Effectiveness assessment of different kinds/configurations of phase-change materials (PCM) for improving the thermal performance of lightweight building walls in summer and winter

Phase change materials (PCM) are very effective in improving the thermal performance of walls with their superb heat storage and release capacity. However, the effectiveness of PCM in different thermal environments is restricted by their inherent phase-transition temperatures, especially in summer and winter. In this study, the influence laws and effectiveness of different kinds/configurations of PCM on the thermal performance of lightweight building walls (LBW) in summer and winter were evaluated by using a validated numerical model, and the suitable PCM configurations were proposed to maximize the application potential of PCM. The results show that: (1) Although a single-layer of PCM performs prominently in one season (summer or winter), a double-layer of PCM is the best choice from a year-round perspective under the same total thickness; (2) The effectiveness of double-layer PCM is closely related to the temperature difference between indoor and outdoor (comprehensive outdoor temperature), which is better in summer than in winter; (3) The narrower the phase-transition temperatures range (ΔT), the higher the PCM utilization under other suitable parameters, but the optimum value exists from the application effectiveness, the double-layer PCM is ΔT = 6 °C (27–33 °C, 12–18 °C). Meanwhile, the effectiveness of PCM reaches saturation when thickness and latent heat exceed 10 mm (5 mm+5 mm) and 125 kJ/kg, respectively; (4) The optimized PCM kinds/configurations are applied in local summer/winter can reduce the attenuation rate by 84.6%/84.3%, the delay time is added to 5 h/4.86h, the peak and average heat flux are decreased by 58.2%/36.4% and 22.1%/19.4%, respectively compared with reference wall (no PCM). The findings of this study can provide data support and theoretical reference for the application of PCM in LBW to maximize economic benefits.