According to different sources, from forty to sixty percent of the overall energy generated in the world today is squandered in waste heat. The existing energy conversion technologies are either close to their efficiency limits or too costly to justify their implementation. Therefore, the development of new technological approaches for waste heat recovery is highly demanded. The field of thermoelectrics can potentially provide an inexpensive, clean and efficient solution to waste heat underutilization, given that a new type of thermoelectric materials capable of meeting those requirements are available. This thesis reports on strategies to optimize a thermoelectric efficiency (ZT) of conducting polymers, more specifically poly(3,4-ethylenedioxythiophene) (Pedot). Conducting polymers constitute a special class of semiconductors characterized by low thermal conductivity as well as electrical conductivity and thermopower that can be readily modified by doping in order to achieve the best combination of thermoelectric parameters. Conducting polymers that have never previously been regarded as hypothetically compatible for thermoelectric energy conversion, can exhibit promising thermoelectric performance at moderate temperatures, which is a sought-after quality for waste heat recovery. A rather substandard thermoelectric efficiency of Pedot-Pss can be markedly improved by various secondary dopants whose addition usually improves polymer’s morphology accompanied by a drastic increase in electrical conductivity and, consequently, in ZT. In order to enable further enhancement in thermoelectric properties, the optimization of the charge carrier concentration is commonly used. The oxidation level of Pedot-Pss can be precisely controlled by electrochemical doping resulting in a tenfold increase of ZT. In contrast to Pedot-Pss, another conducting polymer Pedot-Tos exhibits superior thermoelectric performance even without secondary doping owning to its partially crystalline nature that allows for an improved electronic conduction. With the aid of a strong electron donor, positively doped Pedot-Tos gets partially reduced reaching the optimum oxidation state at which its thermoelectric efficiency is just four times smaller than that of Be2Te3 and the highest among all stable conducting polymers. The downsides associated with chemical doping of Pedot-Tos such as doping inhomogeneity or chemical dopants air sensitivity can be surmounted if the doping level of Pedot-Tos is controlled by acidity/basicity of the polymer. This approach yields similar maximum thermoelectric efficiency but does not necessitate inert conditions for sample preparation. Optimized Pedot-Tos/Pedot-Pss can be functionalized as a p-type material in organic thermogenerators (OTEG) to power low energy electronic devices. If printed on large areas, OTEGs could be used as an alternative technique for capturing heat discarded by industrial processes, households, transportation sector or any natural heat sources for electricity production.

Este estudo procura abordar os interesses da Petrobras S.A. nos seus investimentos em geração termelétrica com gás natural. Para tanto, analisa, primeiro, as características da matriz energética brasileira e a possibilidade de inserção do gás natural nessa matriz, confrontando-se com as restrições existentes ao suprimento deste energético, bem como dos meios para a superação destas restrições. Após esboçar a crise que se configurou no setor elétrico brasileiro nas décadas de 80 e 90, passa a tratar das medidas governamentais e privadas para a superação desta crise, buscando incentivar acréscimos rápidos na capacidade de geração. Em seguida, detém-se na caracterização dos contratos de project finance, suas características e sua aplicação no Brasil. Por fim, considera os objetivos da Petrobras S.A. na sua decisão de investir em geração termelétrica, via contratos project finance, para, então, avaliar em que medida estes objetivos foram alcançados. / This study is intended to analyze the interests of PETROBRAS S.A. concerning its investments in thermoelectric generation powered by natural gas. In order to achieve that aim, initially the characteristics of the Brazilian energetic matrix and the possibility of insertion of natural gas in such matrix are analyzed considering the current restrictions to the supply of that fuel and the means for overcoming those restrictions. After an outline of the crisis that developed in the Brazilian electrical sector during the eighties and nineties, this study starts to deal with the governmental and private measures aiming the recovery from that crisis, trying to encourage quick additions to the capacity of generation. Next it draws attention to the making of project finance contracts, to their characteristics and to their use in Brazil. Finally, it considers the objectives of PETROBRAS S.A. concerning that company´s decision to invest in thermoelectric generation via project finance contracts for, then, evaluate to which measure those objectives have been fulfilled.

