Can Solar-Powered Desalination Prevent the World Shortage of Water?

 by Liberty Mitchell Brock

Water is a major factor in everything we do, it is a necessity for almost everything we do. Out of all the world's water resources, the oceans occupy 97% whilst freshwater is less than 3%. Studies have shown that the amount of available freshwater per person has dropped from 4000m³ to 1000m³ from the early 1950s. The World Resources Institute has predicted that by 2025 at least 3.5 billion people will experience water shortages. The process of desalination has been around for just over 7 decades and some countries use it as their main source of creating potable water. However it requires lots of energy which causes it to be quite expensive. 

There are two different types of solar desalination processes; reverse osmosis and solar humidification-dehumidification (HDH). Reverse osmosis is when sea water passes through a semipermeable membrane at high pressure to separate freshwater from other substances. This process is used mainly in large-scale desalination systems with readily available electricity from solar panels. The HDH system is similar to the natural water cycle as water is evaporated and then condensed which separates the salt and other substances from the freshwater. Each desalination system is independent in design, but are all fundamentally based on the same concept. Water is heated by thermal energy from the sun until it evaporates, it will then condense onto a surface before dripping off and being collected as fresh, potable water. The majority of places who are struggling to have enough fresh water are small, coastal places. These locations have an abundance of sunlight and also saltwater from the sea. Solar powered desalination combines the two to provide these places with independence and resilience. 

I came across an inspiring project conducted during a masters program in Architecture in Extreme Environments. Henry Glogau, from New Zealand, travelled to a remote informal settlement called Nueva Esperanza in Chile during 2019. Over the month he was there he learnt about the significant challenges that these communities face in their day to day lives. The main problems were having reliable and safe sources of electricity, sanitation and water. Lots of communities like Nueva Esperanza are cut off and disconnected from formal systems. This leaves these people with unsafe, unreliable and expensive solutions to mitigate their problems. Firstly, Glogau created a solar desalination skylight which was essentially a HDH system incorporated into a lantern shape which is attached to a hole in the ceiling. The skylight is filled with seawater and the sun causes the process of desalination to occur. The collected salt brine is then used as a salt battery for an LED to provide light during the night. Henry then went on to design a portable solar distiller which won the Lexus Design Award of 2021. His ingenuity and design skills have allowed him to create a low-tech solution which has the capability to help lots of people. 

Solar-powered desalination has zero-carbon emissions. We’re living in a society where the only solution to calm down climate change is for everyone to be carbon-neutral. This simple solution, if deployed to a variety of places in time, could help avoid a world with a water shortage issue. Desalination systems have the ability to be set up on either onshore or offshore sites. They are generally lightweight and easy to transport. They are also inexpensive and have low maintenance cost. Through the benefits of versatility, simplicity and efficiency, solar-desalination has the potential to stop water scarcity in the most at-risk regions.