Desenvolvimento de uma bancada para a realização de ensaios de auto-amortecimento em cabos condutores de energia elétrica

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2015.

A contribution towards the performance and structural understanding of copper and nickel salts as ammonia stores

The ongoing depletion of fossil fuels and the severe consequences of the greenhouse effect make the development of alternative energy systems crucially important. While hydrogen is, in principle, a promising alternative, releasing nothing but energy and pure water. Hydrogen storage is complicated and no completely viable technique has been proposed so far. This work is concerned with the study of one potential alternative to pure hydrogen: ammonia, and more specifically its storage in solids. Ammonia, NH3, can be regarded as a chemical hydrogen carrier with the advantages of strongly reduced flammability and explosiveness as compared to hydrogen. Furthermore, ammine metal salts presented here as promising ammonia stores easily store up to 50 wt.-% ammonia, giving them a volumetric energy density comparable to natural gas. The model system NiX2–NH3 ( X = Cl, Br, I) is studied thoroughly with respect to ammine salt formation, thermal decomposition, air stability and structural effects. The system CuX2–NH3 ( X = Cl, Br) has an adverse thermal decomposition behaviour, making it impractical for use as an ammonia store. This system is, however, most interesting from a structural point of view and some work concerning the study of the structural behaviour of this system is presented. Finally, close chemical relatives to the metal ammine halides, the metal ammine nitrates are studied. They exhibit interesting anion arrangements, which is an impressive showcase for the combination of diffraction and spectroscopic information. The characterisation techniques in this thesis range from powder diffraction over single crystal diffraction, spectroscopy, computational modelling, thermal analyses to gravimetric uptake experiments. Further highlights are the structure solutions and refinements from powder data of (NH4)2[NiCl4(H2O)(NH3)] and Ni(NH3)2(NO3)2, the combination of crystallographic and chemical information for the elucidation of the (NH4)2[NiCl4(H2O)(NH3)] formation reaction and the growth of single crystals under ammonia flow, a technique allowing the first documented successful growth and single crystal diffraction measurement for [Cu(NH3)6]Cl2.

El desarrollo del sistema energético solar-hidrógeno en América Latina: potencialidades, oportunidades y barreras

El Sistema Energético Solar-Hidrógeno (SESH) constituye un sistema energético cuya fuente primaria es la energía solar, directa o indirecta, y la secundaria el hidrógeno. Actualmente, se considera como la mejor opción para complementar en el mediano y sustituir en el largo plazo, al actual sistema energético basado en fuentes fósiles. En este contexto se desenvuelve este trabajo, cuyo objetivo es identificar y analizar los factores intervinientes en el desarrollo del SESH en el ámbito latinoamericano, mediante una investigación documental basada en una amplia revisión bibliográfica. Se obtiene que la mayoría de países latinoamericanos disponen de ingentes potenciales aprovechables de energías renovables que harían posible y atractiva económicamente la implantación del SESH; que la hidrogenaría y biomasa son las fuentes más adecuadas como base para esta implantación, tanto por su potencial como por su presencia en la matriz energética y costos del SESH. Los estudios indican que la energización rural y el transporte urbano constituyen nichos de oportunidad para la penetración del SESH. También se reportan barreras: acciones de investigación escasas y concentradas en pocos países, un exiguo talento humano formado y capacitado para operar y desarrollar esta tecnología, como resultado de una débil oferta formativa; y la carencia de un marco legal e institucional que incentive el desarrollo de este sistema. Se concluye que sólo con la acción concertada de centros de investigación, universidades y la empresa privada, bajo la tutela del estado, se logrará que este elemento químico singular conduzca el desarrollo humano de la región por caminos sustentables.

