Dissertations / Theses on the topic 'Thermoeconomic analysi'

The ready availability of biomass in Brazil makes this type of fuel a major candidate to integrate the country's energy matrix. Although this fuel is used as a primary energy source, its use for electricity generation is still modest. On the other hand, high efficiency and power density achieved by modem gas turbine engines make them a promising option for the power generation market. Thus, this thesis has as main objective to analyse the marriage between the solid fuel, biomass in this case, and gas turbines. Two main types of power plants are studied; the biomass integrated gasification gas turbine cycle (BIGGT) and the externally fired cycle (EFGT), which for the first time is thoroughly studied for the use of biomass fuel, plus the intercooled and recuperated variants of these power plants. The results are compared with the ordinary natural gas fuelled cycle. The method involves on- and off-design point performance and exergy analysis. The economic performance and optimisation for each cycle is also explored in order to assess their feasibility. The optimisation technique adopted is the Genetic Algorithm (GA) connected to the conventional hill-climbing methodology. This merge uses the GA to identify the region of optimum values, which are then passed on to the hill-climbing algorithm. In this way the long time demanded by the GA to converge is shortened and the unreliability of the hill-climbing method in finding the global optimum is overcome. The codes developed for design-point performance analysis and optimisation, compared with a commercial package, proved reliable and robust. The tools developed for exergy analysis (on- and off-design) are also robust and flexible, with the capability of analysing and calculating the properties of mixtures made of 23 different gases. The emissions equations are sufficiently accurate for the purposes of this thesis. The relationship proposed for calculating the variable operating and maintenance costs proved to be consistent with the current knowledge. The results show that the optimised cycles are competitive with current technology in terms of cost of electricity, the EFGT being the more competitive biomass cycle, with costs of electricity (US$ 0.07/kWh) comparable with those of the natural gas fuelled power plants. The BIGGT in its turn shows a cost of electricity 29 percent higher than its natural gas and externally fired counterparts (US$0.09/kWh) counterparts. The method used to work out the best investment - the required revenue (RR) method - demonstrated that the EFGT is again comparable with the NGGT cycle, with its RR being only 7 percent higher. The BIGGT cycle shows a higher RR due to its costly gasification/cleaning system. The minimisation of the exergy destruction ratio indicates that little improvement would be achieved after the reduction of this parameter, and a penalty - an 85 percent increase in the cost of electricity - must be paid. The environmental advantage of the biomass-fuelled cycles over the natural gas cycle is clear, making these systems very promising as low emissions alternatives. Both BIGGT and EFGT cycles presented very low CQ2 emissions. Regarding NO., emissions, the EFGT cycle has the lowest rates, whereas the BIGGT has the highest.

The provision of a sustainable energy supply is one of the most importantissues facing humanity at the current time, and solar thermal power hasestablished itself as one of the more viable sources of renewable energy. Thedispatchable nature of this technology makes it ideally suited to forming thebackbone of a future low-carbon electricity system.However, the cost of electricity from contemporary solar thermal power plantsremains high, despite several decades of development, and a step-change intechnology is needed to drive down costs. Solar gas-turbine power plants are apromising new alternative, allowing increased conversion efficiencies and asignificant reduction in water consumption. Hybrid operation is a furtherattractive feature of solar gas-turbine technology, facilitating control andensuring the power plant is available to meet demand whenever it occurs.Construction of the first generation of commercial hybrid solar gas-turbinepower plants is complicated by the lack of an established, standardised, powerplant configuration, which presents the designer with a large number ofchoices. To assist decision making, thermoeconomic studies have beenperformed on a variety of different power plant configurations, includingsimple- and combined-cycles as well as the addition of thermal energy storage.Multi-objective optimisation has been used to identify Pareto-optimal designsand highlight trade-offs between costs and emissions.Analysis of the simple-cycle hybrid solar gas-turbines revealed that, whileelectricity costs were kept low, the achievable reduction in carbon dioxideemissions is relatively small. Furthermore, an inherent trade-off between thedesign of high efficiency and high solar share hybrid power plants wasidentified. Even with the use of new optimised designs, the degree of solarintegration into the gas-turbine did not exceed 63% on an annual basis.In order to overcome the limitations of the simple-cycle power plants, twoimprovements were suggested: the integration of thermal energy storage, andthe use of combined-cycle configurations. Thermal energy storage allowed thedegree of solar operation to be extended, significantly decreasing carbondioxide emissions, and the addition of a bottoming-cycle reduced the electricitycosts. A combination of these two improvements provided the bestperformance, allowing a reduction in carbon dioxide emissions of up to 34%and a reduction in electricity costs of up to 22% compared to a combination ofconventional power generation technologies.
Hållbar energiförsörjning är för närvarande en av de viktigaste frågorna förmänskligheten. Koncentrerad solenergi är nu etablerad som en tillförlitlig källaav förnybar energi. Den reglerbara karaktären hos tekniken gör den specielltintressant för uppbyggnaden av ett framtida koldioxidsnålt elsystem.Kostnaden för elektricitet från nuvarande termiska solkraftverk är hög trottsflera decennier av utveckling. Ett genombrått på tekniknivå krävs för att drivaned kostnaderna. Sol-gasturbiner är ett av de mest lovande alternativen, somger en ökad verkningsgrad samtidigt som vattenkonsumtionen reducerasdrastiskt. Sol-gasturbintekniken gör det möjligt att blandköra solenergi ochandra bränslen för att möta efterfrågan vid alla tidpunkter, en attraktiv aspekt iförhållande till alternativa lösningar.Uppbyggnaden av första generationens kommersiella hybrida solgasturbinkraftverkförsvåras dock av bristen på etablerade och standardiseradekraftverkskonfigurationer. Dessa ger planeraren ett stort antal valmöjlighetersom underlag för beslutsfattande. Termoekonomiska studier har genomförtsför ett flertal olika kraftverkskonfigurationer, däribland kraftverk med enkelcykel, kombikraftverk samt möjligheten att utnyttja termisk energilagring.Pareto-optimala konfigurationer har identifierats med hjälp av multiobjektsoptimeringför att belysa balansen mellan kostnader och utsläpp.Analysen av det enkla hybrida sol-gasturbinkraftverket visade attelektricitetskostnaden hållits på en låg nivå, men att den möjliga minskningen avkoldioxidutsläpp är relativt liten. Dessutom identifierades en inre balans mellanatt bibehålla en hög verkningsgrad hos konfigurationen och en hög andelsolenergi i produktionen. Andelen av solenergi i gasturbinen överskred aldrig63% på årlig bas, även med optimerade kraftverkskonfigurationer.Två förbättringar föreslås för att övervinna begränsningarna hos kraftverk medenkel cykel: integration av termisk energilagring samt nyttjande avkombikraftverkskonfigurationer. Termisk energilagring tillåter en ökad andelsolenergi i driften och reducerar koldioxidutsläppen drastiskt, medan denytterligare cykeln hos kombikraftverket reducerar elektricitetskostnaden.Kombinationen av dessa förbättringar ger den bästa prestandan, med enreduktion av koldioxidutsläppen på upp till 34% och reducerade elektricitetskostnaderpå upp till 22% i jämförelse med andra kombinationer avkonventionella kraftverkskonfigurationer.

