Renewable water: Direct contact membrane distillation coupled with solar ponds

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.

Raw project data is available by contacting [e-mail]

利用可再生能源驱动的海水淡化技术，是解决全球水资源短缺问题、同时不显著增加温室气体排放的有吸引力的解决方案。低温直接接触膜蒸馏（DCMD）系统，尤其是由盐梯度太阳能池塘（SGSP）等热太阳能系统驱动的系统，是一种具有潜力的可再生能源海水淡化系统。本研究首次对DCMD/SGSP耦合系统的淡水生产进行了实验研究。本工作的目标是确定系统的实验淡水生产率和不同组件的能量需求。从实验室结果来看，DCMD/SGSP耦合系统处理的水流量大约是类似由SGSP驱动的空气隙膜蒸馏单元组成的系统的六倍。在能量需求方面，SGSP提取的热量中有约70%被用于驱动热淡化，其余部分则在系统的不同位置损失。在膜模块中，只有一半的有用热量被用于跨膜水分传输，其余部分则通过膜传导损失。研究还发现，通过减少整个系统的热损失可以提升水通量，这突显了在整个DCMD/SGSP耦合系统中提高效率的必要性。因此，未来必须进一步研究膜特性、系统隔热或太阳能池塘的最优设计。原始项目数据可通过联系[e-mail]获取。