Made available in DSpace on 2016-12-12T20:27:37Z (GMT). No. of bitstreams: 1 Joao Cabral.pdf: 4385545 bytes, checksum: c09296f90add051ed37bd87320b15421 (MD5) Previous issue date: 2013-03-06 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This Master Thesis proposes a high gain non-isolated DC-DC converter applied on the processing of PV energy. The proposed converter is a boost converter with quadratic characteristic and with central point at its output. Basic operations and electric characteristics of a PV cell are described, including the procedures to determine its parameters. A model for numeric simulation is presented. A review of the high gain non-isolated DC-DC converters topologies is presented. Shows the converter´s transfer functions and the control strategy adopted as well as the design of control circuits. The control system is consisting of three loops, an internal loop of input current control, an external loop of total output voltage control and an additional loop of voltage unbalance control. The simulation and experimental results are shown to validate the analysis developed and demonstrate the performance of the control system adopted. / Esta Dissertação de Mestrado propõe um conversor CC-CC não isolado de elevado ganho para aplicação no processamento de energia solar fotovoltaica. O conversor proposto é um boost com característica quadrática e com ponto médio na sua saída. Descrevem-se o funcionamento básico e as características elétricas de uma célula fotovoltaica, incluindo-se o procedimento da determinação dos parâmetros e da modelagem dos módulos fotovoltaicos, apresentando-se um modelo para simulação numérica. Apresenta-se uma revisão de topologias de conversores CC-CC não isolados com elevado ganho estáticos. Apresentam-se as funções de transferência do conversor e a estratégia de controle adotada bem como o projeto dos circuitos de controle. O sistema de controle composto por três malhas de controle, uma malha interna de corrente de entrada, uma malha externa de tensão total e uma malha adicional de equalização de tensão. Resultados de simulação e experimentais são apresentados para validar as análises desenvolvidas e demonstrar o desempenho do sistema de controle adotado.

Made available in DSpace on 2016-08-31T13:33:38Z (GMT). No. of bitstreams: 1 RomeniaGV_DISSERT.pdf: 3190598 bytes, checksum: 478a0cda7a4c2391088f6946ab2c42c1 (MD5) Previous issue date: 2014-08-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The photovoltaics energy has been explored as one of the solutions to the decline in oil production, and environmental worries. However, generating electric energy throw the sun is still considered uncompetitive when considering other sources, because it shows low efficiency and high production costs. Trying to turn it more attractive to the financial point view, sun trackers are been used to increase the photovoltaics system efficiency. Considering it, this work aims to perform a comparative study between a static photovoltaic solar panel and a one axis mobile panel, both installed in Mossoró/RN. The city is located on northeast semi-arid, under high levels of solar radiation, on dry and hot climate regions, achieving high temperatures during day. Initially are discussed concepts related to solar photovoltaics energy, and tracking technologies. Then, are described the control components, sensing and structures used on the photovoltaics systems proposed. Lastly, the analyses about the functioning and comparing study about the performance of the static and mobile system were realized, allowing to conclude that the sun tracker panel showed low gain on the generated power when compared to the static panel / A energia solar fotovoltaica vem sendo explorada como uma das soluções energéticas ao declínio da produção de petróleo, e preocupações ambientais. No entanto, geração de energia elétrica através do sol ainda é considerada pouco competitiva frete à outras fontes, por apresentar baixo rendimento e alto custo de produção. Na tentativa de torna-la mais atrativa do ponto de vista financeiro, rastreadores solares têm sido utilizados a fim de aumentar o rendimento dos sistemas fotovoltaicos. Neste sentido, o presente trabalho tem por objetivo realizar um estudo comparativo entre um painel solar fotovoltaico estático e um painel com mobilidade em um eixo, instalados na cidade de Mossoró/RN. O município em questão está localizado no semiárido nordestino, sob altos índices de radiação solar, em uma região de clima seco e quente, atingindo elevadas temperaturas durante o dia. Inicialmente são abordados conceitos relativos à energia solar fotovoltaica, e tecnologias de rastreamento do sol. Em seguida, descreve-se os componentes de controle, sensoriamento e estruturas utilizadas nos sistemas fotovoltaicos propostos. Por fim, foram realizadas as análises de funcionamento e o estudo comparativo de desempenho do sistema estático e do móvel, que permitiram concluir o que painel com rastreio do sol apresentou baixo ganho médio na potência gerada em relação ao painel fixo

