The aim of this diploma work is the study and the modeling of an Organic Rankine Cycle (ORC). Organic Rankine Cycle is used for heat recovery from low-potential heat sources. Their working fluid is a refrigerant or a hydrocarbon whose properties are adapted to the conditions in which the heat recovery is performed. The other chapters include the technical resolution of exhaust-heat exchanger of cogeneration unit for application ORC and partially economic study use in Czech Republic.

Ce travail s'inscrit dans l'effort d'optimiser l'utilisation des ressources énergétiques en valorisant des rejets thermiques industriels à basse température tels que ceux trouvés dans les alumineries québécoises. Deux systèmes de valorisation de chaleur sont détaillés et analysés. Le premier système est constitué de deux échangeurs de chaleur, l'un situé à la source de chaleur et l'autre à la charge, et d'une boucle intermédiaire dans laquelle circule un fluide caloporteur chargé de transférer la chaleur d'un site à l'autre. Le deuxième système est constitué d'un cycle de Rankine organique (ORC), qui produit de l'électricité, et d'une pompe à chaleur (PAC), qui consomme de l'électricité et produit de la chaleur. La question fondamentale à laquelle ce travail essaie de répondre est: Quel est le meilleur système ? Quatre critères ont été utilisés pour répondre à cette question: 1) le rendement énergétique, 2) le rendement exergétique, 3) l'attrait économique et 4) l'impact sur l'environnement. Concernant le rendement énergétique, le système 1 est plus attrayant avec un rendement de 70% contre 21% pour le système 2. Concernant le rendement exergétique, le système 1 est également plus attrayant avec 30% contre 9% pour le système 2. Le système 1 semble légèrement plus intéressant que le système 2 pour l'attrait économique avec un coût d'investissement plus faible se traduisant pour un taux de rendement interne (TRI) sur 15 ans de 10.9% contre 7.5%. L'analyse économique est toutefois sensible aux hypothèses émises, qui peuvent varier grandement d'un site à l'autre. L'analyse du cycle de vie démontre de manière non équivoque que le système 1 est plus dommageable pour l'environnement, notamment en raison de la quantité de béton nécessaire à sa construction. Ce travail contient deux articles de conférence et un article de journal (soumis, mais non accepté à la date de dépôt de ce mémoire). L'analyse à l'aide de nombres sans dimension du système 1 permet d'identifier les variables non-dimensionnelles qui ont le plus d'influence sur les indices de performance de ce système. La méthode des moindres carrés est utilisée pour développer des corrélations entre chacun des indicateurs de performance et les variables non-dimensionnelles, et l'application de ces corrélations pour la conception d'un tel système est démontrée par un exemple qui utilise un algorithme génétique qui détermine les conditions maximisant l'efficacité exergétique.