QC 20130503

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Neste trabalho é desenvolvida uma metodologia para a alocação dos custos dos produtos por uma mini-estação de tratamento de esgotos, com vistas a realizar a análise da viabilidade econômica do investimento necessário para a sua implantação, inclusive caracterizando-a como a melhor escolha a ser adotada na solução de saneamento básico em zonas rurais e em regiões de limitado poder aquisitivo, além de que tem potencial energético face à sua capacidade de transformar em eletricidadea energia contida no biogás gerado. Essa metodologia á aplicada ao sistema instalado no campus de Guaratinguetá da Faculdade de Engenharia da Universidade Estadual Paulista, tendo sido estabelecidas as condições iniciais a partir da realidade vivida no campus e sendo relacionadas as características termodinâmicas do sistema, a partir do seu diagrama de processo. As características associadas ao diagrama de processo possibilitam construir o diagrama funcional termoeconômico do sistema e determinar as equações referentes às funções exergéticas desse sistema e os respectivos valores das exergias associados. Após esses cálculos, elabora-se um modelo estrutural para avaliar os custos de seus produtos (biogás, biofertilizante, água em condições de re-uso e energia elétrica) e avaliar a viabilidade econômica em função do retorno de capital investido. A seguir, a mesma metodologia á aplicada a um sistema comercialmente disponível, com características de tratamento muito próximas às da mini-ETE. A partir dos resultados obtidos, é possível verificar que a mini-estação de tratamento de esgoto é uma alternativa viável e muito atraente sobre o ponto de vista técnico-econômico, pois além de apresentar auto-suficiência energética, possui um retorno de investimento de aproximadamente um terço do tempo do sistema comercialmente disponível com características semelhantes para tratamento.
In this work a methodology that allows for the allocation of costs of the generated products for a small wastewater treatment station is developed, and used to perform an analysis of its economic feasibility, to justify the investment, beside its characterization as one of the best choice to be adopted as a basic sanitation solution in rural areas, and in areas characterized by low income population, together with a major energy potential because of its capability to transform the generated biogas into electric energy. For this purpose, the methodology is applied to a system established at Guaratinguetá Campus, School of Engineering, São Paulo State University. After establishing initial conditions based on site evaluation, the thermodynamics features of the system are related based on its process diagram. Such features, associated to process diagram, make it possible to build the thermoeconomi functional diagram for the system under analysis and, after words, the equations related to exergetic functions for the system are determined and the exergy values are calculated. After these calculations, a structural model is developed, in order to provide its products costs (biogas, biofertilizer, water in reuse conditions and electric energy). The economic viability is evaluated as a function of the estimated return on investment. The same methodology is then applied to a commercially available system, with characteristics close to a small wastewater treatment station. Based on the results of this work it is possible to verify that the small wastewater treatment station is a viable and attractive alternative in the technical and economic point of view, showing self-sufficiency in energy, and a pay-back period about one-third of estimated time of the commercial system referred to with similar features.

The need for modern energy systems to embrace the requirements of energy security, sustainability and affordability in their designs has placed emphatic importance on exploitation of renewable resources, such as solar and wind energy, etc. However, these resources often lead to reduced reliability and dispatchability of energy systems; less-efficient conversion processes; high cost of power production; etc. One promising way to ameliorate these challenges is through hybridization of renewable energy resources, and by using organic Rankine cycle (ORC) for power generation. Thus, this PhD research project is aimed at conceptual design and techno-economic optimization of hybrid solar-biomass ORC power plants. The methodologies adopted are in four distinct phases: - First, novel hybrid concentrated solar power (CSP)-biomass scheme was conceived that could function as retrofit to existing CSP-ORC plants as well as in new hybrid plant designs. Thermodynamic models were developed for each plant sub-unit, and yearly techno-economic performance was assessed for the entire system. Specifically, the ORC was modelled based on characteristics of an existing CSP-ORC plant, which currently operates at Ottana, Italy. Off-design models of ORC components were integrated, and their performance was validated using experimental data obtained from the aforementioned real plant. - Second, detailed exergy and exergoeconomic analyses were performed on the proposed hybrid plant, in order to examine the system components with remarkable optimization potentials. The evaluation on optimization potentials considered intrinsic irreversibilities in the respective components, which are imposed by assumptions of systemic and economic constraints. This has been termed enhanced exergy and enhanced exergoeconomic analyses here. - Third, the techno-economic implications of using siloxane mixtures as ORC working fluid were investigated, with the aim of improving heat transfer processes in the ORC plant. The studied fluid pairs were actively selected to satisfy classical thermodynamic requirements, based on established criteria. - Fourth, the biomass retrofit system was optimized multi-objectively, to minimize biomass consumption rate (maximize exergetic efficiency) and to minimize exergy cost rate. Non-dominated Sorting Genetic Algorithm (NSGA-II) was adopted for multi-objective optimization. The conceptual scheme involves parallel hybridization of CSP and biomass systems, such that each is capable of feeding the ORC directly. Results showed that the proposed biomass hybridization concept would increase both thermodynamic efficiency and economic performance of CSP-ORC plants, thereby improving their market competitiveness. Total exergy destroyed and exergy efficiency were quantified for each component, and for the whole system. Overall system exergetic efficiency of about 7 % was obtained. Similarly, exergoeconomic factor was obtained for each system component, and their implications were analysed to identify system components with high potentials for optimization. Furthermore, it was observed that thermodynamic performance of the hybrid plant would be optimized by using siloxane mixtures as ORC working fluid. However, this would result in larger heat exchange surface area, with its attendant cost implications. Lastly, biomass combustion and furnace parameters were obtained, which would simultaneously optimize exergetic efficiency and exergy cost rate for the hybrid plant. In sum, a novel scheme has been developed for hybridizing solar and biomass energy for ORC plants, with huge potentials to improve techno-economic competitiveness of solar-ORC systems.

