The use of biomass-based combined heat and power (CHP) plants is considered by the EU administration to be an effective way to increase the use of renewables in the energy system, to reduce greenhouse gas emissions and to alleviate the dependency on imported fossil fuels. At present in Sweden, most of the CHP plants are operated in part-load mode because of variations in heat demand. Further use of the potential heat capacity from CHP plants is an opportunity for integration with other heat-demanding processes. Retrofitting the conventional CHP plants by integration with bioethanol and pellet production processes is considered a feasible and efficient way to improve the plants’ performances.   Modeling and simulation of the CHP plant integrated with feedstock upgrading, bioethanol production and pellet production is performed to analyze the technical and economic feasibility. When integrating with bioethanol production, the exhaust flue gas from the CHP plant is used to dry the hydrolysis solid residues (HSR) instead of direct condensation in the flue gas condenser (FGC). This drying process not only increases the overall energy efficiency (OEE) of the CHP plant but also increases the power output relative to the system using only a FGC. Furthermore, if steam is extracted from the turbine of the CHP plant and if it is used to dry the HSR together with the exhaust flue gas, pellets can be produced and the bioethanol production costs can be reduced by 30% compared with ethanol cogeneration plants.   Three optional pellet production processes integrated with an existing biomass-based CHP plant using different raw materials are studied to determine their annual performance. The option of pellet production integrated with the existing CHP plant using exhaust flue gas and superheated steam for drying allows for a low specific pellet production cost, short payback time and significant CO2 reduction. A common advantage of the three options is a dramatic increase in the total annual power production and a significant CO2 reduction, in spite of a decrease in power efficiency.   The retrofitted biomass-based CHP plants play a crucial role in the present and future regional energy system. The total costs are minimized for the studied energy system by using wastes as energy sources. Analyses of scenarios for the coming decades are performed to describe how to achieve a regional fossil fuel-free energy system. It is possible to achieve the target by upgrading and retrofitting the present energy plants and constructing new ones. The conditions and obstacles have also been presented and discussed through optimizing the locations for proposed new energy plants and planting energy crops. / REMOWE, CSC

The use of renewable energy such as water and wind to produce electricity has been proven extremely effective in Sweden. The ability of these renewable resources to produce clean output energy counters the adversities caused by non-renewable resources. The use of hydraulic turbines is a good example of favoured technique for energy and power production using renewable resources. The hydro-turbines are designed to operate at best efficiency point (BEP). Varying energy demands in recent years implies on the need of flexible operation of hydraulic turbines. The issue of pressure pulsations in the draft tube of hydro-turbines, observed at lower operating conditions has been unresolved for many years. These pressure pulsations are related to the ‘rotating vortex rope’ (RVR) observed at part load operation and, affects the lifespan and performance of the hydro-turbine adversely. Several techniques have been investigated in the past to reduce the pressure pulsations in the draft tube at part load operation and enhance the flexibility of the turbine. During the present research study, a passive flow control technique was investigated numerically by implementing a guide vane system in the draft tube of the Francis-99model turbine. Guide vanes are mechanical devices that can direct the flow in a desired direction. The current study presents the possibility of reducing the pressure pulsations in the draft tube by mitigating the RVR using a guide vane system in the draft tube. At the initial stages of the research study, a reduced numerical model of the Francis model turbine was developed by only considering the draft tube domain. The motive was to develop a reduced model to perform the parametric analysis for the guide vane system in the draft tube with reduced computational time, power, and storage. The results obtained from the numerical study were found to be in good agreement with theFrancis-99 semi-model with passage domains. A parametric study was performed to achieve a guide vane system design that could mitigate RVR with minimum losses. During this study, the number of guide vanes, the chord and the span of the guide vanes were investigated. It was found that a set of three guide vane system with chord of 86% of runner radius and leading-edge span of 30% of runner radius is an ideal design that mitigates RVR above 95%.