Researchers at University of SA say they have found a cheap way of producing drinkable water from salty and contaminated water.
Less than 3 per cent of the world's water is fresh while 1.42 billion people, including 450 million children, live in areas of high or extremely high water vulnerability with that figure expected to grow.
Researchers at UniSA's Future Industries Institute say they have developed a new process that could eliminate water stress for millions of people including those living in many of the world's most vulnerable and disadvantaged communities.
A team led by Associate Professor Haolan Xu has refined a technique to produce fresh water from sea water, brackish water or contaminated water through solar evaporation.
Dr Xu said the system could deliver enough daily fresh drinking water for a family of four from just one square metre of source water.
"In recent years there has been a lot of attention on using solar evaporation to create fresh drinking water but previous techniques have been too inefficient to be practically useful," he said.
"We have overcome those inefficiencies and our technology can now deliver enough fresh water to support many practical needs at a fraction of the cost of existing technologies like reverse osmosis."
He said at the heart of the system was a highly efficient photothermal structure that sits on the surface of a water source and converts sunlight to heat, focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the liquid.
While other researchers had explored similar technology, previous efforts had been hampered by energy loss with heat passing into the source water and dissipating into the air above, he said.
"Previously many of the experimental photothermal evaporators were basically two dimensional; they were just a flat surface and they could lose 10 to 20pc of solar energy to the bulk water and the surrounding environment," Dr Xu said.
"We have developed a technique that not only prevents any loss of solar energy but actually draws additional energy from the bulk water and surrounding environment, meaning the system operates at 100pc efficiency for the solar input and draws up to another 170pc energy from the water and environment."
Dr Xu and his team developed a three-dimensional, fin-shaped, heatsink-like evaporator.
Their design shifts surplus heat away from the evaporator's top surfaces (ie, solar evaporation surface), distributing heat to the fin surface for water evaporation, thus cooling the top evaporation surface and realising zero energy loss during solar evaporation.
"This heatsink technique means all surfaces of the evaporator remain at a lower temperature than the surrounding water and air, so additional energy flows from the higher-energy external environment into the lower-energy evaporator.
"We are the first researchers in the world to extract energy from the bulk water during solar evaporation and use it for evaporation and this has helped our process become efficient enough to deliver between 10 and 20 litres of fresh water per square metre per day.
"In addition to its efficiency, the practicality of the system is enhanced by the fact it is built entirely from simple, everyday materials that are low cost, sustainable and easily obtainable.
"One of the main aims with our research was to deliver for practical applications, so the materials we used were just sourced from the hardware store or supermarket," Dr Xu said.
"The only exception is the photothermal materials but even there we are using a very simple and cost-effective process and the real advances we have made are with the system design and energy nexus optimisation, not the materials.
"In remote communities with small populations, the infrastructure cost of systems like reverse osmosis is simply too great to ever justify but our technique could deliver a very low cost alternative that would be easy to set up and basically free to run."
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