833 resultados para 090608 Renewable Power and Energy Systems Engineering (excl. Solar Cells)
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Conferências internacionais sobre o clima, bem como crescente conscientização sobre as questões de sustentabilidade lançaram luz sobre o papel fundamental que as energias renováveis poderiam desempenhar na transição energética. Ao contrário de combustíveis fósseis, elas podem ser regeneradas em um curto período de tempo e, por conseguinte, espera-se que sejam uma parte da solução para reduzir o aquecimento global. O Brasil sempre teve um forte setor hidrelétrico, mas agora está na vanguarda em relação a todas as outras fontes de energias alternativas, como energia eólica, biomassa o energia solar. Estas indústrias são uma promessa para um futuro próspero, graças ao potencial natural do país, bem como uma legislação de apoio, e estão atraindo muitas empresas locais e internacionais. Este estudo tem como objetivo preencher uma lacuna na literatura analisando o exemplo de uma empresa estrangeira que entra no mercado da energia renovável no Brasil. Baseando-se na literatura como um fundo conceptual, um único estudo de caso têm sido realizados para delinear todos os aspectos do processo de entrada. Neste desenvolvimento, relações causais entre as orientações estratégicas e a evolução do negócio foram identificadas. Esta pesquisa traz uma contribuição para as discussões acadêmicas sobre as dinâmicas de entrada no setor de energia renovável através de evidências do mercado brasileiro.
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This work presents a methodology to analyze transient stability (first oscillation) of electric energy systems, using a neural network based on ART architecture (adaptive resonance theory), named fuzzy ART-ARTMAP neural network for real time applications. The security margin is used as a stability analysis criterion, considering three-phase short circuit faults with a transmission line outage. The neural network operation consists of two fundamental phases: the training and the analysis. The training phase needs a great quantity of processing for the realization, while the analysis phase is effectuated almost without computation effort. This is, therefore the principal purpose to use neural networks for solving complex problems that need fast solutions, as the applications in real time. The ART neural networks have as primordial characteristics the plasticity and the stability, which are essential qualities to the training execution and to an efficient analysis. The fuzzy ART-ARTMAP neural network is proposed seeking a superior performance, in terms of precision and speed, when compared to conventional ARTMAP, and much more when compared to the neural networks that use the training by backpropagation algorithm, which is a benchmark in neural network area. (c) 2005 Elsevier B.V. All rights reserved.
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In this paper, is presented an economical and technical feasibility study of a combined cycle cogeneration system proposed to be used in a pulp plant located in Brazil, where around 95% of country's pulp production is done by the use of Kraft Process. This process allows the use of black liquor and other by-products as fuel. This study is based upon actual data from a pulp plant with a daily production of 1000 tons., that generates part of the energy demanded by the process in a conventional cogeneration system with condensing steam turbine and two extractions. The addition of a gas turbine was studied to compare electricity production level and its related costs between original system and the new one, considering that the former can use industrial by-products and firewood as fuel, when required. Several parameters related to electric generation systems operation and production costs were studied. The use of natural gas in the combined cycle, in comparison with the use of firewood in the conventional system was studied. The advantages of natural gas fuel are highlighted. The surplus availability and the electricity generation costs are presented as a function of pulp and black liquor production.
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In this report we investigate the optical properties and energy-transfer upconversion luminescence of Ho3+- and Tb3+/Yb 3+-codoped PbGeO3-PbF2-CdF2 glass-ceramic under infrared excitation. In Ho3+/Yb 3+-codoped sample, green(545 nm), red(652 nm), and near-infrared(754 nm) upconversion luminescence corresponding to the 4S 2(5F4) → 5I8, 5F5 → 5I8, and 4S2(5F4) → 5I 7, respectively, was readly observed. Blue(490 nm) signals assigned to the 5F2,3 → 5I8 transition was also detected. In the Tb3+/Yb3+ system, bright UV-visible emission around 384, 415, 438, 473-490, 545, 587, and 623 nm, identified as due to the 5D3(5G6) → 7FJ(J=6,5,4) and 5D4→ 7FJ(J=6,5,4,3) transitions, was measured. The comparison of the upconversion process in glass ceramic and its glassy precursor revealed that the former samples present much higher upconversion efficiencies. The dependence of the upconversion emission upon pump power, and doping contents was also examined. The results indicate that successive energy-transfer between ytterbium and holmium ions and cooperative energy-transfer between ytterbium and terbium ions followed by excited-state absorption are the dominant upconversion excitation mechanisms herein involved. The viability of using the samples for three-dimensional solid-state color displays is also discussed.
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In this work, experimental results are reported for a small scale cogeneration plant for power and refrigeration purposes. The plant includes a natural gas microturbine and an ammonia/water absorption chiller fired by steam. The system was tested under different turbine loads, steam pressures and chiller outlet temperatures. An evaluation based on the 1st and 2nd Laws of Thermodynamics was also performed. For the ambient temperature around 24°C and microturbine at full load, the plant is able to provide 19 kW of saturated steam at 5.3 bar (161 °C), corresponding to 9.2 kW of refrigeration at -5 °C (COP = 0.44). From a 2nd law point-of-view, it was found that there is an optimal chiller outlet temperature that maximizes the chiller exergetic efficiency. As expected, the microturbine presented the highest irreversibilities, followed by the absorption chiller and the HRSG. In order to reduce the plant exergy destruction, it is recommended a new design for the HRSG and a new insulation for the exhaust pipe. © 2013 Elsevier Ltd. All rights reserved.
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Includes bibliography
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Includes bibliography
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Includes bibliography
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Incluye Bibliografía
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Señala algunas actividades concretas que podrían iniciar los países en desarrollo para la cooperación en el campo de las fuentes de energía nuevas y renovables. Dichas actividades consisten en una serie de programas que, según su naturaleza, se clasifican en: a) programa de planificación energética, b) programa de desarrollo científico y tecnológico, y c) programas de apoyo comunes.
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Informe de la reunion consultiva sobre promocion de proyectos de America Latina y el Caribe en el area de fuentes de energia nuevas y renovables. Contiene el resumen de los debates y conclusiones acerca del conjunto de proyectos presentados por OLADE y CARICOM.
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Includes bibliography
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Informa acerca de las actividades efectuadas por el Comité Preparatorio de la Conferencia de las Naciones Unidas sobre Fuentes de Energía Nuevas y Renovables.