Orientador: Prof. Dr.Antônio Garrido Gallego / Dissertação (mestrado) - Universidade Federal do ABC. Programa de Pós-Graduação em Energia, 2017. / Atentando-se à diversificação da matriz energética, expansão da oferta de energia e a aproximação do fim da vida útil de usinas nucleares, como Angra I, planejado para 2025, este trabalho apresenta um estudo de repotenciação de usinas nucleares PWR (Pressurized Water Reactor). A estratégia de repotenciação utilizada baseou-se na combinação da usina nuclear com turbinas a gás, compondo um arranjo similar aos ciclos combinados tradicionais, mas que utiliza energia nuclear e do gás natural paralelamente. A conexão entre as duas fontes ocorre por meio de caldeiras de recuperação, que utilizam os gases de exaustão das turbinas a gás para geração de vapor, que é utilizado na usina nuclear, o que possibilita a redução da potência térmica do reator. Efetuaram-se análises de energia nos ciclos propostos e constatou-se que os ciclos podem atingir eficiências energéticas entre 44% e 46%, no caso de ciclos que ultrapassam a potência nominal da antiga usina nuclear, e eficiências energéticas por volta de 39% no caso de ciclos com potência limitada à da antiga usina nuclear. Também foi possível avaliar qualitativamente as configurações que exigiriam menores modificações na usina nuclear. Foi realizada análise econômica onde estimou-se o custo de geração de energia elétrica dos ciclos propostos, obtendo 69,5 US$/MWh, que foi menor que o custo de uma nova usina a gás natural (80,8 US$/MWh) e uma nova usina nuclear (110,9 US$/MWh). Entretanto, os ciclos de repotenciação apresentaram custo de energia maior do que a possibilidade de extensão da vida útil de usinas nucleares por meio de investimentos em trocas de equipamentos e programas de manutenção (36,2 US$/MWh - Extensão das operações LTO ¿ do inglês: Long Term Operation). / Considering the diversification of the energy matrix, expansion of the energy supply and the approximation of the end of life of nuclear power plants, such as Angra I, planned for 2025, this work presents a repowering study of PWR (Pressurized Water Reactor). The repowering strategy was based on combination of the nuclear power plant with gas turbines, composing an arrangement like traditional combined cycles, but utilizing nuclear and natural gas in parallel. The connection between the two sources occurs through recovery boilers, which use the exhaust gases from gas turbines for steam generation, which is used in the nuclear power plant, which allows the reduction of the reactor thermal power. Energy analyzes were carried out in the proposed cycles and it was found that the cycles can achieve energy efficiencies between 44% and 46% in the case of cycles exceeding the nominal power of the former nuclear power plant, and energy efficiencies around 39% in the case of cycles with power limited to that of the old nuclear power plant. It was also possible to qualitatively evaluate the configurations that would require minor modifications at the nuclear power plant. An economic analysis was carried out to estimate the cost of generating electricity from the proposed cycles, obtaining 69.5 US$/MWh, which was lower than the cost of a new natural gas plant (80.8 US$/MWh) and a new nuclear power plant (110.9 US$/MWh). However, the repowering cycles had a higher energy cost than the possibility of extending the life of nuclear power plants through investments in equipment exchanges and maintenance programs (36.2 US$/MWh, LTO - Long Term Operation).

