Optimization of cool roof and night ventilation in office buildings: A case study in Xiamen, China

Increasing roof albedo (using a “cool” roof) and night ventilation are passive cooling technologies that can reduce the cooling loads in buildings, but existing studies have not comprehensively explored the potential benefits of integrating these two technologies. This study combines an experiment in the summer and transition seasons with an annual simulation so as to evaluate the thermal performance, energy savings and thermal comfort improvement that could be obtained by coupling a cool roof with night ventilation. A holistic approach integrating sensitivity analysis and multi-objective optimization is developed to explore key design parameters (roof albedo, night ventilation air change rate, roof insulation level and internal thermal mass level) and optimal design options for the combined application of the cool roof and night ventilation. The proposed approach is validated and demonstrated through studies on a six-storey office building in Xiamen, a cooling-dominated city in southeast China. Simulations show that combining a cool roof with night ventilation can significantly decrease the annual cooling energy consumption by 27% compared to using a black roof without night ventilation and by 13% compared to using a cool roof without night ventilation. Roof albedo is the most influential parameter for both building energy performance and indoor thermal comfort. Optimal use of the cool roof and night ventilation can reduce the annual cooling energy use by 28% during occupied hours when air-conditioners are on and reduce the uncomfortable time slightly during occupied hours when air-conditioners are off

SRC and its applications to building thermal control

Energy-efficient building design requires, the use of advanced thermal simulation programs and respective complex building models, for the estimation of the annual building energy demand. This complexity, limits the use of such models in model-based building climate control design, mainly because it entails additional difficulty in finding appropriate controllers. To meet the above requirements, a novice climate control method is introduced, which is based on SRC (a building thermal simulation program, which is complex enough for the initial building design phase and at the same time, simple enough for model-based climate control design tasks). In the suggested method, the problem of finding energy-efficient operation schedules of building devices, is formulated as a convex optimization problem and solved using a finite number of iterations, until a certain comfort criterion is met. The method is tested on a two zone building with external and internal openings, where the advantages of interzone air mixing and coupled building model thermal dynamics, are taken into account. The obtained operation schedules, when applied to the passive (openings) and active (HVAC) devices of the test building, exhibited higher energy savings than the schedules provided by a rule-based controller, while conforming to the same thermal comfort requirements

Parallel object-oriented algorithms for simulation of multiphysics : application to thermal systems

The present and the future expectation in parallel computing pose a new generational change in simulation and computing. Modern High Performance Computing (HPC) facilities have high computational power in terms of operations per second -today peta-FLOPS (10e15 FLOPS) and growing toward the exascale (10e18 FLOPS) which is expected in few years-. This opens the way for using simulation tools in a wide range of new engineering and scientific applications. For example, CFD&HT codes will be effectively used in the design phase of industrial devices, obtaining valuable information with reasonable time expenses. However, the use of the emerging computer architectures is subjected to enhancements and innovation in software design patterns. So far, powerful codes for individually studying heat and mass transfer phenomena at multiple levels of modeling are available. However, there is no way to combine them for resolving complex coupled problems. In the current context, this PhD thesis presents the development of parallel methodologies, and its implementation as an object-oriented software platform, for the simulation of multiphysics systems. By means of this new software platform, called NEST, the distinct codes can now be integrated into single simulation tools for specific applications of social and industrial interest. This is done in an intuitive and simple way so that the researchers do not have to bother either on the coexistence of several codes at the same time neither on how they interact to each other. The coupling of the involved components is controlled from a low level code layer, which is transparent to the users. This contributes with appealing benefits on software projects management first and on the flexibility and features of the simulations, later. In sum, the presented approaches pose a new paradigm in the production of physics simulation programs. Although the thesis pursues general purpose applications, special emphasis is placed on the simulation of thermal systems, in particular on buildings energy assessment and on hermetic reciprocating compressors.Las expectativas puestas en el uso de la computación en paralelo plantean un cambio generacional en simulación y computación. Las más modernas instalaciones computacionales de alto nivel -High Performance Computing (HPC)- alcanzan ya la capacidad de realizar gran cantidad de operaciones por segundo -hoy del orden de peta-FLOPS (1e15 FLOPS) y dirigiéndose hacia exaFlops (1e18 FLOPS)-. Esto abre la posibilidad de usar la simulación por ordenador en un amplio espectro de nuevas aplicaciones en ciencia e ingeniería. Por ejemplo, los códigos de CFD&HT van a poder usarse de una forma más efectiva en la fase de diseño de dispositivos industriales ya que se obtendrán resultados muy valiosos en tiempos de ejecución razonables. Por el momento, hay muchos códigos disponibles para el estudio individual de fenómenos de transferencia de calor i de masa con distintos niveles de modelización. Sin embargo, estos códigos no se pueden combinar entre sí para abordar problemas más complejos, en los cuales varios fenómenos físicos interactúan simultáneamente. Bajo este contexto, en esta tesis doctoral se presenta el desarrollo de una metodología de estrategia paralela, y su implementación en una plataforma informática, para la simulación de sistemas multi-físicos. De éste modo, ahora los distintos códigos pueden ser integrados para la creación de nuevas herramientas de simulación destinadas a aplicaciones específicas de interés tanto social como industrial. Esto se hace de una manera intuitiva y simple de manera que los investigadores no tienen que preocuparse ni por la coexistencia de varios códigos simultáneamente ni en cómo hacer que interactúen entre ellos. El acoplamiento entre los diferentes componentes involucrados en una simulación se realiza mediante un código más básico con el cual el usuario solamente interacciona a través de una interfase. Esto aporta interesantes beneficios tanto en la gestión de los proyectos de programario como en la flexibilidad y las características de las simulaciones. En resumen, la estrategia que se propone plantea un nuevo paradigma en la producción de programas de simulación de fenómenos físicos. Aunque la tesis persigue aplicaciones de propósito general se ha puesto especial atención en la simulación de sistemas térmicos, en particular en la evaluación energética de edificios y en compresores herméticos alternativos.Postprint (published version

Energy: A continuing bibliography with indexes, issue 38

This bibliography lists 1367 reports, articles and other documents introduced into the NASA scientific and technical information system from April 1, 1983 through June 30, 1983

Building Thermal Envelope

This book results from a Special Issue published in Energies, entitled “Building Thermal Envelope"". Its intent is to identify emerging research areas within the field of building thermal envelope solutions and contribute to the increased use of more energy-efficient solutions in new and refurbished buildings. Its contents are organized in the following sections: Building envelope materials and systems envisaging indoor comfort and energy efficiency; Building thermal and energy modelling and simulation; Lab test procedures and methods of field measurement to assess the performance of materials and building solutions; Smart materials and renewable energy in building envelope; Adaptive and intelligent building envelope; and Integrated building envelope technologies for high performance buildings and cities

Advances in Computer Science and Engineering

The book Advances in Computer Science and Engineering constitutes the revised selection of 23 chapters written by scientists and researchers from all over the world. The chapters cover topics in the scientific fields of Applied Computing Techniques, Innovations in Mechanical Engineering, Electrical Engineering and Applications and Advances in Applied Modeling