This thesis presents an experimental study of the incorporation and optimization of sol-gel processed aluminum doped zinc oxide (AZO) thin films in solar cell devices. I first optimized the optoelectronic properties of AZO thin films by manipulating the dopant incorporation, choice of precursor chemicals and post deposition anneal treatments. Results showed that improved performance could be attributed to several factors, including improved charge carrier concentration, mobility and conductivity. AZO thin films with transmittance of over 90% and resistivity values of the order of 10-2 Ω•cm have been achieved. I also demonstrated the successful application of these AZO thin films in organic photovoltaics (OPV), to serve as an alternative to ITO electrodes. I demonstrated greater than 2-fold improvement in device efficiency through the modification of the front contact/polymer interface using zinc oxide buffer layers. This improved the charge selectivity of the electrodes and energy level alignment at the interface while reducing the recombination of separated charges and the device's series resistance. Finally, I showed that the efficiency of inverted ZnO/PbS quantum dots solar cells can be enhanced by optimizing the p-type PbS thickness, UV treating the n-type ZnO layer and exposing the devices in the dark to nitrogen. Both ZnO and AZO systems were studied, and efficiency enhancement were demonstrated for a range of Al content from 0 to O.4at.%.

Master of Science in Engineering (Electrical) University of the Witwatersrand July, 2016 / This dissertation uses historical electrical consumption/load and actual solar radiation data to design a solar array for the University of the Witwatersrand’s West Campus. The array must meet the campus’s minimum demand as selling excess generated power back to the utility is not possible at this stage. The financial and spatial impact of adjusting the size of the array, design losses and cloud cover are also investigated. In addition to this, the influence on the payback period of financial variables such as taxes, electricity and start-up costs are also explored. The solar array system design process starts by determining the amount of power that the array must produce or supplement. Thereafter, load estimates and electrical consumption figures that are provided by utility bills or measured with load monitoring equipment are analysed. Furthermore, system losses are factored in which ultimately increases the size of the array. Once all the input variables are analysed, the amount of available solar radiation in the area where the array will be installed is required to determine the amount of energy that the array can produce. Several free databases with this information are available but it is found that this data over predicts the availability of solar radiation. The University has been monitoring the electrical consumption of West Campus since 2012 and solar radiation data is also available for this site. Comparing the satellite derived and measured datasets found that the ground monitored data is 25 % more accurate and therefore better suited for designing a solar array. Individually adjusting the design and financial variables changes the payback period between 3 – 17 %. Combining all the variables can reduce the payback of option 1 from 9.6 years to 6.1 years. Clear legislation needs to be developed for the uptake of renewable energy resources and supported by better rebates for renewable users and harsher taxes for non-renewable users. Should legislation change and if additional capital is available, a larger array will benefit the University more and should be installed as the difference between payback periods is not significant. This is mainly due to decreased costs associated with a higher yield. The financial benefits of a larger array will also be more lucrative if better rebates are enforced. / MT2017

Thesis Submitted in Partial Fulfilment of the Requirements for the Degree of Master of Technology: Electrical Engineering (Energy) in the Department of Electrical, Electronic and Computer Engineering at the Cape Peninsula University of Technology, South Africa. / In photovoltaic power systems, the DC/AC conversion efficiency depends on weather conditions causing PV inverters to operate under fluctuating input power from PV modules. The peak efficiency stated by the inverter manufacturers are often used by project designers to estimate how much power PV plants can produce. However, the varying nature of the DC input power to the inverters, occasioned by varying irradiation and temperature, leads to deviations of the actual efficiency from the peak efficiency. Literature surveys prove that inverter efficiencies must be evaluated against local irradiation profiles to get more precise annual energy yield estimations, since meteorological conditions and solar irradiation profiles vary from one site to another around the planet.

