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

Highlights: [•] In the novel RO-PRO system, the energy produced by PRO is utilized to offset the energy consumed by the RO. [•] The specific energy consumption of a RO-PRO system was modeled for the first time. [•] A novel module-based PRO model for full-scale applications was developed. [•] The minimum net specific energy consumption of the modeled RO-PRO system was 1.2kWh/m3 at 50% RO recovery. [•] A sensitivity analysis showed a min RO-PRO specific energy consumption of 1.0kWh/m3 and a max power density of 10W/m2. [Copyright &y& Elsevier]

Highlights: [•] Experiments and numerical models were analyzed to understand solar pond efficiency. [•] Boundary effects typically reduce the efficiency of small-scale solar ponds. [•] Artificial lighting affects the energy that reaches the lower convective zone. [•] Turbidity is more important in large-scale solar ponds and decreases its efficiency. [•] Large-scale solar ponds collect more energy than small-scale solar ponds. [ABSTRACT FROM AUTHOR]

Highlights: [•] Evaporation, temperature, and heat content for a covered solar pond were monitored. [•] Floating discs decrease evaporation and increase temperature and heat content. [•] Reduced evaporation enables operation where water supply is limited. [•] Increased heat content significantly improves solar pond thermal efficiencies. [•] A buoyant, transparent disc is recommended for large scale solar ponds. [ABSTRACT FROM AUTHOR]