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Musings of an Energy Nerd

Making Water from Air

Atmospheric water generators can manufacture clean drinking water from thin air

When humid air encounters a cold coil, moisture in the air condenses on the cold surface. Water that drips from the cold coil can be collected in a pan or tank. Appliances designed to collect water from the air are called atmospheric water generators. [Public domain image from Wikipedia]

Unless you live in a drought-stricken region, you probably take your water service for granted. After all, most North American homes have safe drinking water on tap, provided by either a municipal water system or a drilled well.

In much of the world, however, water is scarce. Rivers may be polluted or nonexistent, and rainfall may be spotty. Ground water may be unavailable at depths accessible to drill rigs. Moreover, climate scientists predict that rising temperatures will increase the frequency of droughts in much of the world.

In these areas with limited water resources, including many Caribbean islands, the traditional solution to the water problem is to gather rainwater that falls on a home’s roof and direct the water to a cistern. If annual rainfall is adequate and dependable, such a rainwater collection system can supply enough water to support a family. This approach won’t work, though, in areas of the world where rainfall is not dependable.

Another possible solution to water shortages is to build a desalination plant—but that solution is expensive, and it doesn’t help communities that are far from an ocean.

For the millions of people who now live in houses without running water, someone in the family (usually a woman or a child) must travel on foot every day to a distant well to draw water, or must stand in line to have the family’s bucket filled from a water truck.

Thinking outside the envelope

What about producing drinking water from air—is that even possible?

The short answer is a qualified yes. The main drawback to water-from-air schemes is the high cost of the water. In addition to the cost issue, there are climate limitations: the water-from-air approach works best in hot, humid climates.

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  1. nicholas_erdenberger | | #1

    This is an excellent and timely article. Looking to use this technology to get to net zero water usage for our Bay Area home.

    Curious if you think there are any legal constraints to using this technology? In CA and other parts of the Cadillac desert where water laws are weird I wonder if use of this technology would violate riparian laws? In SF it technically wasn't legal to collect rainwater until an explicit law was passed (I think in 2013) to allow it because water could not be "damned" unless you had rights to it.

    1. GBA Editor
      Martin Holladay | | #2

      As far as I know, there are no legal restraints on using this technology.

    2. nickdefabrizio | | #4

      Your question reminds me of a law school exam hypothetical! Here is how it would be argued in class:

      In certain arid places, water is seen as a scarce commodity (property right) which has already been allocated according to a set of property rights agreements that establish ownership interests (this presumes the laws you are talking about were designed to ensure the continued flow of water into the system where it is later divvied up among those with riparian rights to it). Thus, collecting rainwater could be seen as ultimately diminishing another stakeholders rights and interests without compensation. In the case of pulling water out of the atmosphere, you would argue that this does not diminish the supply to the other stakeholders and is therefor not the behavior intended to be controlled by these laws. To counter that argument, these stakeholders would probably have to show that pulling humidity from the air somehow reduces the amount of rainwater that enters the system.

  2. nickdefabrizio | | #3

    Interesting article....In NJ we have a 900 ft well that does not frack well (no pun intended) and so we conserve water. When I run the Fujitsu mini splits for dehumidification or cooling I collect the water in a big vat for use in watering our gardens. It is amazing how many gallons it produces on humid Spring or Summer days. Why waste it?

    These machines may work in certain third world areas. In Central Africa where my organization is involved in rural villages, the problem with this approach is often a lack of electricity. We ended up running 4000 feet of pipe to springs to bring water to one village: sometimes a less expensive approach compared to installing these machines with solar PV to run them. I will note that in other areas, the problem is not lack of water but poor water quality/polluted water, particularly water that is contaminated with sewerage and the cost of decontamination to potable standards. In such cases perhaps these machines could provide a relatively small supply of potable water but local water could be conditioned enough for other uses.

  3. Robert Opaluch | | #5

    Producing water from air at about 50 cents a gallon seems cheap compared to the $1+ per gallon water at grocery stores in the northeast US.

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