Análise comparativa de um sistema de refrigeração solar

Nesta dissertação são comparadas duas tecnologias de refrigeração. Uma tecnolo-gia é um sistema que usa a energia elétrica para fazer funcionar um ciclo de com-pressão de vapor, sistema comum em instalações de refrigeração. A outra solução é um sistema de absorção, em que a energia necessária para o funcionamento do sistema é energia térmica obtida através de coletores solares térmicos. Estas tecnologias são estudadas e comparadas para a refrigeração de um arma-zém de produtos agrícolas à temperatura constante de 5ºC para a região de Alque-va, região onde estão a ser desenvolvidos projetos hortofrutícolas a que estão as-sociadas necessidades de preservação dos produtos que envolvem refrigeração e em que a acessibilidade à rede elétrica é reduzida. É mostrado que a tecnologia do sistema de absorção com os coletores se apresenta a médio prazo mais vantajosa em termos económicos e ambientais; Abstract: Comparative analysis of a solar refrigeration system In this dissertation two refrigeration technologies are compared when used for the same objective. One is a technology using the electric energy to operate a vapour compression cycle, commonly used in refrigerated installations. The alternative technology is an absorption system driven by thermal energy, provided by solar thermal collectors. Both technologies are studied and compared for the refrigeration of an agricultural products warehouse at a constant temperature of 5ºC in the Alqueva region, where horticultural projects are being developed with associated needs of preservation of the products involving refrigeration, and where accessibility to the electrical grid is reduced. In the referred conditions it was shown that the absorption technology with collec-tors in the medium term surpasses the usual compression system, both from eco-nomic and environmental viewpoints.

Determination of a Mean Solar Radiation Year and of a Typical Meteorological Year for the region of Funchal in the Madeira Island

This paper presents the determination of a mean solar radiation year and of a typical meteorological year for the region of Funchal in the Madeira Island, Portugal. The data set includes hourly mean and extreme values for air temperature, relative humidity and wind speed and hourly mean values for solar global and diffuse radiation for the period 2004-2014, with maximum data coverage of 99.7%. The determination of the mean solar radiation year consisted, in a first step, in the average of all values for each pair hour/day and, in a second step, in the application of a five days centred moving average of hourly values. The determination of the typical meteorological year was based on Finkelstein-Schafer statistics, which allows to obtain a complete year of real measurements through the selection and combination of typical months, preserving the long term averages while still allowing the analysis of short term events. The typical meteorological year validation was carried out through the comparison of the monthly averages for the typical year with the long term monthly averages. The values obtained were very close, so that the typical meteorological year can accurately represent the long term data series. The typical meteorological year can be used in the simulation of renewable energy systems, namely solar energy systems, and for predicting the energy performance of buildings.

Análise do monitoramento de descargas atmosféricas na área de concessão da companhia força e luz do oeste em Guarapuava, Estado do Paraná

Aiming to analyze the monitoring of the atmospheric discharges incidence, the concession area of Companhia Forca e Luz do Oeste (CFLO) - Western Power and Light Company, located in the district of Guarapuava, state of Parana was chosen for a study developed in 2003, from January to December. After the air masses dynamics description, it was possible to identify the occurrence of atmospheric discharges and to compare them to the energy interruptions. To that end, atmospheric discharges density maps were created within the CFLO concession area for a later analysis of their influence in the electric energy supply. The monitoring of the atmospheric discharges and the comparison between this phenomenon and the occurrence of interruptions in the electric energy supply enabled this study. Results showed that such events are directly related, and that the rural area of the region under study underwent a major interference.

Reasoning over knowledge-based generation of situations in context spaces to reduce food waste

With the ever-growing amount of connected sensors (IoT), making sense of sensed data becomes even more important. Pervasive computing is a key enabler for sustainable solutions, prominent examples are smart energy systems and decision support systems. A key feature of pervasive systems is situation awareness which allows a system to thoroughly understand its environment. It is based on external interpretation of data and thus relies on expert knowledge. Due to the distinct nature of situations in different domains and applications, the development of situation aware applications remains a complex process. This thesis is concerned with a general framework for situation awareness which simplifies the development of applications. It is based on the Situation Theory Ontology to provide a foundation for situation modelling which allows knowledge reuse. Concepts of the Situation Theory are mapped to the Context Space Theory which is used for situation reasoning. Situation Spaces in the Context Space are automatically generated with the defined knowledge. For the acquisition of sensor data, the IoT standards O-MI/O-DF are integrated into the framework. These allow a peer-to-peer data exchange between data publisher and the proposed framework and thus a platform independent subscription to sensed data. The framework is then applied for a use case to reduce food waste. The use case validates the applicability of the framework and furthermore serves as a showcase for a pervasive system contributing to the sustainability goals. Leading institutions, e.g. the United Nations, stress the need for a more resource efficient society and acknowledge the capability of ICT systems. The use case scenario is based on a smart neighbourhood in which the system recommends the most efficient use of food items through situation awareness to reduce food waste at consumption stage.

