Researchers Develop Cheap Sunlight Powered Water-Purifier

The Solar vapor generator being tested. Qiaoqiang Gan/SUNY Buffalo

The clean water shortage is a terrible problem affecting millions of people, but now researchers may have found a solution to purify saltwater and contaminated water at a fraction of the cost.

The scientists improved on the common solar still. They improved the efficiency and the freshwater generation rate via a cheap portable device that can convert clean water 2.4 times faster than leading commercial products. Their results are published in Global Challenges.

“Using extremely low-cost materials, we have been able to create a system that makes near maximum use of the solar energy during evaporation,” lead researcher Qiaoqiang Gan, an associate professor of electrical engineering in the University at Buffalo School of Engineering and Applied Sciences, said in a statement. "At the same time, we are minimizing the amount of heat loss during this process."

The device is a solar vapor generator, which uses the heat from the Sun to evaporate the water and thus separate it from bacteria, salt, and soot. The water vapor is then condensed into drinkable water.

“People lacking adequate drinking water have employed solar stills for years, however, these devices are inefficient,” says Haomin Song, also at the University of Buffalo and one of the study’s leading co-authors. “For example, many devices lose valuable heat energy due to heating the bulk liquid during the evaporation process. Meanwhile, systems that require optical concentrators, such as mirrors and lenses, to concentrate the sunlight are costly.”

The breakthrough for the team was to use paper coated in carbon black that absorbs the water and maximizes the amount of sunlight absorption. The device, which is as big as a mini-fridge, floats and uses only surface water, so it can be used on any body of water. The generator, according to the team, can produce between 3 and 10 liters of freshwater a day.

Based on the current cost of the material, the device is roughly $1.60 per square meter. It could be brought down even further if they were produced in bulk.

“The solar still we are developing would be ideal for small communities, allowing people to generate their own drinking water much like they generate their own power via solar panels on their house roof,” added Zhejun Liu, a co-author at Fudan University.

With almost 700 million people lacking access to clean water, finding a cost-effective and efficient solution is needed now more than ever.

The Solar vapor generator being tested. Qiaoqiang Gan/SUNY Buffalo

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