Este trabalho apresenta um estudo de Qualidade de Energia Elétrica (QEE) no sistema elétrico industrial de uma concessionária geradora de energia elétrica do Brasil. O estudo teve enfoque na distorção harmônica gerada nos serviços auxiliares da usina termoelétrica. Para tanto, foi necessária a simulação e análise da planta da termoelétrica, com atenção nos serviços auxiliares pertencentes a ela, devido aos altos níveis de distorções harmônicas registrados. A simulação foi feita com o programa ATP (Alternative Transients Program) no domínio do tempo, através de sua interface gráfica, o ATP Draw. Nele foram modelados os principais componentes que pertencem ao Sistema Elétrico de Potência (SEP) em questão, como geradores, transformadores, linhas e cargas não lineares. Com a modelagem do SEP da termoelétrica, é possível determinar os níveis da distorção harmônica em diversos locais da planta, e aprofundar o estudo para que seja possível fazer a mitigação desses distúrbios. A diminuição da distorção harmônica junto ao aumento do fator de potência permite um melhor desempenho da usina, aumentando a faturamento da empresa através do aumento da energia entregue ao sistema elétrico. / This dissertation presents a study of Power Quality in an electrical system of a thermoelectric power plant in Brazil. The study focused on the harmonic distortion generated in the auxiliary services of the plant. Therefore, it was necessary to simulate and analyze the thermal plant, with attention to auxiliary services belonging to it, due to high levels of harmonic distortion registered. The simulation was performed using the ATP (Alternative Transients Program) in the time domain through its interface, the ATP Draw. It were modeled the main components that belong to the Power System in question, such as generators, transformers, lines and non-linear loads. With the modeling of the thermoelectric plant, is possible to determine the levels of harmonic distortion at various locations within the plant. The reduction of harmonic distortion along with the increase of power factor allows a better plant performance, increasing company revenue by increasing the energy delivered to the electrical system.

Este trabalho apresenta um estudo de Qualidade de Energia Elétrica (QEE) no sistema elétrico industrial de uma concessionária geradora de energia elétrica do Brasil. O estudo teve enfoque na distorção harmônica gerada nos serviços auxiliares da usina termoelétrica. Para tanto, foi necessária a simulação e análise da planta da termoelétrica, com atenção nos serviços auxiliares pertencentes a ela, devido aos altos níveis de distorções harmônicas registrados. A simulação foi feita com o programa ATP (Alternative Transients Program) no domínio do tempo, através de sua interface gráfica, o ATP Draw. Nele foram modelados os principais componentes que pertencem ao Sistema Elétrico de Potência (SEP) em questão, como geradores, transformadores, linhas e cargas não lineares. Com a modelagem do SEP da termoelétrica, é possível determinar os níveis da distorção harmônica em diversos locais da planta, e aprofundar o estudo para que seja possível fazer a mitigação desses distúrbios. A diminuição da distorção harmônica junto ao aumento do fator de potência permite um melhor desempenho da usina, aumentando a faturamento da empresa através do aumento da energia entregue ao sistema elétrico. / This dissertation presents a study of Power Quality in an electrical system of a thermoelectric power plant in Brazil. The study focused on the harmonic distortion generated in the auxiliary services of the plant. Therefore, it was necessary to simulate and analyze the thermal plant, with attention to auxiliary services belonging to it, due to high levels of harmonic distortion registered. The simulation was performed using the ATP (Alternative Transients Program) in the time domain through its interface, the ATP Draw. It were modeled the main components that belong to the Power System in question, such as generators, transformers, lines and non-linear loads. With the modeling of the thermoelectric plant, is possible to determine the levels of harmonic distortion at various locations within the plant. The reduction of harmonic distortion along with the increase of power factor allows a better plant performance, increasing company revenue by increasing the energy delivered to the electrical system.

