Researchers at the University at Buffalo have created a highly efficient device that uses sunlight and black carbon-dipped paper to clean water. The paper is placed in a triangular arrangement, which enables it to vaporize and absorb water with nearly 100 percent efficiency. The simple, inexpensive technology could be deployed in regions where clean drinking water is chronically unavailable or areas that have been acutely affected by natural disasters.
“Our technique is able to produce drinking water at a faster pace than is theoretically calculated under natural sunlight,” said lead researcher Qiaoqiang Gan in a statement. The solar still concept, which uses sunlight to purify water, is ancient; Aristotle described a similar technique more than 2,000 years ago. The difference is the new device’s ability to achieve ultra-high efficiency. “Usually, when solar energy is used to evaporate water, some of the energy is wasted as heat is lost to the surrounding environment,” Gan explained. “This makes the process less than 100 percent efficient. Our system has a way of drawing heat in from the surrounding environment, allowing us to achieve near-perfect efficiency.” The carbon-dipped paper’s sloped orientation is key in achieving this efficiency, allowing the bottom edges to soak up water while the outer coating absorbs solar heat to be used in evaporation.
The research team prioritized simplicity and accessibility in its design. “Most groups working on solar evaporation technologies are trying to develop advanced materials, such as metallic plasmonic and carbon-based nanomaterials,” Gan said. “We focused on using extremely low-cost materials and were still able to realize record-breaking performance.” Through their recently launched start-up, Sunny Clean Water, the team hopes to increase access to their device for areas in need. “When you talk to government officials or nonprofits working in disaster zones, they want to know: ‘How much water can you generate every day?’ We have a strategy to boost daily performance,” said Haomin Song, an electrical engineering PhD graduate, in a statement. “With a solar still the size of a mini fridge, we estimate that we can generate 10 to 20 liters of clean water every single day.”