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This dissertation introduces a new operational tool for integrating a photovoltaic (PV) system into the utility's generation mix. It is recognized at the outset, that much of the existing research concentrated on the central PV system and its operations have concluded that technical problems in PV operation will override any value or credit that can be earned by a PV system, and that penetration of a PV plant in the utility will be severely limited. These are real problems and their solutions are sought in this dissertation. Judging from the drawbacks of the static approach, it is felt that a new approach or methodology needs to be developed which would give a central station PV plant its due share of credit. This dissertation deals mainly with the development and implementation of this new approach -- a dynamic rule-based dispatch algorithm which takes into account the problems faced by the dispatch operator during a dispatch interval and channels those into a knowledge base. The new dynamic dispatch requires forecasts of photovoltaic generations at the beginning of each dispatch interval. A Box-Jenkins time-series method is used to model the sub-hourly solar irradiance. The irradiance data at any specific site is stripped of its periodicities using a pre-whitening process which involves parameterization of certain known atmospheric phenomena. The pre-whitened data series is considered stationary, although some non-stationarity might be introduced by the discontinuities in the data collection during night hours. This model is extended to yield forecast equations which are then used to predict the photovoltaic output expected to occur at certain lead times coinciding with the economic dispatch intervals. A rule-based (RB) dispatch algorithm is developed in this dissertation. The RB is introduced to operate as a substitute for the dispatch operator. Some of the dispatcher's functions are routine jobs, while some require specialized knowledge or experience. The RB is given these two qualities through a number of rules. This algorithm works in tandem with a conventional economic dispatch algorithm. The functions of the two are coordinated by another algorithm which oversees the now of information and records them. The RB gives one of 16 possible solutions as and when required. These solutions are written as rules which manipulate the non-committable generation to achieve an optimal solution. The RB system during its operation supervises the fact that the PV generation are kept at the maximum level possible under all constraints. The case study revealed that the thermal generating units which are scheduled by the unit commitment are able to absorb most of the small to medium variations present in the PV generations. In cases of large variations during a single interval, the thermal generators reach their response limits before they can reach their maximum or minimum generation, thus causing mismatches in the load and generation. The mismatches are then picked up by the non-committable sources of generation, comprised of pumped storage units, hydro generation plant, or by interconnection tie-lines. If none of these are sufficient, changes are made in the PV generation schedule. It is concluded that results depend on the time of the year and the specific utility. The time of the year information is reflected in the load demand profile. Most utilities in the U.S. have single peaks in summer and double peaks in winter. Also, the time of the peak load occurrence varies with season. The utility generating capacity mix influences the results greatly. / Ph. D.

This thesis presents an investigation into a wide range of potential materials for organic photovoltaic (PV) devices. A variety of optical techniques are used to define physical parameters for each material such as the photoluminescence quantum yield (PLQY), absorption coefficient and exciton diffusion length. Electrical characterisation is used to determine the optimal structure for devices fabricated with these materials. A number of novel materials are presented in this thesis. These include new polymers, both soluble and precursor, and a relatively new class of material, the conjugated dendrimer. These are highly configurable branching molecular structures that enable fine tuning of material properties. Work on polymers presented in this thesis investigates how such materials can be improved by testing the effect of small changes to their molecular structure. One of these changes had significant effects upon the overall material characteristics. The introduction of a dipole across a polymer successfully created a charge separating material without the need for an extra species such as C60 to be present. The introduction of the conjugated dendrimer to PV applications allows significant scope for molecular engineering. Dendrimers enable tight control over certain aspects of the molecular properties. Small changes can be made such as colour tuning or solubility that enable optimisation to be performed on the molecular level, rather than on device structure. Such changes produced significantly higher internal quantum efficiencies (> 90%) than typical polymer devices and offer the prospect of power conversion efficiencies in excess of 10%. Time-resolved luminescence (TRL) spectroscopy was used to characterise the behaviour of photogenerated excitons within organic films. The investigation of exciton diffusion length was performed upon two polymers, each utilising two different time-resolved methods; diffusion to a quencher and exciton-exciton annihilation. It was found that diffusion in polythiophene films is anisotropic and the photoluminescence lifetime is dependent upon film thickness. This is explained by the formation of self-ordered microstructures during the spin coating process. Data modelling was performed which took into account both the thickness variation and the interaction of excitons with a quenching interface producing a much more realistic approach than previously published work.

