Made available in DSpace on 2014-08-13T14:51:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-05-05Bitstream added on 2014-08-13T17:59:35Z : No. of bitstreams: 1 000776616.pdf: 4325824 bytes, checksum: 557feea50cbc02fd024a9a6c5abda8d8 (MD5) / 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. / 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.

abstract: In this study I investigate the organizational strategies that Chinese power generation companies may use to reduce the impact of coal price increases on their profits. Organizations are open systems in that no organization possesses all the resources that it needs and all organizations must obtain resources from their external environments in order to survive. Resource dependent theory suggests that the most important goal of an organization is to find effective mechanisms to cope with its dependence on the external environments for resources that are critical to its survival. Chinese power generation companies traditionally rely heavily on coal as their raw materials, and an increase in coal price can have a significant negative impact on their profits. To address this issue, I first provide a systematic review of the resource dependence theory and research, with a focus on the strategies such as vertical integration, diversification, and hedging that organizations can undertake to reduce their dependence on the external environment as well as their respective benefits and costs. Next, I conduct a qualitative case analysis of the primary strategies the largest Chinese power generation companies have used to reduce their dependence on coal. I then explore a new approach that Chinese power generation companies may use to cope with increases in coal price, namely, by investing in an index of coal companies in the stock market. My regression analysis shows that coal price has a strong positive relation with the price of the coal company index. This finding suggests that it is possible for firms to reduce the negative impact of raw material price increase on their profits by investing in a stock market index of the companies that supply the raw materials that they depend on. / Dissertation/Thesis / Doctoral Dissertation Business Administration 2015

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018. / Until recently, the focus of most solar technology development for space was towards more efficient, more radiation-resistant and increasingly powerful arrays. During a space mission, solar cells are not only exposed to irradiation by electrons, but also to a range of other particles, like protons. Thus, solar cells on robust nanosatellites are extremely exposed to an environment, which includes the high-energy electrons and protons of the earth’s radiation belts, which leads towards the degradation process of the individual solar cell. Solar cell radiation shielding design ensures the protection of the solar cells from the particular radiation environment found in space. While the design principles of a solar photovoltaic automatic switching fault tolerant system which can detect and bypass faulty photovoltaic cells will be presented through this research work. The ability of such a system to be reconfigured using implemented switching matrix system makes it efficient under various environments and faulty conditions. / National Research Foundation (NRF)

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

Orientador: Ennio Peres da Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-20T13:25:32Z (GMT). No. of bitstreams: 1 Strangueto_KarinaMaretti_M.pdf: 19906367 bytes, checksum: cfc584b8248827cae84c86e393a1870f (MD5) Previous issue date: 2012 / Resumo: Desde a Revolução Industrial, as atividades desenvolvidas pelo homem têm provocado um crescimento maciço das emissões de gases de efeito estufa e poluentes para a atmosfera da Terra, devido, entre outros fatores, à constante e crescente necessidade de energia. Um grande esforço vem sendo realizado nas últimas décadas para a redução dessas emissões, com especial atenção ao setor de transporte, principalmente pelos efeitos provocados nas populações das grandes cidades devido à concentração de veículos em espaços reduzidos. Neste caso, busca-se aumentar: a eficiência dos veículos convencionais, o uso de biocombustíveis e de veículos híbridos, e, mais recentemente, o uso de veículos elétricos (VEs). Com o avanço da utilização de veículos elétricos como meio de transporte "limpo", são necessários maiores estudos para avaliar a quantidade de energia necessária para o abastecimento das frotas destes veículos e, também, uma análise da quantidade evitada de emissões de gases de efeito estufa (gás carbônico) comparativamente aos modelos à combustão interna. Assim, esse trabalho teve como objetivo desenvolver esses temas. A geração de energia através painéis fotovoltaicos foi a escolha para essa dissertação, onde foi realizado um estudo de caso para uma usina de 1 MWP, determinando a quantidade de energia efetivamente produzida, considerando a usina localizada em Campinas, São Paulo. Dessa forma, pôde-se estimar que a frota de veículos que poderia ser abastecida com a energia gerada por essa usina teria um valor entre 955 e 1.118 veículos, dependendo de diferentes logísticas de abastecimento consideradas. Com a frota estimada, também foi possível calcular que emissões de até 2.004 toneladas anuais de CO2 poderiam ser evitadas pela substituição dos veículos convencionais pelos por esta frota de VEs / Abstract: Since the Industrial Revolution, human activities have been causing a massive growth in greenhouse gases and pollutants emissions to the Earth's atmosphere, due to, between other factors, the continuing and growing need for energy. A great effort has been made in recent decades to reduce these emissions, with special attention to the transport sector, mainly caused by the effects on populations of large cities due to the concentration of vehicles in confined spaces. In this case, seeks to improve: the efficiency of conventional vehicles, the use of biofuels and hybrid vehicles, and, more recently, the use of electric vehicles (EVs). With advancing of Electric Vehicle use as a means of "green" transport, more studies are needed to assess the amount of energy required to supply fleets of this kind of vehicles and, also, an analysis of the amount of avoided emissions of greenhouse gases (carbon dioxide) compared with internal combustion models. Thus, this study aimed to develop these themes. The generation of energy through photovoltaic panels was the choice for this dissertation, which was conducted a case study for a generating station of 1 MWP, determining the amount of energy effectively produced, considering the generating station located in Campinas, Sao Paulo. Thus, it was estimated that the fleet of vehicles that could be supplied with energy generated by this plant would have a value between 955 and 1.118 vehicles, depending on different logistical supply considered. With the fleet estimated, it was also possible to calculate that 2.004 tons of CO2 could be avoided by the replacement of conventional vehicles by EVs / Mestrado / Engenharia Mecanica / Mestre em Planejamento de Sistemas Energéticos

