Solar Stills: What Are They and How Do They Work?

Solar Stills: What Are They and How Do They Work?

Say you happen to be cast away somewhere in nature with no viable source of drinkable water. There’s plenty of river, brackish, dirty, or saltwater nearby, but neither of these are safe for consumption. You might initially think it’s not such a big deal. Unfortunately, it is.

Humans cannot survive without water for more than 3 or, tops, 4 days. In fact, dehydration is one of the most common reasons why stranded people die, so knowing how to make a solar still work might save your life. Precisely because of this, drinkable water is one of the first priorities in survival training for military or special operations troops.

What is a Solar Still?

Being able to fulfill one’s basic needs in any situation is a major motive behind the recent surge in the popularity of survival series and subsistence-themed shows. In a world that is increasingly dependent on access to amenities and technologies omnipresent in developed countries, but scarce in developing or under-developed ones, self-reliance is a virtue. Food and water are such necessities that are not readily available everywhere, so knowing how to procure them safely in any environment is of utmost significance.

A simple, high-tech water purifier can be a god-sent in emergency situations. However, there’s nothing to say you’ll always have one handy, not to mention they’re not the most affordable things you can buy. The hydrological cycle of water in nature can be harnessed in order to make 100% safe, drinkable water out of any source you might have nearby. This is what a solar still does: it purifies any type of water with the help of the sun.

Solar stills are incredibly cheap to make and you can do it literally anywhere – for instance in a desert, at sea, or in the forest. All you need are a few basic materials.

How Does a Solar Still Work

How Does a Solar Still Work?

A DIY solar still reproduces nature’s hydrological cycle to turn any water that is readily available, but not safe for consumption, into potable water. The main driving force behind this process is the sun. This is where the energy for the entire process comes from. In nature, the sun is responsible for evaporating dirty water from rivers, seas, lakes, and other sources. Water vapors then rise and condense together to form what we commonly call clouds. The latter are moved around with the help of wind and, during the right conditions, they fall back down to Earth in the form of precipitation.

A solar still helps you achieve the same progression of the natural water cycle, only in an artificial environment and in such a way so as to make it possible for you to gather the condensed, purified water in a container. The best part about DIY solar stills is that they use no fossil fuels in order to generate drinkable water. The sun’s energy can easily heat up non-potable water and turn it into vapor. The latter can be collected and, as it cools, it will turn back into liquid. The only difference is that, this time around, the liquid is free of impurities and completely safe to drink.

Below, you’ll find a list of basic components you need in order to make a solar still.

What You Need for a DIY Solar Still

1. Contaminated Water Container. First and foremost, you need something to store your contaminated water. A trough with a dark or completely black bottom, such as a cast-iron pan, is the best way to go, since it helps focus the sun’s energy on the water you need to purify. If you don’t have anything of the sort, any kind of water-tight container will do.

2. Glass or Plastic Wrap. Glass is preferable to plastic, but either can work just fine. This will be placed on top of your contaminated water trough in order to collect vapor. You’ll also need to fix it at an inclination towards your second trough intended for drinkable water in order to help the purified liquid gather in it.

3. Purified Water Container. A glass jar is often best for gathering the product of your solar still. However, a plastic bottle can also work.

Perhaps the easiest version of a working solar still is to place a glass jar straight into the contaminated water trough. Then, you cover it with a plastic wrap and place a stone or small weight on top of the jar in order to incline the surface and help the water collect in the middle. If the still is airtight, in just several hours, perhaps less, depending on how bright and strong the sun is shining, you’ll have some pure water to drink.

Benefits of Solar Stills

Making a small solar still in the wild is not difficult. While the latter collects, you are free to do other tasks that might be equally important, such as finding food or gathering fuel for your fire. Here are the pros of a homemade solar still:

  • Any type of softened water can be used, including dirty tap water, a nearby body of fresh water, and even the ocean.
  • Assuming you haven’t used any water-absorbing materials to make your solar still, cleaning it will take very little time. There are no moving parts, so maintenance is almost inexistent.
  • If you happen to be shipwrecked or lost at sea, this is the only viable way to get potable water.
  • Zero transportation costs for the water.
  • No fuel or electricity is needed to generate purified water from a DIY solar still. Like a solar food dehydrator, all it needs is some sun.

Unfortunately, homemade solar stills also have some downsides:

  • The rate of purification is very slow. Unless you have a massive solar still, a full day’s worth of sunlight will generate little water. A rough calculation tells us we’d be able to make approximately 2 liters of drinkable water for a solar still with a surface of 10 square feet (0.9 square metre). This is just enough to get by, but still a bit less than ideal.
  • In the case of large solar still systems meant to collect water for more than one person, there’s a considerable up-front cost. You’ll need a fairly large basin, as well as a big enough glass cover to go on top of it. This is, of course, in the off chance that these materials are not just readily available.

How to Use a Solar Still

How to Use a Solar Still

Solar stills is are intuitive to use. However, there are some things you should keep in mind when trying to generate water through this affordable process.  Designs can vary widely in performance. First and foremost, you should prepare your system well before the sun rises, preferably the previous night or before sunrise.

Like the panels for solar water heaters, the solar still should be placed in an area that receives uninterrupted sunlight throughout the day. Higher locations are usually better, provided that you have easy access to them for water collection. As we mentioned before, anything that can help boost or focus the sun’s energy, such as a black bottom to your trough, is of great use. Air flow can also have a dramatic effect on the efficiency of a solar still.

In case you’re using a distiller that has the purified water container placed inside the contaminated one, make sure the entire bottom of the latter trough is covered. You want enough of it to account for a day’s worth of distilling, but not enough to get into your condensed water vessel.

After setting it up, check again to see if the system is completely sealed. If there’s any way that vapor can come out, then you won’t be collecting water. Once every three to four hours, make a trip to see if there’s enough water left to distill or if your purified container is full. (For other, related ways to prevent water from stagnating, check out these solar pond aerators.)

What DIY Solar Stills Can Teach Us

You might not be using a solar still to purify water for yourself and your family anytime soon. Despite this, knowing how to make one can be a life saver given a truly dire situation. Sometimes, you might need to hang on for a little while longer, until help reaches you. Similar to building a DIY solar heater, building a solar still from scratch is an incredibly educational experience that can inspire both you, as well as your children to be more self-reliant.

There are several other lessons to be learned here, notwithstanding the fact that we take for granted many basic amenities that other people have to work hard to obtain. In developing or third-world countries, access to drinkable water is often difficult and sometimes even impossible. These people have to be creative and expend great resources in order to get their daily water requirement.

Secondly, the sun’s energy is abundant and renewable. Instead of relying on handy fossil fuels that pollute and work to the detriment of our environment, we can improve upon those technologies that are clean and create other products, like this solar pool ionizer.

With this in mind, you are now ready to make a solar still and transform dirty water into purified one. It might not be very efficient or as easy as using a commercially available purifier, but it’s something anyone can do with a few basic resources. (Looking for more cool solar products? Check out these solar pool cover reels!)

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