Performance of hybrid cooling control for the thermal storage effect of PCM-integrated floor in hot-humid climates

Phase change materials (PCMs) integrated into building constructions with night ventilation have been shown to be effective for cooling indoor spaces during the daytime owing to the thermal storage effect; however, they have limited applicability under high nocturnal temperature conditions. Therefore, this study proposes a hybrid cooling mode that uses control logic to switch between night ventilation and mechanical cooling, which supplies adequate cooling capacity to enable nighttime heat discharge of PCMs. A PCM-integrated floor system equipped with hybrid cooling was designed for indoor thermal comfort and cooling energy savings considering the lifestyles of Indonesian residents. The switching setpoint (27.0°C) was determined based on a comprehensive analysis, involving PCM phase change, resident thermal comfort, and local typical meteorological year data. Field measurements were conducted in apartment units in Tegal, Indonesia to evaluate system performance and hybrid cooling effectiveness. Relative to the non-cooling mode, the system under forced night cooling reduced the peak floor surface temperature by up to 0.6°C and extended the average daytime comfort duration by 231 min, with the effect significant in low-height zones below FL+1.1 m. Relative to AC-only mode, the hybrid cooling mode consumed 29.3% less energy. Although its daytime comfort was slightly lower under hotter measurement conditions, hybrid cooling is essential for sustaining PCM nighttime heat discharge, because most nights in the local climate are too warm for night ventilation alone. Hybrid cooling therefore provides a reliable and energy-saving strategy for PCM-integrated floors in hot-humid climates with high nocturnal temperatures.