Experimental investigation of a sorption-based atmospheric water harvesting system using a LiCl/CaCl₂–silica gel composite

Sorption-based atmospheric water harvesting (SAWH) represents a promising approach for decentralized freshwater production, particularly in regions affected by water scarcity. However, the translation of material-level performance into effective system operation remains limited by kinetic constraints, operating conditions, and incomplete water recovery. This study presents an experimental investigation of a semi-open, single-bed SAWH system employing a LiCl/CaCl₂–silica gel composite integrated into a fin-and-tube heat exchanger, with the objective of linking sorbent behaviour to system-level performance and cycle optimization. A systematic experimental campaign was conducted to assess the influence of adsorption and desorption temperatures, air velocity, and inlet humidity on water uptake and process dynamics. Adsorption temperature was identified as the most influential parameter: decreasing the adsorption temperature from 42 °C to 25 °C increased the measured water uptake from approximately 0.42 g/g to 0.72 g/g. In contrast, increasing the desorption temperature from 60 °C to 90 °C improved the working capacity from about 0.35 g/g to 0.56 g/g. A dynamic analysis was carried out to identify cycle times: under optimized air flow (≥0.6 m/s), adsorption times were in the range of 18–22 min, enabling up to three cycles per hour. This represents a significant improvement compared to conventional slower systems and confirms the Finally, theoretical analysis under realistic climatic conditions (Messina, Italy) indicated a yearly water production of 900 L water /kg sorbent , with higher values observed during more humid seasons. The findings provide experimentally validated insights for the development of efficient and scalable SAWH technologies.