Dissertations / Theses on the topic 'Buildings – Energy conservation – Mathematical models'

Current global efforts for energy conservation and optimization are focused on improvements in energy supply and production systems, and on encouraging the adoption of energy-efficient devices and equipment. However, systematic assessments of economic and technical implications when adopting energy-efficient alternative systems in buildings have not yet been explored thoroughly. The uncertainty about the consequences of investing in alternative energy-efficient systems has led to a prolonged utilization of obsolete building systems (underperforming HVAC systems, inefficient lighting systems, badly maintained and equipment, and so forth). This has led to overall poor energy efficiency, creating considerable burden on the building operation budget. This research discusses the procedure for formulating an investment strategy to improve existing building energy performance. The approach is suitable for large building portfolios where a plethora of potential refurbishment interventions can be considered. This makes our approach especially suited for use on university campuses and most of this report will focus on that particular application utilization protocols especially for use on campuses. This investment model only looks at the energy related savings versus investments; it is well understood that the ultimate selection of the optimal set of improvement options of a portfolio will be determined by additional considerations, such as overall value, occupant satisfaction, productivity improvements, aesthetics, etc. Nevertheless, many campus managers are confronted with the question how much energy they can save with a given investment amount. This is exactly what our approach helps to answer. The investment optimization strategy is implemented in software "InvEnergy," which systematically calculates the costs and benefits of all possible building-technology pairings, taking uncertainties in the saving/investment calculations and estimates into account. This tool empowers decision makers in facility management to make complex investment decisions during continuous building commissioning.

A theoretical model was developed to predict the air distribution pattern and thus to design perforated ventilation ducts equipped with a fan. The analysis of the air distribution pattern of such systems requires accurate measurement procedures. Several experimental methods were tested and compared. Accordingly, the piezometric flush taps and thermo-anemometer were selected to measure respectively the duct air pressure and the outlet air flow.
Based on the equations of energy and momentum conservation, a model was formulated to predict the air flow performance of perforated ventilation ducts and to evaluate the outlet discharge angle and the duct regain coefficients without evaluating frictional losses. The basic assumptions of the model were validated by experimentally proving the equivalence of the friction losses expressed in the 2 cited equations. When compared to experimental results measured from four wooden perforated ventilation ducts with aperture ratios of 0.5, 1.0, 1.5, and 2.0, the model predicted the outlet air flow along the full length of perforated duct operated under turbulent flow conditions with a maximum error of 9%. The regain coefficient and the energy correction factor were equal to one, and the value of the discharge coefficient remained constant at 0.65, along the full length of the perforated duct. The outlet air jet discharge angle varied along the entire duct length, and was not influenced by friction losses for turbulent flow.
Assuming a common effective outlet area, the model was extended to match the performance of the fan and the perforated duct and to determine their balance operating point.

One of the greatest challenges that will face humanity in the 21st century is the issue of climate change brought about by emissions of greenhouse gases. Energy use is one of the primary sources of greenhouse gas emissions. However, it is also one of the most important contributors to improved human welfare over the past two centuries and will continue to be so for years to come. This quandary has led a number of researchers to suggest that geoengineering may be required in order to allow for continued use of fossil fuels while at the same time mitigating the effects of the associated greenhouse gas emissions on the global climate. The goal of this research was to develop a model that would allow decision-makers and policy analysts to assess the optimal mix of energy and geoengineering resources needed to meet global or regional energy demand at the lowest cost while accounting for appropriate emissions, greenhouse gas concentration, or temperature rise constraints. The resulting software model is called the Combined Energy and Geoengineering Optimization Model (CEAGOM). CEAGOM was then used to analyze the recently announced U.S.-China emissions agreement and to assess what the optimal global energy resource mix might be over the course of the 21st century, including the associated potential need for geoengineering. These analyses yielded optimal mixes of energy and geoengineering resources that could be used to inform regional and global energy and climate management strategies.