Selective Exhaust Gas Recirculation (S-EGR) consists of selectively transferring CO2 from the exhaust gas stream of a gas-fired power plant into the air stream entering the gas turbine compressor. Unlike in “non-selective” Exhaust Gas Recirculation (EGR) technology, recirculation of, principally, nitrogen does not occur, and the gas turbine still operates with a large excess of air. Two configurations are proposed: one with the CO2 transfer system operating in parallel to the post-combustion carbon capture (PCC) unit; the other with the CO2 transfer system operating downstream of, and in series to, the PCC unit. S-EGR allows for higher CO2 concentrations in the flue gas of approximately 13-14 vol%, compared to 6.6 vol% with EGR at 35% recirculation ratio. The oxygen levels in the combustor are approximately 19 vol%, well above the minimum limit of 16 vol% with 35% EGR reported in literature. At these operating conditions, process model simulations show that the current class of gas turbine engines can operate without a significant deviation in the compressor and the turbine performance from the design conditions. Compressor inlet temperature and CO2 concentration in the working fluid are critical parameters in the assessment of the effect on the gas turbine net power output and efficiency. A higher turbine exhaust temperature allows the generation of additional steam which results in a marginal increase in the combined cycle net power output of 5% and 2% in the investigated configurations with S-EGR in parallel and S-EGR in series, respectively. With aqueous monoethanolamine scrubbing technology, S-EGR leads to operation and cost benefits. S-EGR in parallel operating at 70% recirculation, 97% selective CO2 transfer efficiency and 96% PCC efficiency results in a reduction of 46% in packing volume and 5% in specific reboiler duty, compared to air-based combustion CCGT with PCC, and of 10% in packing volume and 2% in specific reboiler duty, compared to 35% EGR. S-EGR in series operating at 95% selective CO2 transfer efficiency and 32% PCC efficiency results in a reduction of 64% in packing volume and 7% in specific reboiler duty, compared to air-based, and of 40% in packing volume and 4% in specific reboiler duty, compared to 35% EGR. An analysis of key performance indicators for selective CO2 transfer proposes physical adsorption in rotary wheel systems as an alternative to selective CO2 membrane systems. A conceptual design assessment with two commercially available adsorbent materials, activated carbon and Zeolite X13, shows that it is possible to regenerate the adsorbent with air at near ambient temperature and pressure. Yet, a significant step change in adsorbent materials is necessary to design rotary adsorption systems with dimensions comparable to the largest rotary gas/gas heat exchanger used in coal-fired power plants, i.e. approximately 24 m diameter and 2 m height. An optimisation study provides guidelines on the equilibrium parameters for the development of materials. Finally, a technical feasibility study of configuration options with rotary gas/gas heat exchangers shows that cooling water demand around the post-combustion CO2 capture system can be drastically reduced using dry cooling systems where gas/gas heat exchangers use ambient air as the cooling fluid. Hybrid cooling configurations reduce cooling and process water demand in the direct contact cooler of a wet cooling system by 67% and 35% respectively, and dry cooling configurations eliminate the use of process and cooling water and achieve adequate gas temperature entering the absorber.

Made available in DSpace on 2014-06-11T19:30:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12Bitstream added on 2014-06-13T19:39:27Z : No. of bitstreams: 1 mogawer_t_me_guara.pdf: 1050701 bytes, checksum: ac5394fa773726920ea684e1c38e8892 (MD5) / Universidade Estadual Paulista (UNESP) / O setor elétrico brasileiro vem continuamente passando por crises energéticas; os consumidores, indústrias que dependem de energia para exercerem as suas atividades passaram a valorizar e a buscar fontes alternativas, confiáveis e ecologicamente adequadas com o objetivo de garantir o fornecimento de eletricidade de forma econômica, possibilitando desta maneira uma certa independência energética. Neste contexto, este trabalho tem a finalidade de selecionar sistemas de cogeração utilizando ciclos combinados com conjuntos a gás associadas a caldeira de recuperação sem queima suplementar e turbina a vapor, assim como realizar o levantamento das curvas de produção de energia e eficiência para os ciclos obtidos. Foram utilizados os parâmetros técnicos e construtivos das turbinas a gás e a vapor de uma mesma empresa fabricante, e através das curvas obtidas é possível selecionar o ciclo combinado mais adequado para cada situação desejada, tanto do ponto de vista energético quanto do ponto de vista econômico. / The electric Brazilian sector is continually subject to energy crisis, the industrial consumers, that depends on energy to do its activities, is nowadays up to valorize and to look for alternative, trustful and environmental appropriate sources with the objective of guaranteeing the supply of electricity in an economic way and warranting a certain energy independence. In this context, this work has the purpose of selecting cogeneration systems based on using combined cycles with gas turbines associated to heat recovery steam generators without supplementary burners and steam turbines, as well as accomplishing the rising of the curves of production of energy and efficiency for the obtained cycles. The technical and constructive parameters of the gas and steam turbines were considered from the same manufacturing company, and through the obtained curves it is possible to select the more appropriate cycle for each process requirement, in the energy and economic point of view.