[pt] Esta simulação considera um ciclo Rankine que utiliza um fluido de trabalho orgânico, com a particularidade que a fonte de energia de entrada ao sistema será solar. Esta energia renovável que provem do potencial do Sol é aproveitada com a utilização de coletores concentradores lineares parabólicos. Estes dois circuitos: do ciclo Rankine orgânico e do conjunto de coletores interatuam termicamente mediante um trocador de calor chamado de gerador de vapor. Adicionalmente, existe um sistema de armazenamento térmico que permite acumular parte da energia solar coletada para ser utilizada em períodos sem radiação solar ou com níveis baixos da mesma. A primeira parte deste trabalho mostra os aspectos teóricos introdutórios e as considerações para trabalhar com um ciclo Rankine de tipo orgânico, o tipo de coletores escolhido e a utilização de armazenamento térmico. O segundo capítulo mostra o modelo matemático apropriado para simular um sistema de geração de potência de baixa capacidade (50 kW) e os componentes de cada circuito: ciclo (bomba, expansor, condensador, recuperador, gerador de vapor), coletores (cobertura, refletor, absorvedor, etc.) e armazenamento (tanques, etc.). A simulação foi desenvolvida no software EES. O terceiro analisa os parâmetros do modelo, seus possíveis valores físicos, a sensibilidade da sua variação e sua seleção adequada com o objetivo de efetuar uma simulação bastante similar à realidade e as incertezas presentes. No capítulo final se apresentam os resultados em base as condições de desenho consideradas. / [en] This simulation considers a Rankine cycle that works with an organic fluid, but has the particularity of using solar power as the font of input energy. This renewable energy that comes from the sun’s potential is taken with the use of parabolic trough collectors. These two circuits: that of the organic Rankine cycle (ORC) and the other of collector’s ensemble interact termically in a heat exchanger called as vapor generator. Adicionally there’s a thermal storage system that allows accumulating part of the collected solar energy to be used for periods of time when there’s no solar radiation or with very low levels of it. The first part of this work shows the introductory theoretical aspects and the considerations to work with an organic Rankine cycle (ORC), the type of chosen collector and the use of heat storage. The second chapter shows the appropriate mathematic model to simulate a system of power generation of low capacity (50 kW) and the components of each circuit: ORC (pump, expander, condenser, recuperator, vapor generator), collectors (glass cover, reflector mirror, absorber tube, etc.) and thermal storage (storage tanks, etc.). The simulation was developed using EES software. The third chapter analyzes the parameters of the model, specially its values and possible variations to approach the simulation to the reality. In the final chapter, some results are presented based on some considered design conditions.

This thesis presents an accurate study about the fluid-dynamics of dense gases and their potential application as working fluids in Organic Rankine Cycles (ORCs). The ORCs are similar to a steam Rankine Cycle where an organic fluid is used instead of steam, which ensures better efficiency for low-temperature sources. Specific interest is developed into a particular class of dense gases, the Bethe-Zel'dovich-Thompson (BZT) fluids, which exhibit negative values of the Fundamental Derivative of Gasdynamics G in the vapor phase , for a range of temperatures and pressures of the order of magnitude of those of the liquid/vapor critical point, just above the upper coexistence curve. Transonic and supersonic flows in a region of negative G are characterized by nonclassical gasdynamic behaviors, such as the disintegration of compression shocks. Owing to this effect, the use of BZT gases as working fluids in ORCs is particularly attractive, since it may reduce losses due to wave drag and shock/boundary layer interactions. This advantage can be further improved by a proper design of the turbine blade. The present work is devoted to improve the understanding of the peculiar fluid-dynamic behavior of dense gases with respect perfect ones and to the research of suitable aerodynamic shapes. To this purpose, a dense-gas Navier-Stokes (NS) numerical solver is coupled with a multi-objective genetic algorithm. The Navier-Stokes solver employs equations of state of high accuracy within the thermodynamic region of interest and suitable thermophysical models for the fluid viscosity and thermal conductivity. Different computations are performed for transonic flows over isolated airfoils and through turbine cascades to evaluate the influence of the upstream kinematic and thermodynamic conditions on the flow patterns and the system efficiency, and possible advantages deriving from the use of a non-conventional working fluid are pointed out. Then, high performance airfoils and turbine blade shapes for transonic flows of BZT fluids are constructed using the CFD solver coupled with a multi-objective genetic algorithm. Shape optimization allows to strongly increase flow critical Mach Number, delaying the appearance of shock waves, while ensuring high lift (for an airfoil) and efficiency. A careful analysis of the convergence behavior of Genetic Algorithms has also been undertaken by means of statistical tools. Genetic Algorithm exhibit a marked sensitivity to the shape of the response surface and to its numerical representation. Some strategies are proposed to systematically evaluate GAs convergence capabilities for a given problem and to enhance their convergence properties for dense gas optimization problems.