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2017-02-08T12:58:24Z No. of bitstreams: 1 Ademilson dos Santos Xavier_.pdf: 9916385 bytes, checksum: 8bcbfe8f2b36b5a58781ce2518c1bb83 (MD5) / Made available in DSpace on 2017-02-08T12:58:24Z (GMT). No. of bitstreams: 1 Ademilson dos Santos Xavier_.pdf: 9916385 bytes, checksum: 8bcbfe8f2b36b5a58781ce2518c1bb83 (MD5) Previous issue date: 2016-10-13 / Nenhuma / Estudos recentes mostraram que uma grande parte da energia elétrica consumida no Brasil destina-se a edificações do setor Comercial e Público. Observando-se que o sistema de HVAC (Heating, Ventilation, and Air Conditioning) apresenta relevante papel no quadro final do consumo energético em edificações, a determinação de seus requisitos mínimos de eficiência energética torna-se o fator chave para o sucesso de qualquer programa de certificação energética em construções. Esse trabalho tem como objetivo avaliar de que forma as condições climatológicas brasileiras podem influenciar o desempenho de um sistema condicionador de ar com tecnologia VRF (Variable Refrigerant Flow) em Condições de Carga Parcial (Part Load Conditions), para uma edificação comercial. Para isso, foi desenvolvida uma metodologia capaz de identificar as localidades que foram objetos desse estudo. As cidades selecionadas foram: São Paulo (SP), Rio de Janeiro (RJ), Fortaleza (CE) e Brasília (DF). Após esta etapa, a caracterização do edifício modelo de referência (hotel) foi concretizada. Características físicas, valores de carga térmica externa e interna, e o perfil de uso (taxa de ocupação) da edificação, foram tópicos abordados. O software de simulação utilizado foi o EnergyPlus e as suas respectivas curvas e equações de desempenho foram ajustadas com base nos dados de performance dos aparelhos condicionadores de ar que foram selecionados. O fabricante Toshiba foi escolhido. A performance dos equipamentos VRF foi analisada através de resultados como Carga Térmica global, Condição de Carga Plena, Condições de Carga Parcial, PLR (Part Load Ratio), COP (Coefficient of Performance) e ICOP (Coeficiente Integrado de Performance). Os resultados mostraram que apesar da Condição de Carga Plena (Full Load Condition) ser recomendada para dimensionar o sistema de HVAC, quando o objetivo principal for avaliar o desempenho energético desse sistema (HVAC) para um período mais longo de operação essa análise deve ser realizada através das Condições de Carga Parcial (Part Load Conditions). Para as quatro localidades estudadas os valores de desempenho obtidos através das simulações mostram que os equipamentos de ar condicionado VRF utilizados atingiram o seu coeficiente máximo de performance (COPmáx) na condição de 50% de PLR e um ICOP de 6,8, contra um COP de 3,4 na condição nominal e um ICOP de 3,7 de acordo com o Regulamento Técnico da Qualidade do Nível de Eficiência Energética de Edifícios Comerciais, de Serviço e Públicos, RTQ-C. / Currently studies have been shown that a large part of the electricity consumed in Brazil is intended to buildings Commercial and Public Sector. The HVAC system (Heating, Ventilation, and Air Conditioning) shows a significant role in the final frame of the energy consumption in buildings, determining its minimum requirements for energy efficiency becomes the key factor for the success of any program energy certification of buildings. This work aims to analyze how the Brazilian climatic conditions can influence the performance of air conditioner systems with VRF technology (Variable Refrigerant Flow) in the Part-Load Condition for a commercial building. Therefore a methodology was developed to identify the locations that were the subject of this study. The cities selected are: São Paulo (SP), Rio de Janeiro (RJ), Fortaleza (CE) and Brasília (DF). In addition the building characteristics have completed, external and internal thermal load values with their use profile have been analyzed. The software applied was EnergyPlus and their performance curves and equations have been adjusted according with the performance data of air conditioning units selected. The manufacturer Toshiba has been chosen. The VRF equipment performance was analyzed through results as Full-Load Condition, Part-Load Conditions, Part Load Ratio (PLR), COP and COP (Integrated Coefficient of Performance). The main results have showed that despite the Full-Load Condition is recommended to dimension the HVAC system, when the objective is the evaluation of the energy performance for a longer operation period this analysis should be carried out through Part-Load Conditions. For all of the four cities have studied the performance values obtained from the simulations show that the air-conditioning equipment VRF used reached their maximum performance coefficient (COPmáx) at 50% of PLR and ICOP 6.8, against a COP 3.4 in nominal condition and ICOP of 3.72 according to the Quality Technical Regulation of the Energy Efficiency Level Commercial Buildings, and Public Service, RTQ-C.

