This thesis is aimed at the optimization of electricity, heat and cold supply for a service building. The profiles of electricity, heat and cold consumptions for a specific building are incorporated in the case study. The main aim is focused on the qualification of the potential of the incorporation of technologies for energy production and conversion for the building namely the cogeneration and trigeneration technologies.

Theme of this thesis is utilizing of liquide biofuels for energy supply in the complex Technicka 2. This work is divided into three parts. The first part dealt with the issue of liquid biofuels, both globally and within the Czech Republic. In the next part are noted technologies for heating, power and cooling of of liquid biofuels. In the third part is noted evaluation of using cogeneration unit from Seva, a.g. for komplex Technicka 2 in different types of traffic.

The energy consumption is continuous to increase around the world and with that follows the demand for sustainable solutions for future energy systems. With growing energy consumption from fossil based fuels the threat of global warming through release of CO2 to the atmosphere increases. The demand for cooling is also growing which would result in an increased consumption of electricity if the cooling demand was to be fulfilled by electrically driven cooling technology. A more sustainable solution can be to use heat-driven absorption cooling where waste heat may be used as driving energy instead of electricity. This thesis focuses on the role and potential of absorption cooling in future energy systems. Two types of energy systems are investigated: a district energy system based on waste incineration and a distributed energy system with natural gas as fuel. In both cases, low temperature waste heat is used as driving energy for the absorption cooling. The main focus is to evaluate the absorption technology in an environmental perspective, in terms of reduced CO2 emissions. Economic evaluations are also performed. The reduced electricity when using absorption cooling instead of compression cooling is quantified and expressed as an increased net electrical yield. The results show that absorption cooling is an environmentally friendly way to produce cooling as it reduces the use of electrically driven cooling in the energy system and therefore also reduces global CO2 emissions. In the small-scale trigeneration system the electricity use is lowered with 84 % as compared to cooling production with compression chillers only. The CO2 emissions can be lowered to 45 CO2/MWhc by using recoverable waste heat as driving heat for absorption chillers. However, the most cost effective cooling solution in a district energy system is a combination between absorption and compression cooling technologies according to the study. Absorption chillers have the potential to be suitable bottoming cycles for power production in distributed systems. Net electrical yields over 55 % may be reached in some cases with gas motors and absorption chillers. This small-scale system for cogeneration of power and cooling shows electrical efficiencies comparable to large-scale power plants and may contribute to reducing peak electricity demand associated with the cooling demand. / QC 20101209

Cooling, Heating and Power (CHP) systems have been recognized as a key alternative for thermal energy and electricity generation at or near end-user sites. CHP systems can provide electricity while recovering waste heat to be used for space and water heating, and for space cooling. Although CHP technology seems to be economically feasible, because of the constant fluctuations in energy prices, CHP systems cannot always guarantee economic savings. However, a well-designed CHP system can guarantee energy savings, which makes necessary the quantification of non-conventional benefits from this technology in order to offset any economic weakness that can arise as consequence of energy prices. Some aspects that could be included in a non-conventional evaluation are: building energy rating, emission of pollutants, power reliability, power quality, fuel flexibility, brand and marketing benefits, protection from electric rate hikes, and benefits from promoting energy management practices. This study focuses on two aspects: building energy rating and emission reduction of pollutants, related to CHP system energy performance. Two methodologies have been developed in order to estimate the energy related benefits from CHP technology. To determine the energy performance, a model has been developed and implemented to simulate CHP systems in order to estimate the building-CHP system energy consumption. The developed model includes the relevant variables governing CHP systems such as: type and size of the components, individual component efficiencies, system operating mode, operational strategy, and building demand for power, heating, and cooling. The novelty of this model is the introduction of the Building Primary Energy Ratio (BPER) as a parameter to implement a primary energy operational strategy, which allows obtaining the best energy performance from the building-CHP system. Results show that the BPER operational strategy always guarantees energy savings. On the other hand, results from a cost-oriented operational strategy reveal that for critical design conditions, high economic savings can be obtained with unacceptable increment of energy consumption. For Energy Star Rating and Leadership in Energy and Environmental Design (LEED) Rating, results show that CHP systems have the ability to improve both ratings.

