New technique could deliver clean, safe drinking water using sunlight

According to UNICEF, globally, more than 1.42 billion people – including 450 million children – live in areas of high, or extremely high, water vulnerability, and that figure is expected to grow in coming decades.

To solve this problem, an engineers team from the University of South Australia (UniSA) announced that they have developed a cost-effective technique that could deliver clean, safe drinking water to millions of vulnerable people using cheap, sustainable materials and sunlight.

The team led by Associate Professor Haolan Xu said that the technique could derive fresh water from seawater, brackish water, or contaminated water through highly efficient solar evaporation. It can produce enough daily fresh drinking water for a family of four (between 10 and 20 liters) from just one square meter of source water.

To achieve this, the team engineered 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.

Previously, many of the experimental photothermal evaporators were basically two dimensional; they were just a flat surface, and they could lose 10 to 20 percent of solar energy to the bulk water and the surrounding environment,” Dr. Xu says.

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 100 percent efficiency for the solar input and draws up to another 170 percent energy from the water and environment.

Instead of a two-dimensional structure, Prof. 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, distributing heat to the fin surface for water evaporation. This cools the top evaporation surface and realizes zero energy loss during solar evaporation.

The new technique is better than similar technologies because it is more efficient, practical, and built entirely from simple, everyday materials that are low cost, sustainable, and easily obtainable. Also, because the equipment is simple and requires almost no maintenance, there is no need for specialized knowledge to keep the machine running, and maintenance costs are minimal.

This technology really has the potential to provide a long-term clean water solution to people and communities who can’t afford other options, and these are the places such solutions are most needed,” Xu said.

In addition to drinking water applications, the engineers are currently exploring a range of other uses for the technology, including treating wastewater in industrial operations.

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