SYDNEY — Australian researchers say a simpler and cheaper method to remove salt from seawater using heat could help combat what they call “unprecedented global water shortages.” The desalination of seawater is a process where salt and impurities are removed to produce drinking water.  

Most of the world’s desalination methods use a process called reverse osmosis. It uses pressure to force seawater through a membrane. The salt is retained on one side, and purified water is passed through on the other. 

Researchers at the Australian National University (ANU) say that while widespread, the current processes need large amounts of electricity and other expensive materials that need to be serviced and maintained.  

Scientists at ANU say they developed the world’s first thermal desalination method. It is powered not by electricity, but by moderate heat generated directly from sunlight, or waste heat from machines such as air conditioners or other industrial processes. 

It uses a phenomenon called thermo diffusion, in which salt moves from hot temperatures to cold. The researchers pumped seawater through a narrow channel, which runs under a unit that was heated to greater than 60 degrees Celsius and over a bottom plate that was cooled to 20 degrees Celsius. Lower-salinity water comes from the water in the top section of the channel, closer to the heat. 

After repeated cycles through the channels, the ANU study asserts, the salinity of seawater can be reduced from 30,000 parts per million to less than 500 parts per million. 

Juan Felipe Torres, a mechanical and aerospace engineer at the Australian National University and the project’s lead chief investigator, explained his pioneering work.  

“We use a phenomenon people have not used before,” he said. “We are exploring its applicability in this context but in essence (it) should be something super simple, something as simple as a channel where you have water flowing through it and you are going to produce some sort of separation, and this is what thermal desalination is doing.”  

The United Nations Food and Agriculture Organization has stated that by 2025, 1.8 billion people around the world are likely to face “absolute water scarcity.”  

Torres said the ANU’s invention could help ensure water supplies to communities under threat because of climate change. 

“Our vision, let’s say, for the future to have a more equitable world in terms of water security and food security is a method that does not require expensive maintenance or to train personnel to continue running it. So, we think thermal desalination would enable that,” he said.  

The ANU team is building a multi-channel solar-powered device to desalinate seawater in the Pacific kingdom of Tonga, which is enduring a severe drought.  

The research is published in the journal Nature Communications. 
…