Solar Stills

In desert areas or where there's a scarcity of water, some people make use of solar water stills. This technique is also used by the military when they have to be in such areas and cannot find other natural sources of water.

So, how do you make a solar still? It's very simple and cheap. Get a transparent sheet of plastic, about 4 x 6 feet. Now, dig up a hole / pit in the ground, about 3 x 5 feet and about 1 foot deep. Place a cup, mug or any vessel at the center of this hole. Cover the hole with the clear plastic sheet and place some weight on all sides of the sheet to make it air tight. You could place mud that you dug up from the ground, stones or anything similar that is available for the purpose.


Now, take a small stone of the size of a medium-sized coin and carefully place it at the center of the sheet, exactly above the mouth of the vessel or cup. Take care while placing it so as not to displace the plastic sheet. And do not fall into the hole / pit, yourself! It may require some adjustment to place the stone at the perfect place above the mouth of the vessel.

Once this is done, leave the still this way in the sun. After a few hours, you can see crystal clear water collected in the vessel. This is pure, distilled water. You can drink it. Its quantity may not be sufficient to pacify your thirst but it is better than no drinkable water at all. You may make many such solar stills and be able to get 1 - 2 liters of water every day. This is free water that you got from thin air!



This can also  be tried at home by using a plastic transparency. Get a large vessel. We will use this as the pit. Place a cup or a glass at the center of the vessel. Cover the vessel with the transparency. Place a small coin or a similar light weight, at the center of the transparency, exactly above the mouth of the cup. The idea is to tilt the transparency towards the center so that the water droplets which condense on the inner side of the transparency, fall into the cup.

Place all these things where you can get direct sunlight fall on the transparency. If you check after a few hours, you'd find clear, distilled water in the cup.

A solar still can also be used to desalinate  sea water or any water that is not drinkable or which is impure. What you do is, put this impure water into the pit (or vessel) and cover it with the sheet (or transparency). Due to the sun's heat, water droplets condense on the inside of the sheet, falling into the cup when they become more in number. The impurities or salt from the impure water, remain at the bottom of the pit or vessel. What you have in the cup is 100% pure, drinkable, distilled water!