Achieving excellent thermal transfer in highly light absorbing conical aerogel for simultaneous passive cooling and solar steam generation

Passive cooling technology is zero-energy and eco-friendly, and has the potential to reduce reliance on energy-intensive cooling techniques such as compression refrigeration. Typically, in order to achieve efficient cooling, the passive system should reflect sunlight as much as possible to minimise the input energy. Here, we demonstrate an unconventional passive cooling process in a system with high light absorption of approximately 99.3%. The main component of the system is an aerogel with a unique conical structure that performs thermal transfer. Solar-thermal and ambient thermal energy are utilized to power the vaporization of water contained in the directional channel of the aerogel, where water keeps in capillary state. Under a simulated condition of one sun irradiation, the average evaporation rate of the conical aerogel is as high as 2.23 kg m-2h−1, and the maximum specific cooling power is 271.56 W m−2. An outdoor prototype demonstrates that the temperature of the cooling room can be up to 13.7 °C lower than that of ambient air on a sunny day of summer. This simultaneous solar steam generation and passive cooling system has great application potential in thermal concentration and environmental cooling processes.