Editing Solar still (section)

=== Reverse still ===
A reverse still uses the temperature difference between solar-heated ambient air and the device to condense ambient water vapour. One such device produces water without external power. It features an inverted cone on top to deflect ambient heat in the air, and to keep sunlight off the upper surface of the box. This surface is a sheet of glass coated with multiple layers of a polymer and silver.<ref name=":1">{{Cite web|last=Irving|first=Michael|date=June 24, 2021|title="Reverse solar still" keeps its cool to wring drinking water from air|url=https://newatlas.com/science/passive-drinking-water-harvester/|access-date=2021-06-27|website=New Atlas|language=en-US}}</ref>

It reflects sunlight to reduce surface heating. Residual heat that is not  reflected is reemitted in a specific ([[infrared]]) wavelength so that it passes through the atmosphere into space. The box can be as much as 15&nbsp;°C (27&nbsp;°F) cooler than the ambient temperature. That stimulates condensation, which gathers on the ceiling. This ceiling is coated in a [[Ultrahydrophobicity|superhydrophobic]] material, so that the condensate forms into droplets and falls into a collector. A test system yielded {{Convert|4.6|ml|usoz|abbr=on}} of water per day, using a {{Convert|10|cm|abbr=on}} surface or approximately 1.3 L/m<sup>2</sup> (0.28 gal/ft<sup>2)</sup> per day.<ref name=":1" />