Tese de mestrado integrado. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 2010

Tese de mestrado integrado. Engenharia Civil. Construções Civis. Faculdade de Engenharia. Universidade do Porto. 2013

Tese de mestrado integrado. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 2010

Depuis quelques années, les exigences des occupants de bâtiments ont sensiblement changé. On observe en effet une demande de confort de plus en plus rigoureux en particulier en période estivale. Cette augmentation des besoins de climatisation induit un accroissement important de la consommation d'énergie électrique dans les bâtiments, dû à une utilisation majoritaire de climatiseurs à compression mécanique de vapeur. Dans ce contexte énergétique difficile, les systèmes de rafraîchissement solaire font partie des alternatives intéressantes aux systèmes de climatisation classiques, dans la mesure où l'énergie primaire est principalement consommée sous forme de chaleur et provenant du soleil donc gratuite. L'autre grand intérêt de ces procédés est que le besoin en rafraîchissement coïncide la plupart du temps avec la disponibilité du rayonnement solaire. La compréhension et le développement de cette technologie passent par une étude expérimentale avec la réalisation d'installations pilotes à échelle réelle dans le but d'acquérir une expérience concrète. C'est dans ce sens que notre laboratoire s'est proposé de mettre en place une plateforme expérimentale d'une puissance frigorifique de 30 kWf chargée de rafraîchir des locaux d'enseignement de l'Institut Universitaire Technologique de Saint Pierre à La Réunion. La première partie de ce manuscrit présente une analyse expérimentale de cette installation. Une seconde approche purement fondamentale a été envisagée avec l'élaboration de modèles numériques permettant de prédire le comportement de l'installation dans son ensemble. Ces modèles numériques décrits sous plusieurs niveaux de finesse, sont validés par les données expérimentales avant d'être utilisés, soit comme outils de pré‐dimensionnement pour les modèles à descriptions simplifiés, soit comme outil d'optimisation et d'analyse pour les modèles détaillés. Le modèle détaillé représentant notre plateforme expérimentale a permis de réaliser une optimisation du fonctionnement de l'installation et de proposer des améliorations pour réduire la consommation d'électricité et augmenter le coefficient de performance électrique global.

An energy analysis was performed on the Texas A & M University at Qatar building in Doha, Qatar. The building and its HVAC systems were modeled using EnergyPlus. Building chilled water and electrical data were collected to validate the computer simulation. The simulated monthly electricity consumption was within plus/minus 5 percent of the metered building data. Ninety-five percent of simulated hourly electricity data in a day were within plus/minus 10 percent of metered data. Monthly chilled water demand was within plus/minus 18 percent of measurements, and simulated monthly demand was correlated to metered monthly values with an R-squared correlation coefficient of 0.95. Once the simulation was verified with the metered data, an optimization of the building's HVAC systems was performed. Better utilizing the building's variable speed fans at part loads showed potential annual electricity savings of 16 percent over the base case, with another 22 percent savings in chilled water energy. After converting chilled water savings to equivalent chiller electricity savings, the potential utility cost savings over the base case were found to be $90,000/yr at local utility rates. Reducing outdoor air intake to ASHRAE indoor air quality minimums yielded an additional 17 percent in potential chilled water savings and brought total monetary savings over the base case to $110,000/yr. Using a dedicated outside air system to precisely control individual zone ventilation showed potential for an additional 12 percent chilled water savings and $14,000 in yearly utility savings, while also eliminating cases of under-ventilation. A hypothetical retrofit of fan powered terminal units (FPTU's) resulted in energy savings only at very low minimum flow rates, below ventilation standards. Savings were never more than 20 percent over the no-fan case. Series FPTU's showed no savings at any flow setting and negligible difference was found between ECM and SCR motor control. Finally, the dependence on climate of each improvement was studied. Simulations were run in the relatively milder climates of Houston and Phoenix and compared to those found for Doha. It was found that variable speed fan operation is a more cost effective option for milder climates, while outside air control is more cost effective in extreme hot and humid climates such as Doha. Future study is needed to make the FPTU model valid for different climates and flow ranges.

