Abstract

Thermal energy storage (TES) systems that are part of the building fabric and are exposed to room air can be described as building-integrated thermal energy storage (BITES) systems. BITES systems with appropriate space conditioning strategies can significantly improve the thermal performance of buildings. The present study focuses on active BITES systems, which embody controllable internal charge/discharge system. Thermal energy can be stored and released in an appropriate manner to control zone temperature for improved comfort and energy performance.

To assist the design and control analysis of active BITES systems, methodologies are first developed for three numerical modeling approaches: time domain lumped-parameter finite difference model, frequency domain analytical model and regression model. The regression model is demonstrated for the charge control of active BITES cooling using outdoor cool air. A frequency domain methodology is presented with guidelines for the design and operation of active BITES systems that facilitate primary space conditioning with low operating energy, relatively flat power demand, and improved thermal comfort. Three key factors considered by the methodology are as follows: sufficient thermal coupling between the BITES systems and their thermal zones, integration of design and operation, and integration of thermal and structural designs. A heuristic approach based on building physics is suggested for establishing a near-optimal room air temperature set-profile. Dynamic response of active systems derived from their frequency domain transfer functions are used to enhance the set-profile. Using the set-profile and corresponding space conditioning load profile as inputs, the charge and discharge rates for the active BITES can be predicted over a desired time horizon. A bounding-condition-based design approach is presented. Finally, a procedure for the integration of structural and thermal designs is demonstrated with focus on ventilated BITES systems using standard structural components and their variations. The methodology and guidelines are general and applicable to different BITES systems and different buildings with different thermal and structural loads.