No description available.

The PhD project aims to develop a smart grid-connected inverter (SGCI) for a micro-grid, which can be applied in a built environment such as a community, and associated power electronic DC/DC converters. The micro-grid generally includes distributed renewable power generators and battery storage. The SGCI is a bi-directional DC/AC inverter for distributed generation with battery storage installed at its DC side. In one aspect, it is expected the DC/AC inverter functions as a controlled inverter that can deliver expected real power to the power grid with quantitative reactive power compensation (RPC). In other words, all the SGCIs in the community microgrid can share the reactive power of the whole community because a SGCI can quantify its active and reactive power output. It is also expected that the inverter can work in both on-grid and off-grid modes. In other words, the DC/AC inverter functions as a controlled rectifier with high quality power factor correction (PFC), which can deliver expected DC power from the AC power grid at unity power factor. With the above features, battery storage on the DC bus of the SGCI can be charged/discharged through a four-phase, interleaved, bi-directional, boost/buck DC/DC converter (IBDBBC) for distributed renewable power system, either wind or solar PV or hybrid wind/solar PV system. The IBDBBC can discharge power from a low voltage battery to a high voltage DC bus as the IBDBBC operates in boost mode, or it can also draw power from the DC bus to charge the battery as the IBDBBC operates in buck mode. Based on MATLAB/Simulink, a mathematical model was developed for the grid-connected bi-directional DC/AC inverter that operates as a rectifier with PFC and as a grid-connected inverter (GCI) with expected real power output and quantitative RPC. In a practical application, the sampling of input signal through AD converter usually has some noise due to common-mode interference; simulation results demonstrate that the second order generalised integrator (SOGI) has great advantages to prevent interference. Therefore, SOGI can be utilised to construct a pair of orthogonal signals in a single-phase system to instantaneously split grid’s active and reactive power to achieve RPC for local community loads. The methodology of the constructed the pair of orthogonal signals was also used to generate the required reference current for the DC/AC inverter when which operated as a single-phase rectifier with PFC. Using three TI C2000 Solar Inverter DSK Boards, a small lab scale distributed power system was developed. In the lab distributed power system, the operating mode of the inverters could be switched between on-grid and off-grid through instruction from the control centre. The lab test outcomes demonstrate that each distributed power system unit worked properly under loss of power grid signal, simulating grid failure.

The main objective of this study was to investigate the performance of grid integrated PV systems. A data acquisition (DAQ) system was developed to monitor the performance of an existing grid integrated PV system with battery storage. This system is referred to as a grid assisted PV system. A data logger was used together with the inverters built in data logger to monitor environmental and electrical data on a grid tie PV system which was deployed during this study. To investigate the performance of these grid integrated PV systems PV and BOS device characterization was performed. This was achieved by using current voltage curve tracers and the DAQ system developed. Energy yield estimations were calculated referring to the literature review and a meteorological reference for comparison with measured energy yields from the grid tie PV system.