Because of the increasing demand for the provision of energy worldwide and the numerous damages caused by a major use of fossil sources, the contribution of renewable energies has been increasing significantly in the global energy mix with the aim at moving towards a more sustainable development. In this context, this work aims at the development of a general methodology for designing PV systems based on ecodesign principles and taking into account simultaneously both techno-economic and environmental considerations. In order to evaluate the environmental performance of PV systems, an environmental assessment technique was used based on Life Cycle Assessment (LCA). The environmental model was successfully coupled with the design stage model of a PV grid-connected system (PVGCS). The PVGCS design model was then developed involving the estimation of solar radiation received in a specific geographic location, the calculation of the annual energy generated from the solar radiation received, the characteristics of the different components and the evaluation of the techno-economic criteria through Energy PayBack Time (EPBT) and PayBack Time (PBT). The performance model was then embedded in an outer multi-objective genetic algorithm optimization loop based on a variant of NSGA-II. A set of Pareto solutions was generated representing the optimal trade-off between the objectives considered in the analysis. A multi-variable statistical method (i.e., Principal Componet Analysis, PCA) was then applied to detect and omit redundant objectives that could be left out of the analysis without disturbing the main features of the solution space. Finally, a decision-making tool based on M-TOPSIS was used to select the alternative that provided a better compromise among all the objective functions that have been investigated. The results showed that while the PV modules based on c-Si have a better performance in energy generation, the environmental aspect is what makes them fall to the last positions. TF PV modules present the best trade-off in all scenarios under consideration. A special attention was paid to recycling process of PV module even if there is not yet enough information currently available for all the technologies evaluated. The main cause of this lack of information is the lifetime of PV modules. The data relative to the recycling processes for m-Si and CdTe PV technologies were introduced in the optimization procedure for ecodesign. By considering energy production and EPBT as optimization criteria into a bi-objective optimization cases, the importance of the benefits of PV modules end-of-life management was confirmed. An economic study of the recycling strategy must be investigated in order to have a more comprehensive view for decision making.

A company in Linköping has a project where a solar power home system is designed. The plan is that families that lack grid connection in rural areas of Mali and other countries shall use this system for cooking food and powering every day items. Designing a solar home system for West Africa is more difficult than for other parts of the world, mainly because of the climate, with heat and dust particles in the air, but also because the installation location often is unreachable in short notice. This makes for several specific requirements like high ambient temperature, passive cooling, high efficiency and a long mean time between service needed. On top of this, to get the system modular and easy to install, each physical panel should be independent and smart. The system designed is a push pull dc step-up converter that can be assembled to the back of a solar panel. A base platform for the converter is built and a method of power line communication is proposed. Tests show promising results and further development is ongoing.