Este estudo procura abordar os interesses da Petrobras S.A. nos seus investimentos em geração termelétrica com gás natural. Para tanto, analisa, primeiro, as características da matriz energética brasileira e a possibilidade de inserção do gás natural nessa matriz, confrontando-se com as restrições existentes ao suprimento deste energético, bem como dos meios para a superação destas restrições. Após esboçar a crise que se configurou no setor elétrico brasileiro nas décadas de 80 e 90, passa a tratar das medidas governamentais e privadas para a superação desta crise, buscando incentivar acréscimos rápidos na capacidade de geração. Em seguida, detém-se na caracterização dos contratos de project finance, suas características e sua aplicação no Brasil. Por fim, considera os objetivos da Petrobras S.A. na sua decisão de investir em geração termelétrica, via contratos project finance, para, então, avaliar em que medida estes objetivos foram alcançados. / This study is intended to analyze the interests of PETROBRAS S.A. concerning its investments in thermoelectric generation powered by natural gas. In order to achieve that aim, initially the characteristics of the Brazilian energetic matrix and the possibility of insertion of natural gas in such matrix are analyzed considering the current restrictions to the supply of that fuel and the means for overcoming those restrictions. After an outline of the crisis that developed in the Brazilian electrical sector during the eighties and nineties, this study starts to deal with the governmental and private measures aiming the recovery from that crisis, trying to encourage quick additions to the capacity of generation. Next it draws attention to the making of project finance contracts, to their characteristics and to their use in Brazil. Finally, it considers the objectives of PETROBRAS S.A. concerning that company´s decision to invest in thermoelectric generation via project finance contracts for, then, evaluate to which measure those objectives have been fulfilled.

Este trabalho apresenta um estudo de Qualidade de Energia Elétrica (QEE) no sistema elétrico industrial de uma concessionária geradora de energia elétrica do Brasil. O estudo teve enfoque na distorção harmônica gerada nos serviços auxiliares da usina termoelétrica. Para tanto, foi necessária a simulação e análise da planta da termoelétrica, com atenção nos serviços auxiliares pertencentes a ela, devido aos altos níveis de distorções harmônicas registrados. A simulação foi feita com o programa ATP (Alternative Transients Program) no domínio do tempo, através de sua interface gráfica, o ATP Draw. Nele foram modelados os principais componentes que pertencem ao Sistema Elétrico de Potência (SEP) em questão, como geradores, transformadores, linhas e cargas não lineares. Com a modelagem do SEP da termoelétrica, é possível determinar os níveis da distorção harmônica em diversos locais da planta, e aprofundar o estudo para que seja possível fazer a mitigação desses distúrbios. A diminuição da distorção harmônica junto ao aumento do fator de potência permite um melhor desempenho da usina, aumentando a faturamento da empresa através do aumento da energia entregue ao sistema elétrico. / This dissertation presents a study of Power Quality in an electrical system of a thermoelectric power plant in Brazil. The study focused on the harmonic distortion generated in the auxiliary services of the plant. Therefore, it was necessary to simulate and analyze the thermal plant, with attention to auxiliary services belonging to it, due to high levels of harmonic distortion registered. The simulation was performed using the ATP (Alternative Transients Program) in the time domain through its interface, the ATP Draw. It were modeled the main components that belong to the Power System in question, such as generators, transformers, lines and non-linear loads. With the modeling of the thermoelectric plant, is possible to determine the levels of harmonic distortion at various locations within the plant. The reduction of harmonic distortion along with the increase of power factor allows a better plant performance, increasing company revenue by increasing the energy delivered to the electrical system.

