What is a solar still and what does it do?

Answer 1

A "solar still" is a device used for purifying water from damp waste or brackish water by evaporation and condensation.

At its simplest form, a "solar still" can be made with a clear plastic sheet and a bucket or container of some sort. If you have a length of plastic tubing such as aquarium tubing or a hose, so much the better.

Dig a shallow pit or depression in a sunlit area, a meter or so in diameter and about 1/2 meter deep. Fill the pit with brackish water such as salt or swamp water, or damp vegetation, or anything containing water. Place a bucket in the center of the pit. Run the tubing or hose from the bucket to someplace outside the pit; this will be a long drinking straw. Cover the pit with a clear plastic sheet, and seal the edges by weighting the sheet with dirt. Place a small stone or weight in the center of the sheet, directly above the bucket.

The Sun will heat the pit, evaporating water from the vegetation or brackish water. No matter how hot it is outside the pit, the pit will be hotter; the cool plastic will cause steam to condense on the plastic sheet. The condensed droplets of water will run down to the lowest point on the sheet, which is where the rock is. Pure water will drip off of the plastic sheet into the bucket. You can drink the water by sucking it through the tube like a drinking straw. A well-built solar still can evaporate two or three quarts of water per day.

The military has inflatable solar stills that are included in the survival equipment with life rafts. Inflate the balloon, put sea water in, get fresh drinkable water out. You may be able to purchase these from "Army-Navy Surplus" stores.