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29Desalination powered by renewable energy sources is an attractive solution to address the 30 worldwide water-shortage problem without contributing significant to greenhouse gas emissions. A 31 promising system for renewable energy desalination is the utilization of low-temperature direct 32 contact membrane distillation (DCMD) driven by a thermal solar energy system, such as a salt-33 gradient solar pond (SGSP). This investigation presents the first experimental study of fresh water 34 production in a coupled DCMD/SGSP system. The objectives of this work are to determine the 35 experimental fresh water production rates and the energetic requirements of the different 36 components of the system. From the laboratory results, it was found that the coupled DCMD/SGSP 37 system treats approximately six times the water flow treated by a similar system that consisted of an 38 air-gap membrane distillation unit driven by an SGSP. In terms of the energetic requirements, 39 approximately 70% of the heat extracted from the SGSP was utilized to drive thermal desalination 40 and the rest was lost in different locations of the system. In the membrane module, only half of the 41 useful heat was actually used to transport water across the membrane and the remainder was lost by 42 conduction in the membrane. It was also found that by reducing heat losses throughout the system 43 would yield higher water fluxes, pointing out the need to improve the efficiency throughout the 44 DCMD/SGSP coupled system. Therefore, further investigation of membrane properties, insulation 45 of the system, or optimal design of the solar pond must be addressed in the future. 46

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