The fresh water is the essence of life and its scarcity is the most threatening concern for mankind. To alleviate the worries of the existing and approaching fresh water crisis, the answer for water sustainability may lie in developing the decentralized small-scale water desalination system. Solar humidification-dehumidification (HDH) is a carrier gas based thermal technique that is ideal for a small-scale decentralized water desalination system. An innovative design approach is to use the bubble column humidifier to enhance the performance of the HDH water desalination system. Therefore, a novel multi-stage stepped bubble column humidifier is proposed that is operated through solar thermal energy as the main source of energy input. The study addresses the relation between the pressure drop variations with varying water column height at different air superficial velocities. Findings revealed that the water column height and air superficial velocity should be optimized according to the geometric features of the perforated plate in order to achieve a higher humidifier performance with a lower pressure drop. The day round performance of the humidifier is investigated in single stage, two stage, and three stage configurations. Findings show that the average day round absolute humidity at the exit of the humidifier is increased by 9 % in two-stage and 23 % in three-stage configurations compared to the single stage humidifier. One major advantages of this proposed humidifier is its ability to have a direct solar thermal heating. Subsequently, it can be located in remote areas.

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