Resumo: Neste trabalho é desenvolvida uma metodologia para a alocação dos custos dos produtos por uma mini-estação de tratamento de esgotos, com vistas a realizar a análise da viabilidade econômica do investimento necessário para a sua implantação, inclusive caracterizando-a como a melhor escolha a ser adotada na solução de saneamento básico em zonas rurais e em regiões de limitado poder aquisitivo, além de que tem potencial energético face à sua capacidade de transformar em eletricidadea energia contida no biogás gerado. Essa metodologia á aplicada ao sistema instalado no campus de Guaratinguetá da Faculdade de Engenharia da Universidade Estadual Paulista, tendo sido estabelecidas as condições iniciais a partir da realidade vivida no campus e sendo relacionadas as características termodinâmicas do sistema, a partir do seu diagrama de processo. As características associadas ao diagrama de processo possibilitam construir o diagrama funcional termoeconômico do sistema e determinar as equações referentes às funções exergéticas desse sistema e os respectivos valores das exergias associados. Após esses cálculos, elabora-se um modelo estrutural para avaliar os custos de seus produtos (biogás, biofertilizante, água em condições de re-uso e energia elétrica) e avaliar a viabilidade econômica em função do retorno de capital investido. A seguir, a mesma metodologia á aplicada a um sistema comercialmente disponível, com características de tratamento muito próximas às da mini-ETE. A partir dos resultados obtidos, é possível verificar que a mini-estação de tratamento de esgoto é uma alternativa viável e muito atraente sobre o ponto de vista técnico-econômico, pois além de apresentar auto-suficiência energética, possui um retorno de investimento de aproximadamente um terço do tempo do sistema comercialmente disponível com características semelhantes para tratamento.
Abstract: In this work a methodology that allows for the allocation of costs of the generated products for a small wastewater treatment station is developed, and used to perform an analysis of its economic feasibility, to justify the investment, beside its characterization as one of the best choice to be adopted as a basic sanitation solution in rural areas, and in areas characterized by low income population, together with a major energy potential because of its capability to transform the generated biogas into electric energy. For this purpose, the methodology is applied to a system established at Guaratinguetá Campus, School of Engineering, São Paulo State University. After establishing initial conditions based on site evaluation, the thermodynamics features of the system are related based on its process diagram. Such features, associated to process diagram, make it possible to build the thermoeconomi functional diagram for the system under analysis and, after words, the equations related to exergetic functions for the system are determined and the exergy values are calculated. After these calculations, a structural model is developed, in order to provide its products costs (biogas, biofertilizer, water in reuse conditions and electric energy). The economic viability is evaluated as a function of the estimated return on investment. The same methodology is then applied to a commercially available system, with characteristics close to a small wastewater treatment station. Based on the results of this work it is possible to verify that the small wastewater treatment station is a viable and attractive alternative in the technical and economic point of view, showing self-sufficiency in energy, and a pay-back period about one-third of estimated time of the commercial system referred to with similar features.
Orientador: José Luz Silveira
Coorientador: Giorgio Eugenio Oscare Giacaglia
Banca: Luiz Octavio Mattos dos Reis
Banca: Joaquim Antonio dos Reis
Banca: José Rui Camargo
Banca: Sebastião Cardoso
Doutor

Liquefied natural gas (LNG) cold utilization in small scale regasification stations is a novel topic in the industry, while such systems have been proven feasible in large scale LNG facilities. Cold recovery and utilization in LNG regasification facilities would increase the thermodynamic efficiency and reduce cold pollution. The aim of the study is to analyze the possibility to apply industry-proven thermodynamic cycles in small scale satellite regasification stations for electricity production, taking the characteristics of a real-world regasification station project in Druskininkai, Lithuania for which useful cold utilization is not currently planned. Direct Expansion (DE) and Rankine (ORC) Cycles are analyzed together with cascading using Aspen Hysys software to find the optimal solution considering thermal and exergy efficiency as well as the payback period. Thermoeconomically feasible retrofit solutions of approximately 13% thermal efficiency and approximately 17% exergy efficiency showing payback periods of 5 to 10 years and 3.3 to 6 thousand euro additional capital expenditure (CAPEX) per net kW of power production are found. Increase in complexity of thermodynamic cycles is directly proportional to both increased thermodynamic efficiencies and capital costs and the study proves that there is a limit at which increase in thermodynamic efficiency of a cycle by cascading becomes economically infeasible. Future work is suggested to improve the accuracy of the results by rigorous design to evaluate pressure drops as well as improvements in economic analysis by utilizing the discounted cash flow methodology. Sensitivity analysis of LNG physical and chemical conditions as well as ambient air could be performed whereas changes in working fluid and better engineering of the part related to intial heat exchange could improve thermodynamic efficiencies. Alternative solutions with a higher temperature heat source are also suggested.

In this thesis, several configurations of combined cycle cogeneration systems proposed by the author and an existing system, the Bilkent Combined Cycle Cogeneration Plant, are investigated by energy, exergy and thermoeconomic analyses. In each of these configurations, varying steam demand is considered rather than fixed steam demand. Basic thermodynamic properties of the systems are determined by energy analysis utilizing main operation conditions. Exergy destructions within the system and exergy losses to environment are investigated to determine thermodynamic inefficiencies in the system and to assist in guiding future improvements in the plant. Among the different approaches for thermoeconomic analysis in literature, SPECO method is applied. Since the systems have more than one product (process steam and electrical power), systems are divided into several subsystems and cost balances are applied together with the auxiliary equations. Hence, cost of each product is calculated. Comparison of the configurations in terms of performance assessment parameters and costs per unit of exergy are also given in this thesis.

