Bayesian Methods for Learning and Eliciting Preferences of Occupants in Smart Buildings

Commercial buildings consume more than 19% of the total energy consumption in the United States. Most of this energy is consumed by the HVAC and shading/lighting systems inside these buildings. The main purpose of such systems is to provide satisfactory thermal and visual environments for occupants working inside these buildings. Providing satisfactory thermal/visual conditions in indoor environments is critical since it directly affects occupants’ comfort, health and productivity and has a significant effect on energy performance of the buildings. Therefore, efficiently learning occupants’ preferences is of prime importance to address the dual energy challenge of reducing energy usage and providing occupants with comfortable spaces at the same time. The objective of this thesis is to develop robust and easy to implement algorithms for learning and eliciting thermal and visual preferences of office occupants from limited data. As such, the questions studied in this thesis are: 1) How can we exploit concepts from utility theory to model (in a Bayesian manner) the hidden thermal and visual utility functions of different occupants? Our central hypothesis is that an occupant’s preference relation over different thermal/visual states of the room can be described using a scalar function of these states, which we call the “occupant’s thermal/visual utility function.” 2) By making use of formalisms in Bayesian decision theory, how can we learn the maximally preferred thermal/visual states for different occupants without requiring unnecessary or excessive efforts from occupants and/or the building engineers? The challenge here is to minimize the number of queries posed to the occupants to learn the maximally preferred thermal/visual states for each occupant. 3) Inferring preferences of occupants based on their responses to the thermal/visual comfort-based questionnaire surveys is intrusive and expensive. Contrary to this, how can we learn the thermal/visual preferences of occupants from cheap and non-intrusive human-building interactions’ data? 4) Lastly, based on the observation that the occupant population decompose into different clusters of occupants having similar preferences, how can we exploit the collective information obtained from the similarities in the occupants’ behavior? This thesis presents viable answers to the aforementioned questions in the form of probabilistic graphical models/frameworks. In future, I hope that these frameworks would prove to be an important step towards the development of intelligent thermal/visual systems which would be able to respond to occupants’ personalized comfort needs. Furthermore, in order to encourage the use of these frameworks and ensure reproducibility in results,various implementations of this work (namely GPPref, GPElicit and GPActToPref) are published as open-source Python packages