The goal of this study is to assess the potential of the Stirling engine in alternative energy applications including combined cooling, heating, and power (CCHP) and novel waste heat recovery (WHR) technologies. A first and second law model is developed to quantify Stirling engine performance and realize the crucial parameters in Stirling engine design. In addition, analysis of systems employing the Stirling engine as a prime mover can help justify particular design interests for the engine regarding certain applications. A model of a CCHP system is developed with a Stirling engine prime mover. Sensitivity analysis is performed on the CCHP system to gain a deeper understanding of how each component affects the overall performance of the CCHP system. The main objective of these analyses is to provide information on the feasibility of Stirling CCHP on the basis of primary energy consumption and cost. Finally, the potential of the Stirling engine as a waste heat recovery device is investigated. A thermodynamic model is developed to provide estimates of Stirling engine performance based on an available waste heat stream from any specific heat source, while suggesting practical design constraints on the engine based on bounds from the second law. These results are provided to strengthen the feasibility of the Stirling engine as a bottoming prime mover rather than the central power plant.

This thesis investigates the different strategies of operation and optimization criteria that a CCHP system can be operated under. As energy concerns increase, a major issue for the United States will be the efficiency of energy production. Due to this desire for the most efficient supply of energy CCHP will play an increasingly important role in both domestic and commercial applications as waste heat utilization provides an added measure of efficiency. The different strategies of operation under which a CCHP system can be operated under, electric load following and thermal load following, are defined in addition to the different optimization criteria that a CCHP system can be operated under. The different strategies and optimization criteria of CCHP operation are simulated for five various climate regions in the United States and the results for primary energy consumption, CO2 emissions, and cost of operation are compared.

Ce mémoire présente l'étude d'un système de trigénération ou CCHP (combined cooling, heating and power) au gaz naturel fournissant les besoins thermiques à un immeuble à logement typique de 13 étages. Un groupe électrogène permettant de générer de l'électricité tout en fournissant de l'eau chaude assure le chauffage du bâtiment et de l'eau chaude sanitaire tandis qu'une machine à absorption ammoniac-eau permet de transformer cette chaleur en puissance frigorifique afin de climatiser le bâtiment en période chaude. Le modèle de cette machine à absorption a spécialement été conçu pour fonctionner avec une température de désorption basse et permet d'évaluer les performances de telles machines dans des situations hors design. Ce modèle a été vérifié à l'aide d'autres modèles avérés et propose des coefficients de performance de l'ordre de 0,7 à 0,8. L'évaluation des performances horaires de ce système est présentée pour une année standard sous trois climats canadiens. Ces performances sont ensuite comparées aux différentes méthodes employées pour assurer ces besoins ainsi que pour générer l'électricité supplémentaire. Les résultats démontrent d'excellentes performances même lorsque comparées aux plus récentes technologies. Les résultats passent d'une légère augmentation de la consommation de gaz naturel dans un climat chaud comme Toronto à une importante réduction dans un climat froid comme Edmonton. Ce système permet donc de combler les besoins thermiques d'un bâtiment tout en générant de l'électricité dans des périodes de pointes annuelles et possiblement journalières. Plusieurs études dont notamment l'optimisation du système et le couplage à d'autres types de bâtiment permettrait cependant de mieux évaluer les possibilités complètes de la trigénération.

In this research, a new combined heat and power (CHP) system configuration has been proposed that uses two power generation units (PGU) operating simultaneously with different operational strategies (D-CHP). The performance of the proposed D-CHP system configuration, with one PGU operated at a constant base load and the other operated following the electric load, is quantified in terms of operational cost savings, primary energy consumption (PEC) savings, and carbon dioxide emissions (CDE) savings over a reference case employing a conventional, separate heat and power system. D-CHP system performance is also compared to standard, single PGU operational strategies. The D-CHP system configuration is first examined for four different building configurations simulated using the weather of Chicago, IL. Then, the D-CHP system feasibility study is extended to examine a full-service restaurant benchmark building in nine different U.S. climate zones. Next, the D-CHP configuration is simulated under a second operational strategy, in which one PGU operates base-loaded while the other follows the thermal load, and the two D-CHP strategies are compared. Additionally, the effect of thermal storage on D-CHP system performance is examined. Finally, the D-CHP configuration is extended to a combined cooling, heating, and power configuration (D-CCHP), and the feasibility of this configuration is examined. In addition to D-CHP and D-CCHP systems performance analyses, the parameters of power-to-heat ratio; cost, emissions and primary energy consumption spark spreads; cost and emission ratios; and thermal difference are proposed and examined as performance indicators. It was determined that D-CHP and D-CCHP system strategies can be a viable alternative to traditional CHP system or combined cooling, heating, and power (CCHP) system operational strategies, in terms of operational cost, PEC, and CDE performance. Generally, the D-CHP and D-CCHP configurations are found to perform comparably to or better than traditional CHP and CCHP configurations.

