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The liberalization of electricity markets and a growing penetration of renewables is changing operation of electrical grids. The boundary conditions for the operation of conventional power plants are changing and, as such, an improved understanding of the varying loads and prices on the electricity grid is required to assess the performance of emerging combined cycle gas turbine (CCGT) concepts and to further optimize their design for these new markets in the pursuit of increasing their profitability, especially when considering combined heat and power (CHP). To increase the flexibility of CCGT-CHP plants, three new plant layouts have been investigated by integrating different storage concepts and heat pumps in key sections of the traditional plant layout. The present study analyses the influence that market has on determining the optimum CCGT-CHP plant layout that maximizes profits (in terms of plant configuration, sizing and operation strategies) for a given location nearby Turin, Italy, for which hourly electricity and heat prices, as well as meteorological data, have been gathered. A multi-parameter approach for design and operation was followed using KTH’s and EPS’ techno-economic modeling tool DYESOPT. Results are shown by means of a comparative analysis between optimal plants found for each layout and the state-of-the art CCGT-CHP. It is shown that a plant configuration in which a cold storage unit is integrated together with a heat pump at the inlet of the gas turbine unit increases the net present value of the plant by approximately 0.3% when compared against conventional plant layouts. Using the same concept with a heat pump alone can improve lifetime profitability by 1.6%. A layout where district heating supply water is preheated with a combination of a heat pump with hot thermal tank increases plant profitability by up to 0.5%. This work has been performed as part of the PUMP-HEAT project, an EU Horizon 2020 research project in which KTH collaborates with other 13 stakeholders including industry and research institutions. The results will directly influence future work of the project.

[pt] Esta tese tem como objetivo encorajar o desenvolvimento da tecnologia híbrida de lixo-energia e sua aplicação em países com acesso a reservas de gás natural, tal como o Brasil. O método consiste em avaliá-la por meio de uma análise integrada de indicadores de desempenho energético, exergético, econômico e ambiental. A tecnologia inclui dois ciclos integrados: um ciclo superior e um inferior que interagem por meio de uma caldeira de recuperação. O lixo urbano não reciclável, in natura, alimenta o ciclo inferior na caldeira de lixo enquanto o gás natural alimenta o ciclo superior na turbina a gás. O objetivo da modelagem destes sistemas consiste em propor um layout de máxima eficiência aliado a um custo acessível de produção de eletricidade/tratamento do lixo, o que é atingido com um design otimizado. O desempenho termodinâmico mais eficiente é proporcional ao percentual de gás natural, isto é, quanto maior a quantidade de lixo em relação ao gás, menos eficiente é a planta, uma vez que o lixo tem menor poder calorífico. Portanto, o desafio é buscar uma maior eficiência com maior percentual de lixo, aliando também o aspecto custo. De uma forma geral, dois cenários coexistem no mundo atual, o dos países desenvolvidos e o dos países em desenvolvimento. Os primeiros possuem inúmeras aplicações de usinas não híbridas, poucas reservas próprias de gás natural e enfrentam redução na produção de lixo, causando a sub-utilização dos sistemas. Esta tese traz uma análise completa de potenciais alternativas para re-potenciamento de plantas sub-utilizadas, demonstrando o quão pior é o seu desempenho em comparação com o ciclo otimizado. Nos países em desenvolvimento ocorre o inverso: há crescente geração de resíduos, reservas pouco exploradas de gás natural e nenhuma usina lixo-energia. Portanto, existe um grande potencial para implantação de usinas híbridas, as quais, conforme a tese demonstra, são uma alternativa muito mais razoável do que implantar usinas convencionais não híbridas. / [en] This thesis aims to foster the development of hybrid waste-energy technology and its application in countries with access to natural gas reserves, such as Brazil. The method consists of evaluating it through an integrated analysis of energy, exergy, economic and environmental indicators. The investigated system consists of a topping and a bottoming cycle integrated through a heat recovery boiler. Raw non-recyclable urban waste feeds the waste boiler while natural gas feeds a gas turbine. The goal is to propose a cycle with high efficiency able to generate electricity/treat waste within affordable costs, which is achieved with an optimized design. The cycle s performance is proportional to the share of natural gas thermal input, that is, the greater the amount of waste the lower the efficiency (waste has lower calorific value). Therefore, the challenge is to seek greater efficiency with higher percentage of waste, including also the cost aspect. In general, there are two scenarios in the world: developed and developing countries. The former has several non-hybrid plants, few natural gas reserves and face reduced waste production, causing underutilization of the existing systems. This thesis provides a complete analysis of potential alternatives for re-potentiation of underutilized plants, demonstrating how worse their performance is compared to the optimized cycle. On the other hand, developing countries present increasing waste generation, under exploited reserves of natural gas and zero waste-to-energy plants. Therefore, there is a great potential for building hybrid waste-to-energy systems, which this work demonstrates are a much more reasonable alternative than nonhybrid conventional waste-to-energy plants.