Highly Efficient Water Harvesting with Optimized Solar Thermal Membrane Distillation Device

Water distillation with solar thermal technology could be one of the most promising way to address the global freshwater scarcity, with its low cost and minimum environmental impacts. However, the low liquid water productivity, which is caused by the heat loss and inadequate heat utilization in solar‐thermal conversion process, hinders its practical application. Here, a compact solar‐thermal membrane distillation system with three structure features: highly localized solar‐thermal heating, effective cooling strategy, and recycling the latent heat, is proposed. The steam generation rate is 0.98 kg m −2 h −1 under solar illumination of 1 kW m −2 in the open system, while the liquid water productivity could be 1.02 kg m −2 h −1 with the solar efficiency up to 72% with a two‐level device. The outdoor experiments show a water productivity of 3.67 kg m −2 with salt rejection over 99.75% in one cloudy day. These results demonstrate an easy and high‐efficiency way for water distillation, especially suitable for household solar water purification.