Engineers develop solar-powered water purifier

The device could aid people lacking drinking water and those affected by natural disasters.

Engineers at the University at Buffalo School of Engineering and Applied Sciences have developed a solar-powered water purifier using carbon-dipped paper, which has the potential to be an efficient and inexpensive way to turn saltwater and contaminated water into potable water for personal use.

To conduct the research, the team built a small-scale solar still the size of a mini refrigerator. It’s made of expanded polystyrene foam, a common plastic that acts as a thermal insulator, and porous paper coated in carbon black. The paper absorbs water, while the carbon black absorbs sunlight and transforms the solar energy into heat used during evaporation.

The device, which they call a ‘solar vapor generator’, cleans or desalinates water by using the heat converted from sunlight. When the sun evaporates the water, salt, bacteria or other unwanted elements are left behind as the liquid moves into a gaseous state. The water vapor then cools and returns to a liquid state, where it is collected in a separate container without the salt or contaminants.  

Qiaoqiang Gan, lead researcher on the project, said: “Using extremely low-cost materials, we have been able to create a system that makes near maximum use of the solar energy during evaporation. At the same time, we are minimizing the amount of heat loss during this process.”

Only 12% of the available energy was lost during the evaporation process, according to the university. This is possible partly because the device converts only surface water, which evaporated at 44°C.

The researchers believe the still is capable of producing 3-10 liters of water per day, an improvement over most commercial solar stills of similar size that produce 1-5 liters per day, according to the team. The idea could help address global drinking water shortages, especially in developing areas and regions affected by natural disasters.

Haomin Song, a PhD candidate at the university, said: “People lacking adequate drinking water have employed solar stills for years, however, these devices are inefficient. 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 research is described in a study published in the journal Global Challenges.