PhD Dissertations

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    Augmenting occupant thermal experience with cyber-physical-social systems : a case study on adaptive vents
    (2020-06-11) Keskin, Cem; Mengüç, Mustafa Pınar; Mengüç, Mustafa Pınar; Ertunç, Özgür; Başol, Altuğ Melik; Kayakutlu, G.; Yurtseven, M. B.; Department of Mechanical Engineering; Keskin, Cem
    Buildings use more than 30% of global energy, while 36% of this energy comes from direct combustion of fossil fuels. Hence, buildings constitute a considerable share of CO2 emissions and has a large contribution to climate change related problems. The highest share (almost half) of the total energy consumption in buildings is due to heating, cooling and air conditioning (HVAC). Particularly, the increasing demand for space cooling is pushing this share up. Thus, HVAC systems are considered as one of the key contributors of the total energy consumption and the adverse environmental impacts of buildings. Recent developments in technology offer promising tools to leverage interactions between occupants and the building systems. The energy efficiency of HVAC operations is not only a technical concern, what is more is that it requires to modifications considering human behavior. The convergence of physical systems in built environment with the information and communication technologies, as well as the human dimension makes it necessary to co-evaluate these distinct realms during the design and operation of building systems. The cyber-physical-social systems (CPSS) approach has a promising potential to facilitate this interdependence. A novel HVAC interface is presented in this thesis study. An Adaptive Vent System (AVS), is proposed to enable localized and customized thermal management in built environment for a better thermal experience of occupants and higher level of energy efficiency for building operators. The system is designed as a CPSS and composed of: (i) a novel diffuser design with individually operable flaps, (ii) thermal agents, (iii) a user interface, and (iv) a control and communication unit. It enables asymmetric air-inlet to manage indoor temperature distribution and aims to match varieties in temperature with the differences in occupant demands. The system is intended to decrease the conditioned air volume that results in HVAC energy efficiency without sacrificing occupant comfort. The design and operation of complex building energy systems like AVS is a challenging task. In order to assist this process, a methodological framework is presented that outlines the development process, from the early definition to prototyping and performance analysis. The framework is based on a novel CPSS modeling approach that combines hybrid dynamic modelling (for cyber and physical aspects) with human behavior modeling (for social aspects). A prototype of the proposed AVS was deployed in an office of an academic building in order to conduct experiments and validate CPSS and computational fluid dynamics (CFD) models. Both experiments and simulation based assessments of system operation shows that system can generate temperature difference between opposite sides of a room in a controllable manner. It is also shown that this difference results in considerable change in thermal sensation of occupants and can pave the way for energy savings with localization inside the rooms. The core reason for efficient HVAC operation with AVS is the usage of less amount of thermally conditioned air by minimizing the conditioning of unnecessary parts of the room. Moreover, the system leverages occupant interaction by delivering advanced control options (enhanced perceived control) for more customized practices. The interplay between the building energy management and the localization and customization of thermal management can maximize demand flexibility of buildings, that is a key concern for demand side management and energy planning. Hence, the new AVS system is to leverage overall thermal experience in built environment in an energy efficient way and help decreasing the environmental impact of buildings.