Actuellement, la flexibilité et le stockage de l'énergie sont parmi les principaux défis de l'industrie de l'énergie. Les stations de transfert d'énergie par pompage (STEP), en utilisant des turbines-pompes réversibles, comptent parmi les solutions les plus rentables pour répondre à ces besoins. Pour assurer un réglage rapide du réseau électrique, les turbines-pompes sont sujettes à de rapides changements entre modes pompage et turbinage. Elles sont souvent exposées à un fonctionnement prolongé dans des conditions hors nominal. Pour assurer la stabilité du réseau, la zone d'exploitation continue de turbines-pompes réversibles doit être libre de toute instabilité hydraulique. Deux sources principales d'instabilités en mode pompage peuvent limiter la plage de fonctionnement continu. Il s'agit de la présence de cavitation et de décollement tournant, tous deux survenant à charge partielle. La cavitation peut conduire à des vibrations, des pertes de performance et parfois même à l'érosion de la turbine-pompe. En outre, en raison de décollements tournants (apparition et décomposition périodique de zones de recirculation dans les régions du distributeur), la machine peut être exposée à un changement incontrôlable entre les points de fonctionnement, avec une modification de charge et une baisse significative des performances. Les deux phénomènes sont très complexes, tri-dimensionnels et délicats à étudier. Surtout le phénomène de décollement tournant dans les turbines-pompes est peu abordé dans la littérature. Le premier objectif de l'étude du doctorat présenté a été d'utiliser un code numérique, testé au laboratoire, et de développer une méthodologie de calcul pour permettre la prévision des phénomènes à charge partielle. L'étude a été faite sur une géométrie à échelle réduite d'une turbine-pompe de haute chute. Des calculs numériques ont été effectués en utilisant le code FINE/Turbo avec le modèle de cavitation barotrope qui a été développé au laboratoire. L'analyse des écoulements cavitants a été faite pour des débits et de niveaux de cavitation différents. Les principales analyses portent sur des valeurs naissantes de cavitation, des courbes de chute et sur le prédiction des formes de cavitation pour différents débits et valeurs de NPSH. Une attention particulière a été portée sur l'interaction entre les formes de cavitation à l'entrée de la roue et la baisse de performance (zone de feston), causée par le décollement tournant qui apparaît dans la région du distributeur. Les résultats numériques ont montré un bon accord avec les données expérimentales disponibles. La deuxième partie de la thèse a concerné la prédiction et l'analyse de décollements tournants. Des simulations ont été utilisées pour prédire les régions d'exploitation stables et instables de la machine. La méthodologie mentionnée pourrait fournir des résultats globaux précis pour différents points de fonctionnement avec un faible coût de calcul. Afin d'obtenir des informations détaillées sur les écoulements instables, des simulations instationnaires plus précises ont été réalisées. L'analyse locale des écoulements a permis la description des mécanismes gouvernant le phénomène de décollement tournant. Les analyses permettent l'étude du nombre, de l'intensité et des fréquences de rotation des cellules tournants. En outre, les calculs instationnaires donnent une très bonne prédiction de la performance de la turbine-pompe. L'approche proposée est fiable, robuste et précise. La méthodologie de calcul proposée peut être utilisée sur plusieurs géométries de turbine-pompe (ou pompe centrifuge), pour une large gamme de débits et de géométries de directrices. Les simulations proposées peuvent être utilisées à l'échelle industrielle pour étudier les effets de géométrie, d'angles d'ouverture de directrices ou de l'influence du jeu entre la roue et le distributeur afin de réduire ou même éliminer les effets négatifs des décollements tournants. / Flexibility and energy storage seem to be the main challenges of the energy industry at the present time. Pumped Storage Power Plants (PSP), using reversible pump-turbines, are among the most cost-efficient solutions to answer these needs. To provide a rapid adjustment to the electrical grid, pump-turbines are subjects of quick switching between pumping and generating modes and to extended operation under off-design conditions. To maintain the stability of the grid, the continuous operating area of reversible pump-turbines must be free of hydraulic instabilities. Two main sources of pumping mode instabilities are the presence of the cavitation and the rotating stall, both occurring at the part load. Presence of cavitation can lead into vibrations, loss of performance and sometimes erosion. Moreover, due to rotating stall that can be observed as periodic occurrence and decay of recirculation zones in the distributor regions, the machine can be exposed to uncontrollable shift between the operating points with the significant discharge modification and the drop of the efficiency. Both phenomena are very complex, three-dimensional and demanding for the investigation. Especially rotating stall in the pump-turbines is poorly addressed in the literature. First objective of the presented PhD study has been to develop the cost-efficient numerical methodology in order to enable the accurate prediction and analysis of the off-design part load