La création du groupe C40 Cities Climate Leadership (C40) en 2005 illustre bien le fait que l'échelle urbaine est dorénavant considérée comme comportant des leviers d'action importants afin d'atténuer les émissions de CO2. Il n'y a cependant toujours pas adéquation entre cette prise de conscience et le nombre d'outils de modélisation capables de quantifier cette marge de manœuvre de manière spatialement explicite et intégrée. Cette thèse vise à combler cette lacune. L'objet produit consiste en un modèle d'équilibre général spatialisé et multi-échelle, pensé de sorte à être relié à toute architecture de modélisation préexistante. Cette thèse s'articule autour de trois chapitres, i.e. la présentation du modèle, sa calibration et son application à la France et aux USA.Dans le premier chapitre, nous décrivons le modèle, baptisé GEMSE, dont l'objectif est d'étudier les interactions entre les dimensions agrégées et locales de l'activité économique tout en quantifiant les émissions de GES associées à la mobilité. Le modèle s'appuie sur l'Economie Urbaine et la Nouvelle Economie Géographique en vue de modéliser sur plusieurs échelles spatiales le développement économique de régions urbanisées en interaction.Dans le deuxième chapitre, nous décrivons les données et calibrons le modèle en utilisant, pour certains paramètres, des techniques d'économétrie spatiale. Nous proposons notamment une méthode pour spécifier la matrice de poids spatial, laquelle méthode est opérationnalisée en utilisant un outil numérique développé à ces fins, PyOKNN, indépendant de GEMSE. Appliqué au Grand Paris, l'outil identifie de façon tangible des éléments clés de sa structure spatiale, et génère pour les paramètres étudiés des valeurs similaires à celles de la littérature.Dans le troisième chapitre, nous appliquons le modèle à la France et aux Etats-Unis. Nous y analysons le scénario de référence, puis les impacts de deux politiques de transport. La première mesure – la baisse des limitation de vitesse des véhicules privés – stimule l'activité économique de manière pro-environnementale en réduisant le PIB dans un premier temps, mais en lui permettant ensuite d'atteindre des niveaux plus élevés, aboutissant à un jeu à somme positive. L'autre mesure simule la mise en place d'une taxe CO2 pour les véhicules privés dont les recettes servent à financer l'augmentation des vitesses des transports publics. Il en résulte qu'un prix de 100€ par tonne de CO2eq n'a qu'un faible effet incitatif car ne représente presque rien par kilomètre-voyageur. Ces deux mesures, le changement de norme ou le recyclage de la taxe, poussent à l'utilisation de modes de transport moins couteux et moins polluants qui stimule une croissance à plus faible intensité carbone.Dans l'ensemble, ces conclusions plaident en faveur de politiques qui internalisent les effets distorsifs, e.g. les changements dans les habitudes de mobilité, la réorientation des demandes, les déséquilibres du marché du travail via les délocalisations des personnes et des changements induits en matière d'économies d'échelle externes. Les résultats ne sont dans leur ampleur que peu généralisables dans l'espace et montrent la nécessité de considérer les spécificités locales et le cadre dans lequel elles s'insèrent en terme d'interactions / The creation of the C40 Cities Climate Leadership group (C40) in 2005 is a noteworthy example that the urban scale is considered as a major leeway to mitigate CO2 emissions. Nevertheless, the adequacy between this recent awareness and the number of modeling tools capable of quantifying this leeway in a spatially explicit integrated way is still missing. This thesis aims at bridging this gap. The outcome consists of a model that incorporates general equilibrium theory with an explicit representation of space at multiple scales. The model is designed as an autonomous numerical entity connectable to any pre-existing modeling architecture. This thesis hinges around three chapters, i.e. the presentation of the model, the calibration of the model and its application to France and the USA.In the first chapter, we describe our so-called GEMSE model whose aim is to investigate the interplays between aggregate and local dimensions of economic activity while quantifying GHG emissions