Konzept umfasste die Entwicklung einer zugehörigen Wandlertopologie,die in jedes Solarmodul der Solaranlage integriert werden kann. Um den Miniaturisierungsaspektfür diese Wandlertopologie noch zu verstärken und somit das Bauvolumen des Wandlerszu reduzieren, wurde eine Erhöhung der Schaltfrequenz einhergehend mit dem Einsatzvon Transistoren mit hohen Elektronenbeweglichkeit (high-electron-mobility transistor; HEMT)festgelegt. Für diese Anwendung wurde ein HEMT basierend auf Gallium-Nitrid (GaN), derkommerziell von der Firma EPC angeboten wird, ausgewählt. Der Schwerpunkt der vorliegendenArbeit war nun die Entwicklung eines neuartigen integrierten und galvanisch-isoliertenTreiberkonzepts das ermöglichen sollte, diese HEMTs bei einer Schaltfrequenz im MegahertzBereich zu betreiben. Zu diesem Zweck wurde, für die Erstellung des ASIC und einer zugehörigenBauteilebibliothek, eine hochtemperaturfähige CMOS Technologie ausgewählt, die vonX-Fab Semiconductor AG zur Verfügung gestellt wurde. Für die Verwendung im Treiber-ASICwurde eine Schaltung entwickelt, die eine stabile Core-Spannung zur Verfügung stellen kann,die sowohl Versorgungsspannungsabweichungen in einem weiten Bereich (5V-18V) als auchTemperaturabweichungen über den gesamten erweiterten Temperaturbereich (-40°C - 175°C)der XA035 Technologie von X-Fab problemlos tolerieren kann. Um die Übertragung eines Datensignalüber die im Modul präsente galvanische Trennung zu ermöglichen, wurden sowohlmehrere galvanisch Isolierte Koppelkonzepte ausgewertet als auch die Entwicklung eines neuartigenmodifizierten Manchester Kodierungsverfahren vorangetrieben, das es ermöglicht, denUmfang der benötigten galvanischen Koppelelemente zu reduzieren. Dieser modifizierte ManchesterCode erlaubt das Dekodieren und die Wiedergewinnung des Takts aus nur einemübertragenen Signals und benötigt nicht die zusätzliche Übertragung des ursprünglichen Taktsignalsfür den Dekodierungsprozess, wie dies bei vielen herkömmlichen Manchester Decoder-Schaltungen der Fall ist. Dies ermöglichte die differentielle Übertragung von Datensignalund Takt über nur zwei galvanisch isolierte Signalpfade. Unter Verwendung dieses Kodierungsverfahrenswurde eine galvanisch isolierte Datenübertragung realisiert, die ein kodiertesPWM Signal mit einer Frequenz von bis zu 50MHz überträgt. Weiterhin wurde die Treiberschaltungselbst einwickelt, die es ermöglicht den verwendeten Gallium-Nitrid (GaN) HEMTmit einer Frequenz von 5MHz mit minimaler Verzögerung zwischen Eingangs- und Ausgangssignaldes Treibers anzusteuern. Damit würde die zuvor erwähnte Erhöhung der Schaltfrequenzdes Wandlers und die damit einhergehende Reduzierung des Bauvolumens erreicht.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:10:35Z No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:10:35Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Microgrids are turning to be one of the most important factors for future power systems. In this thesis, the considered system consists of two resourses, namely Solar and Wind energy. These renewable energy sources are generally connected parallel in Microgrid system. In order to get better performance from Microgrid, the existing system has to be modified. This thesis presents the modeling and control of PV/wind Microgrid. Selection of suitable wind turbine and AC or DC Microgrid is clearly presented in thesis.             Microgrid concept integrates large amounts of micro sources without disrupting the operation of main utility grid. This hybrid Microgrid consists of PV/wind energy sources for DC and AC networks respectively. Energy storage systems may be connected to either AC or DC Microgrids. The proposed hybrid Microgrid operates in grid-tied or isolated mode. AC sources and loads are connected to AC network, whereas DC sources and loads are connected to DC network. Uncertainty and intermittent characteristics of wind speed, solar irradiation level, ambient temperature and load are additionally considered in the system model and operation.