Voir résumé étendu en français en fin de thèse. / In the actual energetic and economic context, energy polygeneration represents the answer regarding the efficient use of a fuel. This solution would diminish the losses associated to the classical methods of energy production and, as a result, would increase the installations' efficiency. The polygeneration systems (cogeneration/trigeneration of energy), consist of various technologies that offer alternatives to the global problems linked to energy, such as energy scarcity, energy supply security, emissions control from the production of energy, economy and energy conservation, etc.. This doctoral thesis examines two types of polygeneration of energy. The first part focuses on the analysis of a high power trigeneration system based on a gas turbine installation for production of electrical energy, the second part of the thesis is dealing with a system of micro-cogeneration of energy powered by a solar Stirling engine. Given the actuality and interest for the polygeneration field of energy production, there is a constant concern to simulate and optimize the operation of this kind of systems in order to achieve significant performance designed to satisfy the consumers' needs

A energia é o maior contribuinte para os custos de operação de uma indústria, portanto, estudos para melhoria da eficiência dos sistemas que utilizam alguma fonte de energia são indispensáveis. O presente trabalho tem por objetivo a obtenção de configurações ótimas para satisfazer demandas de eletricidade e cargas térmicas de aquecimento e refrigeração a partir de uma fonte primaria de energia, avaliando o impacto dessas nos custos de produção de eletricidade, vapor e água gelada. Estes tipos de sistemas são conhecidos como sistemas de trigeração. A avaliação de desempenho dos sistemas de trigeração é conduzida através da aplicação da análise exergética e exergoeconômica das alternativas propostas para a determinação do rendimento exergético e custos em base exergética de produção de utilidades desse tipo de sistema. Após apresentar uma breve discussão sobre o uso eficiente e racional de energias primárias e mostrar um panorama da situação para a aplicação de sistemas de trigeração para satisfazer demandas energéticas na indústria e o setor terciário, são descritas diferentes tecnologias envolvidas neste tipo de sistemas e algumas configurações propostas por vários pesquisadores nos anos recentes. O trabalho mostra o impacto das tecnologias de trigeração nos custos em base exergética dos produtos: eletricidade, vapor para processo e água gelada. Sistemas de refrigeração por absorção de efeito simples, duplo efeito e o sistema híbrido de absorção/ejeto compressão são analisados, como parte do estudo dos sistemas de trigeração. Diversos sistemas de trigeração, incluindo o sistema tetra-combinado, são comparados satisfazendo demandas energéticas para três aplicações diferentes: indústria de laticínios, hospital e indústria de bebidas. As configurações em estudo são otimizadas usando o método de algoritmo genético. Os resultados mostram que o sistema de refrigeração híbrido de absorção/ejeto compressão é uma boa alternativa para a produção da água gelada porque o coeficiente de desempenho (COP) e a eficiência exergética são maiores do que no sistema de refrigeração por absorção de efeito simples. Observando o impacto na formação dos custos de conversão de energia para os sistemas de trigeração propostos, os sistemas que utilizam unidade de refrigeração por absorção de duplo efeito são os que apresentam menor impacto. O sistema tetra-combinado apresenta um menor impacto quanto comparado com o ciclo combinado com unidade de refrigeração por absorção de simples efeito. O consumo de combustível e a destruição de exergia dos diferentes sistemas são refletidos nos custos em base exergética dos diferentes produtos. A otimização com algoritmos genéticos mostrou ganhos importantes nos custos em base exergética dos produtos, mediante a maximização da eficiência exergética dos diferentes sistemas de trigeração. O método dos algoritmos genéticos mostra-se como um método robusto para a otimização de sistemas de conversão de energia, mesmo que exija um grande esforço computacional. / Energy is the largest contributor to operating costs of any industry; therefore, studies for improving systems efficiency that use some energy source are essential. This work aims to obtain optimal configurations in order to satisfy required demands for electricity and thermal loads for heating and cooling from a primary source of energy, evaluating the impact of the electricity, steam and chilled water production costs. These types of systems are known as trigeneration systems. The performance evaluation of trigeneration systems is carried out by the application of exergy and exergoeconomic analysis of the proposed alternatives in order to determine exergy efficiency and exergy based costs on production of this type of system utilities. After presenting a brief discussion about efficient and rational use of primary energies and an overview of situation for trigeneration systems application, various technologies involved in this type of systems and some configurations proposed by several authors are described. This research shows the impact of trigeneration technologies in exergy-based costs of products: electricity, steam process and chilled water. Absorption refrigeration systems of simple effect, double effect and the hybrid absorption/ejecto compression are analyzed, as part of the trigeneration systems study. Several trigeneration systems, including the tetra-combined system, are compared with each other, satisfying energetic demands for three different applications: a dairy industry, a hospital and a drinks industry. The configurations in study are optimized using the Genetic Algorithm method. The results show that the hybrid absorption/ejecto compression refrigeration system is a good alternative for chilled water production due to that the coefficient of performance (COP) and the exergetic efficiency are higher than simple effect absorption refrigeration system. Observing the impact in the formation of the energy conversion costs for trigeneration systems proposed, the systems that use a double effect absorption refrigeration system presents the less impact. When tetra-combined system is compared with the system using a simple effect absorption refrigeration system, the results show a reduction in the impact of costs formation. The fuel consumption and exergy destruction of the different systems is reflected in the exergy based costs of the different products. The optimization with genetic algorithms shown important profits in the exergy based costs of products, by means of the exergetic efficiency maximization of the different trigeneration systems. The genetic algorithm method is a robust method for energy conversion systems optimization, even that it demands a great computational effort.