The growing worldwide energy demand and the impacts of climate change due to anthropogenic greenhouse gases emissions are among the major issues facing humanity. The global energy system, responsible for most of the greenhouse gases emissions, is therefore at the heart of global concerns. In particular, the search for a reliable, sustainable and environmentally friendly means of generating electricity is a crucial matter, with growing worries about the scarcity of fossil resources, air pollution and water acidification. For these reasons, alternatives for the sustainable production of electricity are to be found.Among the plethora of alternatives available, concentrated solar power (CSP) appears as one of the most favourable options. The stability and dispatchability of production achievable by the integration of storage and fuel-solar hybridisation are amidst the major advantages of this technology. Nevertheless, conventional CSP plants are based on stream-turbine cycles which consume large amounts of water. In addition to the low thermodynamic efficiency of this type of cycle, the installation of such plants in water-scarce areas is complicated by their reliance on water resources. Thus, the study of new concepts that overcome these drawbacks is necessary for the future of this technology. The availability of high temperature solar receivers for solar tower systems opens the way for the use of gas-turbines in hybrid solar-natural gas configurations. In order to increase the efficiency of the cycle while keeping the water consumption as low as possible, a promising alternative to the recovery of the waste heat in steam-turbines is to use a low-temperature intercooled-recuperated gas-turbine cycle.This work focuses on the analysis and optimisation of the performance of an innovative hybrid solar gas-turbine power plant with an air-based bottoming cycle (ABHSGT). The evaluation considers thermodynamic performance, economic viability and environmental impact as interrelated concerns. With this in mind, detailed steady-state and dynamic models of the power plant have been developed and validated by comparison with existing components. A second model without bottoming cycle has been built for comparison. A multi-objective optimisation using an evolutionary algorithm has then been performed, optimising both capital cost and specific CO2 emissions and resulting in a Pareto-optimal set of possible designs.The analysis of the trade-off curves resulting from the optimisation reveals promising outcomes. The global minimum for the levelised cost of electricity, found at relatively high solar shares, proves the economic potential of the technology. The integration of the bottoming cycle decreases significantly the levelised cost of electricity and the CO2 emissions of the system compared to the reference plant, and higher efficiencies are achieved.The optimal design selected for an in-depth thermoeconomic and environmental analysis exhibits a levelised cost of electricity of 109 [USD/MWhe] for a solar share of 20% and an overall exergetic efficiency 38.5%. The specific CO2 emissions are reduced by 33% compared to simple gas-fired power plant. The water consumption is kept at very low levels compared to other CSP plants, making the system suitable for the deployment in water-scarce areas. In addition, the environmental impact induced by the land use requirements is considerably lower than that of other renewable energy technologies. The sensitivity analysis performed to assess the consequence of changes in varying financial conditions on the levelised cost of electricity and the net present value reveals that the system studied represents a profitable investment in the presence of feed-in tariffs.In the light of the performance obtained in the three aspects considered (thermodynamic, economic and environmental), it can be concluded that the ABHSGT represents a promising alternative to other renewable energy technologies, especially in water-scarce areas.

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid solid oxide fuel cell (SOFC) – gas turbine (GT) – steam turbine (ST) systems ranging in size from 1.5 MWe to 10 MWe. The fuel cell model used in this thesis is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The SOFC/GT subsystem is based on previous work done by Francesco Calise during his doctoral research (Calise, 2005). In that work, a HRSG is not used. Instead, the gas turbine exhaust is used by a number of heat exchangers to preheat the air and fuel entering the fuel cell and to provide energy for district heating. The current work considers instead the possible benefits of using the exhaust gases in an HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this M.S. thesis work: a single-pressure, a dual-pressure, a triple-pressure, and a triple-pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost.
Master of Science

