A compact flat solar still with high performance

Abstract Solar still is a convenient off-grid device for desalination, which can provide fresh water for families, ships, islands, and so on. The conventional inclined solar still (ISS) suffers from low efficiency and low productivity. To improve the performance of solar still, a flat solar still (FSS) is proposed, which has a working principle similar to the solar cell. The condensate water in FSS is collected by the capillary grid attached under the ultra-hydrophilic glass cover, instead of by gravity. Therefore, FSS avoids the inclined structure and is much more compact than ISS. The daily productivity of FSS reaches up to 4.3 kg/m2 under 6.3 kWh/m2 of solar insolation. Theoretical analysis shows that the enhanced mass transfer in FSS by the compact structure is an important factor for high performance. More interestingly, FSS can also be easily extended to more stages for latent heat recovery. The results show that the daily productivity and energy efficiency of a double-stage FSS reaches up to 7 kg/m2 and 72%, respectively, under 6.7 kWh/m2 of solar insolation, which is much higher than the conventional solar still. FSS paves a new way in designing and optimizing solar still.