Introduction: Solar Still

Picture of Solar Still

In a desert environment finding or producing water is a most important skill for survival. This is a technique for extracting water from the soil or from plants by condensation.

Step 1: Materials

Picture of Materials
  • Clear Plastic Wrap
  • Cup or Container
  • Green Plant Material (optional)

Energy from the sun is used to evaporate water from the soil, or green plants if available, which condenses on the plastic wrap and drips into the container.

Step 2: Setup

Picture of Setup

Dig a hole small enough to cover with your plastic wrap. The more exposed surface there is on the sides of the hole, the faster water will evaporate, but the hole must be completely covered by the plastic wrap. If the hole is to deep the bottom will be shaded much of the time which reduces the efficiency of the still. Make sure the hole is just deep enough to leave about two or three inches above the top of the container.

Step 3: Water Source

Picture of Water Source

While not necessary, adding plants will greatly speed up the evaporation process. I'm using a cactus here. The cactus has soft flesh full of water, so it works well for this purpose, but any leafy plant will work. Peeling off the skin or cutting it open allows the water to evaporate faster.

Step 4: Finish

Picture of Finish

Place the container and the plants in the bottom of the hole, leaving the opening of the container unobstructed. You can add more plant material than pictured.

Stretch the plastic wrap over the hole and weight down the edge with dirt. Make sure you have an airtight seal. Pinning the corners down with sticks will help hold it in place. Finally place a pebble or some dirt directly over the container. This will ensure the water will collect inside the container.

The sun will heat up the interior, like a greenhouse, evaporating water out of the plants and soil. As the temperature inside of the hole exceeds the temperature outside, water will begin to condense on the cooler plastic and drip into the container.

By constructing several of these, and keeping them stocked with fresh plants, you can generate enough fresh water to survive.


gollumses (author)2015-08-01

So, you had to wait six hours and got 3/4 of an ounce of water, when you could have just eaten all three parts of the Prickly Pear Cactus (Nopal, Flower Petals, and Fruit) right away? If you had used a Barrel Cactus, I would have understood. The oxalic acid can make people not used to it very ill, and if you are trying to survive in the desert, the last thing you want to do is to eat something that will make you puke and dehydrate. When you do this, don't use plant matter that you can actually eat. Yank up roots, pick leaves, and crush them together, then throw them in the still.

pantherj12 (author)2014-04-23

What other plants can you use? And how much of that plant to get water quickly?

Cacti are good because of their high water content, but any living plant will work. Particularly green leaves or shoots. Basically use as much as you can fit around your container without burying to much. This method really wont work quickly, which is why you need to have several out at once.

Just remember that if you put toxic plants in the solar still you will get toxic water.

Money_Illusion (author)2014-04-22

How much water did you collect and how long did it take?

In six hours I got about 3/4 of an ounce, which is a lot for a small one
like this (I added more cactus). After that the still was utterly
destroyed by a rogue chicken.

Bolensgoldrush (author)2014-04-22

Saw this in a survival book I read. Very interesting, I've gotta try it. Thanks!

zorro1701 (author)2014-04-22

ive seen the same thing with sal water near ocean.

painrude (author)2014-04-22

nicely done

carsam (author)2014-04-21

what if I put more cactus or plants in the same hole? does that make more water?

fletcherjeremiah (author)carsam2014-04-21

Yes. Because there is more water in the plants than in the soil lining the hole with plants will produce more water than just a single cactus.

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