Water scarcity and high irradiance overlap in the southwestern United States. This thesis explores solar energy as a method to power desalination in the Southwest. Ten solar desalination plants were modeled using photovoltaic reverse osmosis and concentrated solar thermal multi-effect distillation. Seawater and brackish water were considered, as well as liquid and zero liquid discharge plants. Using borrowed capital amortization, levelized energy costs were estimated to be 0.067 $/kWh-electric for photovoltaic systems and 0.009 $/kWh-heat for thermal systems. Photovoltaic reverse osmosis with liquid plant waste showed the best short-term financials while optimal long-term solar desalination methods were shown to be arbitrary, limited by solar conversion and desalination thermodynamics. A conceptualization and proof of desalination minimum work is presented. This study concludes that solar desalination cost remains higher than conservation, but has considerable potential as a new source of water in the Southwest, filling the gap between overdraft and renewable supply.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
A disposição final de resíduos sólidos urbanos, em aterros ou lixões, é um problema das grandes cidades. A utilização do lixo urbano em processos de tratamento térmico com recuperação energética vem ao encontro da busca de fontes alternativas, preferencialmente as renováveis, para a geração de energia. Assim, usinas de incineração com reaproveitamento de energia vêm sendo apresentadas como uma solução tanto para o destino do lixo quanto para a diversificação da matriz energética. Além disso, a prática da incineração proporciona máxima redução da massa e volume e inertização do lixo, estando o aproveitamento energético de resíduos (Waste-to-Energy) dentre as alternativas mais coerentes para a gestão de resíduos sólidos municipais. No Brasil, práticas como esta ainda são incipientes, porém apresentam grande potencial de estudo para aplicações nos centros urbanos em um futuro próximo. O presente trabalho apresenta uma proposta de uma usina lixo-energia, aplicável ao município do Rio de Janeiro, baseada na planta de Zabalgarbi/Bilbao (Espanha), que funciona em ciclo combinado a gás natural e incinera resíduos, aproveitando seu conteúdo energético para produzir eletricidade. Uma análise energética e exergética é realizada juntamente com uma estimativa do custo de geração de eletricidade, influenciada por um indicador de ecoeficiência que leva em consideração as emissões atmosféricas. Como conclusão, mostra-se a capacidade do sistema proposto em destinar os resíduos sólidos urbanos e atender a demanda elétrica do município do Rio de Janeiro/Brasil a um custo competitivo.
The final disposal of municipal solid waste in landfills or dumps is a regular problem to the big cities. The use of municipal waste in processes of thermal treatment with energy recovery meets the search for alternative and renewable sources of energy production. Thus, energy recovery incineration facilities are being presented as a solution to both the waste disposal problem and the growing energy demand in the cities. Additionally, incineration provides the maximum reduction of mass, volume and dangerousness of the waste and the waste-to-energy practice stands out among the most coherent alternatives for municipal solid waste management in the world. In Brazil, however, it is still incipient and therefore presents a great potential for feasibility and application studies in the urban centers. This work presents a proposal of a waste-to-energy facility that could operate in the city of Rio de Janeiro (Brazil), based on the Zabalgarbi/Bilbao (Spain) plant, which operates in combined cycle fueled by natural gas and urban solid waste and generates electrical power. It is performed an energetic and exergetic analysis along with a cost estimate influenced by an eco-efficiency indicator that takes into account the air pollution emissions. The conclusion shows the capacity of the proposed facility to treat the municipal solid waste of Rio de Janeiro (Brazil) and supply its electricity demand with a competitive cost.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O bagaço e a palha são resíduos do processamento industrial da cana-de-açúcar que constituem uma importante fonte de recurso para cogeração de energia no setor sucroalcooleiro. Os sistemas de cogeração neste setor geram potência mecânica ou elétrica e vapor, que são utilizados no próprio processo e o excedente é vendido as concessionárias de energia. Porém, estes sistemas encontram-se bem abaixo do potencial real. Uma alternativa tecnológica que poderá contribuir com a oferta de excedentes de energia elétrica é a introdução da tecnologia BIG-GT (gaseificadores de biomassa associados a turbina a gás e caldeira de recuperação). O presente trabalho, tem como objetivo o estudo termoeconômico da incorporação desta tecnologia em usinas sucroalcooleiras como alternativa para o aumento de geração de eletricidade. As análises energéticas e exergéticas foram realizadas para quatro possíveis configurações de uma usina sucroalcooleira com a integração da tecnologia BIG-GT com o objetivo de avaliar a eficiência de geração de eletricidade e vapor de processo, bem como o aproveitamento global de energia de cada uma delas. Na análise termoeconômica, é determinado o custo de produção de gás de gaseificação, eletricidade e vapor do processo no sistema proposto, assim como, tempo de recuperação do investimento. Na parte final do trabalho foi realizada a otimização multiobjetiva do sistema considerando três funções objetivo: tecnológica, econômica e ambiental, para identificar a configuração com melhor comportamento. De acordo com os resultados obtidos no estudo conclui-se que o caso III que estuda a gaseificação em leito fluidizado circulante pressurizado e mistura de oxigênio-vapor de gaseificação e o caso IV que além da gaseificação em leito fluidizado circulante pressurizado com mistura de oxigênio-vapor estuda a queima suplementar de palha na caldeira de recuperação, apresentam-se como as melhores das opções propostas.
Bagasse and straw are residues from the industrial processing of sugarcane that constitute an important source for cogeneration of energy in the sugar-alcohol sector. The cogeneration systems in this sector generate mechanical or electrical power and steam, which are used in the process itself and the surplus is sold to energy distribution companies. However, these systems are well below real potential. One of the technological alternatives that may improve the supply of surplus electricity is the introduction of BIG-GT technology (biomass gasifier associated with gas turbine and Heat recovery steam generator). In this work, it is proposed to conduct thermoeconomic studies of the incorporation of this technology in the sugarcane ethanol plants as an alternative to increasing the supply of electricity generation. The energetic and exergetic analyses were performed for four possible configurations of a sugarcane ethanol plant with the integration of BIG-GT technology with the objective of evaluating the efficiency of electricity generation and process steam as well as the global energy utilization of each one of them. In the thermoeconomic analysis, it is determined the cost of production of producer gas, electricity and steam of the process in the proposed system, as well as the investment payback period. In the final part of the work, it is developed the multiobjective optimization of the system considering three objective functions: technological, thermoeconomic and environmental, for identifying the configuration with better behavior. According to the results obtained in the study, it is concluded that case III and case IV are presented as the best of the proposed options.
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Les réseaux de chauffage urbain (DHN) sont un moyen efficace de fournir de l'énergie thermique aux consommateurs. L'état actuel de la technique montre que les DHN évoluent vers des réseaux thermiques intelligents dans des systèmes énergétiques intégrés alors que leur conception est basée sur les principes de durabilité. Sur cette base, cette thèse couvre deux domaines de recherche principaux : Fonctionnement et conception des systèmes de chauffage urbain. Dans la partie A de cette thèse, des méthodes avancées pour le fonctionnement de la DHN sont développées à l'aide d'analyses exergétiques et thermoéconomiques. Cela inclut la formulation de bilans de coûts exergétiques pour les modèles de réseau basés sur des graphiques. La partie intrinsèque est le déploiement d'une matrice algébrique, qui détermine les coûts exergétiques pour la modélisation dynamique du système. Une étude de cas d'un réseau réel prouve que la méthodologie proposée offre de nouvelles perspectives sur l'allocation individuelle des coûts, ce qui aide à évaluer la faisabilité de l'intégration par des tiers et l'intégration des sources d'énergie distribuées. Dans la partie B de cette thèse, un nouvel indicateur appelé «load deviation index (LDI)» est proposé pour lier les mesures de la demande (DSM) à la conception durable des systèmes DHN. Pour cela, un cadre de conception axé sur les affaires est proposé, qui prend en compte les influences critiques dans le DHN tout en évitant un trop grand détail. Le comportement du DSM est analysé du point de vue du système et son impact sur la conception du DHN est étudié dans deux études de cas. Alors que l'un se concentre sur les benchmarks pour différentes options de conception en utilisant une métrique de durabilité multicritères, un autre donne des indications détaillées sur l'utilité du cadre proposé pour la conception en évaluant l'impact de DSM sur les améliorations de conception possibles
District heating networks (DHN) arean efficient way of providing thermal energy to consumers. Current state of the art shows that DHNs are developing towards smart thermal networks in integrated energy systems while their design is based upon the principles of sustainability. Based on that, this thesis covers two main research areas: Operation and design of district heating systems. In part A of this thesis, advanced methods for DHN operation are developed with the help of exergetic and thermoeconomic analysis. This includes the formulation of exergetic cost balances for graph-based network models. Intrinsic part is the deployment of an algebraic matrix, which determines the exergetic costs for dynamic system modeling. A case study of areal-existing network provides evidence that the proposed methodology offers new insights into individual allocation of costs which helps to assess the feasibility of third-party integration and the integration of distributed energy sources. In part B of this thesis, a new indicator called “load deviation index (LDI)” is proposed to link demand side measures (DSM) with the sustainable design of DHN systems. For that, abusiness-focused design frameworks proposed which takes the critical influences of DHN into account while avoiding a too high detail. DSM behavior is analyzed from a system perspective and its impact on DHN design is studied in two case studies. While one focuses on benchmarks for different design options using a multi-criteria sustainability metric, another gives detailed insights into the usefulness of the proposed framework for design purposes through assessing the impact of DSM on possible design improvements using a multi-objective optimization approach

