What is a Solar Still?

We’re all learning more about our impact on the Earth’s climate every day. As global temperatures rise, we’re going to face numerous challenges. To address these challenges each of us will have to step up.

Climate change and rising global temperatures have created water scarcity all over the world. Where it hasn’t created it; it has exacerbated existing water shortages. People are looking for innovations to address this problem.

The growing pace of climate change has also necessitated a change in our lifestyles. We must alter the way we behave and live more sustainably. There are many ways to address this, but reducing our carbon footprint is a major one.

What is a Solar Still

Solar stills can address both of the concerns mentioned above. They’re by no means a new innovation but are quite effective. They’re completely sustainable and eco-friendly because they rely on the sun. They can also provide clean water in areas where it is limited.

You must now be wondering – what is a solar still any way? Luckily, that is the focus of our guide today. So read on to learn the answer!

Introduction to Solar Water Distillation

Few things in life are as important as water. Yet, there are many people who don’t have access to clean drinking water. Addressing water scarcity is one of the sustainable development goals put forward by the UN.

Solar water distillation is the process by which clean water is obtained from fresh water. This is done by concentrating energy from the sun onto freshwater. The energy input results in the separation of salt and contaminants from the water.

Heat energy, supplied by the sun increases the temperature of the water. As the water starts to heat, it begins evaporating. The water turns into vapor, cools and condenses. The contaminants are left behind. The condensed water is collected and stored.

This is the basic principle by which a solar still operates. It can provide water in small quantities, for low capacity systems. The water produced by solar stills is not drinkable. For it to become so, you should instead use saltwater or soft water.

Just because it isn’t drinkable doesn’t mean that it’s not usable. It can be utilized for emergencies, cleaning, washing and cooking.

How Does a Solar Still Work?

Solar stills use two scientific principles to create clean water from contaminated water. These principles are a part of the water cycle so you should already be familiar with them. The two principles are evaporation and condensation.

Scientists discovered a long time ago that most substances have fixed melting and boiling points. Solar stills take advantage of the fact that water’s boiling point is lower than that of salt and minerals.

Everyone knows water boils at 212 degrees Fahrenheit. What most people don’t know is that it takes 5 times that temperature to boil minerals and salt. This is how solar still are able carry out this conversion.

Solar energy boils the water, causing it to evaporate. As it evaporates, it cannot take anything else along, so it separates from the impurities. The contaminants are left behind in the container, while water has left.

The water then starts to cool, transforming from vapors to water again. This process is not instantaneous but is utilized by solar stills to relieve people’s worries.

Benefits and Drawbacks of Solar Stills

Now that you know what is a solar still, it’s time to analyze its benefits and drawbacks.


Solar stills have several advantages, such as:

  • Cheaper than alternate methods
  • Suitable for low and high-volume needs (if properly scaled)
  • Zero mechanical parts makes it easy to construct and maintain
  • Zero energy costs means it is practically free to operate
  • Sustainable energy source


Some disadvantages of solar stills include:

  • Usage and results are dependent on the sun. It is limited to daytime, and bright sunny days
  • Becomes inefficient for larger water needs
  • Rate of water distillation is slow. Other methods may be faster
  • Can cause environmental pollution if by-products are not disposed of properly

Solar Still Types

There are several types of solar stills divided into two broad categories – active and passive. Passive solar stills utilize energy only from the sun. As such, they are inefficient and slow. Active systems were developed to speed up the process.

This is done by using a secondary heat source to increase the water temperature. The faster the water boils, the faster clean water is available. The heat source can be anything from preheating the water to providing heat through a separate thermal or solar device.

Single Effect Stills

This is the most popular type out there. The reason for their popularity is the simplicity of design. You only need a single interface to heat the contaminated water and collect the condensed water.

Multi Effect Stills

Far more efficient than the previous option, multi-effect stills are also quite popular. Though, these require more technical expertise to ensure the seal is air tight. The increased water production makes them an appealing choice nonetheless.

Basin-Type Stills

These trap the water in an impenetrable container as part of the entire system. They are among the most popular options.

Our Final Thoughts

We hope this guide has been helpful in answering what is a solar still. Now that you know, you can begin constructing one for personal use, or for a science project.

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