Improving the mass transfer rate and energy efficiency of solar still by enhancing the inner air circulation

Solar still is an eco-friendly and convenient desalination system that can provide fresh water for remote areas and emergencies. The energy efficiency and productivity of conventional solar still are unsatisfying and need improvement, which requires a deep understanding of the heat and mass transfer process in solar still. In this work, the effect of the inner air circulation on the system's heat and mass transfer performance and energy efficiency are studied theoretically and experimentally. The theoretical results reveal that a weak acceleration of the air circulation inside the SS will significantly increase its performance, due to the improved mass transfer process. By enhancing the inner air circulation, the evaporation and condensation in the solar still can reach up to the limit, and the theoretical energy efficiency reaches up to 87%, 91.5%, and 94.5%, for the input power density at 300 W/m2, 500 W/m2, and 700 W/m2, respectively. Besides, lower ambient temperature and higher ambient convective heat transfer coefficient will decrease the energy efficiency. Given the heat loss, the experimental energy efficiencies are only 3% to 6% lower than the theoretical results, which indicates that the great performance predicted by the theory can be realized in practical application. This work provides a new understanding and strategy for improving the performance of the solar still.