La optimización de los sistemas de conversión de energía gana cada vez más importancia debido a su impacto ambiental y los limitados recursos de combustibles fósiles. Entre estos sistemas los de refrigeración tienen una contribución creciente en el consumo total de energía y en las emisiones de CO2. Los sistemas de absorción operados con energía solar son una de las alternativas más sostenibles frente a los sistemas de refrigeración convencionales. Por lo tanto, este trabajo se centra en su mejora siguiendo los métodos de optimización termo-económica y de programación matemática. El análisis exergético y la optimización termo-económica basada en el método estructural se han realizado para distintas configuraciones de ciclos de refrigeración por absorción con las mezclas de trabajo agua-LiBr y amoniaco-agua. En la sección de programación matemática se incluye la optimización multi-objetivo (frontera de Pareto), la optimización bajo incertidumbre de los precios de la energía, el uso de varios indicadores de impacto ambiental y el efecto del impuesto sobre las emisiones de CO2. Los resultados demuestran que se pueden obtener reducciones importantes del impacto ambiental frente a los sistemas convencionales. Los sistemas de refrigeración solar no sólo son atractivos para reducir el impacto ambiental, sino también pueden ser económicamente competitivos. Su implantación dependerá, en gran medida, del impuesto sobre las emisiones de CO2 y del coste de la energía.
Optimizations of energy conversion systems become more important because of their environmental impact and the limitations of the fossil fuel resources. Among these systems cooling and refrigeration machines have an increasing share in the total energy consumption and contribution to CO2 emissions. Solar assisted absorption cooling systems are sustainable alternatives compared to the conventional cooling systems. Hence, this work is focused on improving the sustainability of cooling systems following the thermoeconomic optimization and mathematical programming approaches. In the first approach the energy, exergy and structural analysis are performed for different configurations of water/LiBr and ammonia/water absorption cooling cycles. In the second approach multi-objective optimization (Pareto frontier), optimization under uncertainty of energy prices, different environmental impact indicators, and the effect of CO2 emissions tax to reduce the global warming are discussed. The results of the multi-objective optimization show that a significant environmental impact reduction can be obtained. Results indicate that these systems are attractive not only to reduce the environmental impact but also in incurring the economic benefits. However, its practical impact largely depends on the CO2 emissions tax and the increase in the energy price.

