Atmospheric water harvesting by using evacuated tube collector: An experimental investigation

•Atmospheric water harvesting system based on evacuated tube solar air heater.•2.130-liter/day of fresh water is produced using an air-to-air heat exchanger.•Thermal efficiency of the developed system is 24.32% with 3.58% overall efficiency.•The produced fresh water costs 0.21 $/liter with 2 years-9 months of payback time. The current global water crisis arises from the combination of limited freshwater resources and a growing world population, which highlights the need for self-sustainable water production system. Atmospheric water harvesting (AWH), leveraging the vast renewable water reservoir of atmospheric air, holds promise as a viable solution to address human water needs. The AWH systems reported in the literature possess low regeneration temperature, vapor leakage and reduced condensation. In the present work, a novel AWH system is developed and experimentally investigated under the ambient conditions. It comprises of 8.46 m2 evacuated tube solar air heater to provide higher regeneration temperature, packed desiccant bed of silica gel to reduce vapor leakage and an air-to-air heat exchanger for improved condensation. Four different cases with 20 and 30 kg desiccant bed are examined at two different mass flow rates of 56.01 kg/h and 102.69 kg/h. The adsorption process is performed during the night-time while the desiccant material regeneration is carried in the day time. The system performance is measured in terms of adsorption rate, regeneration rate, thermal efficiency, overall efficiency and productivity. The developed system demonstrates optimum results for case 1 with 20 kg desiccant bed at 56.01 kg/h mass flow rate. The average adsorption and regeneration rate observed were 0.592 kg/h and 0.461 kg/h, respectively. The maximum fresh water produced is 2.13 L/day with thermal and overall efficiencies of 24.32% and 3.58%, respectively. The cost of produced fresh water is 0.21 $/liter with the system’s payback time of 2 years & 9 months. The quality of the generated water is also tested, which ensures that it is safe to drink.