Development of a PCM-Integrated Radiant Cold-Storage System: Radiative-Cooling Film, Water Tank Design, and Outdoor Performance Validation

Outdoor environments typically require intensive cooling during the day, while nighttime cooling demands are comparatively modest. Conventional radiative-cooling systems deliver strong cooling at night but often underperform during daytime solar exposure. Here, we develop a PCM-integrated radiative cold-storage system (RCSS) that couples a polymer metasurface radiative-cooling (PMRC) film with a paraffin cold-storage tank via a helical-tube heat exchanger, and validate it through outdoor tests supplemented by CFD-based analysis. Under representative outdoor conditions, the RCSS cools circulating water at an average nighttime rate of 3.1 K h−1 and maintains stable performance for initial water temperatures of 25–55 °C. Using PMRC’s cooling power as the benchmark for effective radiative-cooling power, we quantify the system-level heat-transfer pathways and provide design sensitivities with respect to film area, exchanger geometry, and tank dimensions. The results establish a practical route to all-day thermal management by storing “cold” at night and releasing it on demand, thereby facilitating scalable deployment of radiative-cooling technologies.