Fresh water shortage and hot weather are common challenges in many countries of the world. In the other hand, the air conditioning systems which are used for indoor cooling cause peak electricity demand during high temperatures hours. This peak hour demand is very important since it is more expensive and mainly is supplied by fossil fuel power plants with lower efficiencies compare to base load fossil fuel or renewable owe plants. Moreover, these peak electricity load fossil fuel power plants cause higher green house gas emission and other environmental effects. So, all these show that any solution for these problems could make life better in those countries and all over the world.In this thesis, a new idea for a Power storage, Cooling storage, and Water production Combined Cycle (PCWCC) is introduced and reviewed. PCWCC is combination of two thermal cycles, Ice Thermal Energy Storage (ITES) and desalination by freezing cycle, which are merged together to make a total solution for fresh water shortage, required cooling, and high peak power demand. ITES is a well known technology for shifting the electricity demand of cooling systems from peak hours to off-peak hours and desalination by freezing is a less known desalination system which is based on the fact that the ice crystals are pure and by freezing raw water and melting resulted ice crystals, pure water will be produced. These two systems have some common processes and equations and this thesis shows that by combining them the resulted PCWCC could be more efficient than each of them. In this thesis, the thermodynamic equations and efficiencies of each PCWCC sub-systems are analyzed and the resulted data are used in finding thermodynamics of PCWCC itself. Also, by using reMIND software, which uses Cplex to find the best combinations of input/output and related processes, the cost of produced fresh water and cooling from PCWCC is compared with total cost of fresh water and cooling produced by each sub-systems of PCWCC in three sample cities all over the world, Kerman, Dubai, and Texas. These cities are chosen since they have similar ambient temperature trend with different electricity and fresh water tariff's. The results show that, the PCWCC is economical where there is a significant electricity price difference between ice charging and ice melting hours, off-peak and peak hours, of the day or when the fresh water price is high compare to electricity price. The results also show that how the revenue from fresh water could cover the used electricity cost and make some income as well.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2015-11-30T14:46:17Z No. of bitstreams: 1 Sérgio Luiz Bohrer Filho_.pdf: 1393460 bytes, checksum: 335661e44d51f93aa77abb3a780e6e5a (MD5) / Made available in DSpace on 2015-11-30T14:46:17Z (GMT). No. of bitstreams: 1 Sérgio Luiz Bohrer Filho_.pdf: 1393460 bytes, checksum: 335661e44d51f93aa77abb3a780e6e5a (MD5) Previous issue date: 2015-10-14 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / PROSUP - Programa de Suporte à Pós-Gradução de Instituições de Ensino Particulares / Este trabalho apresenta um estudo de viabilidade de inserção de energia solar térmica na matriz elétrica brasileira, através de integração de um campo de energia termosolar concentrada com uma usina termelétrica de ciclo combinado localizada na Região Centro-Oeste. A atual conjuntura do setor elétrico, que apresenta crescimento do despacho termelétrico e consequente elevação dos custos de geração de energia elétrica, provocados principalmente por períodos de Energia Natural Afluente (ENA) abaixo da média, justifica o desenvolvimento de fontes alternativas. O objetivo principal deste estudo é apresentar um modelo de empreendimento de produção de eletricidade por meio de fonte solar térmica, compatível à realidade tecnológica e econômica do mercado de energia. O estudo baseia-se na simulação de integração de um campo solar com tecnologia de concentração Fresnel linear e geração direta de vapor superaquecido, junto à Usina Termelétrica Luís Carlos Prestes (UTE-LCP), no município de Três Lagoas, no estado de Mato Grosso do Sul. O desempenho do campo solar é verificado através do software System Advisor Model (SAM) da National Renewable Energy Laboratory (NREL) e a produção adicional de termeletricidade é determinada com base na análise de eficiência do ciclo de Rankine da UTE-LCP. Por fim, é realizada a análise financeira do projeto através de ferramentas de engenharia econômica, onde identifica-se um custo nivelado da energia elétrica (LCOE) de pelo menos 139,24 USD MW-1h-1, uma redução de 42,7% em relação às estimativas de custo internacionais para usinas heliotérmicas. Análises de sensibilidade indicam que o custo do capital tem impacto crítico sobre o LCOE, fato atribuído ao caráter de alta dependência