Doutoramento em Engenharia Mecânica
The PhD project addresses the potential of using concentrating solar power (CSP) plants as a viable alternative energy producing system in Libya. Exergetic, energetic, economic and environmental analyses are carried out for a particular type of CSP plants. The study, although it aims a particular type of CSP plant – 50 MW parabolic trough-CSP plant, it is sufficiently general to be applied to other configurations. The novelty of the study, in addition to modeling and analyzing the selected configuration, lies in the use of a state-of-the-art exergetic analysis combined with the Life Cycle Assessment (LCA). The modeling and simulation of the plant is carried out in chapter three and they are conducted into two parts, namely: power cycle and solar field. The computer model developed for the analysis of the plant is based on algebraic equations describing the power cycle and the solar field. The model was solved using the Engineering Equation Solver (EES) software; and is designed to define the properties at each state point of the plant and then, sequentially, to determine energy, efficiency and irreversibility for each component. The developed model has the potential of using in the preliminary design of CSPs and, in particular, for the configuration of the solar field based on existing commercial plants. Moreover, it has the ability of analyzing the energetic, economic and environmental feasibility of using CSPs in different regions of the world, which is illustrated for the Libyan region in this study. The overall feasibility scenario is completed through an hourly analysis on an annual basis in chapter Four. This analysis allows the comparison of different systems and, eventually, a particular selection, and it includes both the economic and energetic components using the “greenius” software. The analysis also examined the impact of project financing and incentives on the cost of energy. The main technological finding of this analysis is higher performance and lower levelized cost of electricity (LCE) for Libya as compared to Southern Europe (Spain). Therefore, Libya has the potential of becoming attractive for the establishment of CSPs in its territory and, in this way, to facilitate the target of several European initiatives that aim to import electricity generated by renewable sources from North African and Middle East countries. The analysis is presented a brief review of the current cost of energy and the potential of reducing the cost from parabolic trough- CSP plant. Exergetic and environmental life cycle assessment analyses are conducted for the selected plant in chapter Five; the objectives are 1) to assess the environmental impact and cost, in terms of exergy of the life cycle of the plant; 2) to find out the points of weakness in terms of irreversibility of the process; and 3) to verify whether solar power plants can reduce environmental impact and the cost of electricity generation by comparing them with fossil fuel plants, in particular, Natural Gas Combined Cycle (NGCC) plant and oil thermal power plant. The analysis also targets a thermoeconomic analysis using the specific exergy costing (SPECO) method to evaluate the level of the cost caused by exergy destruction. The main technological findings are that the most important contribution impact lies with the solar field, which reports a value of 79%; and the materials with the vi highest impact are: steel (47%), molten salt (25%) and synthetic oil (21%). The “Human Health” damage category presents the highest impact (69%) followed by the “Resource” damage category (24%). In addition, the highest exergy demand is linked to the steel (47%); and there is a considerable exergetic demand related to the molten salt and synthetic oil with values of 25% and 19%, respectively. Finally, in the comparison with fossil fuel power plants (NGCC and Oil), the CSP plant presents the lowest environmental impact, while the worst environmental performance is reported to the oil power plant followed by NGCC plant. The solar field presents the largest value of cost rate, where the boiler is a component with the highest cost rate among the power cycle components. The thermal storage allows the CSP plants to overcome solar irradiation transients, to respond to electricity demand independent of weather conditions, and to extend electricity production beyond the availability of daylight. Numerical analysis of the thermal transient response of a thermocline storage tank is carried out for the charging phase. The system of equations describing the numerical model is solved by using time-implicit and space-backward finite differences and which encoded within the Matlab environment. The analysis presented the following findings: the predictions agree well with the experiments for the time evolution of the thermocline region, particularly for the regions away from the top-inlet. The deviations observed in the near-region of the inlet are most likely due to the high-level of turbulence in this region due to the localized level of mixing resulting; a simple analytical model to take into consideration this increased turbulence level was developed and it leads to some improvement of the predictions; this approach requires practically no additional computational effort and it relates the effective thermal diffusivity to the mean effective velocity of the fluid at each particular height of the system. Altogether the study indicates that the selected parabolic trough-CSP plant has the edge over alternative competing technologies for locations where DNI is high and where land usage is not an issue, such as the shoreline of Libya.
O projeto de Doutoramento aborda o potencial de usar centrais de energia solar concentrada (CSP) como um sistema de produção de energia alternativa disponível na Líbia. Uma análise nas vertentes exergética, energética, económica e ambiental foi realizada para um tipo particular destas centrais – um sistema de 50 MW com receção parabólica, porém ela é suficientemente geral para ser aplicada a outras configurações. A originalidade do estudo, para além da modelação e análise da configuração selecionada encontra-se na utilização do estado da arte em termos da análise exergética combinada com a avaliação do ciclo de vida (LCA). A modelação e simulação da central CSP selecionada são efetuadas no terceiro capítulo tendo em consideração as duas componentes: ciclo de potência e campo de coletores solar. O modelo computacional para a análise do sistema foi desenvolvido com base em equações algébricas que descrevem o sistema, e que são resolvidas usando o software EES. Deste modo, são definidas as propriedades em cada ponto de interesse para os diferentes elementos do sistema, o que assim permite determinar as energias, eficiências e irreversibilidades desses elementos. O modelo desenvolvido tem o potencial de se tornar uma ferramenta de grande utilidade para o projeto preliminar de engenharia de centrais CSP, e também para a avaliação da eventual reconfiguração de centrais elétricas solares comerciais em operação. Além disso, o modelo pode ser utilizado no estudo de viabilidade da operação de centrais CSP, através da análise energética, económica e ambiental, para regiões diferentes da que foi escolhida no presente estudo -Trípoli (Líbia). O cenário total da viabilidade da operação da central CSP é completado através da análise horária com base anual apresentada no quarto capítulo. Esta análise permite a comparação de diferentes sistemas e, eventualmente permite fazer a seleção com base nas componentes económicas e energéticas, que são determinadas dentro do contexto do software greenius. A análise também toma em conta o impacto de financiamento e incentivos dados aos projetos no custo da produção de energia. O principal resultado desta análise é a verificação que o desempenho é mais elevado, com o consequente menor custo nivelado da eletricidade, para a Líbia em comparação com o Sul da Europa (Espanha). Assim a Líbia tem o potencial de se tornar um candidato atrativo para o estabelecimento de centrais CSP com o objetivo, como foi considerado em várias iniciativas europeias, de exportar eletricidade gerada através de fontes de energia renováveis de países do Norte de África e Médio Oriente para a Europa. A análise apresenta uma breve revisão do custo corrente da eletricidade e o potencial para reduzir o custo da energia a partir da tecnologia de receção parabólica de centrais CSP. A avaliação do ciclo de vida com base exergética (ELCA) e a avaliação do ciclo de vida convencional são realizadas para a centrais CSP específicas no quinto capítulo. Os objetivos são 1) avaliar o impacto ambiental e custo, em termos de do ciclo iv de vida exergético do sistema; 2) identificar pontos fracos em termos da irreversibilidade dos processos; e 3) verificar se as centrais CSP podem reduzir o impacto ambiental e o custo de geração de eletricidade em comparação com centrais que consomem combustível fóssil. O capítulo ainda apresenta uma análise termoeconómica com base na metodologia do custo específico da exergia (SPECO), que avalia o custo relacionado com a destruição de exergia. A análise verificou que o impacto mais importante é a contribuição apresentada pelo campo solar (79%), e os materiais com maior impacto são: aço (47%), sal fundido (25%) e óleo sintético (21%). A análise ELCA mostra que a maior demanda de exergia é devida ao aço (47%); a análise existe uma considerável demanda de exergia relacionada com o sal fundido e ainda o óleo sintético. Em comparação com as centrais que consomem combustível fóssil (NGCC e óleo) a central sistema CSP apresenta menor impacto ambiental, enquanto o pior desempenho ambiental é o da central com queima de óleo seguida pela central a gás natural (NGCC). Na central CSP, o campo solar apresenta o custo mais elevado, enquanto o gerador de vapor, entre os componentes do ciclo de potência, apresenta o maior custo. O armazenamento de energia térmica permite que as centrais CSP superem a intermitência de radiação solar para responder à procura de energia elétrica independentemente das condições climáticas, e também possam estender a produção de eletricidade para além da disponibilidade da radiação solar diária. A análise numérica do transiente térmico de um sistema de armazenamento de gradiente térmico é realizada durante a fase de carregamento. O sistema de equações que descreve o modelo numérico é resolvido através da utilização de diferenças finitas implícitas no tempo usando o software Matlab. Os resultados da análise indicam que as previsões estão em boa concordância com os dados experimentais para a evolução no tempo da região de gradiente térmico, em particular para regiões mais afastadas da entrada. Nesta região os desvios observados são provavelmente causados pelo alto nível de turbulência devido à penetração do jato no seio do tanque de armazenamento. O modelo analítico simples para simular a turbulência que foi desenvolvido melhora os resultados. Esta abordagem não requer esforço computacional adicional e determina a difusidade térmica efetiva ao longo do tanque.