This study addresses 5 uncertainties that exist in the operation of HVAC systems, which will presumably affect the actual energy consumption of the HVAC system in comparison to the consumption under idealized bahavior. We consequently add these parameters and their uncertainty range into the source code, eventually resulting in an EnergyPlus program in which the HVAC operation uncertainty is embedded as so-called model form uncertainty. The upgraded EnergyPlus is tested for each parameter uncertainty separately, and to show the impact of each uncertainty albeit for hypothetical uncertainty ranges of the parameters.

abstract: Phase Change Material (PCM) plays an important role as a thermal energy storage device by utilizing its high storage density and latent heat property. One of the potential applications for PCM is in buildings by incorporating them in the envelope for energy conservation. During the summer season, the benefits are a decrease in overall energy consumption by the air conditioning unit and a time shift in peak load during the day. Experimental work was carried out by Arizona Public Service (APS) in collaboration with Phase Change Energy Solutions (PCES) Inc. with a new class of organic-based PCM. This "BioPCM" has non-flammable properties and can be safely used in buildings. The experimental setup showed maximum energy savings of about 30%, a maximum peak load shift of ~ 60 min, and maximum cost savings of about 30%. Simulation was performed to validate the experimental results. EnergyPlus was chosen as it has the capability to simulate phase change material in the building envelope. The building material properties were chosen from the ASHRAE Handbook - Fundamentals and the HVAC system used was a window-mounted heat pump. The weather file used in the simulation was customized for the year 2008 from the National Renewable Energy Laboratory (NREL) website. All EnergyPlus inputs were ensured to match closely with the experimental parameters. The simulation results yielded comparable trends with the experimental energy consumption values, however time shifts were not observed. Several other parametric studies like varying PCM thermal conductivity, temperature range, location, insulation R-value and combination of different PCMs were analyzed and results are presented. It was found that a PCM with a melting point from 23 to 27 °C led to maximum energy savings and greater peak load time shift duration, and is more suitable than other PCM temperature ranges for light weight building construction in Phoenix. / Dissertation/Thesis / M.S. Mechanical Engineering 2010

O objetivo dessa dissertação foi estudar a relação entre o desenho da abertura e o comportamento térmico de ambientes internos de simulação. Para tanto, o comportamento foi quantificado a partir da energia consumida pelo ar-condicionado para manter o ambiente interno com temperaturas aceitáveis para o conforto térmico. Dessa forma, quanto menor a energia consumida, melhor o comportamento térmico do ambiente. A energia consumida foi obtida através de simulação com o software EnergyPlus 7.0. Os parâmetros investigados foram baseados nas variáveis das equações do RTQ-R (Regulamento Técnico da Qualidade para o Nível de Eficiência Energética das Edificações Residenciais). Para o estudo foram simulados ambientes onde em cada simulação era variada a orientação (norte, nordeste, leste, sudeste, sul, sudoeste, oeste e noroeste) o tamanho (cinco diferentes tamanhos) e a existência ou não de dispositivos de sombreamento das aberturas. Como análise complementar, foi também estudado a influência da intensificação da ventilação durante as noites de verão no comportamento térmico de ambientes. No total, o mesmo ambiente foi simulado 240 vezes. O estudo se concentrou no contexto climático da cidade de Porto Alegre. O foco da pesquisa foi a abertura porque esse elemento de construção, dependendo de seu tamanho em relação à parede, de sua orientação, de sua vedação, ou de outras características, pode permitir uma troca térmica significativa entre o interior e o exterior da edificação, independentemente das características de isolamento das paredes. A relação entre o desenho da abertura e o comportamento térmico de ambientes é discutida tendo como base o RTQ-R, pois esse é o regulamento de classificação do nível de eficiência energética de edificações residenciais vigente no país. Ao