Investigation of PCM cooling saving potential under variable building envelope structures and Chinese climatic regions

The integration of PCM (phase change material) into building envelopes has been proven as an effective strategy for maintaining indoor thermal comfort and reducing building energy demand. However, the performance of PCM critically depends on the PCM position within the envelope, the original wall components, the phase transition temperature and the climatic conditions. In this study, the cooling saving performance of PCM for a two-story building in Hong Kong was optimized using Energy Plus, focusing on the impact of envelope component materials and their optimal arrangement order. Additionally, the optimal phase transition temperature under variable indoor temperatures and seasons was studied to optimize PCM performance. Then, the cooling savings of PCM were evaluated in different Chinese climate zones. Key findings revealed that arranging the PCM layer on the interior side of the insulation layer effectively extends the phase transition time and enhances cooling saving performance. Secondly, the application of PCM can increase the thermal mass of lightweight wallboards to yield significant cooling savings ratio up to 18 %, while that is decreased to 2.5 % in the heavyweight wallboards. Moreover, increasing the insulation thickness reduces the cooling saving of PCM. However, PCM still retains a certain level of effectiveness, as it can absorb the heat gains caused by solar radiation and other internal heat sources. Thirdly, it was found that the phase transition temperature should align with the desired indoor thermostat temperature, regardless of ambient temperature. For the regional analysis, cities with larger diurnal temperature ranges, such as Wuhan and Kunming, exhibit higher cooling energy savings potential. Coastal cities like Hong Kong and Shanghai showed less prominent cooling saving benefits.