China is the largest energy consumer worldwide, with a fast-growing rate. But the energy and environmental problems brought by its unbalanced energy structure and low energy efficiency restrict the sustainable development of China. The Distributed Energy System (DES) is one of the internationally recognized solutions to the problems. To enhance the implementation of the DES under China’s scenario, the thesis develops computational models for the Combined Cooling, Heat, and Power (CCHP) and Separated Cooling, Heat, and Power (SCHP) systems for a Micro Energy Grid in northeast China using MATLAB. The objective is to minimize the overall expenditure, energy use, and carbon emission equivalents. The results show that the CCHP system reduces 18.62% of the overall expenditure and 35.02% of the carbon emission equivalents than the SCHP system. The CCHP system has a promising prospect in China with better Greenhouse Gas emissions reduction and economic performance. / Kina är världens största energikonsument, med en snabb tillväxttakt. Men de energi- och miljöproblem som orsakas av den obalanserade energistrukturen och den låga energieffektiviteten begränsar Kinas hållbara utveckling. Distribuerade energisystem (DES) är en av de internationellt erkända lösningarna på dessa problem. För att förbättra implementeringen av DES enligt Kinas scenario utvecklar avhandlingen beräkningsmodeller för kombinerad kylning, värme och kraft (CCHP) och separerad kylning, värme och kraft (SCHP) för ett mikroenerginät i nordöstra Kina med hjälp av MATLAB. Målet är att minimera de totala kostnaderna, energianvändningen och koldioxidutsläppen. Resultaten visar att CCHP-systemet minskar de totala utgifterna med 18,62 % och koldioxidutsläppen med 35,02 % jämfört med SCHP-systemet. CCHP-systemet har lovande utsikter i Kina med bättre minskning av växthusgasutsläpp och ekonomisk prestanda.

Combined Cooling Heating and Power (CCHP) systems have been recognized as a viable alternative to conventional electrical and thermal energy generation in buildings because of their high efficiency, low environmental impact, and power grid independence. Many researchers have presented models for comparing CCHP systems to conventional systems and for optimizing CCHP systems. However, many of the errors and uncertainties that affect these modeling efforts have not been adequately addressed in the literature. This dissertation will focus on the following key issues related to errors and uncertainty in CCHP system modeling: (a) detailed uncertainty analysis of a CCHP system model with novel characterization of weather patterns, fuel prices and component efficiencies; (b) sensitivity analysis of a method for estimating the hourly energy demands of a building using Department of Energy (DOE) reference building models in combination with monthly utility bills; (c) development of a practical technique for selecting the optimal Power Generation Unit (PGU) for a given building that is robust with respect to fuel cost and weather uncertainty; (d) development of a systematic method for integrated calibration and parameter estimation of thermal system models. The results from the detailed uncertainty analysis show that CCHP operational strategies can effectively be assessed using steady state models with typical year weather data. The results of the sensitivity analysis reveal that the DOE reference buildings can be adjusted using monthly utility bills to represent the hourly energy demands of actual buildings. The optimal PGU sizing study illustrates that the PGU can be selected for a given building in consideration of weather and fuel cost uncertainty. The results of the integrated parameter estimation study reveal that using the integrated approach can reduce the effect of measurement error on the accuracy of predictive thermal system models.