dos recursos de capital da tecnologia solar térmica. / This work presents a study of concentrated solar power insertion in the Brazilian energy matrix, through integration of the solar energy with Luís Carlos Prestes Thermoelectric Power Plant (UTE-LCP) in Três Lagoas city. The current situation of the Brazilian electricity sector, which has presented strong growth of thermoelectric dispatch in recent years and the consequent increase in the cost of electricity generation, justifies the development of alternative energy sources. The purpose of this study is to present a model of electricity generation through thermal solar source compatible to technological and economic realities of the energy market. The study is based on evaluation of the linear Fresnel reflector with direct steam generation, because this configuration has investment, operation and maintenance attractive costs. The performance of the solar field is simulated in the System Advisor Model software (SAM) of the National Renewable Energy Laboratory (NREL). The predict performance is used with UTE-LCP operational database to estimate the additional electricity generation. Finally, the financial analysis is carried out through economic engineering tools, which identifies a Levelized Cost of Electricity (LCOE) of the 139.24 USD MW-1h-1 at least. This LCOE is 42.7% less than cost estimates for Concentrating Solar Power plants. Sensitivity analysis indicates that the cost of capital has critical impact on the LCOE, which was attributed to the character of high dependence on Concentrating Solar Power (CSP) capital resources.

This thesis focuses on the application of model predictive control approaches to optimize the combined cycle power plants start-ups. Generally, the optimization of start-up is a very problematic issue that poses significant challenges. The development of the proposed approaches is progressive. In the first part a physical model of plant is developed and adapted to optimization purposes, by using a methodology which transforms Modelica model components into optimization-oriented models. By applying this methodology, a library suitable for optimization purposes has been built.In the second part, based on the developed model, an optimization procedure to improve the performances of the start-up phases is suggested. The proposed solution optimizes, in continuous time, the load profile of the turbines, by seeking in specific sets of functions. The optimal profile is derived by considering that this profile can be described by a parameterized function whose parameters are computed by solving a constrained optimal control problem. In the last part, the open-loop optimization procedure has been integrated into a receding horizon control strategy. This strategy represents a robust solution against perturbation and models errors, and enables to improve the trade-off between computation time and optimality of the solution. Nevertheless, the control approach leads to a significant computation time. In order to obtain real-time implementable results, a hierarchical model predictive control structure with two layers, working at different time scales and over different prediction horizons, has been proposed.

Combined cycle power plants haven becoming one of the mainstream power plants in the twenty-one century. The emergence of high 600¢J exhaust temperature of the gas turbine, due to the recent rapid enhancement of aerospace material and blade cooling methods, upgrades the gas turbine from low efficiency dual pressure non-reheat unit to high efficiency triple pressure reheat combined cycle power plants. In addition, the increase of turbine inlet temperature by 10~15¢J every year leads to the renewal of the advanced models gas turbine less than ten years. There are three-turbine inlet temperature (TIT) definitions in the gas turbine: (1) TA defines firing temperature as the mass flow mean total temperature before the first-stage stationary diagram edge plane.( Westinghouse or MHI product) (2) TB defines fire temperature as the mass flow mean total temperature at the first-stage nozzle trailing edge plane, ( GE product). (3) TC defines ISO firing temperature; it is a stoichiometric combustion temperature. It is not a physical temperature. ( Siemens ¡® Alstom ABB product). This study shows how to calculate compressor inlet mass flow balance, turbine power balance and heat balance on the combustion chamber system. In order to prove correctness of the balance equation, the data are taken from the heat balance diagram and acceptance test of Nan-pu power station combined cycle. The result shows that the study is sultable for application of the optimum analysis for CCPP operation performance. This type of combined cycle power plant suits not only for the base-load but also for the cycling-load operation.

