Theoretically predicting extraterrestrial passive daytime radiative cooling on Earth

Passive daytime radiative cooling (PDRC) has emerged as a promising technology, enabling cooling below ambient temperature without external energy input. To date, extensive research has been dedicated to exploring the cooling performance of PDRC materials in terrestrial settings, while comprehensive and systematic investigations concerning PDRC in extraterrestrial environments remain notably scarce. Due to the difficulties in studying PDRC performance in extraterrestrial environments, an appropriate relationship should be established between PDRC performance on Earth and in space. To bridge this knowledge gap, the present study probes into the principal factors governing the cooling limit of PDRC materials in extraterrestrial environments. From the vantage points of cold source temperature and heat conductivity, a systematic analysis was carried out to identify the factors influencing the attainment of maximum temperature drop in ground-based simulated extraterrestrial environments. Correspondingly, recommendations for cold-source temperature and conductive heating selection are put forward to enhance the fidelity and reliability of such ground-based simulations, thereby facilitating a more profound understanding and optimized application of PDRC in space exploration.