Researchers at the Australian National University have developed a new way to desalinate water without using electricity.
This method uses solar energy and can be deployed in remote locations, even in low-income countries.
With fresh water in short supply in multiple parts of the world, countries are turning to seawater and desalination to meet their water needs.
The World Bank estimates that up to 300 million people in 150 countries depend on desalination to meet their water needs.
However, desalination consumes a lot of energy. In 2018, it consumed 100 billion kilowatts of electricity, a quarter of the energy spent on saving water. This can be attributed to technologies such as reverse osmosis, which uses high pressure to separate water or heat to evaporate water.
A research team led by Juan Felipe Torres, a professor at ANU’s Faculty of Engineering, has turned to solar energy to reduce energy consumption by up to 80 percent.
Low temperature desalination
The researchers use a phenomenon called thermal diffusion, a temperature gradient to move salt from the warmer side to the cooler side to effect desalination. In this process, the water remains in the liquid state, and no energy is spent converting it into steam and cooling it again.
In a technical demonstration, the researchers used a narrow channel of seawater. They placed it between two plates kept at different temperatures. The top plate was heated to over 140 F (60 C), while the bottom plate was cooled to 68 F (20 C).
The canal was a little more than a foot and a half long, with brackish water coming out of its top and brackish water coming out of its bottom. After one pass, the colder, more salty water was removed, and the warmer, less salty water was returned to the setup.
Each pass saw the water salinity drop by three percent, and using multiple cycles, the salinity dropped from 30,000 ppm to less than 500 ppm.
Interestingly, the heat needed to carry out the process can come directly from sunlight or even waste heat generated during industrial processes.
Solving water desalination problems
Conventional desalination methods can consume up to 100 kilowatt-hours of electricity per cubic meter of clean water generated. This process consumes a lot of energy and requires expensive materials, such as membranes that require high maintenance and are susceptible to corrosion.
This has made desalination an expensive approach, and difficult to deploy in low- and middle-income countries or remote areas.
“Thermal diffusion desalination is the first thermal water desalination method that does not require a phase change,” Torres said in a press release. “It operates entirely in the liquid phase, and most importantly, it does not require membranes or other types of ion-absorbing materials to purify the water.”
The lack of membranes makes thermal diffusion desalination ideal for large-scale deployment. Researchers are now building a multi-channel device for use on the island of Tonga, which is facing severe drought.
The device will be powered by a solar panel, no larger than a human face.
“Our dream is to enable a paradigm shift in desalination technology, based on methods that can be driven by the low temperatures in our surrounding environment,” Torres said. Tech Explore.
About the editor
Amiya Baliga Amiya is a science writer based in Hyderabad, India. Being a molecular biologist, he traded micropipette for writing about science during the pandemic and doesn’t want to go back. He loves writing about genetics, microbes, technology, and public policy.
(Tags for translation)Inventions and machines
