Experimental investigation of a two-stage solar humidification–dehumidification desalination process

•A multistage HD process was investigated to improve efficiency of HD desalinator.•2-Stage process is the best choice from cost and performance point of view.•A 2-stage solar HD desalination unit constructed and tested in an arid area•Production is presented and compared during hot and cold days.•Improvement in productivity and reduction of solar collector area were obtained.

This paper experimentally evaluates a two-stage technique to improve the humidification–dehumidification process in fresh water production from brackish water. According to modeling results of multi-stage process and on the basis of construction cost estimation, using a two-stage process is the most suitable choice that can improve important parameters such as specific energy consumption, productivity and daily production per solar collector area and thus, investment cost. A pilot plant was designed and constructed in an arid area with 80 m2 solar collector area to evaluate the two-stage process. This unit was tested on cold and hot days. The effect of main parameters on fresh water production of the unit is studied. Experimental results show that two-stage HD desalination unit can increase heat recovery in condensers and hence, reduce thermal energy consumption and investment cost of the unit. Moreover, productivity can be increased by 20% compared with the single-stage unit.