Directional radiative cooling and solar heating-assisted atmospheric water harvesting for all-day water production

Atmospheric water harvesting (AWH) is a promising approach for freshwater production, yet its overall water yield remains constrained by inefficient thermal & mass management and discontinuous water production. Here, an AWH system was designed that integrated photonics and interface engineering to enhance heat and mass transfer behaviors for all-day water production. At night, dual vertical radiative cooling assisted by a thermal reflector was achieved for both sorption and condensation, resulting in the dew collection. In the daytime, directional solar heating drove the desorption at the sorption/desorption end, and vapor was condensed at the condensation end by directional radiative cooling, resulting in sorption-based water collection. The vertical layout and distance between these two ends were optimized to improve the interior heat and mass transfer behavior via natural convection, and a bio-inspired heterogeneous wettability condensation surface was also designed to promote droplet nucleation and shedding for all-day water collection. As a result, the system achieved an outdoor daily water yield of 2.12 kg m^-2 with an average daily water collection rate of 1.74 kg m^-2. These results demonstrate that collaborative design of thermal and mass transfer behaviors is essential for high-performance AWH systems.