Cette étude porte sur l‘identification de modèles dynamiques pour l‘évaluation des performances et le diagnostic énergétique de bâtiments existants. Le travail de thèse se place donc dans un contexte d‘économie d‘énergie et d‘efficacité énergétique accrue qui sont d‘intérêt primordial aujourd‘hui. Nous nous adressons à des bâtiments de bureaux occupés mais relativement bien instrumentés. Nous disposons des mesures horaires de température extérieure, de rayonnement solaire, de puissance de chauffage, de puissance électrique et de température de l‘air intérieur. L‘objectif étant de proposer une démarche méthodologique permettant de quantifier les performances énergétiques de l‘enveloppe du bâtiment à partir des données disponibles, d‘une part, et de préconiser des voies pour leur amélioration, d‘autre part. Les étapes majeurs de la démarche d‘évaluation/diagnostic proposée s‘ajuste pour l‘essentiel sur celles d‘une procédure classique d‘identification : a) analyse préliminaire des données disponible ; b) choix des structures mathématiques susceptibles de reproduire convenablement le comportement dynamique du bâtiment ; c) estimation du modèle et validation ; et exploitation du modèle pour des fins d‘évaluation et de diagnostic. Grâce aux résultats obtenus par une première approche « boîte noire » nous effectuons une tentative de diagnostic énergétique approfondi en s‘appuyant sur une modélisation physique du bâtiment (« boîte blanche »)
This study concerns the identification of dynamic models for performance evaluation and energy diagnosis of existing buildings. The work of this PhD takes place in a context of energy conservation and energy efficiency which are of essential interest today. We are dealing with occupied office buildings but relatively well instrumented. We have hourly measurements of outdoor temperature, solar radiation, heating power, electrical power and indoor air temperature. The aim is to propose a methodological approach to quantify the energy performance of building envelope from the available data, on the one hand, and to recommend ways to improve them, on the other. Major steps of the process evaluation / diagnosis given for the most fits with those of a standard procedure of identification: a) preliminary analysis of available data, b) choice of mathematical structures for well describing the building behavior c) model estimation and validation, and operation of the model for evaluation and diagnosis. With the results obtained by a first approach "black box" we make a tentative of detailed diagnosis based on physical building model ("white box")

Orientador: Roger Josef Zemp
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-21T18:17:49Z (GMT). No. of bitstreams: 1 Valente_BrunoSelimAvian_M.pdf: 588713 bytes, checksum: 01c679f3515305f57994ddc3e8057bb5 (MD5) Previous issue date: 2012
Resumo: A abordagem tradicional da estimativa da área no procedimento de síntese de redes de trocadores de calor exige a escolha de um conjunto típico de coeficientes de transferência de calor. Uma vez obtida a topologia da rede de trocadores de calor, o projeto detalhado dos trocadores pode exigir a consideração de restrições nas quedas da pressão disponíveis, alterando os valores dos coeficientes de transferência de calor utilizados inicialmente na avaliação da rede e invalidando a otimização econômica da mesma. Com isso tem-se um aumento nos custos de projeto tanto na parte construtiva como na forma de bombas e/ou compressores do processo. Esta dissertação tem como finalidade elaborar uma nova abordagem que possibilite estimar a área de troca térmica a partir de uma relação entre quedas de pressão e coeficientes de transferência de calor no lado do casco e dos tubos. Assim, partindo das quedas de pressão permitidas das correntes pode-se estimar a área e os coeficientes de transferência de calor de um trocador de calor, munido de dados de processo como carga térmica, temperaturas, propriedades físicas e quedas de pressão no lado do casco e dos tubos, e possibilitando uma análise econômica mais correta da rede de trocadores de calor. Os métodos já disponíveis para esta finalidade possuem limitações uma vez que são baseados no método de Kern, que inclui severas simplificações no seu modelo, e o de Bell, que utiliza equações empíricas dependentes de aspectos geométricos. O procedimento de análise de trocadores de calor tipo casco e tubos de Wills & Johnston, utilizado neste trabalho, é uma alternativa bastante viável para este tipo de problema por ser considerado teoricamente mais preciso, baseando-se em equações hidráulicas para o cálculo da queda de pressão no lado do casco considerando os diversos caminhos do fluido no interior do casco
Abstract: In the traditional approach of heat exchanger network synthesis the procedure for area targeting requires de choice of a set of typical heat transfer coefficients. After the heat exchanger network structure has been defined the individual exchangers are design. However, due to pressure drop restrictions the final heat exchanger design might require heat transfer coefficients that are very different from the one originally chosen, leading to increased exchanger area and increased capital cost. This work aims to develop a new that allows the estimate of a correct set of heat transfer coefficients and exchanger area based on available pressure drops. The propose procedure allows for the estimate of heat transfer coefficients and area based on the available pressure drops. Methods already available for this purpose show limitations: the method of Kern includes severe simplifications while the method of Bell uses empirical equations dependent on geometric aspects. The method of Wills & Johnston, used in the present work, is a very feasible alternative for this type of problem as it is based on the pressure drop of the different fluid paths inside the shell side of the exchanger
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestre em Engenharia Química