phenomena. The investigations have been made on the reduce-scaled high head pump-turbine design (nq = 27rpm) provided by Alstom Hydro. Steady and unsteady numerical calculations have been performed using code FINE/Turbo with barotropic cavitation model implemented and developed before in the laboratory. Some of the numerical results have been compared to the experimental data. Cavitating flow analysis has been made for various flow rates and wide range of cavitation levels. Flow investigation has been focused on the cavitation influence on the flow behavior and on the performance of the machine. Main analyses include incipient cavitation values, head drop curves and cavitation forms prediction for wide ranges of flow rates and NPSH values. Special attention has been put on the interaction between cavitation forms and the performance drop (hump zone) caused by the rotating stall. Cavitation results showed good agreement with the provided experimental data. Second part of the thesis has been focused on the prediction and analysis of the rotating stall flow patterns. Computationally fast steady simulations has been presented and used to predict stable and unstable operating regions. The analyses have been done on 4 different guide vanes openings and 2 guide vanes geometries. In order to get detailed information about the unsteady flow patterns related to the rotating stall, more exact unsteady simulations have been performed. Local flow study has been done to describe in details the governing mechanisms of the rotating stall. The analyses enable the investigations of the rotating stall frequencies, number of stalled cells and the intensity of the rotating stall. Moreover, the unsteady calculations give very good prediction of the pump-turbine performance for both, stable and unstable operating regions. Numerical results give very good qualitative and quantitative agreement with the available experimental data. The approach appears to be very reliable, robust and precise. Even though the numerical results (rotating stall frequencies, number of cells...) on the actual geometry should be confirmed experimentally, author believes that the methodology could be used on any other pump-turbine (or centrifugal pump) geometry. Moreover, the simulations can be used industrially to study the effects of the guide vanes geometries, guide vanes opening angles and influence of the gap between the impeller and the distributor in order to reduce or even eliminate the negative effects of the rotating stall.

La réduction des besoins dans les bâtiments à basse consommation d'énergie (BBC) nécessite un réexamen de l'approche de modélisation des systèmes énergétiques dans les outils de simulation. L'approche proposée repose sur une modélisation plus fine des phénomènes physiques incluant la régulation en boucle fermée du système énergétique couplé au bâtiment. A partir de l'identification des phénomènes propres au comportement énergétique des BBC, des recommandations, ou règles de modélisation, sont établies pour le développement des modèles de leurs systèmes énergétiques. Ces recommandations sont mises en application dans deux études. Tout d'abord, une simulation dynamique d'un bâtiment et de son système conduit à un dimensionnement plus adapté comparé aux méthodes classiques dans le cas de BBC avec des répercussions sur les appels de puissance et la consommation d'énergie. Ensuite, une analyse de sensibilité par la méthode de Morris sur une représentation générique du système énergétique a permis d'identifier les paramètres nécessitant d'être connus avec précision. La différence entre l'approche développée et la simulation horaire avec régulation idéale n'est que de quelques pourcents en besoins énergétiques pour un bâtiment existant mais elle passe à plus de 20% dans un bâtiment BBC. Un écart du même ordre de grandeur peut être identifié pour la détermination de la performance énergétique globale du système par une prise en compte plus détaillée des phénomènes de cyclage, de charge partielle ou de consommation des auxiliaires. / The decrease of heat demands in low energy buildings requires to examine again modeling approaches in building energy simulation tools. The developed approach is based on a more accurate modeling of physical phenomena including the closed loop control between the HVAC system and the building. From the identification of the phenomena that specifically impact the energy behavior of the low energy buildings, some recommendation, or modeling rule, are established for the development of their HVAC systems. Those recommendations are applied in two case studies. Firstly, a dynamic simulation of a building and its system offers a better evaluation of the design power for a low energy building, affecting power demands and energy consumption. Then, a sensitivity analysis from Morris method on a generic representation of the HVAC system identifies the parameters to be accurately known. The difference between the developed approach and an hourly simulation with an ideal control is low for the evaluation of the heat load in an existing building but it is more than 20% in a low energy buildings. A difference of the same order of magnitude can be identified in the determination of the overall energy performance of the system by a more detailed consideration of the phenomena of cycling, the part load or the consumption of auxiliaries.