Multistage interfacial thermal desalination system with metallic evaporators

Abstract

Small scale and passive solar-thermal desalination system hold promise to be employed in decentralized and off-grid areas to address scarcity of potable water. Here, we present a compact multistage thermal desalination system based on interfacial evaporation and latent heat recovery. We develop a textured metallic evaporator substrate that serves as a wick and reduces the thermal resistance for interfacial evaporation. We demonstrate that the rate of evaporation can be increased by tuning the wettability of the condenser surface. Patterned wettability-contrast surfaces are shown to enhance the rate of condensation compared to an unpatterned substrate with spatially uniform wettability. In a single stage desalination system, with patterned condenser surfaces, the evaporation rate increases by ~11 % and the water collection increases by ~21 % compared to that using an unpatterned condenser substrate. The thermal to vapor efficiency of ~56 % in a single stage increases to ~185 % with the use of multistage system. We achieve a water collection of ~2.17 Lm−2 h−1 using a 5-stage system. A theoretical model based on heat and mass transport analysis is used to determine the influence of the system geometry and ambient conditions on the overall efficiency of the desalination system.