final do trabalho, a influência dos parâmetros tamanho, orientação e sombreamento para o comportamento térmico de ambientes é discutida tendo como base os resultados do EnergyPlus 7.0 – ferramenta de quantificação – e do RTQ-R – ferramenta de qualificação. Como resultado das simulações feitas com o EnergyPlus 7.0, obteve-se informação sobre a forma pela qual o tamanho, a orientação e o sombreamento das aberturas influenciam o comportamento térmico de ambientes. As análises feitas com o uso das equações do RTQ-R levaram a resultados de maneira geral compatíveis com as simulações, apesar da menor sensibilidade dessa ferramenta qualitativa. Nas análises com o EnergyPlus 7.0, o tamanho foi a variável que apresentou maior influência. Com o uso do RTQ-R, a variável que se mostrou mais influente foi o sombreamento. Foi observado ainda que as equações do RTQ-R ajudam na definição da orientação, do tamanho e do sombreamento das aberturas, características que são essenciais para aprimorar o comportamento térmico de ambientes. Portanto, o uso das equações como ferramenta de suporte ao desenvolvimento de projetos é recomendável. O EnergyPlus também se mostrou uma ferramenta capaz de auxiliar a escolha das melhores estratégias de projeto. Sendo assim, as duas ferramentas se complementam. / The objective of this dissertation was to demonstrate the relationship between the design of the window and the thermal behavior of simulated internal environments. The thermal behavior was quantified from the energy consumed by the air conditioning system to maintain the internal environment with acceptable temperatures for thermal comfort. Thus, the lower the energy consumed, the better the thermal performance of the internal environment. The amount of energy consumed was obtained by simulation with the software EnergyPlus 7.0. The parameters investigated were based on the variables of the equations of RTQ-R (Quality Technical Regulation for the Level of Energy Efficiency of Residential Buildings). For the study internal environments were simulated, where in each simulation were varied orientation (north, northeast, east, southeast, south, southwest, west and northwest) size (five different sizes) and the presence or absence of shading window devices. As a complement, was also studied the influence of the intensification of ventilation during the summer nights on the thermal behavior of internal environments. In total, the same internal environment was simulated 240 times. The study focused on the climatic context of the city of Porto Alegre. The focus of the research was the window because this construction element, depending on its size relative to the wall, on its orientation, on its thermal isolation, or on other characteristics, can allow a significant heat exchange between the interior and the exterior of the building, independently of the characteristics of the isolation of the walls. The relationship between the design of the window and the thermal behavior of buildings is discussed based on the RTQ-R, because this is the classification regulation of the level of energy efficiency of residential buildings present in the country. At the end of the work, the influence of the parameters size, orientation and shading for thermal behavior of internal environments is discussed based on the results of the EnergyPlus 7.0 - quantification tool - and RTQ-R - qualification tool. As a result of the simulation made with the EnergyPlus 7.0, information was obtained about how the size, the orientation and the shading of the windows influence the thermal behavior of the internal environment. The analysis made with the RTQ-R equations led to results which are in general compatible with the simulations, despite the lower sensibility of this qualitative tool. In the analysis made with the EnergyPlus 7.0, the size was the variable with the greatest influence. Using the RTQ-R, the variable that was the most influential was the shading. It was also observed that the equations of the RTQ-R are useful for the definition of orientation, size and shading of windows, characteristics which are essential to improve the thermal behavior of internal environments. Therefore, the use of the equations as a tool to support the development of projects is recommended. The EnergyPlus was also showed as a tool able to help select the best design strategies. Thus, the two tools are complementary.

