Approximately 2.2 billion people in the world don’t have access to crisp, contaminant-free water. In the U.S., we, too, are concerned with having continued access to clean water as well as what lurks in our water — so much so that we reach for bottled water and look for solutions to the water problems that plague our homes.
Scientists are trying to find ways to use renewable resources like solar power to find a viable solution. A favorite is solar distillation, which can not only solve the growing water crisis but also boasts an environmentally conscious aspect, making it a win-win situation.
If you’re unfamiliar with solar distillation, have no fear! In the following sections, we will break down what solar distillation is, how it works, and whether or not it is a viable option for an additional way for us to filter municipal and well water.
What is Solar Distillation?
What if the sun, which provides light, heat, and helps us build strong bones, could also provide us with crisp, clean, and contaminant-free water? That is the idea behind solar distillation. It is the process of using energy from the sun to separate freshwater from salts and other contaminants present in water. It is a simple and cheap technology that has benefitted many.
This purification method is commonly used in remote areas and countries with limited access to clean water or have water scarcity. Alongside fellow purification method reverse osmosis, distillation is recognized as one of the best methods for water purification. It can remove heavy metals, arsenic, salts, nitrates, bacteria, some carcinogens, and arsenic among many others.
How Does It Work?
The easiest way to describe how solar distillation works is that the sun purifies the water by removing it. Although it sounds like something out of a sci-fi movie, the process of solar distillation has actually been around for centuries. It works by mimicking the natural water cycle in the way that it purifies water.
First, untreated water is placed in a basin and the sun heats the contaminated water. Because most chemicals have a higher vaporization point than water, when the untreated water reaches boiling point, it evaporates, leaving the contaminants behind. The evaporated purified water forms droplets on the overlying cover as it recondenses. Now contaminant-free and safe to use, it can be collected and used for drinking or industrial use.
The structures that house the distillation process are called stills, and they come in many forms, each varying in size, dimension, and even the materials it uses. Solar distillation is classified as two different systems, passive and active stills. Here is how they operate:
Passive Solar Stills
Passive solar stills are the most widely known and used of the still categories. It is more convenient and much more cost-efficient. However, its efficiency is dependent upon how air-tight the seal is on the still. As you’ll find, this is a common issue in solar distillation, as vapor exploits the cracks and crevices in the structure’s designs. There are multiple types of passive stills, each created to make up for these flaws and increase efficiency.
- Single-effect still: The simplest and most common form of solar distillation stills. It uses one interface to evaporate and collect the condensate water.
- Multi-effect still: Similar to the single-effect still, except it features multiple components, which help speed up productivity.
- Basin-type still: Instead of being housed in a plastic container painted black, the water is contained in an impenetrable material that keeps steam from escaping.
- Wick still: In this version, a cloth-like material uses capillary action to draw the liquid up through the system, helping the distillation process.
- Multi-wick still: Like the multi-effect still, the multi-wick still doubles the materials used to distill the water. For this still, multiple wicks are used to boost productivity.
- Diffusion still: This still is further advanced than the multi-effect and multi-wick stills, although it still has the same purpose of boosting distillation speed. It features a series of closely spaced parallel partitions that are in contact with saline-soaked wicks.
Active Solar Stills
These solar still consist of the same process as passive solar stills, but with one extra component. Active solar stills use alternative heat sources to speed up the thermal process and enable faster and larger freshwater generation quantities. Like passive solar stills, its efficiency is determined by how tight the seal is on the structure, as a poorly secured still can result in wasting precious steam and risk re-contaminating the water.
What Are the Pros and Cons?
Solar distillation is a cousin to desalination, which can use electric distillation to remove contaminants like salt from water. However, unlike electric distillation, its solar counterpart doesn’t need electricity to boil the water. The sun can heat the water to 212 degrees Fahrenheit, which causes the water to evaporate and makes for an energy-efficient process.
One of the most significant concerns with alternative water treatment methods is that they waste more water than purify. Another benefit to solar distillation is that it wastes no water in its purification process. All of the water that is distilled returns the same volume of water it had while untreated. Water is such a precious resource, so it is an excellent benefit to conserve it while using it.
Cheap and Low Maintenance
As we touched on before, solar distillation still is a straightforward technology and can be made with many types of materials, including cheap ones like plastic. And because they don’t use any electricity or have any moving parts, it makes it a low cost and low maintenance option for water-stressed areas or may not have the budgets to dedicate to more expensive setups.
Although solar distillation has many pros, it does have a few notable challenges, namely that it is a slow process. Its distillation speed is approximately six liters of water per sunny day, which means that in order to get the best experience from your still, you will likely have to wait 24 hours before collecting the water. Talk about being something worth waiting for!
Not Suitable for Large Consumption Needs
It’s not just solar distillation’s slow rate of purification that poses a challenge for areas in need, it is also the fact that in its basic form, it isn’t suitable for large water needs. Communities will need to invest in multiple stills or larger setups to be able to accommodate a large population in need, which may be a little more costly than people may be ready for.
Perhaps the most significant con to solar distillation is that it only works during the daytime. The sun is a key component in this purification method’s success, and unfortunately, it is a limited resource. Those who use it as a water supply will need to find an alternative light source or purification method to keep producing water around the clock.
The Science of Water
Although solar distillation has the potential to do a lot of good, there are still some areas of the purification process that need to be worked out before it can become a viable water technology for the many regions and countries that could benefit from it.
It may be years before the world adopts a purification solution like solar distillation. However, you can benefit from technologies like reverse osmosis today with Puronics’ whole house water filtration system installed by the Science of Water. We have more than 35 years in the water industry, and after taking one of our free water tests, we can help you resolve your household water issues.
Want to request a free water test or learn more about our services? Contact our team at (352) 745-7070 or (904) 580-0000.