associated to mobility. The model is based on Urban Economics and the New Economic Geography to model on multiple spatial scales the economic development of urban areas in interaction.In the second chapter, we describe the data and calibrate the model by using, for some parameters, spatial econometric techniques. Notably, we propose a new method to specify the spatial weight matrix, operationalized by using a numerical tool developed on purpose, namely PyOKNN, independent of GEMSE. Applied to Greater Paris, the tool identifies in a tangible way some key elements of its spatial structure, and yields values for the parameters under study that are similar to those of the literature.In the third chapter, we run simulations of our model for both France and the USA. We analyze the baseline case and the impacts of two transport policies on several relevant dimensions for the long-term development of urban areas. The first measure – the decrease in private vehicle speed limitation – stimulates economic activity in a pro-environmental fashion by contracting GDP in a first phase but then allowing it to reach higher levels, resulting in a positive sum game. The second measure is the implementation of a CO2 tax to private vehicles whose collected revenues are used to finance an increase in public transport speeds. The main policy insight is that setting a price of 100€ per tonne of CO2eq represents virtually nothing once converted per commuter-kilometer and deters only marginally the use of cars. These two measures, the change in speed limitation or the recycling of the tax, encourage the use of cheaper and less polluting modes of transport, which induces a low-carbon growth.Overall, these conclusions call for policy designs that internalize distortive effects, e.g. changes in mobility habits, the reorientation of demands, unbalances in labor markets via people’s relocations and firms’ improvements in terms of economies of scale. The results can rarely be generalized in terms of magnitude from one region to another, which shows the necessity to consider local specificities as well as the framework within which they interact

Este trabalho tem como objetivo analisar estratégias de iluminação natural utilizadas nos estágios iniciais do projeto de arquitetura capazes de aumentar a qualidade da iluminação e a conservação de energia nos edifícios escolares. Essas estratégias têm sido aplicadas com sucesso em edifícios escolares em vários países, melhorando o desempenho e o bem-estar dos estudantes e conservando energia. Entre essas estratégias, o autor selecionou um dispositivo zenital para iluminação natural com seleção angular e difusores opacos, realizou um ensaio experimental em um modelo físico reduzido de uma sala de aula padrão, sob condições de céu real e analisou comparativamente os resultados. O estudo mostrou que a adoção de uma metodologia para utilizar estratégias como a analisada neste trabalho pode conseguir um adequado controle da radiação solar para evitar a incidência direta da luz do Sol, evitar o ofuscamento e o aquecimento excessivo de ambientes de salas de aula em climas quentes e, ao mesmo tempo, aproveitar a iluminação natural, tanto difusa quanto direta refletida, para obter maior conforto visual e economizar energia. / This work aims to analyse daylighting strategies applied in early stages of architectural design as to improve lighting quality and energy savings in school buildings. Similar strategies have already been successfully applied in many countries around the world, enhancing student?s performance and well being while helping to save energy. Among the strategies studied, the author describes an experiment under real sky conditions using a physical scale model of a standard classroom equipped with a roof monitor combined with an overhang and interior vertical diffusing baffles as a way to check its influence in interior lighting conditions. The experiment has shown that the use of daylighting strategies can promote an adequate control of solar radiation, avoiding direct sunlight penetration inside the classrooms, limiting glare problems and excessive heat of hot climates. At the same time, such strategies optimise both direct and defuse use of daylight to improve visual comfort and energy savings.

