How Solar Stills Work – Life of Pi

November 13, 2012

For those of you who read the book or saw the movie Life of Pi you may have wondered how he was able to purify drinking water through the use of sunlight.  A solar still is an invention that uses sunlight to purify water.  Sounds easy enough, but how does a solar still actually work?

The process is not as easy as sticking some saltwater on a tray in the sun and presto — drinking water!  There are several things that need to be set correctly to make this work.  Take a look at the diagram below, and read through our step-by-step guide to get a thorough understanding of the mechanics needed to turn salt water or dirty water into something you can drink.

1. Once you have the contraption in place you will need to fill the center trough with the water you are trying to purify.  The center trough usually will have a black bottom, which helps to attract sunlight.

2. The heat from the sun evaporates the salt water that is sitting in the center trough.  The process of evaporation only lifts pure molecule of H2O into the air of the container, leaving the dirty parts of the water sitting in the trough.

3. Next, the process of condensation occurs.  This is when the water vapor molecules hit the glass or plastic ceiling of the solar still and turn into water droplets.  This is the same type of condensation you see when you are drinking cold water out of a glass or cold can.

4. After condensation, the water droplets are forced by gravity and to slide down the glass or plastic ceiling into a second clean trough along the inside edge of the solar still.  They cling to the edge of the glass or plastic and follow it all the way down into an outer rim that flows into the ‘clean water’ area.  Because the water is clinging to the angled glass or plastic, it does not get mixed back in with the dirty water.

5.  After a certain amount of time enough water is collected and the water is ready to drink.  This is usually done with a hose that is connected from the clean trough to the outside of the contraption.

Solar Still Diagram

Here is an actual picture of a Solar Still in action.