Les services Web sont des applications logicielles avec des implémentations hétérogènes, dont les interfaces et les incarnations peuvent être définis, décrits et découverts sur un réseau. Une orchestration de tels services Web fournit un flux de contrôle centralisé pour les services composites, qui peuvent invoquer d'autres services en utilisant une série de constructions (séquentielle, parallèle, avec des timeouts par exemple). L'objectif de cette thèse est d'étudier l'effet des paramètres de Qualité de Service (QoS) dans la performance et les obligations contractuelles de ces orchestrations. Tout d'abord, nous générons un modèle précis pour étudier la QoS probabiliste multi-dimensionnelle dans les services Web. Lorsque la dépendance des données est présente dans les orchestrations, les conditions pour assurer la monotonie sont nécessaires et sont intégrées. Nous présentons une algèbre riche pouvant gérer plusieurs dimensions de la QoS et fournir une composition de contrat probabiliste. Une conséquence de cela est l'entrelacement des paramètres de QoS en spécifications fonctionnelles des orchestrations, qui peut fournir d'autres fonctionnalités intéressantes comme l'ordonnancement causal d'un flux de contrôle d'orchestration. Ensuite, nous étudions les effets de ces modèles de QoS sur la gestion améliorée des SLAs (Service Level Agreement). Les applications de cette architecture de gestion de la QoS sont diverses et comprennent la prise en compte de la variabilité au sein de la gamme de produits, des progiciels mathématiques pour la prise de décision, des techniques de simulation avancées pour quantifier les contrats et des protocoles de négociation améliorés. Certaines de ces techniques sont implémentées au dessus d'Orc, un langage de programmation concurrente ayant des constructions pour gérer plusieurs aspects de spécifications d'orchestration.

In this thesis, an experimental research is conducted on scroll-based Organic Rankine Cycle (ORC) focusing on the expansion process. An important feature of the ORC is the ability to utilize low or moderate temperature heat sources derived from renewable energy such as concentrated solar radiation, biomass/biofuels combustion streams, geothermal heat and waste heat recovery. The ORC is more appropriate than steam Rankine cycle to generate power from low capacity heat sources (5-500 kW thermal). For example, expansion of superheated steam from 280oC/1000 kPa to a pressure corresponding to 35oC saturation requires a volume ratio as high as 86, whereas for the same operating conditions toluene shows an expansion ratio of 6 which can be achieved in a single stage turbine or expander. The objective of this work is to experimentally study the performance of a selected refrigeration scroll compressor operating in reverse as expander in an ORC. To this purpose, three experimental systems are designed, built and used for conducting a comprehensive experimental programme aimed at determining the features of the expansion process. In preliminary tests the working fluid utilized is dry air while the main experiments are done with the organic fluid R134a. Experimental data of the scroll expander are collected under different operating conditions. Power generation in various conditions is analyzed in order to determine the optimum performance parameters for the scroll expander. In addition, thermodynamic analysis of the system is conducted through energy and exergy efficiencies to study the system performance. Based on the experimental measurements, the optimum parameters for an ORC cycle operating with the Bitzer-based expander-generator unit are determined. The cycle energy and exergy efficiencies are found 5% and 30% respectively from a heat source of 120oC. / UOIT

The growth in renewable electricity generation is forecast to continue as fossil fuel levels decrease and carbon dioxide emissions are penalized. The growth in geothermal is becoming constrained as conventional high-temperature sources are fully exploited. Geothermal can be a cost competitive base load power source. Governments and utilities are looking at the potential of electricity generation from low temperature geothermal resources for future development. This technology, unlike the high and medium temperature, is not mature and there are a number of companies looking at entering the Organic Rankine Cycle (ORC) market. This thesis aims to provide a necessary step for reliable commercial develop this technology by developing the first draft of a low temperature geothermal ORC standard. The standard outlines the critical stages of a geothermal ORC project as the Prospecting stage; Pre-Feasibility stage, Feasibility stage, and the Detailed Design stage. The standard is unlike other standards that are used to design one component; this standard guides the engineers though the various critical steps of the ORC design to correctly assess the geothermal resource and to inform design and investment decisions. The standard provides particular guidance on critical factors in ORC design, primarily the working fluid selection and component selection limitations. Experienced industry engineers have provided advice and insight regarding the critical design points and processes. The draft standard was reviewed by a number of geothermal industry engineers who have worked with large scale, conventional ORCs. They each commented on the standard from their prospective in the industry and gave general feedback was that it is a technically relevant standard that can be used as a potential start point to develop a new standard for the low temperature binary ORC industry. The final draft standard has been submitted to the ISO for consideration. This thesis first sets out the general background on the state of the art and the industry for lowtemperature binary ORC power plants, and provides the review assessment of the standard draft. However, the bulk of the thesis is the standard itself. The standard represents a substantial contribution to the mechanical and thermal systems engineering field.

