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How to Make a Solar Water Purifier
You are stranded on a dingy, your ship just having sunk. You are in the middle of the ocean with 'water, water, everywhere, but not a drop to drink'. The sun looms high on the horizon. The heat is oppressive and the salty sweat drips off your tired body. Becoming more dehydrated by the minute, you look out to sea, hoping desperately for a rescue vessel but none is in sight at the present time. You realize that you have only a day or so of survival without water before your moisture starved body succumbs to the elements. Suddenly, you remember a lesson from a high school science class. It looked at obtaining pure water from salty water. If you remember correctly, it required only a few meagre materials. Checking through the possessions you managed to salvage you find a large bucket, a small cup and the remains of a plastic tarpaulin. A piece of rope and some coins from your pocket are the remaining materials required to fashion a solar water purifier. Your survival is looking better as you have more than an adequate supply of solar energy to fuel your purifier. Your memory of the water cycle provides hope as you realize the power of the sun's heat to evaporate water from the sea. Now, how to collect that evaporated, pure drinking water to quench your thirst. Read on to discover a solar purifier, able to collect that life saving drink, that you could make in a pinch if ever shipwrecked or marooned by your crew on a tiny island in the sea!
Main Materials for the Solar Water Purifier
Materials to Make a Solar Water Purifier
- sea salt or table salt
- large bowl
- short glass that will fit inside the bowl and be shorter than the top of the bowl.
- plastic wrap
- small weight like a screw, nut or small rock
How to Assemble the Solar Water PurifierClick thumbnail to view full-size
Making the Solar Water Purifier
- Add 4 tsp of salt to two or three cups of water.
- Stir until the salt dissolves.
- Pour the solution into the bowl.
- Put the short glass into the middle of the bowl. The glass should be above the level of the salt water while at the same time being shorter than the bowl. Adjust water level if necessary.
- Cover the bowl with the plastic wrap sealing the wrap to the bowl tightly with tape.
- Place the weight on the plastic wrap directly over top of the small glass.
- You may need to anchor the weight with a piece of tape so that it stays centred.
- Put the bowl outside in the sun.
- Leave it for several hours. Come back periodically to check on what you see happening.
- After several hours there should be a significant amount of water in the cup.
Would you have the skills to fashion a Solar Water Purifier if stranded without fresh water?
Science Behind the Solar Water Purifier
The Solar Water Purifier uses principles from the water cycle to procure fresh water from salty water or from a source of water which may or may not be palatable due to high mineral or other chemical impurities. Note: boiling water is the only sure way to kill pathogens like bacteria and viruses.
The Solar Water Purifier works as follows:
- Sitting out in the sun, the water in the bowl is heated and evaporation of water occurs. The minerals and contaminants do not evaporate with the water and return to their form prior to being dissolved in the water.
- When the water vapour hits the plastic wrap, it condenses back into liquid water.
- As the plastic wrap is angled towards the small cup, the drops of condensation roll towards the centre and drop into the cup when enough drops have accumulated at that point.
- This process will take several hours to produce enough water to quench your thirst and stave off death by dehydration.
Use the Salt Water Circuit outlined in another of my hub's to test the purity of the water. Dissolved salts and minerals create positive and negative ions which conduct electricity. The salt water circuit will determine if there are these ions present and; thus, if your solar water purifier has worked!