The aim of this study is to investigate, analyse and evaluate the installed off-grid PV system in Mavuno girls’ secondary school that is located in a rural area in northwest Tanzania. The original motivation behind this study was the rapid degradation of the installed battery bank within less than 3 years. The PV system was installed before the actual operation of the school, so the study aimed to answer a very pressing question which is "What is the actual load profiles in the school?". There was a high need to identify the actual school load profiles to enable several concerned social actors to evaluate the system and to decide for future extensions. Therefore, the study aimed to analyse the implementation of electricity in the school by creating actual load profiles, analysing the system performance versus the users’ needs and evaluating the sustainability and utilization of implementation. The study followed a multi-disciplinary approach combining the social and technical aspects of PV systems implementation to seek further understanding of the users’ consumption behaviours. It thus included a 1-month of field work in June 2018 during which participant observations and semi-structured interviews together with load measurements were carried out so as to create load profiles that are considering the patterns and deviations in users’ behaviours. During the field work, 2/3 of the students were in holidays so the taken measurements corresponded to the school at 30 % capacity. That is why the study also included 4 days of inverter data logging after the 1-month field work by the technical head of the school to overcome the limitations in held measurements. The observations showed that the actual installed system was slightly different from the documentation. In addition, the local installation practices are not fully appropriate from the technical point of view, and are affected by local social norms, as will be discussed. Besides, the participant observations and held interviews with relevant social actors showed that the daily behaviours of energy users do not exactly follow the school daily routine. Consequently, the social study was important to create actual effective load profiles. The observations and responses from interviews together with measurements were used to categorize the school loads into 29 different units. Those units can be used for current load prioritizations and for future load extrapolations. The created load profiles also represent a useful addition to load databases used by energy researchers who work on similar rural electrification projects. After the field work, several characteristics were calculated by Microsoft Excel such as apparent power consumptions, active power consumptions, battery bank state of charge, load power factor and PV generated energy. The characteristics were used in calculations evaluating the energy balance in the system. The results of held calculations showed that lighting during dark hours accounted for on around 78 % of the logged daily apparent energy use, as it has a low a low average power factor of 0.28. It also showed that some loads if time-bounded, they will significantly decrease the daily energy consumption. The calculations were also used to run PVSyst simulations to evaluate the system sizing which resulted in the recommendation that either the array size should be doubled, or the apparent energy consumption should be decreased to half. The study included suggestions for possible improvements such as decreasing the reactive consumed energy by either replacing the currently used light bulbs with ones that have higher power factor ( ≥0.8 for example) or by installing a capacitive compensation for power factor correction. In addition, it was recommended to quantify the school loads according to their priority or importance and to regulate observed time-unbounded loads such as "pumping water" and "ironing". Lastly, the study discussed how generated electricity is utilized in the school and what opportunities for women empowerment have become potentially possible with the provision of electricity.

Made available in DSpace on 2014-06-11T19:32:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12-20Bitstream added on 2014-06-13T19:03:06Z : No. of bitstreams: 1 seabrajunior_s_dr_botfca.pdf: 725253 bytes, checksum: 63ae443c8f6290ceb25a9148ff0290f4 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O brócolis (Brassica oleracea var. italica) é uma espécie exigente em nutrientes, destacando-se os elementos nitrogênio e potássio, que são exigidos em maiores quantidades pelas plantas, podendo influenciar na produção, qualidade e também na severidade de diversas doenças. Com o objetivo de estudar os efeitos desses elementos na severidade da podridão negra, causado por Xanthomonas campestris pv. Campestri (Xcc) e a sua influência na produção de brócolis tipo inflorescência única, foi realizado o experimento no Departamento de Produção Vegetal/Horticultura da FCA/UNESP - Botucatu. O delineamento utilizado foi em parcela subdividida com fatorial na subparcela, em blocos casualisados com quatro repetições. Na parcela avaliou-se a influência da inoculação (plantas não inoculadas e inoculadas com Xcc) e na subparcela avaliou-se o fatorial 4 x 4, doses de potássio (0, 275, 550 e 825 kg ha-1) e nitrogênio (0, 150, 300 e 450 kg ha-1). O híbrido de brócolis utilizado foi o BRO68 (Rogers). A semeadura foi realizada em 18/02/2004 e as plântulas foram transplantadas aos 33 dias após semeadura (DAS) em vasos de dez litros, sob ambiente protegido. Realizou-se a inoculação pelo método de palito (64 DAS) e