Modeling and performance evaluation of radiative cooling-assisted interfacial evaporation for all-day freshwater harvesting

The shortage of freshwater resources is one of the major challenges that need to be addressed urgently. Solar-powered interfacial evaporation technologies also face problems such as efficient condensation recovery of vapors and inability to evaporate at night. In this work, an all-day evaporation-freshwater harvesting device is designed by coupling solar interfacial evaporation and radiative cooling technologies. The system utilizes passive radiative cooling to accelerate water vapor condensation and, at the same time, meets the nighttime condensation collection of freshwater to improve the efficiency of freshwater collection. The freshwater collection performance of the device was first tested experimentally. According to the experimental results, the device can collect 3.27 kg m⁻² of freshwater in a day, and the average collection rates during daytime and nighttime reached 0.24 kg m⁻² h⁻¹ and 0.074 kg m⁻² h⁻¹, respectively. In addition, a numerical model of systematic all-day evaporation and condensation with freshwater collection was constructed based on the theory of heat and mass transfer and energy conversion, and the accuracy of the numerical model was verified using experimental results. The potential of the evaporation collection device to collect freshwater across China was studied by the verified model using environmental data from typical meteorological years, and analyzed the renewable energy in different regions. Finally, the effects of relative humidity, cloudiness, and convective heat transfer coefficients on the collection of freshwater in the system are discussed, and this work provides important insights into how evaporative collection devices can achieve widespread deployment in the future.