The use of solar chimneys to improve natural ventilation in buildings has been shown to yield energy savings while maintaining thermal comfort... Show moreThe use of solar chimneys to improve natural ventilation in buildings has been shown to yield energy savings while maintaining thermal comfort in some climate zones. However, one disadvantage is that the ability to control passive ventilation with solar chimneys is often limited by temporal variations of building function and diurnal weather patterns. The unique thermal properties of phase change materials (PCMs) may provide opportunities to manage some of the limitations of solar chimney strategies in buildings through the timed storage and release of thermal energy, which can aid in minimizing daytime heat gains and increasing the effectiveness of nighttime flushing by natural ventilation. This work explores the potential of PCMs combined with solar chimneys to support the passive ventilation of buildings using whole building energy simulation. Results are intended to inform architects and engineers on best practices for incorporating PCMs in buildings with solar chimneys. A model of a prototype office building designed to ASHRAE Standard 90.1 was developed in EnergyPlus and investigated in five U.S. climate zones. A total of 1023 energy simulations were performed to address the following research questions: (1) In what U.S. climate zone is the use of PCMs most appropriate? (2) Can PCMs improve night flushing ventilation when used with a solar chimney? (3) What are the optimal locations for installation of PCMs in building and solar chimney construction in order to provide optimal cooling load reductions? and (4) How do PCM properties influence cooling load reductions? Results demonstrate that the solidification and melting process of PCMs can indeed be used to prolong natural ventilation for night flushing in the evening and nighttime, particularly in climate zones with large diurnal outdoor temperature fluctuations. Results also suggest the following: (1) the optimal location for installation of PCMs in most climates is within the structure of south-facing envelope assemblies; (2) the PCM melting temperature should be equal to or greater than the zone set point temperature; (3) thicker PCMs can yield slightly more cooling energy savings than thinner PCMs; and (4) the thermal conductivity of PCMs does not appear to have a substantial influence on performance. Ph.D. in Architecture, December 2014 Show less
