Hello Tatooine! An unpowered device can harvest water vapor in a desert

Enlarge (credit: Evelyn Wang/MIT)

Luke Skywalker may have been unimpressed with the life of a Tatooine moisture farmer, but a simple device that could economically harvest water from desert air would really be pretty exciting. According to Wookieepedia, the "moisture vaporators" the young Skywalker tended utilized refrigeration coils to chill air to the dew point and collect the water that condensed. We can certainly do that today (as they could "a long time ago... "), but the amount of energy required makes collecting condensation impractical.

Enter a new study device developed by MIT's Hyunho Kim. His idea is to work with a unique class of materials called "metal-organic frameworks." Organic, carbon-based molecules form links between metallic ions to create interesting 3D structures that can have lots of open space internally. This allows the structures to do strange things, like make a high-pressure tank hold far more hydrogen gas after it's first filled with granules of the right metal-organic framework material.

Kim worked with a zirconium oxide paired with an organic molecule. The combination has the useful quality of grabbing and holding on to water vapor at lower temperatures, but also letting go of that water as the heat rises. So the basic idea is that a device based on this material could passively harvest water vapor from the air at night and then release it (to be collected) in the heat of the day.

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