Atmospheric water harvesting using a desiccant-based solar still: experimental investigation and economic analysis

Abstract Water scarcity is currently a major worldwide issue, and many unconventional solutions are being tested to provide water to populations in remote areas. A promising method involves harvesting water from ambient air using a humidity adsorbent and solar energy. This approach was explored through a desiccant-based solar still, using river sand impregnated with a calcium chloride solution. The sorption-desorption stability of the bed sorbent was studied over five consecutive days. Absorption occurred at night, allowing the bed to capture water vapor from the surrounding air. Various parameters that influenced the kinetics of water vapor absorption were studied. The results showed that the bed could harvest 671.02 ml m −2 of water vapor from the ambient air at an average ambient temperature of 25 °C and an average relative humidity of 80%. The daytime process involved simultaneous desiccant regeneration and water vapor condensation. Several parameters were recorded during the trials to evaluate their influence on the evaporation rate and collected condensate. Experimental findings showed that the total amount of evaporated water is affected by the initial desiccant concentration in the bed and the cumulative solar energy. Optimal conditions yielded 908.67 ml m −2 of evaporated water at an initial desiccant concentration of 50% and 25.47 MJ m −2 of solar energy. The water yield ranged from 561.51 ml m −2 to 645.39 ml m −2 , with a maximum energy efficiency of 24.60%. The estimated cost of collected water was $0.086 per liter, with a payback period of 18.25 months.