[pt] O presente trabalho tem por objetivo analisar e comparar sistemas de trigeração (produção simultânea de eletricidade, aquecimento e refrigeração) de diferentes arquiteturas com base nas eficiências energética e exergética e nas emissões de CO2. Sistemas de trigeração são considerados mais eficientes na conversão de energia, se comparados a sistemas convencionais, devido ao reaproveitamento do calor de rejeito do motor térmico para outros fins (aquecimento, acionamento de chiller, ou geração de eletricidade). Quatro configurações (com chiller de compressão de vapor, com chiller de absorção, com a combinação dos ciclos anteriores, e combinado com um ciclo Rankine orgânico) foram estudadas a partir de modelos matemáticos resultantes dos balanços de energia e de exergia, e do cálculo de emissão de CO2 considerando as demandas energéticas (eletricidade, aquecimento e refrigeração) como independentes do desempenho do sistema. Todas as arquiteturas de trigeração aqui analisadas apresentaram um ponto ótimo de operação, onde o calor de rejeito recuperado para aquecimento se iguala à respectiva demanda. Neste ponto, o fator de utilização de energia (indicador de desempenho pela primeira Lei) e a eficiência exergética são máximos, e a emissão de CO2, mínima. A solução das equações resultantes mostrou também que a melhor arquitetura, do ponto de vista energético, exergético ou ambiental, dependerá da combinação das demandas energéticas. / [en] The present work aims at analyzing and comparing trigeneration systems (for the simultaneous production of electricity, heating and refrigeration) of different architectures based on energetic and exergetic efficiencies and on CO2 emissions. Trigeneration systems are regarded as more efficient in energy conversion, if compared to conventional systems, due to the recovery of waste heat from the heat engine. The waste heat is used for different purposes, including heating, chiller driving or electricity generation. Four trigeneration configurations (with vapor compression chiller, absorption chiller, with a combination of the two previous cycles, or combined with an organic Rankine cycle) were studied. Mathematical models resulting from the energy and exergy balances and from the calculation of CO2 emissions were developed taking into account that the three energy demands (electricity, heating and refrigeration) are independent from the trigeneration system performance. Solution of the resulting equations indicated an optimal point of operation, for all trigeneration architectures under study, where the waste heat recovered for heating equals the heating demand. At this point, the energy utilization factor (first Law indicator) and the exergy efficiency reach their maximum value, and the CO2 emissions, its lowest. Another important finding is that the configuration with best performance, from the energetic, exergetic, or environmental point of view, will depend on how the energy demands relate to each other.

Submitted by Geandra Rodrigues (geandrar@gmail.com) on 2018-09-25T13:55:05Z No. of bitstreams: 1 arthurgoncalvesgivisiez.pdf: 15097769 bytes, checksum: e434481fde7014f783d8b75137429fba (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-10-01T18:11:02Z (GMT) No. of bitstreams: 1 arthurgoncalvesgivisiez.pdf: 15097769 bytes, checksum: e434481fde7014f783d8b75137429fba (MD5) / Made available in DSpace on 2018-10-01T18:11:02Z (GMT). No. of bitstreams: 1 arthurgoncalvesgivisiez.pdf: 15097769 bytes, checksum: e434481fde7014f783d8b75137429fba (MD5) Previous issue date: 2018-08-29 / O mundo está tentando mudar para um ambiente de energia mais limpa, especialmente no setor de geração de eletricidade, que é responsável por uma grande parcela das emissões de CO2. No Brasil, fontes renováveis são responsáveis por grande parte da geração de eletricidade, mas mudanças atuais no clima brasileiro trouxeram uma necessidade de diversificação na matriz energética. Logo, a geração distribuída é uma boa maneira de diversificar a matriz energética brasileira. Considerando que os sistemas de cogeração se enquadram na geração distribuída, e que os prédios brasileiros necessitam de resfriamento, devido ao clima quente, o uso de cogeração adicionado à um chiler de absorção ou absorção pode ser muito útil. O sistema de trigeração é um processo altamente eficiente, que pode produzir eletricidade, aquecimento e resfriamento a partir da mesma fonte de energia primária. No entanto, existem poucas pesquisas sobre os sistemas de trigeração no Brasil, especialmente em pequena e micro escala. Assim, esta dissertação fará uma avaliação técnica e econômica de sistemas de micro e trigeração para diferentes edifícios sob políticas tarifárias distintas no Brasil. Para tanto, este trabalho otimizará o dimensionamento e o cronograma de despacho mensal dos sistemas de trigeração para cada um dos quatro estudos de caso. Em seguida, avaliará o valor presente líquido máximo (VPL) considerando a variação da taxa de desconto e da taxa de conversão do dólar norte-americano. Na sequência, o índice de dependência da rede (GDI), o payback descontado, o custo nivelado da energia (LCOE) e a razão da energia primária (PER) para os melhores VPLs serão apresentados e analisados. Como resultado, esta dissertação mostrará que as plantas de trigeração podem ser lucrativas e certamente ser uma maneira eficiente de utilização de uma geração distribuída confiável e controlável. Além disso, provará que é possível encontrar situações em que a planta de trigeração possa oferecer uma alta taxa de energia primária (PER), um adequado custo de energia nivelado (LCOE) e, ao mesmo tempo, pode proporcionar economia financeira com tempo de retorno razoável em edifícios brasileiros. / The world is trying to move to a cleaner energy environment, especially on the electricity generation sector, which is responsible for a large share of CO2 emissions. In Brazil,crenewable energy sources are responsible for a great part of the electricity generation, but current changes in the Brazilian climate brought a necessity of diversification on the energy matrix. Then, distributed generation is a good way to diversify the Brazilian power matrix. Considering that cogeneration systems are distributed generation, and Brazilian buildings have need of cooling, due to the warm weather, the use of cogeneration equipped with an absorption or adsorption chiller could be beneficial. The trigeneration system is a highly efficient process, which can produce electricity, heating and cooling from the same primary energy source. However, there are really few researches concerning trigeneration systems in Brazil, especially on small and micro plants. Thus, this thesis will make and provide a technical and economical evaluation of small and micro trigeneration systems to different buildings under distinct tariff policies in Brazil. To do so, this work will optimize the sizing and monthly schedule the dispatch of the trigeneration systems to each one of the four study cases. Then, it will evaluate the maximum net present value (NPV) considering the variation of discount rate and US Dollar conversion rate. In the sequence, the grid dependence index (GDI), the discounted payback, the levelized cost of energy (LCOE) and the primary energy ratio (PER) to the best NPVs will be presented and analysed. As a result, this thesis will show that trigeneration plants can be profitable and can be certainly an efficient way to adopt a reliable and controllable distributed generation. Also, it will prove that it is possible to find situations in which the trigeneration plant can offer a high primary energy ratio, a fair levelized cost of energy, and in the meantime, it can provide financial savings with fair payback time in Brazilian buildings.