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Orientador: Osmar de Carvalho Bueno / Banca: Paulo André de Oliveira / Banca: Leonardo de Barros Pinto / Banca: Osmar Delmanto Junior / Banca: Zacarias Xavier de Barros / Resumo: A energia é fundamental para a vida humana, já a energia elétrica é um fator determinante para o desenvolvimento e facilitador das atividades diárias. Para a geração da mesma no Brasil há diversas fontes, que podem ser classificadas como renováveis ou não renováveis. Buscando uma matriz elétrica mais limpa, no país procura-se investir cada vez mais em fontes renováveis, dentre elas a energia hídrica, a partir de Pequenas Centrais Hidrelétricas (PCHs). Porém, a implantação desses projetos vem sendo afetada pela dificuldade de obtenção de licenças ambientais e pela resistência por parte da comunidade do local da implantação. O presente trabalho tem como objetivo analisar a importância da comunicação no processo de estudo, autorização e implantação de PCHs e verificar a efetividade da comunicação entre os atores envolvidos no caso do rio Pardo - SP. O material utilizado foi a realidade brasileira no que tange a legislação para implantação de PCHs realizando um estudo de caso na bacia do rio Pardo - SP. O presente estudo foi elaborado por meio de pesquisa exploratória e descritiva; tendo suas informações sido coletadas em publicações de institutos, agências, departamentos e órgãos envolvidos no processo, bem como na bibliografia especializada existente. Com base no resultado deste estudo, conclui-se que a comunicação é de grande importância para o processo. Para que essa aconteça de maneira satisfatória é necessário que a comunidade conheça o estudo realizado e contribua com dado... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Energy is fundamental for human life, but electric power is a determining factor for development and facilitator of daily activities. For its generation, Brazil has several sources, which can be classified as renewable or non-renewable. Searching for a cleaner electrical matrix, the country seeks to invest more and more in renewable sources, among them hydroelectric power from Small Hydroelectric Power Plants (SHPs). However, the implementation of these projects has been affected by the difficulty of obtaining environmental licenses and by the local community's resistance. The present work aims to analyze the importance of the communication in the process of study, authorization and implementation of SHPs and to verify the effectiveness of communication among the actors involved in the Pardo river - SP case. The material used was the Brazilian reality regarding the legislation for the implementation of SHPs conducting a case study in the Pardo river basin - SP. The present study was elaborated through exploratory and descriptive research; having its information been collected in publications of institutes, agencies, departments and institutions involved in the process, as well as in the existing specialized bibliography. Based on the result of this study, it is concluded that the communication is of great importance for the process. For this to happen in a satisfactory way, it is necessary that the community be aware of the study and contribute with consistent data and information and that the entrepreneur knows the community's afflictions and endeavors to develop a project in line with the studied area, covering economic, environmental and social spheres, so that the project contemplates the expectation of sustainability. In the case of projects planned for the Rio Pardo-SP, the local community had several actors, including the Rio Pardo Vivo Association ("Vivo" means alive), which one has great... / Doutor

Orientador: Teófilo Miguel de Souza / Coorientador: José Luz Silveira / Banca: Paloma Maria Silva Rocha Rizol / Banca: Francisco Antonio Lotufo / Banca: José Rui Camargo / Banca: Osiris Canciglieri Junior / Resumo: A proposta dessa Tese é o projeto e desenvolvimento de um sistema de fornecimento de energia elétrica conectada à rede sem a utilização de circuitos eletrônicos complexos. O sistema eletroeletrônico convencional utiliza um inversor de frequência que transfere a potência ativa do nível de tensão e corrente CC para o nível compatível com a rede elétrica CA em frequência, tensão e sincronismo de fases. Já o desenvolvimento do projeto teve como parte experimental a utilização de indutores adequados com valores variáveis de 200 mH a 500 mH entre os painéis fotovoltaicos e a rede convencional. A tensão e a corrente máxima de CC foi de 29,6 V e a máxima possível foi de 20 amperes. Utilizou-se do princípio do casamento de impedâncias entre o painel fotovoltaico e o sistema de fornecimento de energia CA. Assim o painel fotovoltaico fornece somente potência ativa para a rede não interferindo no sincronismo. Na onda de tensão e corrente CA há uma pequena alteração no nível CA em relação a simetria do eixo dos tempos, dentro dos limites previstos para a rede convencional de energia. Logo evidencia-se o fornecimento de potência ativa para a rede CA. Os resultados obtidos permitiram inserção na rede de cerca de 10% da potência ativa dos painéis fotovoltaicos, com a otimização dos valores dos indutores, ocorrendo a transferência de potência ativa dos painéis fotovoltaicos para a rede convencional de energia CA / Abstract: The purpose of this thesis is the design and development of a delivery system of electricity connected to the network without the use of complex electronic circuits. The electronics system uses a frequency inverter that transfers the active power level voltage and DC current to the level compatible with the mains AC frequency, voltage and phase synchronization. But the project was to develop experimental part the use of suitable inductors with variable values of 200 mH to 500 mH between the PV panels and the conventional network. The maximum current was 20 amperes. We used the principle of impedance matching between the photovoltaic panel and the power supply system CA. So the photovoltaic panel supplies only active power to the grid not interfering with the timing. In the wave of AC voltage and current for a small change in CA level against the symmetry axis of time. Logo is evident in the supply of active power to the grid CA. The results allowed inclusion in the network of about 10% of the active power of photovoltaic panels by optimizing the values of the inductors for the occurrence of power transfer of conventional photovoltaic panels for energy occurs CA / Doutor

Methods of generating renewable energy such as through solar photovoltaic (PV) cells and wind turbines offer great promise in terms of a reduced carbon footprint and overall impact on the environment. However, these methods also share the attribute of being highly stochastic, meaning they are variable in such a way that is difficult to forecast with sufficient accuracy. While solar power currently constitutes a small amount of generating potential in most regions, the cost of photovoltaics continues to decline and a trend has emerged to build larger PV plants than was once feasible. This has brought the matter of increased variability to the forefront of research in the industry. Energy storage has been proposed as a means of mitigating this increased variability -- and thus reducing the need to utilize traditional spinning reserves -- as well as offering auxiliary grid services such as peak-shifting and frequency control. This thesis addresses the feasibility of using electrochemical storage methods (i.e. batteries) to decrease the ramp rates of PV power plants. By building a simulation of a grid-connected PV array and a typical Battery Energy Storage System (BESS) in the NetLogo simulation environment, I have created a parameterized tool that can be tailored to describe almost any potential PV setup. This thesis describes the design and function of this model, and makes a case for the accuracy of its measurements by comparing its simulated output to that of well-documented real world sites. Finally, a set of recommendations for the design and operational parameters of such a system are then put forth based on the results of several experiments performed using this model.

