Research on the practice of large-scale utilization of Earth's long-wave infrared cooling in Hainan

Hainan Province, located in a subtropical high-humidity climate zone, requires air conditioning and refrigeration systems for over 10 months annually, leading to substantial energy consumption. To mitigate this energy burden and reduce overall societal energy consumption, this study proposes a refrigeration system that harnesses the Earth's LWIR. The system consists of four parallel/series-connected modules of fine capillary tubes (each measuring 1m×2m), forming a complete cooling network. The system operates during the lowest temperature period of the day to maximize energy efficiency. The proposed design adopts a parallel fin network configuration, which demonstrates superior radiative performance and faster cooling rates compared to the series fin network. Experimental results show that the fine capillary network installed at a height of 2 m achieves enhanced radiative decay suppression and benefits from vertical gravitational effects. This results in a cooling time of 10–40 min across the coverage area for individual rooms, while also exhibiting directional radiative characteristics. Based on the Predicted Percentage of Dissatisfied (PPD) ≤ 25 % and a maximum temperature gradient within the active zone not exceeding 3 °C, the system's thermal comfort was validated. Furthermore, the LWIR emitted by cooling water flowing through the fin network was analyzed using blackbody radiation theory to assess its contribution to the room's cooling load. The results indicate that this system can effectively meet the 25 °C refrigeration requirement. Additionally, the study confirms the feasibility of directly utilizing the Earth's infrared energy during the coldest period of the day. These findings provide both theoretical support and practical guidance for reducing societal energy consumption in Hainan Province while demonstrating the potential for optimizing energy utilization based on natural environmental characteristics.