Membrane distillation (MD) has been proven promising in solar-driven desalination. Moreover, its unique characteristics such as simple process, module compactness, high salt rejection rate, etc. allow for a small-scale device in a distributed system. Both theoretical and experimental researches on the coupling between solar collectors and MD aiming at compact and autonomous desalination system have been devoted to enhance freshwater productivity and energy efficiency. In this paper, certain critical gaps are summarized upon a panoramic review of the current status, including limited production and energy performance compared with commercial-scale desalination, unclear relation between solar collecting area and membrane area, and few discussions on efficient condensation, etc. To tackle these challenges, perspectives on the essential future research directions are proposed. Solar direct heating and solar concentration constitute the possible resolution to enhance solar energy utilization for higher water production, which also raise the question of optimizing solar/MD areas. Meanwhile, module stacking, module internal heat recovery and external evaporation heat recovery are deemed prospective in further reducing MD energy consumption. Subsequently, an enhanced vapor condensation needs more exploration. Those aspects and a potential combination among them are the main tasks in the near future, together with more field tests on small distributed solar-driven MD systems.

膜蒸馏（MD）已被证明在太阳能驱动的脱盐中很有前途。而且，其独特的特性，例如简单的过程，模块的紧凑性，高的脱盐率等，使得在分布式系统中可以使用小型设备。以紧凑和自主的脱盐系统为目标的有关太阳能收集器和MD耦合的理论和实验研究都致力于提高淡水生产率和能源效率。本文对当前状况进行了概述，总结了某些关键差距，包括与商业规模的海水淡化相比产量和能源性能有限，太阳能集热面积与膜面积之间关系不明确以及关于有效冷凝的讨论很少等。为了应对这些挑战，提出了关于未来必不可少的研究方向的观点。太阳能直接加热和太阳能集中度是提高太阳能利用率以提高水产量的可能解决方案，这也提出了优化太阳能/中压面积的问题。同时，模块堆叠，模块内部热回收和外部蒸发热回收被认为可以进一步降低MD能耗。随后，增强的蒸汽冷凝需要更多的探索。这些方面以及它们之间的潜在组合是不久的将来的主要任务，以及对小型分布式太阳能驱动MD系统的更多现场测试。这也提出了优化太阳能/ MD面积的问题。同时，模块堆叠，模块内部热回收和外部蒸发热回收被认为可以进一步降低MD能耗。随后，增强的蒸汽冷凝需要更多的探索。这些方面以及它们之间的潜在组合是不久的将来的主要任务，以及对小型分布式太阳能驱动MD系统的更多现场测试。这也提出了优化太阳能/ MD面积的问题。同时，模块堆叠，模块内部热回收和外部蒸发热回收被认为可以进一步降低MD能耗。随后，增强的蒸汽冷凝需要更多的探索。这些方面以及它们之间的潜在组合是不久的将来的主要任务，以及对小型分布式太阳能驱动MD系统的更多现场测试。