Drought and Atmospheric Condensers.

California is dealing with a severe water shortage now, as I am sure most of you know. (I’d hate living there. I drink and use a lot of water during the average day;).)

Anyways, I have a simple proposition. Why don’t they just build “atmospheric condensers”?

To be fair, I largely heard the term on Star Trek: The Next Generation, the episode The Inner Light to be specific. (To summarize, Kamin suggests this option to his friend Batai, on the drought-stricken world [Kataan] they live in.)

I know most people don’t get their information from sci-fi. But actually, I think the theory is factually sound. I once heard that people stuck in a desert can get water by placing a large plastic sheet over the sand. So the water, even in a desert, is clearly already there. So how hard could it be to collect it? In short, why not an atmospheric condenser for the water shortage in CA (and other places)?


Probably capacity and cost. If you want to do it with unpowered systems, it’d take a lot of dew, over a lot of surface area, to replace all that natural rain and snowfall. If you want it do it with powered systems, it’d take a lot of energy. One study thought about pumping seawater to cool dew collectors but concluded it’d cost more than just plain reverse osmosis. There are other systems like this that are more efficient but still require electrical input power, such as from a wind turbine or solar panel.

Basically the water that is there wants to stay in the air, and forcibly getting it out of the air requires either energy or condensation surfaces; the former is expensive and the latter requires a lot of artificial building and is probably still more expensive than just waiting it out or buying water from other regions.

In a survival or no-alternatives situation they’d make sense, but California politicians are probably just more keen on waiting it out. They would probably far sooner ration water or increase rates than to do anything truly revolutionary that would risk upsetting the status quo.

Here’s one paper looking into radiative (passive) dew collector performance, if you’re interested: http://library.queensu.ca/ojs/index.php/ijsle/article/download/3188/3578

It can supplement but not really replace regular rainfall.

Wind Traps? But how will we hide them from the Guild, if we can’t afford the Spice bribes?


So, they should switch to Moisture Farming? Maybe next Harvest…

mmm, this does crop up a lot in SF.

I was going to suggest Dune as a better reference than Star Trek.

Here’s a billboard that does this, in Lima Peru.

Kind of small output, though.

I found a value of 30.4 g/m[sup]3[/sup] at 30 C and 9.4 g/m[sup]3[/sup] at 10 C for water content in air.

So with perfect efficiency you could extract 21 g/m[sup]3[/sup] if you can induce a temperature drop of 20 C. Say the average wind speed is 10 km/h (2.7m/s) and you have an ideal extraction of 56 g/m[sup]2[/sup]s or 204 l/m[sup]2[/sup]hr.

Say you set up a system 10m tall and 100m wide you would have 204,000 l/hr (54,000 gal/hr) in an ideal setup.

The USGS has California extracting 15,000,000,000 to 25,000,000,000 gallons per day for irrigation. For the system to provide just 1% of that need would require between 2800 and 4700 units.

Agriculture is such a massive consumer of water in western states that this type of solution would be just a drop in the ocean.

I saw what you did there:)