Nguyen Ngoc Anh and his associate Pham Duy Linh from Can Tho University have invented a system that uses sunlight to desalinate water, and successfully tested it in a house in the Mekong Delta province of Ben Tre .

Residents in drought-hit areas and those with brackish water struggle to find fresh water for daily use and need a household-sized water treatment system, the students said.

Anh uses a softwood tank covered with glass on top of which water evaporates and condenses before being collected through a pipe.

One square metre of the tank can produce 5.25 litres of fresh water a day that is good enough for cooking and coliform levels meeting Ministry of Health standards.

The system operates efficiently from 9am to 3pm during the dry season.

The inventors use simple and recycled materials like glass, soft wooden panels, plastic, recycled aluminium pipe, and coconut husk to keep the cost down to around 400,000 VND per square metre.

"Since coastal residents face water shortage, I thought of developing a cheap system that could help them get fresh water," Anh said.

"I came up with a system that uses solar energy and cheap materials."

The system won for the duo this year's Holcim Prize worth 50 million VND (2,300 USD) in an annual competition held at Can Tho University, and 150 million VND from Holcim Vietnam for installing the system in houses in Kien Giang province. They defeated nine other contestant teams to win the prize.

The competition, organised by the Swiss cement maker and five universities – the HCM City University of Architecture, HCM University of Polytechnic, HCM City University of Social Science and Humanity, Can Tho University, and Hanoi University of Architecture – since 2009, is meant for research into the environment, economic development, and social welfare./.