Tuesday, July 25, 2017

Be (Solar) Still

It's the height of summer, and it's been a scorcher. If you found yourself stranded where I live, you might not make it 3 days without water.

Running out of water doesn't have to be a death sentence, though. Using just minimal gear, you can pull water right out of the ground. In addition, the same technique can be used to purify questionable water.

All of this operates on the principle of distillation, but instead of using a pot and a stove, we'll be using the sun and simple dirt.

Building a Portable Solar Still
  1. Pick a site that gets full sun for as much of the day as possible. 
  2. Dig a hole 1-2 feet deep and 3-6 feet in diameter. 
  3. Place a wide-mouth vessel on the bottom of your hole near the center to catch water. 
  4. Cover the entire hole with a trash bag or other plastic sheet, anchoring the edges with rocks or dirt. 
  5. Place a small rock or weight on the plastic and over your catch vessel.
If the dirt in your hole is wet or moist
Just sit back and let the sun go to work. The plastic sheet traps heat in the hole, causing water to evaporate from the ground. This water condenses on the plastic, then runs down to the low spot created by the weight before dripping into your vessel.

If the soil is dry or you want to generate more water
You can give your still a bit of a kick start by adding green vegetation or brackish water to your still to be processed. You can also urinate beside your still and reclaim some of that water.

The Extreme, Fixed-in-Place, Solar Still
If you have the time, energy, and materials to make this, you will find it much more efficient than the portable version above. The Extreme Solar Still comes from a March 2012 Survivalblog aricle by Jim B.

 When laying this shell shape out on the ground in the size that you would need, you will have to make sure that the top rounded side of the shell points away from the sun’s tracking through the sky. In North America that would be to the north. 
The top rounded section, or north side, would function much the same as the conventional still with sloping sides with approximately 25-45 degree angles, to as deep as you need the hole. The slopes would end not in the center, but on the bottom side of the shell shape about three quarters of the way down from the top, on the south side.  
The bottom of the hole is not one level. At the bottom, the “tail” end of the shell is a raised shelf. This shelf will hold the catch pot.
The added vegetation makes two things happen. First, it will add more moisture to the distillation process, and second, it will help the bottom of the hole to be a darker color, if you have a light soil. Dark colors absorb more heat. This is also the time to add any other items of moisture. 
The second thing that you should add is small rocks. Not too small, about fist or palm size or bigger, and flat if possible, any shape is okay if not. The ideal rocks would be very dark river rocks about 4-6 inches around and 1-3 inches thick. [...]The rocks should be placed along the inner sides and bottom of the still. They serve two purposes. The first is that they collect heat, being a darker and a denser material. And second, they hold that heat past the time when the sun drops below a level that hits your solar still. This will change the name of your solar still to the “stored heat radiation still”.
Not everyone will be carrying a length of tubing long enough to reach comfortably from the top to the bottom of the still and also be secured. Not having to open the still after its closed, however, will help with maintaining continuous heat trapped in the solar still. Any loss of heat will take a period of time to regenerate. 

While not a long-term solution, a solar still can generate 1.5-2 quarts of water per day if you provide moisture for it to distill. It can keep you alive for quite a while after running out of the water you brought, with minimal effort on your part.

There's water, water everywhere, so find a way to drink.


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