Analytical model to study the heat storage of phase change material envelopes in lightweight passive buildings: Fid-Bau Portal

Analytical model to study the heat storage of phase change material envelopes in lightweight passive buildings

Bai, Lu / Xie, Jingchao / Farid, Mohammed M. / Wang, Wei / Liu, Jiaping

Abstract Integrating phase change materials (PCMs) into building envelopes can improve the heat storage ability of buildings and prevent overheating when the outdoor air temperature and solar radiation are high. However, simply adding a PCM to a building does not ensure that the temperature of a room can be controlled; hence, a suitable design method is necessary. Nevertheless, the heat storage mechanism of PCM envelopes is very complicated because it is affected by several factors, including the climate, building parameters, and the properties of the PCM employed. This study develops a mathematical model for passive buildings, and the factors affecting the heat storage process of PCM envelopes in summer are analyzed to determine an efficient method to control the temperature of the room with PCMs. A theoretical analysis demonstrates that PCMs reduce the indoor temperature, but not the average room temperature. The effectiveness of PCMs in buildings is influenced by both climate and building parameters. If the average outdoor air temperature is higher than the boundary of the humans' comfort level, overheating will occur even when using PCMs. Before using PCMs, the average room temperature should be calculated and previewed using the proposed theoretical model. If the effectiveness of PCM is limited, the average room temperature is reduced via ventilation.

Highlights • A mathematic model of heat transfer for passive PCM buildings is developed. • Factors affecting the heat storage of the PCM in summer are analyzed. • Methods to control room temperature using PCMs in a passive way are given.