Preliminary characterization of three-source air conditioning integrating radiative sky cooling and direct evaporative cooling

Normal high-temperature air sources are not conducive to condensing heat dissipation of conventional air conditioning, resulting in reduced refrigerating efficiency. Radiative sky cooling (RSC) and evaporative cooling (EC), as passive and sustainable cooling techniques, are exploratively introduced to the condenser of air conditioning direct or indirect to optimize condensing dissipation. However, the uncertainty of climatic conditions and the limitations of cooling power hinder their practical application. To address this issue, a novel three-source air conditioning (TSAC) has been proposed, incorporating radiative sky cooling and direct evaporative cooling (DEC). A distribution parameter model has been developed and validated, providing a comprehensive analysis of the effects of outdoor air temperature, indoor air temperature, evaporator wind speed, solar radiance, relative humidity, and outdoor wind speed on the variation of thermodynamic parameters and the system's steady-state performance. The computational findings reveal a significant reduction in the system's energy consumption, and the refrigeration capacity exhibits higher stability in response to outdoor environment variations. The coefficient of performance in various outdoor boundary conditions has increased by 0.14 %–31.67 % compared to traditional air conditioning. Additionally, the phenomenon of adverse convection, arising from the plate surface temperature dropping below the air temperature as a result of passive cooling was thoroughly analyzed. The study confirms that the proposed system optimizes cooling source temperature throughout the day by incorporating radiative sky cooling, evaporative cooling, and air-cooling, which ensures stable and efficient refrigerating performance under complex weather conditions, expanding the application of passive cooling in air conditioning.