A economia mundial é fortemente dependente da disponibilidade de óleo, no entanto as reservas de óleo leve, mais atrativas ao mercado, tendem nos próximos anos ao esgotamento, trazendo à luz as reservas de óleo pesado para atender as demandas do mercado. No entanto, os processos associados ao transporte e processamento desses óleos viscosos consomem muita energia, impondo um grande desafio para a indústria do petróleo. Nesse contexto, se transportar óleos viscosos com água através de um escoamento bifásico em padrão Core Annular Flow (CAF) é muito promissor. Nessa prática, uma película anular de água envolve o núcleo que contém o óleo, minimizando o contato entre este e a parede do duto e reduzindo as perdas de energia por atrito. Visou o presente estudo mapear os padrões de escoamento de óleo pesado com água em dutos horizontais e verticais, mensurar os fatores de redução de potência e do diferencial de pressão associados à um trecho reto e à uma válvula de gaveta aberta e determinar o holdup para avaliar a eficiência do CAF. Para atingir esses objetivos, uma unidade de bancada foi construída, consistindo de tanques de armazenamento e de separação da mistura. Interligando os tanques, foram dispostos dutos transparentes com 27 mm de diâmetro interno e 8 m de extensão, contendo duas seções horizontais e uma vertical para análise e diversos acessórios hidráulicos. O óleo utilizado possuía viscosidade de 3200 cP a 22 °C e densidade de 945 kg/m3 . Os resultados experimentais demonstraram haver diversas configurações de fluxo segundo o posicionamento do duto, e que a diferença de densidade dos fluidos descentraliza o óleo nos escoamentos horizontais. Além disso, o trecho vertical intercalado entre os trechos horizontais se comportou como um retificador de fluxo, melhorando os índices do CAF. Foi determinado um fator de redução de perda de pressão máximo de 250 vezes para o trecho reto e de 12 vezes para a válvula de gaveta. O fator global máximo de redução de potência foi mensurado em 2,2 vezes. Concluiu-se que, para um trecho reto, o projeto de instalações hidráulicas para o escoamento bifásico deve considerar 15 % a mais de perda de carga em relação ao escoamento de água pura. Já para a válvula de gaveta, esse fator deve ser de 700 %. / The world economy is strongly dependent on the availability of oil, however, light oil reserves, more market-oriented, tend to deplete in coming years, bringing to light the heavy oil reserves to meet the demands of the market. However, the processes associated with the transportation and production of these viscous oils consume a lot of energy and pose a great challenge for the oil industry. In this context, transporting viscous oils through a liquid-liquid two-phase oil-water flow in a core annular pattern (CAF) is very promising. In this method, an annular water film surrounds the oil-containing core, minimizing its contact with the pipe wall and reducing energy losses by friction. The aim of the present work was to map the flow patterns of a biphasic oil-water flow in horizontal and vertical pipes, to evaluate the overall energy savings provided by the CAF technique, to measure the pressure gradient reduction factor along the pipe and in a gate valve and to determine the holdup as a way of assessing the energy efficiency of the biphasic oil-water flow transport. To achieve these goals, an experimental facility was built and it consisted of cargo and separation tanks. Connecting these tanks, approximately 8 m of 27mm-ID clear transparent PVC pipes, two horizontal and one vertical sections and various hydraulic fittings. It was used in the tests lubricating oil with 3200 cP and 945 kg/m3 at 22°C and distilled water. The experimental results showed that there are several flow configurations according to the pipe positioning, and that the oil and the water density difference decentralizes the oil core in horizontal flows. In addition, the vertical section placed between the two horizontal ones behaved like a flow rectifier, improving the core annular flow energy savings basis. An average pressure gradient reduction factor of 250 times in a straight pipe and of 12 times in a gate valve was determined. The maximum overall power reduction factor was measured as being 2.2 times. It was concluded that the design of a hydraulic installation to transport heavy oil with water in a core annular pattern should consider a pressure drop increase by a factor of 15 % in a straight pipe and by a factor of 700 % in a gate valve based on the monophasic water transport at similar flow rates.

Este trabalho tem como objetivo analisar estratégias de iluminação natural utilizadas nos estágios iniciais do projeto de arquitetura capazes de aumentar a qualidade da iluminação e a conservação de energia nos edifícios escolares. Essas estratégias têm sido aplicadas com sucesso em edifícios escolares em vários países, melhorando o desempenho e o bem-estar dos estudantes e conservando energia. Entre essas estratégias, o autor selecionou um dispositivo zenital para iluminação natural com seleção angular e difusores opacos, realizou um ensaio experimental em um modelo físico reduzido de uma sala de aula padrão, sob condições de céu real e analisou comparativamente os resultados. O estudo mostrou que a adoção de uma metodologia para utilizar estratégias como a analisada neste trabalho pode conseguir um adequado controle da radiação solar para evitar a incidência direta da luz do Sol, evitar o ofuscamento e o aquecimento excessivo de ambientes de salas de aula em climas quentes e, ao mesmo tempo, aproveitar a iluminação natural, tanto difusa quanto direta refletida, para obter maior conforto visual e economizar energia. / This work aims to analyse daylighting strategies applied in early stages of architectural design as to improve lighting quality and energy savings in school buildings. Similar strategies have already been successfully applied in many countries around the world, enhancing student?s performance and well being while helping to save energy. Among the strategies studied, the author describes an experiment under real sky conditions using a physical scale model of a standard classroom equipped with a roof monitor combined with an overhang and interior vertical diffusing baffles as a way to check its influence in interior lighting conditions. The experiment has shown that the use of daylighting strategies can promote an adequate control of solar radiation, avoiding direct sunlight penetration inside the classrooms, limiting glare problems and excessive heat of hot climates. At the same time, such strategies optimise both direct and defuse use of daylight to improve visual comfort and energy savings.

