Rotating evaporator for sustainable urban cooling and electricity generation

Abstract

We have developed, for the first time, a rotating evaporator that synergistically performs sustainable urban cooling and electricity generation. Fabricated using 3D printing, it features a nature-inspired hierarchical water path that mimics tree transpiration. Under 1-sun illumination, the rotating evaporator achieved an evaporation rate of 2.08 kg/m²h, and in the presence of wind at a speed of 4 m/s, the evaporator began rotating, enhancing the evaporation rate to 19.58 kg/m²h. When the rotator was fixed to prevent rotation, the evaporation rate decreased by 24 %, highlighting the advantage of rotation in water evaporation by effectively preventing vapor accumulation near the evaporating surface and supplying environmental energy. Notably, the rotating evaporator provided evaporative cooling 12.2 times greater than the incident solar energy, cooling 25.6 m³ of air by 1 °C in one hour, highlighting its potential to mitigate the urban heat island effect. This rotation also generated electricity, achieving a voltage of 1.07 V and a power density of 4.73 W/m², which was sufficient for practical applications such as lighting and water purification.