Ce travail de thèse concerne l’étude de la faisabilité des cycles organiques sous-critiques et supercritiques de Rankine pour la valorisation de rejets thermiques industriels à basse température. Dans un premier temps, un état de l’art des cycles ORC (acronyme anglais pour Organic Rankine Cycle) et leurs fluides de travail a été réalisé. Nous avons réalisé une comparaison préliminaire de plusieurs configurations à partir de la littérature scientifique. Dans un second temps, les méthodes d’analyse énergétique et exergétique ont été appliquées pour évaluer et optimiser les performances des cycles ORC. En effet, la seule méthode d’analyse énergétique n’est pas suffisante pour juger de la bonne utilisation du potentiel énergétique de la source de chaleur disponible correspondant à un rejet industrielle de chaleur (chaleur fatale). L’analyse exergétique, intervient en complément de l’analyse énergétique du système, afin de permettre de localiser les pertes des ressources énergétiques dans les différentes composantes du système et de déterminer leurs importances relatives et leurs causes. Une optimisation thermo-économique des installations de valorisation de rejets thermiques utilisant un cycle sous-critique ou supercritique de Rankine a été effectuée. Nos résultats montrent que la valorisation de rejets thermiques industriels à basse température (ex. source thermique de 150 °C) en utilisant un cycle ORC sous-critique est plus intéressante sur le plan énergétique que celle opérée en utilisant un cycle supercritique de Rankine
This thesis concerns the feasibility study of subcritical and supercritical organic Rankine cycles for industrial waste heat recovery at relatively low temperature. Initially, a state of the art of ORCs (Organic Rankine Cycles) and their working fluids has been achieved. We conducted a preliminary comparison of several configurations from the scientific literature. In a second step, methods of energy and exergy analysis were applied to evaluate and optimize the performance of the ORCs. Indeed, sole energy analysis is not enough to access the proper use of the energy potential of the available heat source that corresponds to an industrial waste heat. Exergy analysis, in a complementary way to the energy analysis, enables us to locate the energy resources losses in the various components of the system and to determine their true magnitude and their causes. A thermo-economic optimization of waste heat recovery systems using a subcritical or supercritical Rankine cycle has been performed. According to the results, the industrial waste heat recovery at low temperature (e.g. heat source 150 ° C) using a subcritical ORC is more interesting on economic point of view than the system using a supercritical Rankine cycle

碩士
國立臺北科技大學
化學工程研究所
99
This study presents the thermodynamic analysis and thermoeconomic optimization of a lithium bromide (LiBr) absorption chiller. The mathematical model of a LiBr absorption chiller is first established based on mass balance relations, energy balance relations, and some constitutive equations of each heat exchanger unit. Then, this study analyzes the thermodynamic properties of the absorption chiller, and calculates the irreversibility and energy loss of each unit. Simulations of the absorption chiller are carried out to investigate the effects of various operating conditions on the coefficient of performance (COP) and exergy efficiency (Ψex) of the absorption chiller. Moreover, this study presents the optimum design of the absorption chiller using a thermoeconomic optimization method, known as the structural method. This method not only takes the thermodynamic considerations into account but also considers their economic optimization. The advantage of using the structural method for thermoeconomic optimization is that the various elements of the system can be optimized on their own. A simple equation to calculate the optimum area of each heat exchanger can be derived by introducing the structural coefficient bond (CSB), and a modified optimization procedure is proposed. Simulation results show that the total cost and COP are improved after the optimization, while the improvement of exergy efficiency depends on the operation time.

碩士
國立中山大學
機械工程學系研究所
89
Natural gas has been considered a clean energy which is more environmental friendly and with higher combustion efficiency. In Taiwan, most LNG was imported from abroad, with large amount of cold energy for application, despite the fact that it has been utilized for only 8% of total. In LNG cold energy utilization process, the change of exergy can be simulated with the second law of Thermodynamics as a means to analyze its energy efficiency. Especially, when the transportation distance is long, the optimal insulation thickness can then be calculated to justify its economic feasibility. In this study, thermoeconomics was applied to analyze the feasibility of LNG cold energy recovery, which warrants it as a powerful design tool in engineering applications.

博士
國立臺北科技大學
能源與冷凍空調工程系碩士班
104
Most research on exergy and thermoeconomic of air-conditioning system were for simple systems at fixed state conditions. There has been no research found on exergy, thermoeconomic and optimization of air-conditioning system for an underground station in operation. Underground train stations are important features in modern metropolitans.The necessity of air-conditioning system causes enormous energy use for underground train stations, especially on that situated in a subtropical region like Taiwan. Therefore, exergy analysis and thermoeconomic analysis, and multi-objective optimization are applied to the annual operation of the air-conditioning system of a large underground train station in Taiwan. Exergy analysis is used to indicate both the quality and the quantity in the energy conversion. Exergy destruction in reverse is the indicator of energy loss in terms of quality and quantity. The current operation of the air-conditioning system and the monitored data are taken to be the base case which is then compared to cases of cost consideration (CC), thermodynamic efficiency (TE) and to multiple-objective of efficiency and economics (MO). Total revenue requirement levelized cost rate and total exergy destruction rate are used to evaluate the merits. The results show that cost optimization objective would obtain lower total revenue requirement levelized cost rate, but at the expense of higher total exergy destruction rate. Optimization of thermodynamic efficiency however leads to lower total exergy destruction rate but would increase the total revenue requirement levelized cost rate significantly. It has been shown that multi-objective optimization would result a small marginal increase in total revenue requirement levelized cost rate but achieve a significantly lower total exergy destruction rate. This study of multi-objective optimization uses the normalized form of the Pareto optimal frontier. Results of four cases in terms of normalized total revenue requirement levelized cost rate and normalized total exergy destruction rate are presented. The multi-objective optimization was represented as the lowest point of the root mean squares of and . For Case MO optimal was obtained at about 0.26 and at about 0.27. It shows that better cost benefits can be obtained when is lower than 0.26, and better thermodynamics when is higher than 0.26. It has been also shown second law analysis when applied to underground train stations, lower annual energy use and lower CO2 emission can be achieved. The research results show the importance of exergy thermoeconomic analysis, and multi-objective optimization. It can be applied to the design, evaluation and comprehensive planning of a large size underground train station air-conditioning system. Results of this study may also provide an important reference of both energy-saving and construction cost consideration for future construction or renovation of underground stations air-conditioning system.