Les diodes électroluminescentes (LEDs) constituent de nouvelles solutions pour créer des luminaires plus robustes, ayant un meilleur rendement de conversion et plus respectueuses de l'environnement. Malgré les avantages indiscutables déjà obtenus aujourd'hui, ce type de luminaire présente encore quelques optimisations possibles et offre des possibilités de fonctionnalités multiples. A travers plusieurs campagnes de tests, l'auteur montre sur des LEDs du commerce, que les points d'optimisation non encore exploités dans les luminaires commerciaux. Ces LEDs ont ainsi été testés sur de larges plages de fonctionnement du point de vue photométrique, électrique mais aussi thermique pour connaitre la reproductibilité des résultats obtenus. Ainsi les influences des conditions d'utilisation notamment en température de fonctionnement et niveaux de courant d'alimentation ont été étudiées. Pour dimensionner au mieux une alimentation électrique spécifique, une recherche de modèles de LED élémentaires a été effectuée. L'objectif est que les modèles tiennent compte des principaux paramètres mais soit suffisamment simple pour être inséré dans un environnement système afin de simuler le luminaire dans son environnement complet. Ainsi, l'étude comparative de plusieurs associations de LEDs a été effectuée permettant d'en déduire des compromis pour proposer de nouvelles solutions faibles consommatrices d'énergie à coût réduit incluant de nouveaux types d'alimentation. / Light emitting diodes (LEDs) bring new possibilities to get luminaires more robust with an improved efficiency and more environmentally respectfull. Despite the benefits already achieved today, this type of luminaire still presents some possible optimizations and provides opportunities for multiple features. Through several tests, the author shows on LEDs in market that optimization points are not operated in commercial luminaires. These LEDs have been tested over a wide range of operation in photometric, electrical but also thermal to know the reproducibility of the results. Thus the influences of operating conditions including operating temperature and supply current levels were studied. To design a specific power supply for each LED type, a search of elementary LED models was performed. The objective is to take into account the main parameters of the models but also to be enough simple to be inserted into a system environment to simulate the luminaire in whole environment. Thus, the comparative study of several associations of LEDs was conducted to deduce the best compromise and propose new solutions to reduce energy consumptions and production costs, including new types of power supply.

