Solar Water Still: The No-Cost Method to Distill Pure Water

Learn how to build your own solar still.
Kashyap Vyas

Water is one of the essential elements required for life to thrive. Virtually every living being on this planet is dependent on water one way or another. Take humans, for example. We can go without food for around three weeks but can only last three-to-four days without water.

And yet, water is not a resource equally available to all people in the world. 

As much as human society has advanced in terms of technology, the idea of pure water for all is something we haven’t been able to put into practice. It is shocking to know that 2.2 billion people around the world don’t have access to safe water.

Water distillation is a process that requires energy and machinery. In underdeveloped places, constructing such a system has many obstacles.


To overcome these obstacles, inventors, and engineers are still researching on efficient water distillation systems that can work on low energy requirements with acceptable levels of volume for filtration.

And the best and easiest way to set up, even in places without electricity, is a solar distillation unit known as solar stills.

The sun remains the largest source of energy in our solar system. It is a fact that most of the energy that we have on earth traces its roots to the sun.

A solar distillation unit separates water from impurities using the heat of the sun.

What is a solar still?

A solar still or a solar water distilling unit is a device that uses the sun’s energy to distill water. Distillation is the process of separating clean water from contaminated water.

The advantage of solar water distiller is that it runs on the energy of the sun, rather than needing an external power source.

Since solar stills use the heat of the sun directly and don’t employ solar cells to generate electricity, the overall cost of a solar still is relatively low.

The working principle behind a solar still

The solar still is made to replicate a version of the water cycle. To be more specific, the moisture inside the distill evaporates due to the sun’s heat and condenses upon cooling down.

When the water vapor condenses, it forms water droplets that get collected and can be used for drinking. The salts or minerals in the water doesn’t evaporate with the water.

Hence, the contaminants are left behind, while only the water gets extracted from the solution.

How to construct a solar still?

The construction and idea behind the solar still are quite simple. You can follow the steps listed below in order to construct basic solar still. You can also use this method in extreme situations when in need of water.

Step 1: Dig a pit that is about 3-to-4-feet deep and 4-feet wide on a sunlit location.

Step 2: Dig another hole inside the pit and place a container in the hole.

Step 3: Next, cover the pit with a plastic sheet and secure its edges.

Step 4: Place a small rock at the center of the plastic sheet so that it creates a dip on top of the container.

Step 5: Wait for 24-hours.

When you open the sheet, you will find water collected in the container placed in the middle. There are methods that you can follow to increase the rate of water collection, like putting some green foliage around the container to increase the moisture content.

Also, ensure that air cannot escape through the sides.

The above example is one of the most primitive types of solar still. Nonetheless, it's very useful in survival situations. However, there are also floating type solar stills that you can build on your own.

There are more advanced solar setups that you can use to distill water with greater efficiency. Such setups use expensive components and often have complex construction.

One such example is a solar still that uses solar panels to distill water electrically.

Solar still with a contaminated water source

In the above solar still unit, water forms from the moisture content in the soil and the foliage. However, if you want to distill water from a contaminated source, you can also do this by changing the design.

The new design must include another tray that contains contaminated water in addition to the collection tray. Both the trays are isolated so that only the tray with contaminated water undergoes evaporation.

The condensed water then falls into the collection tray by the use of a slope. This method of distilling water from contaminated water is best suited for areas where people have limited access to fresh water.

Advantages of solar still

There are numerous advantages to creating solar stills, and you might have picked up on some yourself. Nonetheless, we'll list the most important ones down below.

No energy requirement: Solar stills can work completely independent of electricity. This makes it an excellent option for places which do not have power lines or limited energy reserve.

Balanced PH levels: Even if the water gets distilled from a contaminated source, the PH of the water remains normal. No contaminants get transferred during the process.

Simple construction: Even if we build top tier solar still, the construction of it is significantly simpler than filtration devices that run on electricity or other forms of fuel.

Low maintenance: Since solar stills don’t have any electronics or moving parts, it requires very low maintenance.

Solar desalination

Solar desalination is not to be confused with solar distills. They use the same solar energy for purifying water, but their source differs.

Solar desalination is the process of separating water from saline water. We know that over 70% of earth’s water derives from the oceans. However, the water is not drinkable due to its dissolved salt.

And that's when Solar desalination comes into play.

Solar desalination aims to separate the salts from the water so that the water is fit for human consumption. This separation is possible using the heat of the sun, or by using solar panels.

Recently, Kenya installed a solar-powered desalination system that can provide safe water to 35,000 people in a day.


Solar stills are in no way perfect, as they currently have only a slow rate of conversion. However, they do offer the most convenient and affordable way to get fresh drinking water.


These eco-friendly water purification systems are indeed helpful in overcoming the safe drinking water crisis of the world. However, the active participation of both individuals and organizations to develop efficient solar stills can make a large scale difference.

Water is one of our fundamental rights, and millions in the world do not get justice in this regard. With inventions like more efficient solar water stills, we can certainly make a difference!

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