The goal of this dissertation is to demonstrate that data from a remotely located building can be utilized for energy modeling of a similar type of building and to demonstrate how to use this remote data without physically moving the data from one server to another using Virtual Information Fabric Infrastructure (VIFI). In order to achieve this goal, firstly an EnergyPlus model was created for Greek Life Center, a campus building located at University of North Texas campus at Denton in Texas, USA. Three thermal comfort models of Fanger model, Pierce two-node model and KSU two-node model were compared in order to find which one of these three models is most accurate to predict occupant thermal comfort. This study shows that Fanger's model is most accurate in predicting thermal comfort. Secondly, an experimental data pertaining to lighting usage and occupancy in a single-occupancy office from Carnegie Mellon University (CMU) has been implemented in order to perform energy analysis of Greek Life Center assuming that occupants in this building's offices behave similarly as occupants in CMU. Thirdly, different data types, data formats and data sources were identified which are required in order to develop a city-scale urban building energy model (CS-UBEM). Two workflows were created, one for an individual scale building energy model and another one for CS-UBEM. A new innovative infrastructure called as Virtual Information Fabric Infrastructure (VIFI) has been introduced in this dissertation. The workflows proposed in this study will demonstrate in the future work that by using VIFI infrastructure to develop building energy models there is a potential of using data for remote servers without actually moving the data. It has been successfully demonstrated in this dissertation that data located at remote location can be used credibly to predict energy consumption of a newly built building. When the remote experimental data of both lighting and occupancy are implemented, 4.57% energy savings was achieved in the Greek Life Center energy model.

Au travers de l’ensemble de ces travaux, l’objectif principal consiste à valider la pertinence de la construction et de l’utilisation de modèles 3D géométriques ou paramétriques orientés BIM/hBIM pour des analyses numériques. Il s’agit notamment d’études structurales dans le cas de bâtiments historiques ainsi que la planification potentielle de travaux de restauration, rénovation énergétique et réhabilitation. Des travaux d’exploitation complémentaires des données et des nuages de points, pour la détection, la segmentation et l’extraction d’entités géométriques ont également été intégrés dans les travaux et la méthodologie proposée. Le processus de traitement des données, modélisation géométrique ou paramétrique et leur exploitation, proposé dans ces travaux, contribue à améliorer et mieux comprendre les contraintes et enjeux des différentes configurations et conditions liées aux cas d’études et aux contraintes spécifiques propres aux types de constructions. Les contributions proposées pour les différentes méthodes de modélisation géométriques et paramétriques à partir des nuages de points, sont abordées par la construction de modèles géométriques orientés BIM ou hBIM. De même, les processus de détection d’éléments surfaciques et d’extraction de données à partir de nuages de points mis en place sont présentés. La mise en application de ces méthodes de modélisation est systématiquement illustrée par différents cas d’étude, dont l’ensemble des travaux relatifs ont été effectués dans le cadre de cette thèse. Le but est dès lors de démontrer l’intérêt et la pertinence de ces méthodes numériques en fonction du contexte, des besoins et des études envisagées, par exemple avec la flèche de la cathédrale de Senlis (Oise) et le site de l’Hermitage (Oise). Des analyses numériques de type éléments finis permettent ensuite de valider la pertinence de telles démarches
Throughout this work, the main objective is to validate the relevance of construction and use of geometric or parametric 3D models BIM or hBlM-oriented for numerical analyzes. These include structural studies in the case of historic buildings, as well as planning for restoration work, energy renovation and rehabilitation. Complementary data mining and use of point clouds for the detection, segmentation and extraction of geometric features have also been integrated into the work and proposed methodology. The process of data processing, geometric or parametric modeling and their exploitation, proposed in this work, contributes to improve and understand better the constraints and stakes of the different configurations and conditions related to the case studies and the specific constraints specific to the types of constructions. The contributions proposed for the different geometric and parametric modeling methods from point clouds are addressed by the construction of geometric models BIM or hBlM-oriented. Similarly, the process of surface detection, extraction of data and elements from point clouds are presented. The application of these modeling methods is systematically illustrated by different case studies, all of whose relative work has been carried out within the framework of this thesis. The goal is therefore to demonstrate the interest and relevance of these numerical methods according to the context, needs and studies envisaged, for example with the spire of the Senlis cathedral (Oise) and the Hermitage site (Oise). Numerical analyzes with finite element method are used to validate the relevance of these approaches