Der Freistaat Sachsen verfügt über große Potenziale hinsichtlich der Elektrizitätserzeugung aus Windkraft, Photovoltaik, sowie Biogas aus landwirtschaftlicher Biomasse. Im Rahmen dieser großteilig auf geographischen Informationssystemen (GIS) basierenden Analyse wird für die Ermittlung des wirtschaftlichen Potenzials bei Windenergie und Photovoltaik jeweils die EEG-Vergütung nach dem EEG 2012 bei Inbetriebnahme der Anlagen im Jahr 2013 herangezogen. Bei voller Ausschöpfung aller Flächen beträgt das Potenzial etwa 43% des Bruttostrombedarfes in Sachsen. Neben dem Potenzial zur Stromerzeugung entspricht das technische Potenzial an Biogas von Überschussflächen nach Abzug des Bedarfes an Biomasse zur Nahrungs- und Futtermittelproduktion ca. 20,5% des Erdgasverbrauches im Freistaat. Bei selben Annahmen können in einem alternativen Nutzungspfad ca. 4,5 TWh an Biokraftstoffen hergestellt werden. Im Einzelnen können durch die Nutzung von Windenergie zwischen 4,3 und 9,9 TWh ohne Berücksichtigung von Waldflächen an Elektrizität pro Jahr bereitgestellt werden. Wird eine Turbine einer höheren Leistungsklasse unterstellt, wie dies für die nächsten Jahre projiziert wird, liegt das wirtschaftliche Potenzial sogar bei 22,6 TWh. Das wirtschaftliche Potenzial zur Stromerzeugung durch Photovoltaik auf Dachflächen liegt bei 3,5 TWh. Im Gegensatz zum wirtschaftlichen Potenzial bei der Windenergie und der Photovoltaik, handelt es sich bei der Biomasse um das technische Potenzial.

Neste trabalho, são avaliadas diferentes configurações de sistemas fotovoltaicos, levando em consideração os principais tipos de módulos fotovoltaicos comercialmente disponíveis e estruturas de suporte. A comparação é delimitada na região Nordeste do Brasil e é baseada, fundamentalmente, em termos de fator de capacidade. Para uma melhor compreensão dos resultados, são mostradas, previamente, as influências que as variáveis meteorológicas exercem na saída do sistema, bem como os efeitos do fator de dimensionamento do inversor (FDI) e do índice de cobertura do terreno (ICT). Os resultados das simulações computacionais realizadas são apresentados em forma de mapas, nos quais é possível verificar as áreas em que os sistemas fotovoltaicos tendem a gerar mais energia elétrica. Entre as configurações estudadas, os maiores valores foram observados para sistemas que utilizam módulos genéricos de filmes finos montados em rastreadores solares de um eixo horizontal, chegando a 36 % de fator de capacidade (em corrente alternada) em algumas regiões do Ceará, Rio Grande do Norte, Paraíba, Pernambuco e Bahia. Além disso, foram evidenciados os ganhos obtidos nos fatores de capacidade ao substituir as estruturas fixas por rastreadores solares. Para um ICT de 0,4, os sistemas que realizam o seguimento, ainda que em um eixo do movimento aparente do Sol, apresentaram ganhos de 18 % a 28 % na energia elétrica anual gerada. / In this work, different configurations of photovoltaic systems are evaluated, considering the main type of commercially available photovoltaic modules and mounting structures. The comparison is delimited to the Northeastern region of Brazil and is based, fundamentally, in terms of capacity factor. The influence on the output of the system of meteorological variables, the inverter loading ratio (ILR 1/FDI) and ground coverage ratio (GCR ICT) are shown in advance for a better understanding of the results. Computational simulations results are presented in maps, in which it is possible to verify the areas where photovoltaic systems tend to generate more electricity. Among the studied configurations, the largest values were observed for systems that use generic thin film modules mounted on one axis horizontal solar trackers, reaching 36 % of capacity factor (in alternating current) in some regions of Ceará, Rio Grande do Norte, Paraíba, Pernambuco and Bahia. Additionally, the gains obtained in the capacity factors when replacing fixed structures by solar trackers were shown. For an GCR of 0.4, systems that track, even on one axis, the apparent motion of the Sun showed gains of 18 % to 28 % on annual generated electricity.

