Hydrophilic radiative cooler for direct water condensation in humid weather

Sub-ambient radiative cooling has been achieved recently by applying advanced nanofabrication technologies, which attracts extensive research attention due to its passive cooling characteristic. Water condensation is an important application of radiative cooling, which is also an unconventional technology for gaining fresh water without consuming energy. However, limited efforts have been devoted to improving the water harvesting using the state-of-the-art radiative cooling materials. To efficiently accomplish dew condensation by radiative cooling, we first take a theoretical approach to analyze the weather conditions for effective dew condensation. Then, we propose the durable enhance specular reflector-metal by 3 M Company (DESR-M) as an efficient material for dew condensation and further improve its dew condensation performance through a simple hydrophilic coating. The dew condensation performance shows significant enhancement over the previously used polytetrafluororoethylene (PTFE) radiative condenser. On-site experiment result shows that the hydrophilic DESR-M can achieve lowest cooling temperature among all the three samples. The dew yield improves by 72.7% and 88.1% compared to DESR-M and PTFE, respectively.