Scientists from the University at Buffalo (UB), the State University of New York (US), have built a solar-powered water purifier with carbon-dipped paper as a potentially highly efficient, cheap and portable way to desalinate and purify water.
According to the researchers, the system made from very low-cost materials makes near maximum use of the solar energy during evaporation, while minimizing heat loss during the process. Concentration of the sunlight is not required.
“We employed a carbon-coated paper on top of a foam floating on top of the water,” says lead researcher Dr Qiaoqiang Gan, who is an associate professor of electrical engineering in UB’s School of Engineering and Applied Sciences. Part of the paper is dipped into the water to wick the water to the paper’s surface for evaporation. “In this case, the absorbed sunlight only needs to heat and evaporate this thin sheet of water rather than heat the entire bulk water, and therefore we are improving the efficiency,” the professor explains.
The project holds the promise of an affordable solar still product for water purification. Gan repeatedly stresses how extremely low-cost these materials are. What is more, he says the UB team has achieved a record high efficiency, compared with recently reported solar vapor systems using advanced materials that are significantly more expensive. “Therefore, we pointed out, the important direction is to develop an efficient solar still system using low cost carbon powder rather than expensive nanomaterials, since the improvement room is small,” the researcher says. “Cost is more important.”
Gan says the biggest challenge in developing this extremely low-cost system is to find a company that will help to commercialize it. The demo system is ready, but he says the next step in commercializing the system cannot be realized without a partner. “In general, it is to improve the overall efficiency of the system,” Gan says, emphasizing how different lab experiments are from a functioning commercial system in an outdoor environment.
“Many people may be surprised we can use the lowest cost materials to realize better efficiency and total evaporation rate, compared with those systems relying on expensive dark materials.”
The researchers believe the still can produce 3–10 liters of drinkable water per day. The materials cost approximately $1.60 USD per square meter and could be even cheaper in production on large scale.
Relevance and application
“This system cannot compete with mainstream membrane-filter-based water desalination technology, since the solar intensity is limited. Therefore, under regular sun illumination, the generation rate cannot be higher than the theoretical upper limit,” Gan points out. “However, this product can be very important for resource-limited areas, where people cannot afford membrane-based desalination technologies.”
The solar still could also be an attractive solution for outdoor activities, such as backcountry camping, or for crews working off-shore or on boats to get drinkable water. Furthermore, Gan adds that the system is also useful for rescue purposes in disaster areas.
New knowledge and next steps
Gan says he and his colleagues conclude that this efficient solar still does not have to rely on expensive advanced nanomaterials. “Low cost material is sufficient,” the researcher stresses. The team is currently developing the prototype product for sale and is preparing for discussions with interested investors.
The article “Extremely Cost-Effective and Efficient Solar Vapor Generation under Nonconcentrated Illumination Using Thermally Isolated Black Paper,” is published in the journal Global Challenges.
Written by Sandra Henderson, research editor Solar Novus Today