La thèse intitulée «Contributions aux systèmes de stockage d’énergie en utilisant des systèmes à partir de sources d’énergie alternatives» propose une étude des technologies de stockage d'énergie en sachant qu'elles sont considérées comme l'une des options qui peuvent faciliter une forte pénétration de sources renouvelables. Dans ce contexte, le travail présenté vise à comprendre les défis liés au stockage de l'énergie et à développer un modèle général d'étude utilisant l'air comprimé comme moyen de stockage d'énergie.La thèse est structurée dans dix chapitres dont les quatre premiers sont consacrés à la présentation potentielle des sources d'énergie renouvelables, à l'évolution du secteur de l'énergie au cours des dernières décennies et aux technologies de stockage d'énergie, notamment sous forme d'air comprimé. Les six autres chapitres concernent les calculs thermodynamiques théoriques dans la mesure où il s'agit d'étudier les performances d'un système de stockage d'énergie hybride et de présenter un modèle mathématique contenant les étapes prises en compte dans la conversion de l'énergie renouvelable en énergie mécanique, stockées dans une forme d'air comprimé et plus tard reconvertis en électricité. De plus, ces chapitres présentent des données expérimentales obtenues sur une installation de laboratoire qui ont contribué à la validation des résultats théoriques obtenus suite à une simulation Matlab, et enfin une étude de cas pour une application à petite échelle, 30 kWh d'énergie stockée, où vise à trouver une configuration optimale. De l'ensemble du système en termes de pression de travail de l'air, analysé sous deux points de vue, technique et économique. La thèse se termine par un chapitre de conclusions générales et nous constatons qu'il reste encore quelques défis à surmonter pour que le stockage de l'énergie sous forme d'air comprimé soit une solution possible d'une perspective économique. / The thesis entitled «Contributions to energy storage using hybrid systems from alternative energy sources» proposes a study of the energy storage technologies knowing the fact that these are considered one of the options that can facilitate a high penetration of renewable sources. In this context, the presented work aims to understand challenges in terms of energy storage and to develop a general studying model using compressed air as an energy storage medium.The thesis is structured in ten chapters from which the first four are dedicated to the presentation of the renewable energy sources potential, to the energy sector evolution in the last decades and to the energy storage technologies, especially in the form of compressed air. The other six chapters are dealing with the theoretical thermodynamic calculations as far as that goes in investigating the performances of a hybrid energy storage system and presenting a mathematical model containing the steps taken into account in the renewable energy conversion into mechanical energy, stored in a form of compressed air and later reconverted into electricity. In addition these chapters present experimental data obtained on a laboratory installation which helped in validating the theoretical results obtained following a Matlab simulation, and finally a case study for a small scale application, 30 kWh of energy stored, where is aiming to find an optimal configuration of the whole system in terms of air working pressure, being analyzed from two points of view, technical and economic. The thesis ends with a chapter of general conclusions and indicates that there are still challenges that must be overcome in order to make the energy storage in a form of compressed air a feasible solution from an economic perspective.