A economia mundial é fortemente dependente da disponibilidade de óleo, no entanto as reservas de óleo leve, mais atrativas ao mercado, tendem nos próximos anos ao esgotamento, trazendo à luz as reservas de óleo pesado para atender as demandas do mercado. No entanto, os processos associados ao transporte e processamento desses óleos viscosos consomem muita energia, impondo um grande desafio para a indústria do petróleo. Nesse contexto, se transportar óleos viscosos com água através de um escoamento bifásico em padrão Core Annular Flow (CAF) é muito promissor. Nessa prática, uma película anular de água envolve o núcleo que contém o óleo, minimizando o contato entre este e a parede do duto e reduzindo as perdas de energia por atrito. Visou o presente estudo mapear os padrões de escoamento de óleo pesado com água em dutos horizontais e verticais, mensurar os fatores de redução de potência e do diferencial de pressão associados à um trecho reto e à uma válvula de gaveta aberta e determinar o holdup para avaliar a eficiência do CAF. Para atingir esses objetivos, uma unidade de bancada foi construída, consistindo de tanques de armazenamento e de separação da mistura. Interligando os tanques, foram dispostos dutos transparentes com 27 mm de diâmetro interno e 8 m de extensão, contendo duas seções horizontais e uma vertical para análise e diversos acessórios hidráulicos. O óleo utilizado possuía viscosidade de 3200 cP a 22 °C e densidade de 945 kg/m3 . Os resultados experimentais demonstraram haver diversas configurações de fluxo segundo o posicionamento do duto, e que a diferença de densidade dos fluidos descentraliza o óleo nos escoamentos horizontais. Além disso, o trecho vertical intercalado entre os trechos horizontais se comportou como um retificador de fluxo, melhorando os índices do CAF. Foi determinado um fator de redução de perda de pressão máximo de 250 vezes para o trecho reto e de 12 vezes para a válvula de gaveta. O fator global máximo de redução de potência foi mensurado em 2,2 vezes. Concluiu-se que, para um trecho reto, o projeto de instalações hidráulicas para o escoamento bifásico deve considerar 15 % a mais de perda de carga em relação ao escoamento de água pura. Já para a válvula de gaveta, esse fator deve ser de 700 %. / The world economy is strongly dependent on the availability of oil, however, light oil reserves, more market-oriented, tend to deplete in coming years, bringing to light the heavy oil reserves to meet the demands of the market. However, the processes associated with the transportation and production of these viscous oils consume a lot of energy and pose a great challenge for the oil industry. In this context, transporting viscous oils through a liquid-liquid two-phase oil-water flow in a core annular pattern (CAF) is very promising. In this method, an annular water film surrounds the oil-containing core, minimizing its contact with the pipe wall and reducing energy losses by friction. The aim of the present work was to map the flow patterns of a biphasic oil-water flow in horizontal and vertical pipes, to evaluate the overall energy savings provided by the CAF technique, to measure the pressure gradient reduction factor along the pipe and in a gate valve and to determine the holdup as a way of assessing the energy efficiency of the biphasic oil-water flow transport. To achieve these goals, an experimental facility was built and it consisted of cargo and separation tanks. Connecting these tanks, approximately 8 m of 27mm-ID clear transparent PVC pipes, two horizontal and one vertical sections and various hydraulic fittings. It was used in the tests lubricating oil with 3200 cP and 945 kg/m3 at 22°C and distilled water. The experimental results showed that there are several flow configurations according to the pipe positioning, and that the oil and the water density difference decentralizes the oil core in horizontal flows. In addition, the vertical section placed between the two horizontal ones behaved like a flow rectifier, improving the core annular flow energy savings basis. An average pressure gradient reduction factor of 250 times in a straight pipe and of 12 times in a gate valve was determined. The maximum overall power reduction factor was measured as being 2.2 times. It was concluded that the design of a hydraulic installation to transport heavy oil with water in a core annular pattern should consider a pressure drop increase by a factor of 15 % in a straight pipe and by a factor of 700 % in a gate valve based on the monophasic water transport at similar flow rates.