Este trabalho buscou entender a situação da atividade de fabricação de módulos fotovoltaicos no Brasil com o objetivo de avaliar a possibilidade de estimular a indústria nacional e o uso dessa fonte alternativa mais acentuadamente. Para tanto, foi necessário analisar os benefícios energéticos e econômicos da cadeia de produção, além de entender o estado da arte atual de todo o processo. É um ramo industrial que está sendo implantado no Brasil e este estudo teve como objetivo obter informações relevantes dos problemas e facilidades que os empreendedores enfrentam, e quais são os custos e benefícios à sociedade em geral, inclusive para obtenção dos sistemas fotovoltaicos pelo consumidor final. O trabalho contém uma avaliação do estado da produção e utilização dos sistemas de energia solar fotovoltaica no mundo e o que ocorre no Brasil. Buscou-se conhecer as possíveis, e/ou mais relevantes, ações regulatórias e iniciativas da área privada para viabilizar este ramo industrial. São considerados os impactos da atividade em pauta, procurando mostrar as relações de custo-benefício em projetos de geração centralizada (Leilões de Energia de Reserva) e de geração distribuída. / This study aims to understand the status of the manufacturing activity of photovoltaic modules in Brazil to evaluate the possibility of stimulating the local production and its widespread use. It was necessary to evaluate the energetic and economic benefits of the production chain. In addition, the study focused the understanding of the current state of the art of the whole process. Photovoltaic solar energy is an industrial branch recently receiving impulse in Brazil. This study aims to obtain relevant information about the difficulties faced by the entrepreneurs and the benefits and costs to the society. The study assess the state of the production and use of solar PV systems in the world and what happens in Brazil. At this study, we sought to understand what are the possible, and/or more relevant, regulatory actions and private area initiatives to enable this industrial branch and its diffusion to the final consumers. The impacts of the related activity are considered, trying to show the cost-benefit relationship in centralized generation projects (Reserve Energy Auctions) and distributed generation.

Neste trabalho, são avaliadas diferentes configurações de sistemas fotovoltaicos, levando em consideração os principais tipos de módulos fotovoltaicos comercialmente disponíveis e estruturas de suporte. A comparação é delimitada na região Nordeste do Brasil e é baseada, fundamentalmente, em termos de fator de capacidade. Para uma melhor compreensão dos resultados, são mostradas, previamente, as influências que as variáveis meteorológicas exercem na saída do sistema, bem como os efeitos do fator de dimensionamento do inversor (FDI) e do índice de cobertura do terreno (ICT). Os resultados das simulações computacionais realizadas são apresentados em forma de mapas, nos quais é possível verificar as áreas em que os sistemas fotovoltaicos tendem a gerar mais energia elétrica. Entre as configurações estudadas, os maiores valores foram observados para sistemas que utilizam módulos genéricos de filmes finos montados em rastreadores solares de um eixo horizontal, chegando a 36 % de fator de capacidade (em corrente alternada) em algumas regiões do Ceará, Rio Grande do Norte, Paraíba, Pernambuco e Bahia. Além disso, foram evidenciados os ganhos obtidos nos fatores de capacidade ao substituir as estruturas fixas por rastreadores solares. Para um ICT de 0,4, os sistemas que realizam o seguimento, ainda que em um eixo do movimento aparente do Sol, apresentaram ganhos de 18 % a 28 % na energia elétrica anual gerada. / In this work, different configurations of photovoltaic systems are evaluated, considering the main type of commercially available photovoltaic modules and mounting structures. The comparison is delimited to the Northeastern region of Brazil and is based, fundamentally, in terms of capacity factor. The influence on the output of the system of meteorological variables, the inverter loading ratio (ILR 1/FDI) and ground coverage ratio (GCR ICT) are shown in advance for a better understanding of the results. Computational simulations results are presented in maps, in which it is possible to verify the areas where photovoltaic systems tend to generate more electricity. Among the studied configurations, the largest values were observed for systems that use generic thin film modules mounted on one axis horizontal solar trackers, reaching 36 % of capacity factor (in alternating current) in some regions of Ceará, Rio Grande do Norte, Paraíba, Pernambuco and Bahia. Additionally, the gains obtained in the capacity factors when replacing fixed structures by solar trackers were shown. For an GCR of 0.4, systems that track, even on one axis, the apparent motion of the Sun showed gains of 18 % to 28 % on annual generated electricity.

