“It’s exciting to see a phenomenon that no one has seen before,” said Shuqi Xu, a PhD candidate at the Australian National University (ANU). “I don’t want people to think I am a workaholic, but I often come to the lab on Sundays. I can’t wait to find out the results of our experiments.”

Xu’s dedication has led to the world’s first thermal desalination method where water remains in the liquid phase throughout the process. This power-saving and potentially lifesaving approach is detailed in a new study published in Nature Communications.

“Severe drought is happening more often due to climate change,” Xu said. “Optimizing water desalination is our best hope to prevent famine caused by lack of water for agriculture.”

Xu first became passionate about water security as an undergraduate when she visited a remote island on the Mekong River in Cambodia as part of a Humanitarian Engineering program with Engineers Without Borders. She observed locals suffering from skin rashes due to river water contamination and relying solely on rainwater for drinking.

“After seeing this, I really wanted to pursue a career where I can make a difference in people’s lives,” she recalled.

In 2019, a course called “Fluid Mechanics and Heat Transfer,” taught by Dr. Juan Felipe Torres, presented a path to combine her passions for groundbreaking science and humanitarian engineering. Dr. Torres, a world-leading researcher and founder of the ANU Heat for Environmental and Aerospace Technologies (HEAT) Lab, impressed Xu with his clear and deep explanations of complex topics. She later sought him out as a supervisor for her Honours research and continued under his guidance as a PhD student.

“My motivation to research thermodiffusion for my PhD had a lot to do with my supervisor,” Xu said. “He is really motivated to use technology to help people, and I had already learned a lot from him. So, I knew it would be a good experience working with him.”

Xu is the first author, and Dr. Torres is the Lead Chief Investigator on the thermodiffusive desalination paper.

Globally, over 70% of freshwater resources are used for agriculture. As the global population grows, agriculture and other vital industries will need more water.

“Our freshwater resources are already under a lot of strain,” said Dr. Torres. “When we add to that the impacts of climate change and longer and more severe periods of drought, we could be facing compounding humanitarian crises.”

Current desalination technologies require significant energy and expensive materials, making them less sustainable in developing nations or rural areas.

“If we continue fine-tuning the current technology without changing the fundamentals, it might not be enough,” Dr. Torres said. “A paradigm shift is essential to ensure we can sustain human life over the next century.”

The new research suggests distributing simpler, more affordable desalination units powered by low-grade heat from sunlight or excess industrial heat.

The phenomenon behind this technology, known as thermodiffusion, has been understood since the 19th century.

“If you have a bucket of salty water and one part of the water is colder and one part is hotter, the sodium chloride will move to the cold side,” Xu explained.

To test this, researchers pushed seawater through a narrow channel heated from above to 60°C and cooled from below to 20°C. The salt migrated to the cooler water, and the device reprocessed the warmer, fresher water through the channel, reducing its salinity by 3% with each cycle. The research showed that repeated cycles could reduce seawater salinity from 30,000 parts per million to less than 500.

The team is now developing a multi-channel device to be deployed in Tonga, where severe drought has impacted agriculture and caused water scarcity. This facility will be powered by a solar panel “no bigger than my face,” Xu said.

“There are thousands of remote regions and dozens of small countries around the world facing water scarcity,” Dr. Torres said. “They are in places where climate change is having the worst impacts, drying their land and destroying their agriculture. We need thermodiffusive desalination to decentralize the process and sustainably bring water security to these regions.”

By Impact Lab