New solar-powered system converts saltwater into drinking water

The KCL research team said the new system works by separating the salt using a set of specialised membranes which channel salt ions into a stream of brine, leaving the water fresh and drinkable. 

By flexibly adjusting the voltage and the rate at which salt water flowed through the system, the researchers developed a system that adjusts to variable sunshine while not compromising on the amount of fresh drinking water produced.

Using data first gathered in the village of Chelleru near Hyderabad in India, and then recreating these conditions of the village in New Mexico, the research team converted up to 10m3 of fresh drinking water. This was enough for 3,000 people a day, with the process continuing to run regardless of variable solar power caused by cloud coverage and rain.

The researchers said that the process is over 20 per cent cheaper than traditional methods and could signal a step change in providing clean water in developing countries and beyond.

In a statement, Dr Wei He from KCL’s department of Engineering said: “By offering a cheap, eco-friendly alternative that can be operated off the grid, our technology enables communities to tap into alternative water sources - such as deep aquifers or saline water - to address water scarcity and contamination in traditional water supplies.

“This technology can expand water sources available to communities beyond traditional ones and by providing water from uncontaminated saline sources, may help combat water scarcity or unexpected emergencies when conventional water supplies are disrupted, for example like the recent cholera outbreaks in Zambia.”

Roughly a quarter of the world’s population face ‘extremely high’ levels of water stress, which leads to a high likelihood of water scarcity. In the global rural population, 1.6 billion people face water scarcity, many of whom are reliant on stressed reserves of groundwater lying beneath the Earth’s surface.

However, worldwide, 56 per cent of groundwater is saline and unsuitable for consumption. This issue is particularly prevalent in India, where 60 per cent of the land harbours undrinkable saline water.

The researchers said that traditional desalination technology has relied either on costly batteries in off-grid systems or a grid system to supply the energy necessary to remove salt from the water. In developing countries’ rural areas, the grid infrastructure can be unreliable and is largely reliant on fossil fuels.

Without regular supplies of energy at use, individual villages and communities must rely on expensive batteries to use renewable energy like solar to provide their fresh water, passing the cost onto individual consumers.

“By removing the need for a grid system entirely and cutting reliance on battery tech by 92 per cent, our system can provide reliable access to safe drinking water, entirely emission free onsite and at a discount of roughly 22 per cent to the people who need it compared to traditional methods,” said Dr He.

The researchers said the system also has the potential to be used outside of developing areas, particularly in agriculture where climate change is leading to unstable reserves of fresh water for irrigation.

Further, the team plan to scale up the availability of the technology across India through collaboration with local partners, create a start-up to commercialise and fund the technology, and apply the technology to other sectors including wastewater and producing alkaline to help the ocean absorb more CO2 from the atmosphere.

The research paper, published today (March 26, 2024) in Nature Water, can be read in full here.