Photovoltaic solar cells can generate electricity directly from sunlight without emitting harmful greenhouse gases. This makes them ideal candidates as large scale future energy producers for the global energy economy. Ideally, solar cells should be efficient and inexpensive to compete in the global energy market. Unfortunately, a number of fundamental limitations exist for the efficiency due to fundamental loss mechanisms of the semiconductor materials used to make solar cells. One of the dominant loss mechanisms from a conventional silicon solar cell is the transparency of sub-bandgap near-infrared photons. Up-conversion is an optical process involving the sequential absorption of lower energy photons followed by luminescence of a higher energy photon. This mechanism could be exploited to minimise photovoltaic sub-bandgap losses. Rare-earth doped materials have ideal up-conversion luminescent properties and have been utilised for many near-infrared to visible applications. This thesis investigates the near-infrared to near-infrared up-conversion processes required for the sub-bandgap photon utilisation within a silicon photovoltaic device. Various sodium yttrium fluoride phosphors doped with rare-earths were characterised theoretically and experimentally. Erbium doped phosphors were found to be ideal for single wavelength power dependent investigations for the non-linear up-conversion processes. The radiative and non-radiative rates of various erbium doped sodium yttrium fluoride phosphors have been approximated and compared with experimental photoluminescence results. These phosphors have been applied to the rear of a bi-facial silicon solar cell and an enhancement in the near-infrared region has been demonstrated. An external quantum efficiency close to 3.4% was measured at 1523nm under 6mW laser excitation. The non-linear dependence on incident pump power has been investigated along with the dominant up-conversion mechanisms involved. It can be concluded that up-conversion phosphors can enhance the near-infrared spectral response of a silicon device. These phosphors have high luminescent efficiencies once up-conversion occurs, but suffer from poor infrared absorption and low up-conversion efficiencies. The results from this study show that relatively high doping levels of selected rare-earths into low phonon energy crystals can improve the absorption and luminescent properties of the phosphor.

Organic solar cells have the potential to be portable power sources that are light-weight, flexible, and inexpensive. However, the highest power conversion efficiency for organic solar cells to date is ~8%, and most high-efficiency solar cells have an area of less than 1 cm². This thesis advances the field of organic solar cells by studying the physics and engineering of the devices to understand the reverse saturation current, which is related to efficiency, and the effects of area scaling. The most commonly accepted models to describe the physics of organic photovoltaic devices are reviewed and applied to planar heterojunction solar cells based on pentacene / C60 as a model system. The equivalent circuit model developed for inorganic solar cells is shown to work well to describe the behavior of organic devices and parameterize their current-voltage characteristics with five parameters. Changes in the parameters with different material combinations or device structures are analyzed to better understand the operation of the presented organic solar cells. A one-dimensional diffusion model for the behavior of excitons and treatment of the organic layers as planes is demonstrated to adequately model the external quantum efficiency and photocurrent in pentacene / C60 solar cells. The origin of the open-circuit voltage is studied using cells with different electrodes and different donor materials. While changing the electrodes does not affect open-circuit voltage, it is greatly modified by changes in the donor. Tests with additional semiconductors show the change in open-circuit voltage is not consistent from donor to donor as the acceptor is varied, suggesting a more complex relation than just the difference in energy levels. Study of the temperature dependence of the equivalent circuit parameters shows that the reverse saturation current, which has a significant role in determining the open-circuit voltage, has a thermally activated behavior. From this behavior, the reverse saturation current is related back to charge transfer at the donor / acceptor heterojunction to suggest that both the effective energy barrier presented by the energy levels and the electronic coupling are important in determining the reverse saturation current and open-circuit voltage. This marks a shift from just considering a built-in voltage or the energy levels to also considering the electronic coupling of the donor and acceptor materials. Temperature-dependent performance characteristics are also used to show key differences between organic and inorganic devices. Finally, the effect of area scaling is explored with pentacene / C60 solar cells having areas of 0.11, 7, and 36.4 cm². Analysis with the equivalent circuit model shows that performance decreases as area increases because of an increasing series resistance presented by the transparent electrode. A metal grid, to provide low resistance pathways for current, fabricated on top of the transparent electrode is proposed to reduce the effective resistance. The grid is unique in that it is placed between the electrode and the semiconductor layer and must be passivated to prevent shorts through the thin semiconductor to the back metal electrode. Analysis of the grid predicts greatly reduced series resistance, and experimental results show reduced resistance and improved performance for the 7 cm² and 36.4 cm² devices when including the grid.

In the current global market, there are plenty solutions for the savings of energy in the different areas of consumption in buildings: Green roofs and walls, cool roofs, daylighting, motion sensors, and others but there are very few sources of renewable energy at the reach of a common person in residential (smaller) scale. Photovoltaic systems are the most well-know and reliable process of harvesting energy at this small scale. The relationship between energy demand and energy production when installing a photovoltaics system in a residence is one of the main drivers while making a decision at the time of purchasing a system. However, architectural decisions in early stages may influence, enhance or even decrease the possible energy generation and interior performance, thus influencing the possible return of investment. This study evaluates the possible architectural variations that may be beneficial or disadvantegous at a particular city and other circumstances. From, roof, angle, location, roof articulation, layout articulation , shading devices and others, this paper shows a spectrum of convenient and inconvenient projects due to current conditions like climate, solar radiation, typical construction, electricity rates and government incentives. As a conclusion a hierarchy of architectural elements when being used with photovoltaics is developed to demonstrate that a common user can strategically play with architectural features of his/her house to take the most out of the system.