The “Integrated Coal Gasification Combined Cycle” (IGCC) represents an advanced approach for green field projects for power generation. This process requires separation of carbon dioxide from the shifted-synthesis gas mixture (fuel gas). Treated fuel gas consists of approximately 40% CO2 and rest H2. Gas hydrate based separation technology for hydrate forming gas mixtures is one of the novel approaches for gas separation. The present study illustrates the gas hydrate-based separation process for the recovery of CO2 and H2 from the fuel gas mixture and discusses relevant issues from macro and molecular level perspectives. Propane (C3H8) is used as an additive to reduce the operating pressure for hydrate formation and hence the compression costs. Based on gas uptake measurement during hydrate formation, a hybrid conceptual process for pre-combustion capture of CO2 is presented. The result shows that it is possible to separate CO2 from hydrogen and obtain a hydrate phase with 98% CO2 in two stages starting from a mixture of 39.2% CO2. Molecular level work has also been performed on CO2/H2 and CO2/H2/C3H8 systems to understand the mechanism by which propane reduces the operating pressure without compromising the separation efficiency.

This thesis proposes a method and develops a model for the participation of a combined cycle power plant to power system frequency control. Through the period of integration to the UCTE system, (Union for Coordination of Transmission of Electricity in Europe) frequency behavior of Turkey&rsquo / s grid and studies related to its improvement had been a great concern, so is the reason that main subject of my thesis became as &ldquo / Power System Frequency Control&rdquo / . Apart from system-wide global control action (secondary control) / load control loops at power plants, reserve power and its provision even at the minimum capacity generation stage, (primary control) are the fundamental concerns of this subject. The adjustment of proper amount of reserve at the power plants, and correct system response to any kind of disturbance, in the overall, are measured by the quality of the frequency behaviour of the system. A simulator that will simulate a dynamic gas turbine and its control system model, together with a combined cycle power plant load controller is the outcome of this thesis.

Cette étude concerne un système de stockage d’électricité basé sur le stockage thermique. Le principe est de convertir de l’électricité issue d’énergies renouvelables en chaleur lorsque la production est supérieure à la demande, de conserver cette chaleur puis de la reconvertir en électricité lorsqu’un besoin se présente. Le système proposé s’appuie sur une technologie de stockage sensible à haute température : le stockage régénératif gaz/solide. Ce stockage est associé à une boucle de charge et à un cycle thermodynamique de restitution électrique. Dans cette étude, deux architectures sont étudiées pour ce dernier : la première est basée sur un cycle gaz, la seconde sur un cycle combiné Joule/Rankine. Un modèle global du système est développé sur la base d’une modélisation de chaque composant à un niveau de détail approprié. Sur la base de ce modèle, une analyse thermodynamique est menée. Celle-ci identifie le rendement exergétique global du procédé, proche de celui d’un cycle à combustion. Une analyse exergétique détaillée du stockage identifie les principaux postes d’irréversibilités dans ce composant. Elle montre qu’il est possible d’optimiser de manière relativement simple ses performances en jouant sur son dimensionnement. Par la suite, une analyse économique montre qu’en dépit de ses performances inférieures, le cycle gaz est associé à des coûts d’investissement limités qui rendent son utilisation pertinente. En termes de coût du stockage, le système étudié est compétitif avec des solutions comme les batteries. / This study concerns an electricity storage system based on thermal energy storage. Its overall purpose is to convert electricity produced by renewable energies into heat when the supply exceeds the demand. This heat is stored for a few hours and converted back to electricity when there is a need for it. The proposed system relies on a high temperature sensible thermal energy storage technology known as the gas/solid packed bed thermal storage. This storage comes with a charging loop and a thermodynamic cycle to carry out the heat to electricity conversion. In this study, two main architectures are considered for this cycle: a simple gas cycle and a Joule/Rankine combined cycle. Each component is modeled with an appropriate level of detail in order to create a global model of the system. This model is used to carry out a thermodynamic analysis. This study calculates the global exergy efficiency of the whole process, which is close to exergy efficiency of a combustion cycle. A detailed exergy analysis of the storage allows to identify the main phenomena behind the availability losses of this component. It shows that it is possible to increase the efficiency of the storage by modifying its sizing. Apart from this study, an economic analysis shows that regardless of its low energy and exergy efficiencies, the gas cycle comes with limited investment costs which insure an interesting profitability. In terms of storage cost, the proposed system is close to other electricity storage solutions like batteries.