In this study, the feasibility of using an organic Rankine cycle (ORC) in trigeneration plants is examined through thermodynamic modeling and thermoeconomic optimization. Three novel trigeneration systems are considered. Each one of these systems consists of an ORC, a heating-process heat exchanger, and a single-effect absorption chiller. The three systems are distinguished by the source of the heat input to the ORC. The systems considered are SOFC-trigeneration, biomass- trigeneration, and solar-trigeneration systems. For each system four cases are considered: electrical-power, cooling-cogeneration, heating-cogeneration, and trigeneration cases. Comprehensive thermodynamic analysis on each system is carried out. Furthermore, thermoeconomic optimization is conducted. The objective of the thermoeconomic optimization is to minimize the cost per exergy unit of the trigeneration product. The results of the thermoeconomic optimization are used to compare the three systems through thermodynamic and thermoeconomic analyses. This study illustrates key output parameters to assess the trigeneration systems considered. These parameters are energy efficiency, exergy efficiency, net electrical power, electrical to cooling ratio, and electrical to heating ratio. Moreover, exergy destruction modeling is conducted to identify and quantify the major sources of exergy destruction in the systems considered. In addition, an environmental impact assessment is conducted to quantify the amount of CO2 emissions in the systems considered. Furthermore, this study examines both the cost rate and cost per exergy unit of the electrical power and other trigeneration products. This study reveals that there is a considerable efficiency improvement when trigeneration is used, as compared to only electrical power production. In addition, the emissions of CO2 per MWh of trigeneration are significantly lower than that of electrical power. It was shown that the exergy destruction rates of the ORC evaporators for the three systems are quite high. Therefore, it is important to consider using more efficient ORC evaporators in trigeneration plants. In addition, this study reveals that the SOFC-trigeneration system has the highest electrical energy efficiency while the biomass-trigeneration system and the solar mode of the solar trigeneration system have the highest trigeneration energy efficiencies. In contrast, the SOFC-trigeneration system has the highest exergy efficiency for both electrical and trigeneration cases. Furthermore, the thermoeconomic optimization shows that the solar-trigeneration system has the lowest cost per exergy unit. Meanwhile the solar-trigeneration system has zero CO2 emissions and depends on a free renewable energy source. Therefore, it can be concluded that the solar-trigeneration system has the best thermoeconomic performance among the three systems considered.

In this study, the feasibility of using an organic Rankine cycle (ORC) in trigeneration plants is examined through thermodynamic modeling and thermoeconomic optimization. Three novel trigeneration systems are considered. Each one of these systems consists of an ORC, a heating-process heat exchanger, and a single-effect absorption chiller. The three systems are distinguished by the source of the heat input to the ORC. The systems considered are SOFC-trigeneration, biomass- trigeneration, and solar-trigeneration systems. For each system four cases are considered: electrical-power, cooling-cogeneration, heating-cogeneration, and trigeneration cases. Comprehensive thermodynamic analysis on each system is carried out. Furthermore, thermoeconomic optimization is conducted. The objective of the thermoeconomic optimization is to minimize the cost per exergy unit of the trigeneration product. The results of the thermoeconomic optimization are used to compare the three systems through thermodynamic and thermoeconomic analyses. This study illustrates key output parameters to assess the trigeneration systems considered. These parameters are energy efficiency, exergy efficiency, net electrical power, electrical to cooling ratio, and electrical to heating ratio. Moreover, exergy destruction modeling is conducted to identify and quantify the major sources of exergy destruction in the systems considered. In addition, an environmental impact assessment is conducted to quantify the amount of CO2 emissions in the systems considered. Furthermore, this study examines both the cost rate and cost per exergy unit of the electrical power and other trigeneration products. This study reveals that there is a considerable efficiency improvement when trigeneration is used, as compared to only electrical power production. In addition, the emissions of CO2 per MWh of trigeneration are significantly lower than that of electrical power. It was shown that the exergy destruction rates of the ORC evaporators for the three systems are quite high. Therefore, it is important to consider using more efficient ORC evaporators in trigeneration plants. In addition, this study reveals that the SOFC-trigeneration system has the highest electrical energy efficiency while the biomass-trigeneration system and the solar mode of the solar trigeneration system have the highest trigeneration energy efficiencies. In contrast, the SOFC-trigeneration system has the highest exergy efficiency for both electrical and trigeneration cases. Furthermore, the thermoeconomic optimization shows that the solar-trigeneration system has the lowest cost per exergy unit. Meanwhile the solar-trigeneration system has zero CO2 emissions and depends on a free renewable energy source. Therefore, it can be concluded that the solar-trigeneration system has the best thermoeconomic performance among the three systems considered.