Comunidades energéticas sustentáveis: estudo de Implementação de uma comunidade eólica no Algarve

Tese de Doutoramento, Gestão da Inovação e do Território, Faculdade de Economia, Universidade do Algarve, 2016

Eficiencia energética en el sector residencial de la ciudad de Cuenca, Ecuador

El estudio se centra en el sector residencial de la ciudad de Cuenca, Ecuador. El objetivo es determinar hasta donde se puede reducir el consumo de energía a la vez que se obtengan óptimas condiciones de confort, estableciendo un indicador de eficiencia energética. Para ello se determina la demanda de energía eléctrica y los factores principales de consumo, mediante una metodología de investigación mixta tanto cualitativa como cuantitativa, pues el consumo energético se ve influenciado por diferentes elementos como la eficiencia de los equipos, diseño y hábitos de uso de los habitantes, entre otros. Se realizan encuestas a una muestra de 280 hogares del sector residencial de Cuenca y por otro lado se mide el consumo y calidad lumínica del ambiente interior de 6 viviendas mediante equipos, simulaciones y encuestas. Posteriormente se analizan los resultados obtenidos y se los compara con los estándares de eficiencia nacional e internacional, se proponen estrategias básicas para la reducción del consumo de energía eléctrica y finalmente el estudio define una clasificación de indicadores de consumo mínimo.

CO-ELECTROPHORETIC DEPOSITION OF LIQUID METAL AND SILICON FOR LITHIUM-ION BATTERY APPLICATION

A low cost electrophoretic deposition (EPD) process was successfully used for liquid metal thin film deposition with a high depositing rate of 0.6 µ/min. Furthermore, silicon nano-powder and liquid metal were then simultaneously deposited as the negative electrode of lithium-ion battery by a technology called co-EPD. The liquid metal was hoping to act as the matrix for silicon particles during lithium ion insertion and distraction. Half-cell testing was performed using as prepared co-EPD sample. An initial discharge capacity of 1500 mAh/g was reported for nano-silicon and galinstan electrode, although the capacity fading issue of these samples was also observed.

WATER TRANSPORT THROUGH POROUS MEDIA AND IN FLOW CHANNELS OF PROTON EXCHANGE MEMBRANE FUEL CELL

Proton exchange membrane (PEM) fuel cell has been known as a promising power source for different applications such as automotive, residential and stationary. During the operation of a PEM fuel cell, hydrogen is oxidized in anode and oxygen is reduced in the cathode to produce the intended power. Water and heat are inevitable byproducts of these reactions. The water produced in the cathode should be properly removed from inside the cell. Otherwise, it may block the path of reactants passing through the gas channels and/or gas diffusion layer (GDL). This deteriorates the performance of the cell and eventually can cease the operation of the cell. Water transport in PEM fuel cell has been the subject of this PhD study. Water transport on the surface of the GDL, through the gas flow channels, and through GDL has been studied in details. For water transport on the surface of the GDL, droplet detachment has been measured for different GDL conditions and for anode and cathode gas flow channels. Water transport through gas flow channels has been investigated by measuring the two-phase flow pressure drop along the gas flow channels. As accumulated liquid water within gas flow channels resists the gas flow, the pressure drop increases along the flow channels. The two-phase flow pressure drop can reveal useful information about the amount of liquid water accumulated within gas flow channels. Liquid water transport though GDL has also been investigated by measuring the liquid water breakthrough pressure for the region between the capillary fingering and the stable displacement on the drainage phase diagram. The breakthrough pressure has been measured for different variables such as GDL thickness, PTFE/Nafion content within the GDL, GDL compression, the inclusion of a micro-porous layer (MPL), and different water flow rates through the GDL. Prior to all these studies, GDL microstructural properties have been studied. GDL microstructural properties such as mean pore diameter, pore diameter distribution, and pore roundness distribution have been investigated by analyzing SEM images of GDL samples.

