Simulative optimization on energy saving performance of phase change panels with different phase transition temperatures

A new type of a phase change material (PCM) room containing CaCl2·6H2O-Mg(NO3)2·6H2O/expanded graphite (EG) with different phase transition temperatures was proposed. PCM panels with a lower phase transition temperature were active in heating seasons, and PCM panels with a higher phase transition temperature were active in cooling seasons. The effects of the PCM panels and different parameters on the thermal behavior of concrete rooms used for annual energy management were investigated by using the validated numerical model. The energy demand was used as an evaluation index. The results indicated that a smaller energy demand could be obtained by placing the PCM panels inside the room. The energy demand was affected by the phase transition temperature. The PCM panels suitable for the roof and south wall were CaCl2·6H2O-2wt%Mg(NO3)2·6H2O/EG and CaCl2·6H2O-15wt%Mg(NO3)2·6H2O/EG, respectively. As the thickness of the PCM panels increased, the energy demand decreased, but the optimal types of PCM panels for the roof and south wall remained the same. Different climate regions influenced the choice of PCM panels. A climate region with large temperature differences between day and night minimized the energy demand. It is revealed that the PCM rooms exhibited better thermal behavior in both cooling and heating seasons.