O objetivo dessa dissertação foi estudar a relação entre o desenho da abertura e o comportamento térmico de ambientes internos de simulação. Para tanto, o comportamento foi quantificado a partir da energia consumida pelo ar-condicionado para manter o ambiente interno com temperaturas aceitáveis para o conforto térmico. Dessa forma, quanto menor a energia consumida, melhor o comportamento térmico do ambiente. A energia consumida foi obtida através de simulação com o software EnergyPlus 7.0. Os parâmetros investigados foram baseados nas variáveis das equações do RTQ-R (Regulamento Técnico da Qualidade para o Nível de Eficiência Energética das Edificações Residenciais). Para o estudo foram simulados ambientes onde em cada simulação era variada a orientação (norte, nordeste, leste, sudeste, sul, sudoeste, oeste e noroeste) o tamanho (cinco diferentes tamanhos) e a existência ou não de dispositivos de sombreamento das aberturas. Como análise complementar, foi também estudado a influência da intensificação da ventilação durante as noites de verão no comportamento térmico de ambientes. No total, o mesmo ambiente foi simulado 240 vezes. O estudo se concentrou no contexto climático da cidade de Porto Alegre. O foco da pesquisa foi a abertura porque esse elemento de construção, dependendo de seu tamanho em relação à parede, de sua orientação, de sua vedação, ou de outras características, pode permitir uma troca térmica significativa entre o interior e o exterior da edificação, independentemente das características de isolamento das paredes. A relação entre o desenho da abertura e o comportamento térmico de ambientes é discutida tendo como base o RTQ-R, pois esse é o regulamento de classificação do nível de eficiência energética de edificações residenciais vigente no país. Ao final do trabalho, a influência dos parâmetros tamanho, orientação e sombreamento para o comportamento térmico de ambientes é discutida tendo como base os resultados do EnergyPlus 7.0 – ferramenta de quantificação – e do RTQ-R – ferramenta de qualificação. Como resultado das simulações feitas com o EnergyPlus 7.0, obteve-se informação sobre a forma pela qual o tamanho, a orientação e o sombreamento das aberturas influenciam o comportamento térmico de ambientes. As análises feitas com o uso das equações do RTQ-R levaram a resultados de maneira geral compatíveis com as simulações, apesar da menor sensibilidade dessa ferramenta qualitativa. Nas análises com o EnergyPlus 7.0, o tamanho foi a variável que apresentou maior influência. Com o uso do RTQ-R, a variável que se mostrou mais influente foi o sombreamento. Foi observado ainda que as equações do RTQ-R ajudam na definição da orientação, do tamanho e do sombreamento das aberturas, características que são essenciais para aprimorar o comportamento térmico de ambientes. Portanto, o uso das equações como ferramenta de suporte ao desenvolvimento de projetos é recomendável. O EnergyPlus também se mostrou uma ferramenta capaz de auxiliar a escolha das melhores estratégias de projeto. Sendo assim, as duas ferramentas se complementam. / The objective of this dissertation was to demonstrate the relationship between the design of the window and the thermal behavior of simulated internal environments. The thermal behavior was quantified from the energy consumed by the air conditioning system to maintain the internal environment with acceptable temperatures for thermal comfort. Thus, the lower the energy consumed, the better the thermal performance of the internal environment. The amount of energy consumed was obtained by simulation with the software EnergyPlus 7.0. The parameters investigated were based on the variables of the equations of RTQ-R (Quality Technical Regulation for the Level of Energy Efficiency of Residential Buildings). For the study internal environments were simulated, where in each simulation were varied orientation (north, northeast, east, southeast, south, southwest, west and northwest) size (five different sizes) and the presence or absence of shading window devices. As a complement, was also studied the influence of the intensification of ventilation during the summer nights on the thermal behavior of internal environments. In total, the same internal environment was simulated 240 times. The study focused on the climatic context of the city of Porto Alegre. The focus of the research was the window because this construction element, depending on its size relative to the wall, on its orientation, on its thermal isolation, or on other characteristics, can allow a significant heat exchange between the interior and the exterior of the building, independently of the characteristics of the isolation of the walls. The relationship between the design of the window and the thermal behavior of buildings is discussed based on the RTQ-R, because this is the classification regulation of the level of energy efficiency of residential buildings present in the country. At the end of the work, the influence of the parameters size, orientation and shading for thermal behavior of internal environments is discussed based on the results of the EnergyPlus 7.0 - quantification tool - and RTQ-R - qualification tool. As a result of the simulation made with the EnergyPlus 7.0, information was obtained about how the size, the orientation and the shading of the windows influence the thermal behavior of the internal environment. The analysis made with the RTQ-R equations led to results which are in general compatible with the simulations, despite the lower sensibility of this qualitative tool. In the analysis made with the EnergyPlus 7.0, the size was the variable with the greatest influence. Using the RTQ-R, the variable that was the most influential was the shading. It was also observed that the equations of the RTQ-R are useful for the definition of orientation, size and shading of windows, characteristics which are essential to improve the thermal behavior of internal environments. Therefore, the use of the equations as a tool to support the development of projects is recommended. The EnergyPlus was also showed as a tool able to help select the best design strategies. Thus, the two tools are complementary.

abstract: Pavement surface temperature is calculated using a fundamental energy balance model developed previously. It can be studied using a one-dimensional mathematical model. The input to the model is changed, to study the effect of different properties of pavement on its diurnal surface temperatures. It is observed that the pavement surface temperature has a microclimatic effect on the air temperature above it. A major increase in local air temperature is caused by heating of solid surfaces in that locality. A case study was done and correlations have been established to calculate the air temperature above a paved surface. Validation with in-situ pavement surface and air temperatures were made. Experimental measurement for the city of Phoenix shows the difference between the ambient air temperature of the city and the microclimatic air temperature above the pavement is approximately 10 degrees Fahrenheit. One mitigation strategy that has been explored is increasing the albedo of the paved surface. Although it will reduce the pavement surface temperature, leading to a reduction in air temperature close to the surface, the increased pavement albedo will also result in greater reflected solar radiation directed towards the building, thus increasing the building solar load. The first effect will imply a reduction in the building energy consumption, while the second effect will imply an increase in the building energy consumption. Simulation is done using the EnergyPlus tool, to find the microclimatic effect of pavement on the building energy performance. The results indicate the cooling energy savings of an office building for different types of pavements can be variable as much as 30%. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2015