as colheitas foram realizadas de 28/05/2004 a 12/06/2004 (99 aos 114 DAS). As adubações foram realizadas no plantio, pela incorporação ao solo de 45% da dose de potássio e 10% da dose de nitrogênio de cada tratamento e em cobertura, aplicados via fertirrigação (55% do potássio e 90% do nitrogênio). Foram avaliadas a severidade da Xcc através do PANC (porcentagem da altura necrosada do caule) e porcentagem das folhas retidas nas plantas (FR), produção e diâmetro das cabeças, teores de macronutrientes, no momento da inoculação e na colheita... / Broccoli is one vegetable specie that demand fertilizers, mainly nitrogen and potassium are required in higher quantity, which can have influence in yields, quality and severity level of diseases. Evaluated the influence of nitrogen and potassium fertilizations in black rot (Xanthomonas campestris pv. campestris) severity and broccoli yields, in the Departamento de Produção Vegetal/Horticultura - FCA/UNESP - Botucatu country, São Paulo State, Brazil. The experimental design was split plot with factorial in plot, in randomized blocks with four replicants. In the plot was evaluated the influence of inoculation (plant no inoculated or inoculated with Xcc (Xanthomonas campestris v. campestris) with four replications, considering potassium rates (0, 275, 550 and 825 kg ha-1) and nitrogen rates (0, 150, 300 and 450 kg ha-1). Hybrid BRO 68 (Rogers) was seeded in 18/02/2004 and transplanted in 33 days after seeding (DAS) for pot with 10 liters of capacity in plastic house conditions. The Xcc inoculation was made using toothpick methods (64 DAS) and the harvesting occurs in 28/05/2004 to 12/06/2004 (99 to 114 DAS). Incorporated in soil before planting with 45% potassium rate and 10% nitrogen rate of each treatment, and after planting fertilization was in fertirrigation system (55% potassium and 90% nitrogen). The severity of Xcc was evaluated with a PANC (percentage of necrosed height of the stem) method and the percentage of leaf kept in plants, the broccoli yield and the diameter of head, macronutrients ratios, was assessment during inoculations and the harvesting. The results showed that interactions among of three factors did not have significance for neither characteristics, potassium x nitrogen fertilizers interactions was significance to yield, head diameter, and PANC and macronutrients ratios (N, P, K, Ca and Mg)...(Complete abstract click electronic access below)

abstract: In recent years, solar photovoltaic (PV) industry has seen lots of improvements in technology and of growth in market with crystalline silicon PV modules being the most widely used technology. Plant inspections are gaining much importance to identify and quantitatively determine the impacts of various visual defects on performance. There are about 86 different types of defects found in the PV modules installed in various climates and most of them can be visually observed. However, a quantitative determination of impact or risk of each of identified defect on performance is challenging. Thus, it is utmost important to quantify the risk for each of the visual defects without any human subjectivity. The best way to quantify the risk of each defect is to perform current-voltage measurements of the defective modules installed in the plant but it requires disruption of plant operation, expensive measuring equipment and intensive human resources. One of the most riskiest and dominant visual defects is encapsulant browning which affects the PV module performance in the form of current degradation. The present study deals with developing an automated image processing tool which can address the issues of human subjectivity on browning level impacting performance. The image processing tool developed in this work can be directly used to quantify the impact of browning on performance without intrusively disconnecting the modules from the plant. In this work, the quantified browning level impact on performance has also been experimentally validated through a correlation study using short-circuit current and reflectance/transmittance measurements of browned PV modules retrieved from aged plants/systems installed in diverse climatic conditions. The primary goal of the image processing tool developed in this work is to determine the performance impact of encapsulant browning without interrupting the plant operation for I-V measurements. The use of image processing tool provides a single numerical value, called browning index (BI), which can accurately quantify browning levels on modules and also correlate with the performance and reflectance/transmittance parameters of the modules. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

abstract: The operating temperature of photovoltaic (PV) modules is affected by external factors such as irradiance, wind speed and ambient temperature as well as internal factors like material properties and design properties. These factors can make a difference in the operating temperatures between cells within a module and between modules within a plant. This is a three-part thesis. Part 1 investigates the behavior of temperature distribution of PV cells within a module through outdoor temperature monitoring under various operating conditions (Pmax, Voc and Isc) and examines deviation in the temperature coefficient values pertaining to this temperature variation. ANOVA, a statistical tool, was used to study the influence of various factors on temperature variation. This study also investigated the thermal non-uniformity affecting I-V parameters and performance of four different PV technologies (crystalline