Made available in DSpace on 2015-04-11T13:47:53Z (GMT). No. of bitstreams: 1 Whylker Frota.pdf: 831426 bytes, checksum: 85b7070b88b58686155dc241d8fa9435 (MD5) Previous issue date: 2011-12-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This study investigated the economic impacts caused by substitution of fuel oil derived from oil to gas, from the Solimões Basin Petroleum, city of Coari (AM), the electrical grid of the city of Manaus - Amazonas state. The study was done through a scene analysis which considers the gas volume and the period specified in the contract, supplying natural gas to the thermal park of Manaus until December 2030. The methodology was based on aspects of electricity generation, energy consumption and cost of fuels (derived from petroleum and natural gas) in order to set the avoided cost of the fuels replacement, as well as present a study of Thermal Plants modulation indicating a better energy efficiency for the use of the volume of gas already contracted. Thus, the research permitted to: (a) identify the avoided cost, with the replacement of fuels to the existing thermoelectric park in the city of Manaus, will be around R$ 1 billion (US$ 529 million) per year from the year 2012, and (b) develop a proposal to use the entire volume of natural gas contracted for electric power generation, with the implementation of a power plant with gas turbines in combined cycle size from 500 to 600 MW of installed rated power, resulting in an increase of about 80% generation capacity with natural gas, as well as an energetic efficiency gain of about 28% in the thermoelectric park system currently installed in Manaus Electric System. / Este trabalho objetivou estudar os impactos econômicos decorrentes da substituição dos óleos combustíveis derivados de petróleo pelo gás natural, proveniente da Bacia Petrolífera do Solimões, município de Coari (AM), na matriz elétrica da cidade de Manaus estado do Amazonas. O estudo foi feito através de uma análise de cenário que considera o volume de gás e o prazo de duração definidos pelo contrato de fornecimento do gás natural para o parque térmico de Manaus até dezembro de 2030. A metodologia foi baseada nos aspectos de geração de eletricidade, consumo e custo dos energéticos (óleos derivados de petróleo e gás natural), visando definir o custo evitado com a substituição dos combustíveis, bem como apresentar um estudo de modulação de usinas térmicas que indique uma melhor eficiência energética para a utilização do volume de gás contratado. Dessa forma, a pesquisa permitiu: (a) identificar que o custo evitado, com a substituição dos energéticos para o parque térmico existente na cidade de Manaus, será da ordem de R$ 1 bilhão (US$ 529 milhões) por ano a partir do ano de 2012; e (b) desenvolver uma proposta para a utilização de todo o volume de gás natural contratado para a geração de energia elétrica, com a implantação de uma usina termelétrica com turbinas à gás em ciclo combinado do porte de 500 a 600 MW de potência nominal instalada, resultando em um aumento da ordem de 80% na capacidade de geração a gás natural, bem como um ganho de eficiência energética de aproximadamente 28% no parque termelétrico instalado atualmente no Sistema Manaus.

Thermoelectric generators (TEGs) are currently a topic of interest in the field of energy harvesting for automobiles. In applying TEGs to the outside of the exhaust tailpipe of a vehicle, the difference in temperature between the hot exhaust gases and the automobile coolant can be used to generate a small amount of electrical power to be used in the vehicle. The amount of power is anticipated to be a few hundred watts based on the temperatures expected and the properties of the materials for the TEG. This study focuses on developing efficient heat exchanger modules for the cold side of the TEG through the analysis of experimental data. The experimental set up mimics conditions that were previously used in a computational fluid dynamics (CFD) model. This model tested several different geometries of cold side sections for the heat exchanger at standard coolant and exhaust temperatures for a typical car. The test section uses the same temperatures as the CFD model, but the geometry is a 1/5th scaled down model compared to an full-size engine and was fabricated using a metal-based rapid prototyping process. The temperatures from the CFD model are validated through thermocouple measurements, which provide the distribution of the temperatures across the TEG. All of these measurements are compared to the CFD model for trends and temperatures to ensure that the model is accurate. Two cold side geometries, a baseline geometry and an impingement geometry, are compared to determine which will produce the greater temperature gradient across the TEG. / Master of Science

