A novel radiative sky cooler system with enhanced daytime cooling performance to reduce building roof heat gains in subtropical climate

Radiative sky coolers (RSCs) can reduce building roof heat gains by radiating heat to outer space. However, their performance during daytime is limited, with substantial roof heat gains still occurring due to high ambient temperatures. Additionally, much of the cooling produced at night is wasted since air conditioners in non-residential buildings are often not operating. To address these limitations, we propose a novel thermal storage-heat pipe-integrated radiative sky cooler system (TS-HP-RSC). It utilizes water thermal storage to capture nighttime sky cooling for use during the day. A gravity-assisted heat pipe unidirectionally transports this stored cooling to the indoor space, preventing losses to the environment. An experimental platform is established integrating the proposed system, a baseline case, and measurement instrumentation. Compared to the baseline, the TS-HP-RSC system not only eliminated daytime cumulative heat gains (0.55–1.27 kJ) but also provided supplemental cooling (1.57–2.75 kJ). This yielded substantial daytime heat gain reductions of 223.62 %–600 % versus the baseline. Similar reductions occurred in peak heat gains. By enhancing daytime cooling, the TS-HP-RSC system can substantially curb roof heat gains in subtropical climates, enabling significant energy savings.