Orientador: Carlos Alberto Canesin / Banca: Falcondes Jose Mendes de Seixas / Banca: Guilherme de Azevedo e Melo / Banca: Marcelo Lobo Heldwein / Banca: Ernesto Ruppert Filho / Resumo: Este trabalho consiste no desenvolvimento e avaliação de conversores eletrônicos de potência para utilização de painéis fotovoltaicos, com conexão à rede de distribuição de energia elétrica em corrente alternada. No cenário de gerações fotovoltaicas as filosofias iniciais, as quais consistiam na instalação de grandes Arrays (associações série e paralelo) de painéis solares utilizando um único conversor centralizado, cariam em desuso devido à baixa eficiência e à impossibilidade de operar todos os painéis simultaneamente no ponto de máxima potência (MPP). Ao mesmo tempo, esta estratégia não permitia a instalação gradativa de painéis exigindo um alto investimento inicial. Estes são alguns dos motivos que levam a pesquisas mais recentes com conversor dedicado ao painel, que possa até ser integrado e comercializado como um único equipamento, denominado de Módulo CA fotovoltaico. Estes módulos seriam painéis fotovoltaicos prontos para a conexão à rede, com conversor que explore melhor o MPP, permitindo a modularidade, a confiabilidade e a facilidade da instalação. Por segurança, o conversor também precisa se desconectar da rede automaticamente na presença de falhas, para evitar a ocorrência do fenômeno conhecido como ilhamento. A dificuldade de construção destes módulos CA se concentra fundamentalmente do desenvolvimento do conversor de eletrônica de potência, também denominado de microinversor, por trabalhar em potências de até 300 W, compatível com a potência máxima de painéis fotovoltaicos comerciais. Para atender a esta aplicação, o conversor requer diversas características, entre as principais estão: baixo custo, alto rendimento e, especialmente, vida útil compatível com a do painel. Neste contexto, este trabalho utiliza conversores com integração de estágios... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work aims the development and evaluation of power electronic converters to be used with photovoltaic (PV) modules connected to the alternating current electric energy distribution grid. In the scenario of photovoltaic generation, the initial philosophies, which were based on large PV solar arrays using a centralized converter, has became unused due to the low efficiency and the impossibility to operate all panels simultaneously on the maximum power point (MPP). At the same time, it is not possible the gradual installation of PV modules and is mandatory a high initial investment. These are some reasons that leaded more recent researches of panel dedicated converter, which could be embedded and sold as a single equipment, called photovoltaic AC module. These modules are PV panels ready for grid connection, with a converter that works at the MPP for each panel. This allows modularity, reliability and ease of installation. For safety reasons, the converter also has to disconnect from the grid automatically once a grid failure is detected, to avoid the phenomenon known as islanding. The construction of these modules is fundamentally a problem for power electronic converter development. This converter is also called micro-inverter due to the nominal power up to 300 W, compatible with commercially available PV panels. The converter needs several features to achieve this application, among them: low cost, high efficiency and, especially, lifetime compatible with the panels. In this context, this work uses converters with integration of stages (DC + AC), aiming to achieve the main requirements needed to turn them into a feasible alternative to the presented application. The main contribution of this work is a novel control strategy which is not found in the literature, which allows independent input-output... (Complete abstract click electronic access below) / Doutor

Orientador: Odivaldo José Seraphim / Banca: Fábio Renan Durand / Banca: José Fernando Presenço / Banca: Alexandre Dal Pai / Banca: Fernando de Lima Caneppele / Resumo: Para avaliar o desempenho dos sistemas de microgeração é necessário coletar dados de produção e consumo de energia. Neste trabalho foi desenvolvido um sistema para monitoramento da produção e consumo de energia em centrais de microgeração fotovoltaicas. Os experimentos foram realizados na central de microgeração distribuída fotovoltaica (MGD-PV) do Sítio Modelo da Fazenda Lageado e no Laboratório de Energias Renováveis do Departamento de Engenharia Rural, na Faculdade de Ciências Agronômicas da UNESP, campus de Botucatu. O sistema utiliza dispositivos baseados em hardware livre para o gerenciamento e transmissão dos dados (Arduinos) e sensores de tensão e corrente para coleta de dados na central MGD-PV. A transmissão é feita via rede sem fios (ZigBee) para uma central de dados onde um microcomputador executa programas que foram desenvolvidos para o projeto e gerenciam o armazenamento local e envio dos dados para a Internet. Para monitorar o funcionamento e acessar os dados foi criada uma página na Internet. O download dos dados pode ser feito em formato CSV - Comma-Separated Values, amplamente utilizado e que permite a importação para diversas ferramentas de software. A eficiência do sistema foi de 96% na quantidade de dados registrados. / Abstract: To evaluate the performance of