using occupant feedback in model predictive control for indoor thermal comfort and energy optimization

Open Access
Author:
Chen, Xiao
Graduate Program:
Mechanical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
None
Committee Members:
  • Qian Wang, Dissertation Advisor
  • Qian Wang, Committee Chair
  • Alok Sinha, Committee Member
  • Bo Cheng, Committee Member
  • Stephen James Treado, Committee Member
  • Jelena Srebric, Special Member
Keywords:
  • building climate control
  • model predictive control
  • thermal comfort
  • energy consumption
  • occupant feedback
Abstract:
Buildings are our society’s biggest energy users. Reducing building energy consumption and creating a better indoor thermal environment have becoming a more and more important topic among policy makers, building scientists/engineers, and the masses. To achieve this target, great efforts have been made in several aspects including but not limited to using better thermal insulation materials, integrating renewable power sources, developing intelligent buildings, and creating better and more efficient building climate control systems. With the ever increasing computation power, advancements in building modeling and simulation, and accurate weather forecast, model predictive control (MPC) reveals its power as one of the best control methods in building climate control to save energy and maintain high level of indoor comfort. Although many researchers have investigated extensively on how to use building’s active or passive thermal storage along with accurate weather forecast and occupants’ schedule prediction to reduce energy consumption or shift loads, not much research has been done on how a better thermal comfort model used in MPC would help reducing energy usage and improve comfort level. Furthermore, unlike lighting control in which occupants have plenty of opportunities to adjust lights and blinds so that visual comfort can be improved, centralized and automated building thermal control systems take away users’ ability to intervene the control system directly. In this dissertation, we study occupant augmented MPC control design in which feedback information from occupants is used to adaptively update the prediction given by a data-driven dynamic thermal sensation model. It is demonstrated both in simulation and chamber experiment that including users directly in the feedback loop of MPC control design provides opportunity to significantly save energy and still maintain thermal comfort. We propose a data-driven state-space dynamic thermal sensation (DTS) model based on data collected in a chamber experiment. The developed model takes air temperature as input, and the occupant actual mean thermal sensation vote as an output. To account for cases in which indoor environmental or occupant associated conditions deviate from the nominal condition conducted in the chamber experiment, a time-varying offset parameter in the model is adaptively estimated by an extended Kalman filter using feedback information from occupants. We develop two different MPC controls based on the proposed DTS model: a certainty equivalence MPC and a chance constrained MPC. By using this thermal comfort model in the MPC design, users are included directly in the feedback loop. We compare the DTS model based MPC with predicted mean vote (PMV) model based MPC. Simulation results demonstrate that an MPC based on occupant feedback can be expected to produce better energy and thermal comfort outcomes than an MPC based on PMV model. The proposed chance-constrained MPC is designed to allow specifying the probability of violation of thermal comfort constraint, so that a balance between energy saving and thermal comfort can be achieved. The DTS model based MPC is evaluated in chamber experiment. A hierarchical control strategy is used. On the high level, MPC calculates optimal supply air temperature of the chamber’s HVAC system. On the low level, the actual supply air temperature of the HVAC system is controlled by the chiller and heater using PI control to achieve the optimal level set by the high level. Results from experiments show that the DTS-based MPC with occupant feedback provides the opportunity to reduce energy consumption significantly while maintain occupant thermal comfort.