After all, this is where fresh water comes from naturally as part of the planet's water cycle—the Sun. Heat yields water vapor, water vapor yields water rain. Fresh-water rain.

Surely we can harness that.

Well, we do actually harness solar energy for desalination purposes through a variety of different schemes, at least one of which has been commercialized. Yet the method remains inefficient relative to other desalination methods, costing between $1.52 and $2.05 per cubic meter of water produced, according to the World Bank. To truly scale, solar desalination will have to be in line with other, dirtier (read: fossil fuel-dependent) desalination methods, which currently cost about half that.

Engineers from Georgia Institute of Technology and Nanjing University have developed a new solar desalination process based on self-assembling nanoparticle membranes. Crucially, the technology is based on low-cost, abundant materials (aluminum, mainly) that remain stable after many uses and can be fabricated with very low overhead. The group's work is described in this week's edition of Nature Photonics.