A energia é o maior contribuinte para os custos de operação de uma indústria, portanto, estudos para melhoria da eficiência dos sistemas que utilizam alguma fonte de energia são indispensáveis. O presente trabalho tem por objetivo a obtenção de configurações ótimas para satisfazer demandas de eletricidade e cargas térmicas de aquecimento e refrigeração a partir de uma fonte primaria de energia, avaliando o impacto dessas nos custos de produção de eletricidade, vapor e água gelada. Estes tipos de sistemas são conhecidos como sistemas de trigeração. A avaliação de desempenho dos sistemas de trigeração é conduzida através da aplicação da análise exergética e exergoeconômica das alternativas propostas para a determinação do rendimento exergético e custos em base exergética de produção de utilidades desse tipo de sistema. Após apresentar uma breve discussão sobre o uso eficiente e racional de energias primárias e mostrar um panorama da situação para a aplicação de sistemas de trigeração para satisfazer demandas energéticas na indústria e o setor terciário, são descritas diferentes tecnologias envolvidas neste tipo de sistemas e algumas configurações propostas por vários pesquisadores nos anos recentes. O trabalho mostra o impacto das tecnologias de trigeração nos custos em base exergética dos produtos: eletricidade, vapor para processo e água gelada. Sistemas de refrigeração por absorção de efeito simples, duplo efeito e o sistema híbrido de absorção/ejeto compressão são analisados, como parte do estudo dos sistemas de trigeração. Diversos sistemas de trigeração, incluindo o sistema tetra-combinado, são comparados satisfazendo demandas energéticas para três aplicações diferentes: indústria de laticínios, hospital e indústria de bebidas. As configurações em estudo são otimizadas usando o método de algoritmo genético. Os resultados mostram que o sistema de refrigeração híbrido de absorção/ejeto compressão é uma boa alternativa para a produção da água gelada porque o coeficiente de desempenho (COP) e a eficiência exergética são maiores do que no sistema de refrigeração por absorção de efeito simples. Observando o impacto na formação dos custos de conversão de energia para os sistemas de trigeração propostos, os sistemas que utilizam unidade de refrigeração por absorção de duplo efeito são os que apresentam menor impacto. O sistema tetra-combinado apresenta um menor impacto quanto comparado com o ciclo combinado com unidade de refrigeração por absorção de simples efeito. O consumo de combustível e a destruição de exergia dos diferentes sistemas são refletidos nos custos em base exergética dos diferentes produtos. A otimização com algoritmos genéticos mostrou ganhos importantes nos custos em base exergética dos produtos, mediante a maximização da eficiência exergética dos diferentes sistemas de trigeração. O método dos algoritmos genéticos mostra-se como um método robusto para a otimização de sistemas de conversão de energia, mesmo que exija um grande esforço computacional. / Energy is the largest contributor to operating costs of any industry; therefore, studies for improving systems efficiency that use some energy source are essential. This work aims to obtain optimal configurations in order to satisfy required demands for electricity and thermal loads for heating and cooling from a primary source of energy, evaluating the impact of the electricity, steam and chilled water production costs. These types of systems are known as trigeneration systems. The performance evaluation of trigeneration systems is carried out by the application of exergy and exergoeconomic analysis of the proposed alternatives in order to determine exergy efficiency and exergy based costs on production of this type of system utilities. After presenting a brief discussion about efficient and rational use of primary energies and an overview of situation for trigeneration systems application, various technologies involved in this type of systems and some configurations proposed by several authors are described. This research shows the impact of trigeneration technologies in exergy-based costs of products: electricity, steam process and chilled water. Absorption refrigeration systems of simple effect, double effect and the hybrid absorption/ejecto compression are analyzed, as part of the trigeneration systems study. Several trigeneration systems, including the tetra-combined system, are compared with each other, satisfying energetic demands for three different applications: a dairy industry, a hospital and a drinks industry. The configurations in study are optimized using the Genetic Algorithm method. The results show that the hybrid absorption/ejecto compression refrigeration system is a good alternative for chilled water production due to that the coefficient of performance (COP) and the exergetic efficiency are higher than simple effect absorption refrigeration system. Observing the impact in the formation of the energy conversion costs for trigeneration systems proposed, the systems that use a double effect absorption refrigeration system presents the less impact. When tetra-combined system is compared with the system using a simple effect absorption refrigeration system, the results show a reduction in the impact of costs formation. The fuel consumption and exergy destruction of the different systems is reflected in the exergy based costs of the different products. The optimization with genetic algorithms shown important profits in the exergy based costs of products, by means of the exergetic efficiency maximization of the different trigeneration systems. The genetic algorithm method is a robust method for energy conversion systems optimization, even that it demands a great computational effort.