silicon, CdTe, CIGS, a-Si). Two new approaches (black-colored frame and aluminum tape on back-sheet) were implemented in addition to the two previously-used approaches (thermally insulating the frame, and frame and back sheet) to study temperature uniformity improvements within c-Si PV modules on a fixed latitude-tilt array. This thesis concludes that frame thermal insulation and black frame help reducing thermal gradients and next best viable option to improve temperature uniformity measurements is by using average of four thermocouples as per IEC 61853-2 standard. Part 2 analyzes the temperature data for two power plants (fixed-tilt and one-axis) to study the temperature variation across the cells in a module and across the modules in a power plant. The module placed in the center of one-axis power plant had higher temperature, whereas in fixed-tilt power plant, the module in north-west direction had higher temperatures. Higher average operating temperatures were observed in one-axis tracking as compared to the fixed-tilt PV power plant, thereby expected to lowering their lifetime. Part 3 focuses on determination of a thermal model coefficients, using parameters similar to Uc and Uv thermal loss factors used in PVsyst, for modules of four different PV technologies experiencing hot-desert climate conditions by statistically correlating a year-long monitored data. Thermal models help to effectively quantity factors influencing module temperatures to estimate performance and energy models. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2016

abstract: The dissertation encompasses the transformer-less single phase PV inverters for both the string and microinverter applications. Two of the major challenge with such inverters include the presence of high-frequency common mode leakage current and double line frequency power decoupling with reliable capacitors without compromising converter power density. Two solutions are presented in this dissertation: half-bridge voltage swing (HBVS) and dynamic dc link (DDCL) inverters both of which completely eliminates the ground current through topological improvement. In addition, through active power decoupling technique, the capacitance requirement is reduced for both, thus achieving an all film-capacitor based solution with higher reliability. Also both the approaches are capable of supporting a wide range of power factor. Moreover, wide band-gap devices (both SiC and GaN) are used for implementing their hardware prototypes. It enables the switching frequency to be high without compromising on the converter efficiency. Also it allows a reduced magnetic component size, further enabling a high power density solution, with power density far beyond the state-of-the art solutions. Additionally, for the transformer-less microinverter application, another challenge is to achieve a very high gain DC-DC stage with a simultaneous high conversion efficiency. An extended duty ratio (EDR) boost converter which is a hybrid of switched capacitors and interleaved inductor technique, has been implemented for this purpose. It offers higher converter efficiency as most of the switches encounter lower voltage stress directly impacting switching loss; the input current being shared among all the interleaved converters (inherent sharing only in a limited duty ratio), the inductor conduction loss is reduced by a factor of the number of phases. Further, the EDR boost converter has been studied for both discontinuous conduction mode (DCM) operations and operations with wide input/output voltage range in continuous conduction mode (CCM). A current sharing between its interleaved input phases is studied in detail to show that inherent sharing is possible for only in a limited duty ratio span, and modification of the duty ratio scheme is proposed to ensure equal current sharing over all the operating range for 3 phase EDR boost. All the analysis are validated with experimental results. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Battery energy storage systems are a key factor for enabling a continuous increase of the fraction of photovoltaics in the Swedish electricity grid. One big challenge is to utilise all potential services of such a storage system. The aim of this study was to improve the supervisory controller for an existing battery storage and photovoltaic solution marketed by the Swedish company Ferroamp AB. This has been done by developing a combined peak reduction and time-of-use bill management algorithm, together with a simulation and evaluation software for optimisation of algorithm parameters. The algorithms and tools were evaluated using an installation made by Ferroamp AB and Vattenfall Eldistribution AB as a case study. Sensitivity analyses has been performed on economic parameters and length of the algorithm training data set. Improvement of economic profit, in this case study, were 300 % compared to the currently used algorithm and 32 % compared to a conventional threshold peak reduction algorithm. Despite this improvement, the battery energy storage system is shown to be non-profitable, with the economic profit only covering 36 % of the investment costs, not taking interest rate into account. Like in many other studies, power storage was found more profitable than energy storage. An increase of the grid power tariff and the grid energy fee of 30 % to 40 % is found to make the system viable. One interesting finding is that by using the proposed optimal algorithm, 55 % of the cycle life of the battery storage is still accessible for other services when considering 10 years of economic depreciation time for the system.