This detailed guide will teach you the important survival skill of how to make a solar still. It’s an easy way to get fresh water in the desert or if you are lost in the woods.
This summer is all about survival in the wild! We discussed the importance of staying hydrated by demonstrating the effect of dehydration on a potato. We also built a solar oven to make our own s’mores!
But what happens when you are lost in the middle of nowhere and have no clean water to drink?
Today, we explore how to make a simple DIY solar still that collects clean water using the power of the sun. This is an easy, fun project that can be completed in a few hours with materials you likely have lying around your house.
Two important things to note:
- A solar needs an ample amount of time to gather water. Make sure you carry enough water and use a solar still as an emergency survival tool.
- While direct sunlight kills pathogens, this solar still may not kill off all the harmful bacteria present in water. If you are doing this experiment at home and not when you are stranded in the wild, I recommend conducting this experiment with filtered water for safety purposes.
What is a Solar Still?
A solar still is a device that uses solar power to create fresh water from salt water or contaminated water. The solar still works by heating the water until it evaporates, leaving behind the impurities. The evaporated water then condenses on a cold surface, where it can be collected and used.
Solar stills are simple devices that can be built using easily available materials, making them an ideal solution for areas where clean water is scarce. They are also very efficient, with some models able to produce up to four liters of fresh water per day.
While solar stills are not a perfect solution to the world’s water crisis, they offer a low-cost, sustainable way to generate clean drinking water in regions where it is needed most. They can also be an important tool in disaster relief and emergency situations.
How to Make a Simple Solar Still
Materials:
- A large container
- A smaller container that can fit inside the large container
- Plastic wrap
- Water
- Salt
- Rock
Instructions:
1. Fill the large container with water, making sure the water level is below the height of the smaller container.
2. Pour a few tablespoons of salt into the water and stir until the salt dissolves completely. If you wish, you can have the kids taste the water to show them that the water is indeed salty and undrinkable.
3. Put the smaller container in the center of the large container, pushing it down so it’s not floating. If the smaller container is not staying still, then you may need to switch it out for a heavier one.
Make sure none of the salty water gets in the smaller container. Pour out some of the salty water if necessary.
4. Cover the top of the large container with plastic wrap, making sure that it’s nice and tightly sealed.
5. Place a rock in the center of the plastic wrap. You may need to switch out the rock if it’s too heavy or too light. You want the plastic wrap to be weighed down in the middle, but not so much that the rock is inside the smaller container.
6. Place the solar still outside under the sun for several hours. The amount of water you collect will depend on how strong the sun is and how long you leave the still out.
7. Peek to see if there is water collected in the smaller container. If so, take off the rock and plastic wrap.
8. Taste the water inside the smaller container. Is it salty?
How a Solar Still Works
Were your kids amazed by how the water inside the smaller container is fresh and not salty? My kids were very surprised!
What exactly happened inside the solar still?
As the inside of the solar still heats up due to the heat from the sun, the water inside the large container evaporates, leaving the salt behind. The water collects on the plastic wrap, and the slope formed by the rock caused the water droplets to run down toward the center of the plastic wrap.
Then as water continues to pool in the middle of the plastic wrap, it gets heavy enough to drop down to the smaller container. This process continues until there is enough in the smaller container to drink!
Science Extensions
Since this DIY solar still experiment was so easy to do, why not try the following:
- Dissolve sugar instead of salt in the water.
- Instead of adding solids like sugar or salt, try adding vinegar to the water.
- Try this solar still experiment on a hot summer day, and then try it again on a cold winter day. Make sure it’s sunny on both days. Did it work when it’s cold outside?
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Ohhh this is an interesting experiment to try – perfect for science enthusiasts!