The development of organic photovoltaics (OPVs) has attracted a lot of attention due to their potential to create a low cost flexible solar cell platform. In general, an OPV is comprised of a number of layers of thin films that include the electrodes, active layers and barrier films. Thus, with all of the interfaces within OPV devices, the potential for failure exists in numerous locations if adhesion at the interface between layers is inherently low or if a loss of adhesion due to device aging is encountered. To date, few studies have focused on the basic properties of adhesion in organic photovoltaics and its implications on device reliability. In this dissertation, we investigated the adhesion between interfaces for a model multilayer barrier film (SiNx/PMMA) used to encapsulate OPVs. The barrier films were manufactured using plasma enhanced chemical vapor deposition (PECVD) and the interfacial fracture toughness (Gc, J/m2) between the SiNx and PMMA were quantified. The fundamentals of the adhesion at these interfaces and methods to increase the adhesion were investigated. In addition, we investigated the adhesive/cohesive behavior of inverted OPVs with different electrode materials and interface treatments. Inverted OPVs were fabricated incorporating different interface modification techniques to understand their impact on adhesion determined through the interfacial fracture toughness (Gc, J/m2). Overall, the goal of this study is to quantify the adhesion at typical interfaces used in inverted OPVs and barrier films, to understand methods that influence the adhesion, and to determine methods to improve the adhesion for the long term mechanical reliability of OPV devices.

Photovoltaics (PV) offers a unique opportunity to solve energy and environmental problems simultaneously since the solar energy is essentially free, unlimited, and not localized any part of the world. Currently, more than 90% of PV modules are produced from crystalline Si. However, wafer preparation of cast multicrystalline Si materials account for more than 40% of the PV module manufacturing cost, which can be significantly reduced by introducing the ribbon-type Si materials. Edge-defined film-fed grown (EFG) and String Ribbon Si materials are among the promising candidates for the cost-effective PV because they are grown directly from the Si melt, which eliminates the need for ingot slicing and chemical etch for surface preparation. However, the growth of these ribbon Si materials leads to relatively high concentration of metallic impurities and structural defects, resulting in very low as-grown carrier lifetime of less than 5 µs. Therefore, the challenge is to produce high-efficiency cells on EFG and String Ribbon Si by enhancing the carrier lifetime during the cell processing and to understand the effect of electrically active defects on cell performance through in-depth device characterization and modeling. The research tasks of this thesis focus on the understanding, development, and implementation of defect passivation to enhance the bulk carrier lifetime in ribbon Si materials for achieving high-efficiency cells. It is shown in this thesis that the release of hydrogen from SiNx layer is initially rapid and then slows down with time. However, the dissociation of hydrogen from defects continues at the same pace. Therefore, a short firing provides an effective defect passivation. An optimized hydrogenation process produces a record high-efficiency ribbon Si cells (4.0 cm2) with photolithography (18.3%) and screen-printed (16.8%) contacts. However, active defects are still present even after the optimized hydrogenation process. An analytical model is developed to assess the impact of inhomogeneously distributed active defects on cell performance, and the model is applied to establish the roadmap for achieving high-efficiency ribbon Si cells in the presence of defects. Finally, PC1D simulations reveal that the successful implementation of the surface texturing can raise the cell efficiency to 18%.

Though relatively young, the field of organic electronics is a rapidly growing market and considerable research is being done in creating a whole range of devices from organic molecules from organic field effect transistors to LEDs to photovoltaic devices. The field of organic photovoltaic in particular has become important in recent years with the push for newer, renewable sources of energy to end the dependence on fossil fuels. While the efficiencies of organic photovoltaic devices continue to rise, one barrier to their commercial adoption has been the limited lifetimes of these devices. While certain degradation methods of organic photovoltaics, such as photo-oxidation, have been extensively studied and solutions to these problems, such as encapsulation, are being researched, certain other degradation mechanisms are less understood and studied. The focus of this thesis is on one such degradation mechanism, UV degradation, specific to the ITO-pentacene interface in pentacene/C60 organic photovoltaic devices. Attempts were made to increase the lifetime of the devices by using phosphonic acids or oxygen plasma to modify the surface of the ITO. While conducting these experiments, the lack of a system to test the lifetime of multiple devices for long periods of time became apparent. As such as system was a requirement for future research into the lifetimes of organic photovoltaic devices a system was designed and built. The system would operate the photovoltaic device in a way comparable to its end-use and would allow over 100 devices to be tested simultaneously for durations exceeding 10,000 hours if necessary. This system would allow for statistically significant lifetime testing to be carried out in the future.