How would you build a moisture harvester?

Yes, the first thing nearly everyone remembers are the moisture farmers on Tatooine in Star Wars. Now, the question is, how would you go about building one?

I was thinking about building a small hoop hut out of PVC but instead of of being a split cylinder, I was thinking of a donut shape of PVC covered with plastic. A center pan to catch water for harvesting the water or smaller holes in the drip pan itself for water delivery to the plants.

Comments

[pleabargain]

Can you suggest a way in which I can do the same without using electricity? I was thinking a sun warmed tub of water completely or partially under a sheet of plastic would induce the condensation which would then drain into a catch basin. Surprisingly, I find very little on the web about people doing this. I did find Groasys: http://www.groasis.com/page/uk/index.php

Very promising but I'd like to find ways to build one.

[jamob]

I had an idea for moisture purification to water that you could take some kind of clearish plastic box kind of. You put a flat peice of plastic on a slant in the box. and narrow the plastic down at the end to maybe a pvc which led to a water bottle. You could put it on grass or maybe make it float. And the evaporation clears it of any pollution and it is deposited as water in the bottle to drink. That is on a small scale though.

[Kiteman]

What you have will collect dew, but no more than the plant can collect with its own roots.

You need to collect water that does not normally reach the ground. On the Canary Islands, they harvest water from drifting fog-banks (the Canaries have little rain) by hanging up hundreds of metres of black plastic mesh.

The black plastic cools quickly at night, so is much more efficient at collecting the morning fogs - water condenses on the cool plastic, and trickles down. I forget whether they allowed the water to soak into the ground, or caught it in channels to run to storage.

[Jayefuu]

Link? That sounds interesting but my googlefuu failed me.

[kelseymh]

http://en.wikipedia.org/wiki/Air_well_%28condenser%29#Radiative_collectors

The Canaries aren't mentioned, but it's a good review of the technique.

[pleabargain]

Thanks, read through that... but no 'how to' build your own/simple one.

[Kiteman]

Ah, no link - this was IRL. I saw them whilst on honeymoon, some time around the Norman invasions...

[orksecurity]

Of course if you have the energy (solar?) to drive it, you can run active cooling. That's how the dehumidifier in your basement operates -- freeze moisture out of the air, let it melt into catchbasin, repeat.

[Re-design]

Read about the solar still.  You idea looks something along those lines.

[Kiteman]

No, this is different - solar stills collect and purify water already in the ground.

Pleabargain is trying to harvest atmospheric moisture.

[pleabargain]

That is correct, atmospheric moisture.

[kelseymh]

Wikipedia has a good review article on many different techniques for collecting moisture, with links to other resources.

[steveastrouk]

The way it can be done is to dig a pit in the desert, line it withpoly, and put a collector at the bottom. Rapidly chilled sand condenses dew, dew runs down pit, into collector.