Small-scale desalination devices driven by solar energy is a promising solution for freshwater in remote off-grid islands where centralized energy supplies are hardly accessible. However, the low water yield and unstable operation caused by energy inefficiency and salt precipitation are tricky problems. To provide a reliable freshwater supply, a desalination device with high water yield and no salt precipitation is the main target of this work. A three-stage photothermal membrane distillation module with free-flow evaporation channel was fabricated and a model was developed accordingly. Upon varying flow patterns and flow rates, the effects of different flow configurations on water production and salt concentration were observed and discussed. It is revealed that the feed from the bottom to the top stage in series connection at a flow rate of 28 ml h⁻¹ can achieve a water production rate of 2.23 kg m⁻² h⁻¹ and a solar energy utilization efficiency as high as 147.9 % without salt precipitation. This work showed a competitive water production among all the previously reported small-scale solar membrane distillation devices. Besides, the flowing design is effective in preventing salt precipitation. A strong potential in providing qualified household freshwater with salinity rejection over 99 % on remote islands was indicated.

由太阳能驱动的小型海水淡化装置是一种很有前途的解决偏远离网岛屿淡水的解决方案，因为这些岛屿很难获得集中能源供应。然而，能源效率低下和盐析造成的产水量低和运行不稳定是棘手的问题。为了提供可靠的淡水供应，高产水量且无盐析的海水淡化装置是这项工作的主要目标。制作了具有自由流动蒸发通道的三级光热膜蒸馏模块，并据此开发了模型。在不同的流动模式和流速下，观察并讨论了不同流动配置对产水量和盐浓度的影响。^-1可实现2.23 kg m ^-2  h ^-1的产水率和高达147.9 %的太阳能利用效率而无盐析。这项工作显示出在所有先前报道的小型太阳能膜蒸馏装置中具有竞争力的产水量。此外，流动设计有效防止盐分沉淀。表明在偏远岛屿上提供具有超过 99% 盐分拒绝率的合格家庭淡水的巨大潜力。