Evaluating passive PCM performance in building envelopes for semi-arid climate: Experimental and numerical insights on hysteresis, sub-cooling, and energy savings

This study evaluates the performance of macro-encapsulated Phase Change Materials (PCMs) integrated into building envelopes for semi-arid climates, focusing on typical Moroccan construction using hollow concrete blocks. The primary objective is to assess the discrepancies between experimental and numerical analyses, particularly in hysteresis, sub-cooling, and energy savings. Given the widespread reliance on numerical tools like EnergyPlus for PCM simulations, the accuracy of manufacturer-provided latent heat values is investigated. The methodology involves constructing two identical test buildings, one equipped with PCM panels and another as a reference. Experimental data were collected in June 2023, assessing temperature fluctuations and energy savings. Differential Scanning Calorimetry (DSC) tests at varying scanning rates were conducted to analyze PCM behavior, including hysteresis and sub-cooling effects. Numerical simulations were then performed to compare energy performance. Besides, the results reveal that sub-cooling significantly limits PCM efficiency, with only 43 % of the PCM's latent heat capacity utilized. At the same time, hysteresis was found to be negligible in the field test. Cooling energy consumption was reduced by 20 %, with a corresponding 2.3 degrees C reduction in temperature fluctuations. However, the PCM's latent heat potential is underutilized due to sub-cooling. This research underscores the need for conducting DSC measurements at specific scanning rates to reflect regional climate conditions and suggests that simulation models should adjust latent heat utilization of the PCM. The study advocates for the use of composite PCMs, which could mitigate sub-cooling and enhance overall performance. These findings contribute to improving PCM integration in passive building designs, offering practical recommendations for better energy efficiency in semi-arid climates.