microgeneration systems is necessary to collect data about production and consumption of energy. In this work, a system was developed for monitoring the production and consumption of energy in micro generation photovoltaic station. The experiments were performed in the central distributed micro generation photovoltaic - MGD-PV in Sítio Modelo in Campus Lageado and Renewable Energy Laboratory, Department of Rural Engineering in College of Agronomic Science (FCA) UNESP / Botucatu. To data collect the system uses voltage and current sensors and devices based on free hardware for managing and transmitting data (Arduinos). Data are transmitted via wireless (ZigBee) to a central database where one computer runs programs developed to store, manage and transmit the data to the Internet. To monitor the operation and access the data was created a page on the Internet. The downloaded data can be done in CSV - Comma-Separated Values, widely used and allows the import for several software tools. The system efficiency was 96% in the amount of recorded data. / Doutor

A geração de energia fotovoltaica continua em crescimento e por isso estudos relacionados à aplicação de diferentes tecnologias fotovoltaicas se tornam muito importantes. A tecnologia de células fotovoltaicas de silício cristalino representa a maior parte da aplicação de energia solar fotovoltaica atualmente. Os módulos com tecnologias de filmes finos foram apresentados ao mercado como uma nova geração de módulos e atualmente são referenciados como módulos fotovoltaicos de segunda geração. As tecnologias de filmes finos possuem algumas vantagens em relação ao silício cristalino, como por exemplo: menor quantidade de material, menor custo de produção e possibilidade de se produzir células e módulos flexíveis, embora em geral apresentem eficiências menores. Existem tecnologias de filmes finos aplicadas à geração fotovoltaica que apresentam instabilidade quando expostas à radiação solar, variando a potência gerada do módulo nas primeiras horas de exposição. Esses efeitos motivaram a padronização de um ensaio de exposição solar, do inglês light-soaking, que atualmente é previsto por uma norma internacional de qualificação de módulos fotovoltaicos (IEC 61646). Neste trabalho, desenvolveu-se uma metodologia para realizar o ensaio lightsoaking e construiu-se uma bancada de testes para obter resultados experimentais a partir de módulos expostos na cobertura do prédio anexo do LABSOL. Para isso, foi realizada uma análise de área livre de sombra disponível, bem como montada a estrutura metálica de sustentação para os módulos. Também foram instaladas resistências elétricas para dissipação de potência dos módulos e montado painel elétrico dentro do prédio centralizando as conexões necessárias. O experimento também contou com o desenvolvimento de um programa em linguagem Visual Basic® para interagir com os instrumentos de medição e realizar o monitoramento do ensaio. Neste trabalho foram ensaiados quatro módulos com diferentes tecnologias de filmes finos, as quais: silício amorfo com tripla junção, silício amorfo com uma junção, CIGS (Disseleneto de Cobre, Índio e Gálio) e por último dupla junção de silício amorfo com silício microcristalino. O experimento foi conduzido por 55 dias, sendo que a cada minuto o programa registrou dados de irradiância, irradiação acumulada e temperatura dos módulos. Ao final do experimento, os módulos receberam no total 347 kWh/m2 de irradiação e, durante o ensaio, foram realizadas ao todo 8 medições de curva característica corrente versus tensão para verificar o desempenho dos módulos. Antes e após a exposição, também foram realizadas medições em um simulador solar a fim de se obter medidas em condições controladas de temperatura e irradiância. Ao aplicar o critério de estabilização previsto na norma IEC 61646, verificou-se que todos os módulos o atenderam. Contudo, os módulos com tecnologia de uma junção de silício amorfo e com tecnologia de tripla junção de silício amorfo voltaram a apresentar degradação acima do máximo estabelecido pela norma IEC 61646 após continuarem expostos à radiação solar. Sendo assim, pode ser necessário alterar o critério para um maior valor de irradiação acumulada entre cada avaliação de degradação destes módulos, principalmente quando o ensaio é realizado com temperatura externa elevada. A metodologia mostrou que esse ensaio pode ser realizado em ambiente externo com luz natural de maneira prática e econômica, porém realizar as medições de curva característica com luz natural e temperatura não controlada implica em adicionar algumas incertezas ao ensaio. / The photovoltaic (PV) power generation continues to grow and so studies related to the application of different photovoltaic technologies become very important. The crystalline silicon solar cells technology is the most current application of PV power generation. The photovoltaic modules with thin film technologies were presented to the market as a new generation of modules and are currently referred to as second generation PV modules. The thin film technologies have some advantages compared to crystalline silicon, for example, less material, lower cost of production and ability to produce flexible cells and modules, although generally have lower efficiencies. There are thin film technologies for photovoltaic conversion that show instability when