Un nouveau procédé de trigénération thermo-hydraulique fonctionnant à partir d'énergie thermique basse température (80 à 110 °C) a été étudié pour assurer les différents besoins du secteur résidentiel. Le terme "thermo-hydraulique" se réfère à l'utilisation d'un liquide incompressible qui permet de transférer le travail hydrauliquement entre différents composants ou sous-systèmes, permettant d'améliorer l'efficacité de la chaine de conversion énergétique. Un modèle quasi-statique a été développé pour évaluer les performances énergétiques des différentes variantes du procédé. Ces calculs ont permis de définir parmi un large choix, quels fluides de travail étaient les plus appropriés. Ces calculs ont été complétés par une étude quasi-dynamique et dynamique permettant un meilleur dimensionnement du procédé. Enfin, une étude de fonctionnement annuel a été réalisée à partir du modèle quasi-statique pour évaluer l'évolution des performances ainsi que sa production d'énergie sur une année complète de fonctionnement. Ces études montrent que le couple fluide R1234yf/R1233zd semble le plus approprié à un fonctionnement en climat méditerranéen. L'étude annuelle montre qu'en considérant les données climatiques de la ville de Perpignan, le procédé permet d'amplifier l'énergie solaire collectée d'un facteur de 1,32 en moyenne et permet d'atteindre un COP solaire de 0,24 en mode rafraichissement. Quand les besoins thermiques sont satisfaits, l'intégralité de l'énergie solaire captée est valorisée pour produire de l'électricité avec un rendement moyen annuel de 4,2%. / A new process based on thermal-hydraulic conversion actuated by low-grade thermal energy (80–110 °C) is investigated and aims at providing trigeneration energy features for the residential sector. "Thermo-hydraulic" term refers to a process involving an incompressible fluid used as an intermediate medium to transfer work hydraulically between different thermal operated components or sub-systems allowing to improve the efficiency of the energy conversion chain. A model, assuming steady-state operations, is developed to assess the energy performances of different variants of this thermo-hydraulic process as well as various pairs of working fluids. These calculations were completed by a quasi-dynamic and dynamic models allowing a better sizing of the process. Finally, an annual study was realized from the quasi-static model in order to estimate the evolution of the performances as well as its power production over a complete year of functioning. For instance, in the frame of a single-family home, located in the Mediterranean region, the working fluid pair (R1234yf/R1233zd) is investigated in detail in order to estimate the annual performances. For domestic houses, the process aims at amplifying the solar energy collected by a factor of 1.32 for heating purpose, provides a cold production with a solar COP of 0.24 and generates electricity from the remaining solar energy with an efficiency of 4.2%.

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.