Based on the above scheme, we propose a number of solutions to reduce the computational complexity and communication cost. To reduce the computational complexity, we propose to aggregate the local data and transit data and route them with a single set of routing variables. To reduce the communication overhead, a different smoothing function is proposed that only requires the information of a set of bottleneck nodes. The optimality conditions are derived and a distributed algorithm is designed accordingly. Simulation results illustrate the effectiveness and efficiency of the proposed solution.
Sleeping scheduling is another approach to save energy consumption for sensor networks. The basic idea is to schedule the duty-cycles of sensor nodes such that off-duty sensors are turned off as long as the network functionality can be maintained by working nodes. For applications whereby coordination of sleeping among sensors is not possible or inconvenient, random sleeping is the only option. We present the Asynchronous Random Sleeping (ARS) scheme whereby sensors (i) do not need to synchronize with each other, and (ii) do not need to coordinate their wakeup patterns. The stationary coverage probability and the expected coverage periods for ARS are derived. For surveillance application, we derive in addition the detection probability and detection delay distribution. We find that the expected detection delay of asynchronous random sleeping is smaller than that of the synchronous random sleeping.
This thesis is focused on the design and analysis of energy conservation methods for wireless sensor networks (WSNs). Unlike traditional wireless networks, sensor nodes in WSNs are collaborating towards a common mission. The failure of some sensor nodes may cause significant topological changes and loss of information at the target region. Therefore, network lifetime is the primary objective for designing energy conservation solutions for WSNs.
We address the energy conservation problem from the aspects of maximum lifetime routing, data aggregation and sleeping scheduling. We first propose a data aggregated maximum lifetime routing scheme for wireless sensor networks. We adopt a data aggregation model that decouples the routing of local data and transit data. The objective is to jointly optimize data aggregation and routing so that the network lifetime can be maximized. A recursive smoothing method is adopted to overcome the nondifferentiability of the objective function. We derive the necessary and sufficient conditions for achieving the optimality of the smoothing function and design a distributed gradient algorithm accordingly. We show that the proposed scheme can significantly reduce the data traffic and improve the network lifetime. The distributed algorithm can converge to the optimal value efficiently under all network configurations.
Hua Cunqing.
"June 2006."
Adviser: Tak-Shing Yum.
Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1825.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2006.
Includes bibliographical references (p. 120-131).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.

Increased consumer demand for fresh fruit throughout the year has created a need for long term storage. Long term storage of fruit uses more energy than fresh market products, thus increasing production cost. Pacific Northwest energy costs and more competition for markets has made energy conservation an important factor to be considered by the fruit industry. A BASICA computer program, RLSIM, was developed to predict the transient refrigeration load throughout the storage season in apple and pear cold storage warehouses. RLSIM accurately predicted the seasonal and component refrigeration system energy demand curves during the 1985-1986 cold storage season. The results also indicated that the largest single energy use component is the continuous operation of evaporator fans. Simulation of a six hours on and six hours off fan cycling technique indicated a reduction of 23.75 percent could be achieved in overall refrigeration system energy use in the cold storage warehouse. Cold storage warehouse management can be improved by using the results of RLSIM. Fan cycling schemes could be properly employed without risk of increasing fruit temperature. Recommendations were made to update research in areas of cooling and respiration rates of various fruits in both controlled atmosphere and common storage.
Graduation date: 1988

Indiana University-Purdue University Indianapolis (IUPUI)
The Air Handling Unit (AHU), which serves the entire basement of Engineering and Technology (ET) building on IUPUI campus, had constant set points of discharge air temperature and supply air static pressure. Two reset schedules were investigated to determine which was the best control strategy to minimize energy consumption of the AHU. In this research, a gray box model was established to create the baseline of energy consumption with constant set points and predict the energy savings using two di↵erent reset schedules. The mathematical model was developed in Engineering Equation Solver (EES). It was validated using two sets of sub hourly real time data. The model performance was evaluated employing Mean Absolute Percentage Error (MAPE) and Root Mean Square Deviation (RMSD). Additionally, uncertainty propagation identified outside air temperature, supply airflow rate and return air temperature were the key parameters that had an impact in overall energy consumption. Discharge air temperature was reset based on return air temperature (RA-T) with a linear reset schedule from March 4 to March 7. Static pressure was reset based on the widest open Variable Air Volume (VAV) box damper from March 20 to March 23. Results indicated that 17% energy savings was achieved using discharge air temperature reset while the energy consumption reduced by 7% using static pressure reset.