exposed to the sun, varying the power generated in the early hours of sun exposure. These effects led to the standardization of a sun exposure test, the light-soaking test, which is currently standardized by an international standard of qualification of photovoltaic modules (IEC 61646). In this study, we developed a methodology to perform the light-soaking test and built a workbench to obtain experimental results from PV modules set out in the LABSOL building. For this purpose, a shadow analysis was performed as well as the metal structure mounted to support the photovoltaic modules. Resistive loads were also installed in order to dissipate the power of the modules. An electrical panel was mounted inside the building to centralize the necessary connections. The workbench also included the development of a program in Visual Basic® to interact with the measuring instruments and carry out the monitoring of the experiment. In this work we tested four modules with different thin film technologies, including: triple junction amorphous silicon, single junction amorphous silicon, CIGS (Copper Indium Gallium Diselenide) and tandem junction of amorphous silicon and microcrystalline silicon. The experiment was conducted over 55 days, and every minute the program recorded irradiance data, accumulated irradiation and module temperature. At the end of the experiment, the modules received 347 kWh/m2 of irradiation. During the test, there were a total of 8 characteristic curve (I x V) measurements to verify the performance of the modules. Before and after exposure, were also performed measurements in a solar simulator. By applying the stabilization criteria presented in IEC 61646 it was found that all the modules have been considered stabilized. However, after being exposed to more hours of sunlight, the single junction amorphous silicon module and the triple junction amorphous silicon module presented degradation above the maximum established by IEC 61646 standard. Thus, it may be necessary to change the criteria for a higher value of accumulated irradiation between assessments of degradation of these modules, especially when the test is performed with high external temperature. The methodology showed that this test may be performed outdoors under natural light in a practical and economical way, but the characteristic curve measurements with natural light and uncontrolled temperature add some uncertainty to the test.

abstract: Solar energy, including solar heating, solar architecture, solar thermal electricity and solar photovoltaics, is one of the primary energy sources replacing fossil fuels. Being one of the most important techniques, significant research has been conducted in solar cell efficiency improvement. Simulation of various structures and materials of solar cells provides a deeper understanding of device operation and ways to improve their efficiency. Over the last two decades, polycrystalline thin-film Cadmium-Sulfide and Cadmium-Telluride (CdS/CdTe) solar cells fabricated on glass substrates have been considered as one of the most promising candidate in the photovoltaic technologies, for their similar efficiency and low costs when compared to traditional silicon-based solar cells. In this work a fast one dimensional time-dependent/steady-state drift-diffusion simulator, accelerated by adaptive non-uniform mesh and automatic time-step control, for modeling solar cells has been developed and has been used to simulate a CdS/CdTe solar cell. These models are used to reproduce transients of carrier transport in response to step-function signals of different bias and varied light intensity. The time-step control models are also used to help convergence in steady-state simulations where constrained material constants, such as carrier lifetimes in the order of nanosecond and carrier mobility in the order of 100 cm2/Vs, must be applied. / Dissertation/Thesis / M.S. Electrical Engineering 2013

abstract: I studied the properties of novel Co2FeAl0.5Si0.5 (CFAS), ZnGeAs2, and FeS2 (pyrite) thin films for microelectronic applications ranging from spintronic to photovoltaic. CFAS is a half metal with theoretical spin polarization of 100%. I investigated its potential as a spin injector, for spintronic applications, by studying the critical steps involved in the injection of spin polarized electron populations from tunnel junctions containing CFAS electrodes. Epitaxial CFAS thin films with L21 structure and saturation magnetizations of over 1200 emu/cm3 were produced by optimization of the sputtering growth conditions. Point contact Andreev reflection measurements show that the spin polarization at the CFAS electrode surface exceeds 70%. Analyses of the electrical properties of tunnel junctions with a superconducting Pb counter-electrode indicate that transport through native Al oxide barriers is mostly from direct tunneling, while that through the native CFAS oxide barriers is not. ZnGeAs2 is a semiconductor comprised of only inexpensive and earth-abundant elements. The electronic structure and defect properties are similar in many ways to GaAs. Thus, in theory, efficient solar cells could be made with ZnGeAs2 if similar quality material to that of GaAs could be produced. To understand the thermochemistry and determine the rate limiting steps of ZnGeAs2 thin-film synthesis, the (a) thermal decomposition rate and (b) elemental composition and deposition rate of films were measured. It is concluded that the ZnGeAs2 thin film synthesis is a metastable process with an activation energy of 1.08±0.05 eV for the kinetically-limited decomposition rate and an evaporation coefficient of ~10-3. The thermochemical analysis presented here can be used to predict optimal conditions of ZnGeAs2 physical vapor deposition and thermal processing. Pyrite (FeS2) is another semiconductor that has tremendous potential for use in photovoltaic applications if high quality materials could be made. Here, I present the layer-by-layer growth of single-phase pyrite thin-films on heated substrates using sequential evaporation of Fe under high-vacuum followed by sulfidation at S pressures between 1 mTorr and 1 Torr. High-resolution transmission electron microscopy reveals high-quality, defect-free pyrite grains were produces by this method. It is demonstrated that epitaxial pyrite layer was produced on natural pyrite substrates with this method. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2013

abstract: This is a two-part thesis: Part 1 of this thesis tests and validates the methodology and mathematical models of the International Electrotechnical Commission (IEC) 61853-2 standard for the measurement of angle of incidence (AOI) effects on photovoltaic modules. Flat-plate photovoltaic modules in the field operate under a wide range of environmental conditions. The purpose of IEC 61853-2 is to characterize photovoltaic modules' performance under specific environmental conditions. Part 1 of this report focuses specifically on AOI. To accurately test and validate IEC 61853-2 standard for measuring AOI, meticulous experimental setup and test procedures were followed. Modules of five different photovoltaic technology types with glass superstrates were tested. Test results show practically identical relative light transmission plots for all five test modules. The experimental results were compared to theoretical and empirical models for relative light transmission of air-glass interface. IEC 61853-2 states "for the flat glass superstrate modules, the AOI test does not need to be performed; rather, the data of a flat glass air interface can be used." The results obtained in this thesis validate this statement. This work was performed in collaboration with another Master of Science student (Surynarayana Janakeeraman) and the test results are presented in two masters theses. Part 2 of this thesis is to develop non-intrusive techniques to accurately measure the quantum efficiency (QE) of a single-junction crystalline silicon cell within a commercial module. This thesis will describe in detail all the equipment and conditions necessary to measure QE and discuss the factors which may influence this measurement. The ability to utilize a non-intrusive test to measure quantum efficiency of a cell within a module is extremely beneficial for reliability testing of commercial modules. Detailed methodologies for this innovative test procedure are not widely available in industry because equipment and measurement techniques have not been explored extensively. This paper will provide a literature review describing relevant theories and measurement techniques related to measuring the QE of a cell within a module. The testing methodology and necessary equipment will be described in detail. Results and conclusions provide the overall accuracy of the measurements and discuss the parameters affecting these measurements. / Dissertation/Thesis / M.S.Tech Technology 2013

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / O uso de substrato de vidro para ser utilizado em sistema fotovoltaico à muito comum, no entanto, os substratos sÃo submetidos a elevadas temperaturas como no caso de obtenÃÃo de vidro recoberto com SnO2 (diÃxido de estanho), onde a temperatura de operaÃÃo atinge valores prÃximos a 600ÂC. Desta forma, um estudo do comportamento da dilataÃÃo do vidro em diferentes espessuras e sob a temperatura de 600ÂC foi realizado com o objetivo de observar a influÃncia dos mesmos nos vidros utilizados como substratos e, assim, prevenir os possÃveis defeitos de trinca e quebra de vidro dentro do forno. AlÃm do estudo associado ao vidro, um projeto teÃrico de um pirolisador com essas caracterÃsticas foi idealizado para a obtenÃÃo das camadas de SnO2 sobre o vidro, agregando inovaÃÃes como o uso de gÃs natural queimando em meio poroso como fonte de calor e o uso de um pirolisador para substituir os fornos resistivos. / The use of a glass substrate for use in photovoltaic system is very common, however, the substrates are subjected to high temperatures as in the case of obtaining glass covered with SnO2 (tin dioxide), where the operating temperature reaches values close to 600  C. Thus, a study of the glass expansion behavior with different thicknesses under temperature of 600  C was conducted in order to observe the influence of the same glass used as substrates, and thus, prevent possible defects cracks and broken glass inside the oven. Besides the study associated with the glass, a theoretical design of a pyrolyzer with these characteristics has been designed for obtaining layers of SnO2 on the glass, adding innovations such as the use of natural gas burning in porous media as heat source and the use of a pyrolyzer to replace the resistive furnaces.