COMPARATIVE ANALYSIS OF EFFICIENCY AND OPERATING CHARACTERISTICS OF AUTOMOTIVE POWERTRAIN ARCHITECTURES THROUGH CHASSIS DYNAMOMETER TESTING

The thesis "COMPARATIVE ANALYSIS OF EFFICIENCY AND OPERATING CHARACTERISTICS OF AUTOMOTIVE POWERTRAIN ARCHITECTURES THROUGH CHASSIS DYNAMOMETER TESTING" was completed through a collaborative partnership between Michigan Technological University and Argonne National Laboratory under a contractual agreement titled "Advanced Vehicle Characterization at Argonne National Laboratory". The goal of this project was to investigate, understand and document the performance and operational strategy of several modern passenger vehicles of various architectures. The vehicles were chosen to represent several popular engine and transmission architectures and were instrumented to allow for data collection to facilitate comparative analysis. In order to ensure repeatability and reliability during testing, each vehicle was tested over a series of identical drive cycles in a controlled environment utilizing a vehicle chassis dynamometer. Where possible, instrumentation was preserved between vehicles to ensure robust data collection. The efficiency and fuel economy performance of the vehicles was studied. In addition, the powertrain utilization strategies, significant energy loss sources, tailpipe emissions, combustion characteristics, and cold start behavior were also explored in detail. It was concluded that each vehicle realizes different strengths and suffers from different limitations in the course of their attempts to maximize efficiency and fuel economy. In addition, it was observed that each vehicle regardless of architecture exhibits significant energy losses and difficulties in cold start operation that can be further improved with advancing technology. It is clear that advanced engine technologies and driveline technologies are complimentary aspects of vehicle design that must be utilized together for best efficiency improvements. Finally, it was concluded that advanced technology vehicles do not come without associated cost; the complexity of the powertrains and lifecycle costs must be considered to understand the full impact of advanced vehicle technology.

Switching Patterns and Steady-State Analysis of Grid-Connected and Stand-Alone Single-Stage Boost-Inverters for PV Applications

Renewable or sustainable energy (SE) sources have attracted the attention of many countries because the power generated is environmentally friendly, and the sources are not subject to the instability of price and availability. This dissertation presents new trends in the DC-AC converters (inverters) used in renewable energy sources, particularly for photovoltaic (PV) energy systems. A review of the existing technologies is performed for both single-phase and three-phase systems, and the pros and cons of the best candidates are investigated. In many modern energy conversion systems, a DC voltage, which is provided from a SE source or energy storage device, must be boosted and converted to an AC voltage with a fixed amplitude and frequency. A novel switching pattern based on the concept of the conventional space-vector pulse-width-modulated (SVPWM) technique is developed for single-stage, boost-inverters using the topology of current source inverters (CSI). The six main switching states, and two zeros, with three switches conducting at any given instant in conventional SVPWM techniques are modified herein into three charging states and six discharging states with only two switches conducting at any given instant. The charging states are necessary in order to boost the DC input voltage. It is demonstrated that the CSI topology in conjunction with the developed switching pattern is capable of providing the required residential AC voltage from a low DC voltage of one PV panel at its rated power for both linear and nonlinear loads. In a micro-grid, the active and reactive power control and consequently voltage regulation is one of the main requirements. Therefore, the capability of the single-stage boost-inverter in controlling the active power and providing the reactive power is investigated. It is demonstrated that the injected active and reactive power can be independently controlled through two modulation indices introduced in the proposed switching algorithm. The system is capable of injecting a desirable level of reactive power, while the maximum power point tracking (MPPT) dictates the desirable active power. The developed switching pattern is experimentally verified through a laboratory scaled three-phase 200W boost-inverter for both grid-connected and stand-alone cases and the results are presented.

Constrained fuzzy power flow models with correlation between nodal injections

This paper extends the symmetric/constrained fuzzy powerflow models by including the potential correlations between nodal injections. Therefore, the extension of the model allows the specification of fuzzy generation and load values and of potential correlations between nodal injections. The enhanced version of the symmetric/constrained fuzzy powerflow model is applied to the 30-bus IEEE test system. The results prove the importance of the inclusion of data correlations in the analysis of transmission system adequacy.

Avoided losses on LV networks as a result of microgeneration

In the scope of the discussions about microgeneration (and microgrids), the avoided electrical losses are often pointed out as an important value to be credited to those entities. Therefore, methods to assess the impact of microgeneration on losses must be developed in order to support the definition of a suitable regulatory framework for the economic integration of microgeneration on distribution networks. This paper presents an analytical method to quantify the value of avoided losses that microgeneration may produce on LV networks. Intervals of expected avoided losses are used to account for the variation of avoided losses due to the number, size and location of microgenerators, as well as for the kind of load distribution on LV networks.