Thermoelectric generators (TEGs) are currently being explored for their potential in harvesting energy from automobile exhaust. TEGs in form of an appropriate TEG- Heat exchanger module can utilize the temperature difference between the hot exhaust gases and the automobile coolant and convert it into electrical voltage. The amount of power is anticipated to be a few hundred watts depending on the temperature gradient and the material of the TEGs. The focus of this study is increasing the hot side heat transfer for improved performance of the thermoelectric generators using two different internal fins — louvered fins and herringbone wavy fins. The multi-louvered fins basically have 'multi flat plate' behavior and will enhance the heat transfer by deflecting the air from its original path and aligning it with the plane of the louvers. Herringbone fins are used to lengthen the path of airflow allowing for greater residence time and better mixing of the flow. They also provide for greater wetted surface area achieving higher heat transfer. The flow and heat transfer behavior inside the exhaust pipe test section with internal fins is modeled using commercial numerical software. The thermal and flow behavior through both these internal fins depends to a large extent on geometric parameters and fin arrangement. Optimization of the fin design is considered to determine the configuration that provides highest heat transfer while providing least pressure drop across the pipe length. The heat transfer and pressure drop characteristics are compared to the baseline flow without any fin enhancement. / Master of Science

Em função do crescente processo de liberalização dos mercados de gás natural e de energia elétrica nos países do hemisfério norte, bem como pelo aumento das restrições ambientais, as projeções de demanda mundial de gás natural indicam um forte crescimento, principalmente no segmento de geração de energia elétrica. Assim, pode-se afirmar que haverá uma convergência cada vez maior entre os mercados de gás natural e de eletricidade. O transporte do gás natural em sua forma liquefeita, o GNL (Gás Natural Liquefeito), representa um importante pivô para essa convergência, bem como para uma integração global crescente dos mercados de gás natural e eletricidade. Essas evoluções sempre estiveram distantes da realidade brasileira, pois a geração elétrica predominantemente hídrica historicamente reservou um papel limitado para a geração termelétrica. No entanto, desde 2001, como resultado da crise de abastecimento de energia elétrica, o Brasil também fez esforços importantes rumo a uma maior convergência entre os mercados de gás e eletricidade. Desde 2005, a importação de GNL tem sido analisada para o caso brasileiro, visando prioritariamente o atendimento de uma demanda termelétrica para o gás natural. A característica principal deste modelo é a necessidade de se garantir uma oferta de combustível flexível para usinas que deverão suprir uma demanda termelétrica igualmente flexível: oferta flexível para demanda flexível. A luz das evoluções em curso no mercado global, o presente trabalho avalia a viabilidade deste modelo a partir da análise das possibilidades do suprimento de GNL ser efetuado de forma flexível, atuando, assim, como mecanismo de flexibilização da oferta de gás natural e garantindo um melhor aproveitamento da capacidade de geração elétrica atualmente instalada no Brasil. / Due to the growth of liberalization process on natural gas and electricity markets on northern hemisphere countries, as well as due to raising environmental restrictions, world natural gas demand projections indicate a strong growth, mainly driven by the power generation segment. Therefore, we can affirm that will have an even higher convergence between natural gas and electricity markets. Natural gas transportation in its liquefied form, the LNG (Liquefied Natural Gas), represents an important pivot for this convergence, as well as for the raising global integration of electricity and natural gas markets. These evolutions were always distant from Brazilian reality, as dominant hydroelectric generation historically reserved a limited role for thermoelectric generation. However, since 2001, as a result from the electricity supply crisis, Brazil also did important efforts towards a greater convergence between natural gas and electricity markets. Since 2005, LNG importation has been analyzed for the Brazilian case, primarily focusing thermoelectric demand utilization for the natural gas. The main characteristic of this model is the necessity to guarantee a flexible fuel supply for power plants that shall supply an equally flexible thermoelectric demand: flexible supply for flexible demand. In light of the evolutions underway on the global market, this study evaluates the viability of this model based on the possibility of LNG supplies be done on flexible way, acting then as a natural gas supply flexibility mechanism and guaranteeing a better utilization of the thermoelectric generation capacity already installed in Brazil.