In order to investigate the influence of parasitic resistances, saturation current and diode ideality factor on the performance of photovoltaic devices, parameter extraction routines employing the standard iteration (SI) method and the particle swarm optimization (PSO) method were developed to extract the series resistance, shunt resistance, saturation current and ideality factor from the I-V characteristics of solar cells and PV modules. The well-known one- and two-diode models were used to describe the behavior of the I-V curve and the parameters of the models were determined by approximation and iteration techniques. The SI and the PSO extraction programmes were used to assess the suitability of the one- and the two-diode solar cell models in describing the I-V characteristics of mono- and multicrystalline silicon solar cells, CISS- and CIGSS-based solar cells. This exercise revealed that the two-diode model provides more information regarding the different processes involved in solar cell operation. Between the two methods developed, the PSO method is faster, yielded fitted curves with lower standard deviation of residuals and, therefore, was the preferred extraction method. The PSO method was then used to extract the device parameters of CISS-based solar cells with the CISS layer selenized under different selenization process conditions and CIGSS-based solar cells with varying i-ZnO layer thickness. For the CISS-based solar cells, the detrimental effect of parasitic resistances on device performance increased when the temperature and duration of the selenization process was increased. For the CIGSS-based devices, photogeneration improved with increasing i-ZnO layer thickness. At high forward bias, bulk recombination and/or tunneling-assisted recombination were the dominant processes affecting the I-V characteristics of the devices. v Lastly, device and performance parameters of mono-, multicrystalline silicon and CIS modules derived from I-V characteristics obtained under dark and illuminated conditions were analyzed considering the effects of temperature on the performance of the devices. Results showed that the effects of parasitic resistances are greater under illumination and, under outdoor conditions, the values further declined due to increasing temperature. The saturation current and ideality factor also increased under outdoor conditions which suggest increased recombination and, coupled with the adverse effects of parasitic resistances, these factors result in lower FF and lower maximum power point. Analysis performed on crystalline silicon and thin film devices utilized in this study revealed that parameter extraction from I-V characteristics of photovoltaic devices and, in particular, the implementation of PSO in solar cell device parameter extraction developed in this work is a useful characterization technique.

The objective of this study is to characterize and analyse defects in solar cell devices. Materials used to fabricate solar cells are not defects free and therefore, there is a need to investigate defects in cells. To investigate this, a topographical technique was developed and employed which uses a non-destructive methodology to analyse solar cells. A system was built which uses a technique based on a laser beam induced current (LBIC). LBIC technique involves focusing light on to a surface of a solar cell device in order to create a photo-generated current that can be measured in the external circuit for analyses. The advantage of this technique is that it allows parameter extraction. Parameters that can be extracted include short-circuit current, carrier lifetime and also the external and internal quantum efficiency of a solar cell. In this thesis, LBIC measurements in the form of picture maps are used to indicate the distribution of the localized beam induced current within solar cells. Areas with low minority carrier lifetime in solar cells are made visible by LBIC mapping. Surface reflection intensity measurements of cells can also be mapped using the LBIC system developed in this study. The system is also capable of mapping photo-generated current of a cell below and above room temperature. This thesis also presents an assessment procedure capable of assessing the device and performance parameters with reference to I-V measurements. The dark and illuminated I-V characteristics of solar cells were investigated. The illuminated I-V characteristics of solar cells were obtained using a defocused laser beam. Dark I-V measurements were performed by applying voltage across the cell in the dark and measuring a current through it. The device parameters which describe the behaviour of I-V characteristic were extracted from the I-V data using Particle Swarm Optimization (PSO) method based on a one-and two-diode solar cell models. Solar cells of different technologies were analysed, namely, single-crystalline (c-Si) and multicrystalline (mc-Si) silicon, Edge-defined Film-fed Growth Si (EFG-Si) and Cu(In,Ga)(Se,S)2 (CIGSS) thin film based cells. The LBIC results illustrated the effect of surface reflection features and material defects in the solar cell investigated. IQE at a wavelength of 660 nm were measured on these cells and the results in general emphasised the importance of correcting optical losses, i.e. reflection loss, when characterizing different types of defects. The agreement between the IQE measurements and I-V characteristics of a cell showed that the differences in crystal grains influence the performance of a mc-Si cell. The temperature-dependence of I-V characteristics of a CIGSS solar cell was investigated. The results showed that, for this material, the photo response is reduced at elevated temperatures. In addition to LBIC using a laser beam, solar spectral radiation was employed to obtained device performance parameters. The results emphasised the effect of grain boundaries as a recombination centres for photo-generated hole-pairs. Lastly, mesa diode characterizations of solar cells were investigated. Mesa diodes are achieved by etching down a solar cell so that the plateau regions are formed. Mesa diodes expose the p-n junction, and therefore mesa diode analysis provides a better way of determining and revealing the fundamental current conduction mechanism at the junction. Mesa diodes avoid possible edge effects. This study showed that mesa diodes can be used to characterize spatial non-uniformities in solar cells. The results obtained in this study indicate that LBIC is a useful tool for defect characterization in solar cells. Also LBIC complements other characterization techniques such as I-V characterization.