The objective of this research is to develop methods for the operation and design of cyber physical systems in general, and energy efficient buildings in particular. The approach is to use an integrated framework: create models of complex systems from data; then design the associated sensing-communication-computation-control system; and finally create distributed estimation and control algorithms, along with execution platforms to implement these algorithms. A special emphasis is placed on adaptation. In particular, buildings and their environments change with time, as does the way in which buildings are used. The system must be designed to detect and respond to such changes.
The proposed research brings together ideas from control theory, dynamical systems, stochastic processes, and embedded systems to address design and operation of complex cyber physical systems that were previously thought to be intractable. These approaches provide qualitative understanding of system behavior, algorithms for control, and their implementation in a networked execution platform. Insights gained by the application of model reduction and adaptation techniques will lead to significant developments in the underlying theory of modeling and control of complex systems.
The research is expected to directly impact US industry through the development of integrated software-hardware solutions for smart buildings. Collaborations with United Technologies Research Center are planned to enhance this impact. The techniques developed are expected to apply to other complex cyber-physical systems with uncertain dynamics, such as the electric power grid. The project will enhance engineering education through the introduction of cross-disciplinary courses.
The objective of this research project was to develop methods for the operation and design of cyber physical systems in general, and energy efficient buildings in particular. Apart from meeting these two original objectives, the project also made significant contributions to another objective: to use buildings as sources of inexpensive ancillary service to the power grid that enables stable operation of the grid in the presence of volatile sources of renewable energy such as solar and wind. The main scientific outcomes of the project can be divided into three categories: (A) Development of novel control system for energy-efficient building climate control: Buildings consume 75% of electricity consumed in the United States. Their HVAC (heating, ventilation, and air conditioning) systems are typically operated inefficiently, leading to large wastage of energy. Our hypothesis was that with intelligent real-time decision-making, significant energy savings could be obtained. Achieving this vision also requires research in the intersection of cyber and physical domains. The physics of the processes being controlled (indoor climate variables) are complex and uncertain, which makes their control challenging. Moreover, novel sensing and software platforms are needed to support optimal decision-making and execution of such decisions in HVAC equipment. The work done in the project culminated in the development of a novel control system that consisted of low-cost wireless sensors and estimation algorithms to provide occupancy estimates in real-time, decision-making algorithms to reduce energy use without adversely affecting indoor climate, and a software platform to integrate the two so that decisions can be executed on HVAC equipment. Apart from new buildings, the control system can be used to retrofit existing building inexpensively. Its effectiveness was demonstrated though a week-long test in a building in the University of Florida campus (Pugh Hall). The use of the control system resulted in approximately 40% reduction in energy use compared to that by the existing control system in the building. (B) Enabling buildings to provide ancillary service to the electric grid: Due to the high thermal inertia of commercial buildings, if the ventilation airflow through the building is increased by 10% for 20 minutes and then decreased by 10% for the next 20 minutes, there will not be any noticeable change in the indoor climate. In effect, the building acts as a virtual battery, charging and discharging energy. Such controllable power consumption can be used as "ancillary services" that are today provided by controllable generators, such as gas turbine. With higher penetration of renewable energy sources that are intermittent and uncertain, such flexibility in consumption will be crucial in ensuring stable operation of the electric grid. A control system to enable buildings to provide ancillary service was developed as part of this project. It was experimentally demonstrated in a building in the University of Florida campus (Pugh Hall). The demonstration test corroborated our predictions – that HVAC systems can provide substantial ancillary service without affecting indoor climate. Based on these experiments and further analysis, we estimate the ancillary service capacity of the commercial buildings in the U.S. is a large part of what the nation needs currently, which at present are procured from fossil fuel generators. Since this service is obtained from buildings with just a software add-on without requiring any equipment installation, it is also harnessed inexpensively. (C ) Science of cyber physical systems: The project also contributed to the science of cyber physical system by making discoveries on the design of control systems for large-scale cyber physical systems, such as power grids, automated vehicle platoons, and large buildings with many actuators and sensors. These discoveries have resulted in a large number of publications in reputed journals and international conferences. There are a number of broader impacts of the proposal, one of them being the educational component. The project supported five PhD students and two MS students to complete their dissertations, and several undergraduate students to obtain research experience. All of these students are now contributing to the high-tech sector of the US economy in their professional capacity. The project also contributed to classroom teaching by motivating changes to course content and serving as a source of semester-long course projects. The technologies developed during the project have the potential positively disrupt the U.S. energy sector. The control system developed for energy-efficient climate control of buildings can reduce their energy use substantially at low cost without impacting indoor climate. If deployed at large scale, this technology can reduce the nation’s emissions and its dependence of fossil fuels. The technology for enabling buildings to provide ancillary service also has similar potential. It will lead to efficiency in a broader sense, by enabling higher use of renewable energy sources and thereby reducing our dependency on carbon emitting fossil fuels. Apart from a large number of journal articles and conference publications, the project has also generated three patents.