This work presents a new energy saving technique for modern digital designs. We propose Time Interleaved Multi-Rail (TIMR) - a method for providing two dynamic supply rails to a circuit. This technique uses the first supply rail to mask the transition delay while changing the voltage of the second rail. We examine the design of TIMR as well as the implementation and considerations. We propose a number of control schemes that range from traditional DVFS to "race to sleep". This thesis also shows simulations of the technique using a existing voltage regulator in order to find the time and energy overhead of implementing the design. We find a 100μs switching time delay and 118μJ energy overhead associated with changing the voltage rail. This work concludes with comparisons to current energy saving techniques. / Graduation date: 2012

In this research, the four valve independent metering configuration is to be investigated. The Independent metering concept will be emphasized and compared to spool valve coupled metering conventional technologies. Research focuses on the energy savings potential of the four valve independent metering configuration in addition to improving performance. The basic model of interest in this research is an actuator that is controlled by the four valve independent metering configuration to move beam like members of mobile hydraulic equipment such as tractor loader backhoes, excavators, and telehandlers. Five distinct (or discrete) metering modes that exist in the literature are initially studied: Powered Extension, High Side Regeneration Extension, Low Side Regeneration Extension, Powered Retraction, and Low Side Regeneration Retraction. The energy saving potential of these modes is studied and comparisons between this system and a conventional spool valve controlled actuator are conducted. The problem of switching between these five modes is treated as an optimal control problem of a switched dynamic system. Before solving the optimal control problem, a dynamic model for the system of interest is first derived. The model is experimentally validated. General theory for the optimal control problem is derived and then applied to the hydraulic system of interest. The results are then interpreted and explained by looking into the force-speed capability of modes. The effect of mode switching on system performance is studied as well. The basic mechanical system used for this analysis is a continuous rotating beam that undergoes structural vibrations due to mode switching in the driving hydraulic actuator. A fully coupled actuator-beam model is investigated. A non-dimensional analysis is pursued to generalize the study results. The optimal switching analysis and the vibrational study lead to the idea of Continuously Variable Modes (CVMs). Instead of having five distinct modes that determines the flow path by opening two of the four valves in the assembly, three Continuously Variable Modes are presented as an alternative way of controlling the four-valve configuration. These three CVMs combine the distinct modes and use three of the four valves to provide the fluid flow path. The five distinct modes become a special case of these three CVMs. It is going to be shown that CVMs have more force-speed capabilities than the distinct modes and provide for better velocity and vibrational performance by virtue of always offering a continuous flow path. The theory behind CVMs is presented and experimental validation follows.

Current designs of high performance buildings utilize hourly building energy simulations of complex, interacting systems. Such simulations need to quantify the benefits of numerous features including: thermal mass, HVAC systems and, in some cases, special features such as active and passive solar systems, photovoltaic systems, and lighting and daylighting systems. Unfortunately, many high performance buildings today do not perform the way they were simulated. One potential reason for this discrepancy is that designers using the simulation programs do not understand the analysis methods that the programs are based on and therefore they may have unreasonable expectations about the system performance or use. The purpose of this study is to trace the origins of a variety of simulation programs and the analysis methods used in the programs to analyze high performance buildings in the United States. Such an analysis is important to better understand the capabilities of the simulation programs so they can be used more accurately to simulate the performance of an intended design. The goal of this study is to help explain the origins of the analysis methods used in whole-building energy simulation, solar system analysis simulation or design, and lighting and daylighting analysis simulation programs. A comprehensive history diagram or genealogy chart, which resolves discrepancies between the diagrams of previous studies, has been provided to support the explanations for the above mentioned simulation programs.

Electrical energy is commonly used in households and in industry - demand continues to rise due to economic and population growth. This requires that energy suppliers must increase their supply capacity. The result is that end–user energy costs continue to increase, therefore a growing need exists to reduce electrical energy demand in South Africa and internationally. Households account for the majority of electrical energy customers, but they only consume a fraction of the total energy supplied. The industrial sector and mines combined consume approximately 42% of the total electrical energy produced. Approximately 10% of this energy goes into compressed air production. This study focuses on methods of reducing the requirement of compressed air in industry so that the demand for electrical energy can be reduced. Many studies have focused on specific methods of reducing energy usage associated with compressed air production. These methods are categorised into methods of reducing compressed air requirements and methods of increasing compressed air supply efficiency. This study aims to combine these efforts into a single optimised solution. Although this study includes industry in general, the central focus is on the South African mining industry. Two different mining sites are considered and analysed as case studies. Methods of reducing energy required to produce compressed air were applied to each case study. Case Study 1 only allowed limited control of the compressed air system. In Case Study 2 integrated control was realised. Energy usage of compressors was reduced by 18.9% and 42.9% respectively. Results show that system savings can be doubled by combining different methods of reducing energy usage of compressed air. This, however, requires continuous monitoring and control of the air network at each section supplied with compressed air. The study is limited to achieving savings by changing the air system. Additional savings can be achieved by training personnel, altering schedules of production activities and implementing a system designed to locate air leaks. / Thesis (M.Ing. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2012.