a. pulling water out of the air
seems like there are two methods of fog farming:

1. relies on cooling air to produce condensation

(a) examples:

– windcatchers:


A traditional Persian architectural device, used in conjunction with subterranean qanats.

While this article suggests that the windtraps (windcatchers) are used for producing water, I think they were more typically used to cool air for climate control and refrigiration:

“Windtraps for water production have been used here on Earth for thousands of years. They are pyramid shaped strutures made out of loose stones so that the wind can blow through them. They work best in desert areas where the difference between day and night temperatures is 30 degrees or more. Moisture in the air condenses on the stones as they are cooled at night like the condensation on a glass of cold water. It drips down and collects in a catchbasin. These devices worked even when the humidity was very low.”

– “WaterMill”

uses a small amout of electricity for refrigeration, see bldgblog

– Whisson windmill

not sure about this one, but here is a link.

2. relies on using a large surface area plus natural condensation (dewing) to trap water

(a) examples:

– fog nets (see older post)

b. what happens to the water after it is condensed?

1. used to feed algae tubes; this would (a) purify the water through biological process (b) produce energy perhaps as well (c) provide shade (providing shade is probably more properly a thought about the affective qualities of the tubes).

Does the potential ease of collecting solar energy in these locales advocate against (because the algae tubes would be unnecessary/redundant) or for (because algae, of course, also depend on solar energy) the use of algae for energy production?  I’m not sure.  I tend to think its a wash.

2. feeds into planting, potentially rooftop planting or other a form of agriculture; this does not require purification, as plants would perform the purification.

3. ultraviolet purification system, a la watermill

4. How does the post-condensation use of the water relate to the urban system?  That is, how is it programmed to effect desirable changes?  For instance, the availability of clean and pure drinking water or potable water for gardening might be social justice issues in a city such as Dubai or Nouakchott.

associated content:
initial post on fog farming