A novel solar-driven direct contact membrane-based water desalination system

This study proposes a novel integrated solar membrane-based desalination system. The system includes vacuum glass tubes to increase absorbed solar energy and to decrease heat loss, heat pipes to transfer the absorbed energy efficiently, and a tubular direct contact membrane distillation module to use the absorbed energy more effectively. To improve the freshwater production rate and overall efficiency of the proposed system, a cooling unit was also added to the permeate loop of the desalination unit. The performance of the system was experimentally investigated without (Case I) and with (Case II) the cooling unit in summer and without the cooling unit in winter (Case III) under climatic conditions of Perth, Western Australia. The experimental results indicated that except a few minutes in the morning, the heat pipe solar system was able to provide all the required thermal energy for the desalination system. The maximum thermal efficiency of the solar system in summer reached similar to 78% and its exergy efficiency fluctuated between 4 and 5% for a noticeable amount of time from 10:30 AM to 3 PM. Moreover, the maximum freshwater production rate were 2.78, 3.81, and 2.1 L/m(2)h in Cases I, 11, and III, respectively. The overall efficiency of the system improved from 46.6% in Case I to 61.8% in Case II showing the technical effectiveness of implementing the cooling unit in the permeate flow loop of the system. In addition, the daily averaged specific energy consumption in Cases I, II, and III were 407, 377, and 450 kWh/m(3), respectively.