Numerical analysis on phase change progress and thermal performance of different roofs integrated with phase change material (PCM) in Moroccan semi-arid and Mediterranean climates

Phase change material (PCM) applied to roofs can weak external heat entering the room to reduce air-conditioning energy consumption. In this study, three forms of macro-encapsulated PCM roofs with different PCMs (RT27, RT31, RT35HC, PT37) are proposed. The effects of PCM thickness, the encapsulation forms, and different PCMs on the thermal performance of the roof are discussed in Moroccan semi-arid and Mediterranean climates. The results show that as the PCM thickness increases, the peak temperature attenuation of the roof inner surface decreases. In two climates, the pure PCM layer among the three encapsulation forms (i.e. pure PCM layer, PCM in aluminum tubes, PCM in triangular aluminum) is the easiest to appear the phenomenon of insufficient heat storage and release, while the reduction of the peak inner surface temperature and time lag is the most satisfying. For the PCM in the aluminum tube, phase change time is the shortest and the latent heat utilization ratio is the highest, while thermal regulation performance is the least satisfying. The PCM in triangular aluminum can improve the latent heat utilization ratio significantly, and its thermal regulation performance is in the middle. In semi-arid climate, the time lag increases with phase change temperature increasing. The time lag could reach up to 6 h with 37 ℃ phase transition temperature. In Mediterranean climate, the longest time lag with RT31 is 5 h, while the lowest peak inner surface temperature appears with RT27. The obtained conclusions could provide guidance for the application of PCM roofs in these two climates.