This dissertation is a collection of several results in the analysis of partial differential equations arising in mathematical physics and biology. The themes we explore are diverse in their quantitative mathematical properties and applications – yet, a common feature of our studies is the necessity of developing and implementing a variety of weak convergence and compactness methods, indispensable when dealing with nonlinear phenomena. In the first part of the thesis, we investigate the relation between regularity and conserved quantities for some equations arising in fluid dynamics. The main results here are a sufficient regularity condition for local conservation of energy for weak solutions of the Euler-Korteweg system, and an analogous study for the compressible Euler and NavierStokes equations in the degenerate case of possible vacuum formation. Next, we study the archetypal equation in the field of structured population dynamics, namely the growth-fragmentation equation, which is a linear integro-differential equation describing competition between the phenomena of aggregation and fragmentation. The main result of this part is proving that solutions emanating from initial data in the space of positive Radon measures converge, in an appropriate weighted sense, to a steady size distribution. Finally, we consider a two-species model motivated by applications in tumour modelling. The two species are coupled by an elliptic equation tying their velocity potential to the total population pressure. This link is usually referred to as Brinkman’s law. A further coupling is given by a relation between the pressure and a power of the total population density. We establish an existence and uniqueness result, and perform an incompressible limit as the stiffness of the pressure law tends to infinity. This establishes a rigorous connection with a free-boundary model of Hele-Shaw flavour.
Niniejsza rozprawa stanowi zbiór wyników dotyczących matematycznej analizy pewnych równań różniczkowych cząstkowych motywowanych zagadnieniami fizyki i biologii matematycznej. Tematy, które badamy, są różnorodne ze względu na własności jakościowe oraz zastosowania – jednakże wspólną ich cechą jest potrzeba starannego rozwijania całego wachlarza metod słabej zbieżności i zwartości, nieodzownych przy analizie zjawisk nieliniowych. W pierwszej części rozprawy badamy związek pomiędzy regularnością a wielkościami zachowywanymi dla pewnych równań obecnych w mechanice płynów. Głównymi wynikami są tutaj warunki wystarczające do zapewnienia spełnienia lokalnej równości energetycznej przez słabe rozwiązania układu Eulera-Kortewega, oraz ściśliwego układu Eulera (a również Naviera-Stokesa) w zdegenerowanym przypadku występowania obszarów próżni. Następnie badamy podstawowe równanie w dziedzinie dynamiki populacji ze strukturą, a mianowicie równanie wzrostu-podziału. Jest to liniowe równanie całkowo-różniczkowe opisujące współzawodnictwo pomiędzy procesami wzrostu komórkowego a fragmentacją. Głównym wynikiem tej części rozprawy jest wykazanie, że rozwiązanie pochodzące z danych początkowych w przestrzeni nieujemnych miar Radona zbiega, w odpowiedniej normie z wagą, do stanu stacjonarnego. W ostatniej części rozprawy rozważamy dwugatunkowy model motywowany zastosowaniami w opisie wzrostu komórek nowotworowych. Równania zadające dynamikę obu gatunków są sprzężone poprzez prawo Brinkmana, tj. równanie eliptyczne wiążące ich prędkość z ciśnieniem, które jest z kolei proporcjonalne do potęgi całkowitej gęstości populacji. Uzyskane wyniki dotyczą istnienia oraz jednoznaczności słabych rozwiązań układu, oraz przejścia asymptotycznego z wykładnikiem zadającym związek pomiędzy ciśnieniem a całkowitą populacją. Ukazuje to powiązanie rozważanego modelu z geometrycznym modelem o swobodnym brzegu.

Indiana University-Purdue University Indianapolis (IUPUI)
Lithium-ion battery is one kind of rechargeable battery, and also renewable, sustainable and portable. With the merits of high density, slow loss of charge when spare and no memory effect, lithium-ion battery is widely used in portable electronics and hybrid vehicles. Apart from its advantages, safety is a major concern for Lithium-ion batteries due to devastating incidents with laptop and cell phone batteries. Overcharge and over-discharge are two of the most common electrical abuses a lithium-ion battery suffers. In this thesis, a fuzzy-rule-based system is proposed to detect the over-charge and over-discharge failure in early time. The preliminary results for the failure signatures of overcharged and over-discharged lithium-ion are listed based on the experimental results under both room temperature and high temperature. A fuzzy-rule-based model utilizing these failure signatures is developed and validated. For over-charge case, the abnormal increase of the surface temperature and decrease of the voltage are captured. While for over discharge case, unusual temperature increase during overcharge phases and abnormal current decrease during overcharge phases are obtained. The inference engine for fuzzy-rule-based system is designed based on these failure signatures. An early warning signal will be given by this algorithm before the failure occurs. This failure detection and early warning system is verified to be effective through experimental validation. In the validation test, the proposed methods are successfully implemented in a real-time system for failure detection and early warning. The result of validation is compatible with the design expectation. Finally an accurate failure detection and early warning system is built and tested successfully.