The Organic Rankine Cycle (ORC) may be the superior cycle for power generation using low temperature and low power heat sources due to the utilization of high molecular mass fluids with low boiling points. They are flexible, simple, easy to operate and maintain, and offer many possible areas of applications including waste heat recovery and power generation from biomass, geothermal and even solar energy. Therefore, they may prove to be of significant importance in reducing global greenhouse gas emission and in the mitigation of climate change. In this thesis the technical feasibility and economic profitability of implementing an ORC in a district heating boiler station is investigated. A model of ORC connected to the hot water circuit of one of the biomass boilers of the boiler station is simulated. The achieved evaporation temperature is estimated to 135 degrees C and the condensation temperature is found to vary in the range of about 70-100 degrees C. The results show that it is both possible and profitable to implement an ORC in the studied boiler station. A maximum net present value of 2.3 MSEK is achieved for a 400 kW system and a maximum internal rate of return of 8.5%, equivalent to a payback period of 9.5 years, is achieved for a 300 kW system. Furthermore, the investment is found to be most sensitive to changes in the electricity price, net electric efficiency and capital expenditure cost.

With growing awareness and necessity for the world to move towards more sustainable (energy saving) forms of power generation, focus on the commercial use of Organic Rankine Cycle (ORC) turbine systems has subsequently increased in turn. ORC systems with their modular design can thus help in recovering heat, obtained as a byproduct from a variety of industrial processes, and thereby increase their overall system efficiency. As with conventional turbine systems, methods to improve their performance is an avenue that is still being actively researched on today. The various sources of losses in a turbine have thus been looked into, while prioritizing the literature study to factors that result in losses associated with the leakage flow over the blade tip. The purpose of this study is to develop a working methodology to investigate factors that affect the tip leakage loss in a small scale ORC turbine. The model and associated data used for comparison is based on an existing system, whose design has been provided by Againity AB, with the subsequent simulations carried out using Ansys CFX.

In this dissertation, different configurations of solar powered organic Rankine cycles (ORC) are investigated. The configurations include: a basic ORC, a regenerative ORC (R-ORC), and a basic ORC with electric energy storage (EES) (ORC-EES). The basic ORC and the R-ORC are evaluated using different dry organic fluids based on the first and second laws of thermodynamics and electricity production. The performance of both ORC systems is based on the potential for primary energy consumption (PEC) and carbon dioxide emission (CDE) savings, the electricity production, and the available capital cost (ACC) for the system. The R-ORC and basic ORC are both evaluated in Jackson, MS and Tucson, AZ to determine the effect of hourly solar irradiation and ambient temperature on both systems. For the basic ORC a parametric analysis is performed to determine the effects of cycle pressure, temperature, solar collector area, and turbine efficiency on the system performance. Similarly, for the R-ORC, a parametric analysis investigating the effect of open feed organic fluid heater intermediate pressure and turbine efficiency on the R-ORC is performed. Finally an ORC connected to an EES device located in Tucson, AZ is studied. The ORC-EES supplies electricity to three different commercial buildings. The ORC-EES is modeled to be charging when irradiation is available and discharging when there is not enough irradiation to generate electricity from the ORC. The performance of the system is based on the amount of electricity supplied, the potential for PEC, CDE, and cost savings, and the ACC. The effect of solar collector area on the percentage of supplied electricity, EES device size, and cost savings is also studied. It was determined that all the evaluated ORC configurations have the potential to produce PEC, CDE, and cost savings, but their performance is affected by the organic working fluid, solar collector area, and the location where the system is installed.