By Amanda Froelich
Using nothing more than paper and water, scientists have found a way to sanitize water at record-breaking rates. The process is similar to a technique described by the Greek philosopher Aristotle over 2,000 years ago.
The researchers developed a method for using sunlight to generate green energy with near-perfect efficiency. How? By draping black, carbon-dipped paper in a triangular shape. As GoodNewsNetwork reports, the bottom edge of the paper hangs in a pool of water. As it soaks up fluid, the carbon coating absorbs solar energy and transforms it into heat for evaporation.
“Our technique is able to produce drinking water at a faster pace than is theoretically calculated under natural sunlight,” said lead researcher Qiaoqiang Gan, associate professor of electrical engineering in the University at Buffalo School of Engineering and Applied Sciences.
“Usually, when solar energy is used to evaporate water, some of the energy is wasted as heat is lost to the surrounding environment. This makes the process less than 100% efficient. Our system has a way of drawing heat in from the surrounding environment, allowing us to achieve near-perfect efficiency,” Gan added.
Because the technology is low-cost, the team believes it could help provide drinking water in drought-stricken regions, or where natural disasters have struck.
Rather than wait for the technology to be funded, Gan and colleagues founded the startup Sunny Clean Water. After gaining support from the National Science Foundation Small Business Innovation Research Program, the company started integrating the new evaporation system into a prototype of a solar still (sun-powered water purifier).
The project is genius, no doubt. There’s just one big problem: even the latest solar still models are inefficient at vaporizing water. To counter this, Gan’s team cooled down their own evaporation system, thereby improving its efficiency.
According to Gan, the paper’s sloped triangular shape keeps it cool by weakening the intensity of the sunlight illuminating it. And because the carbon-coated paper stays under room temperature, it can draw heat in from the surrounding area. This step compensates for the usual loss of solar energy that takes place during the vaporization process.
With this set-up, the researchers were able to evaporate the equivalent of 2.2 liters of water per hour for every square meter of area lit up by the regular sun. That’s higher than the theoretical upper limit of 1.68 liters.
“Most groups working on solar evaporation technologies are trying to develop advanced materials, such as metallic plasmonic and carbon-based nanomaterials,” Gan says. “We focused on using extremely low-cost materials and were still able to realize record-breaking performance,” said Gan.
“Importantly, this is the only example I know of where the thermal efficiency of the solar evaporation process is 100 percent when you consider solar energy input. By developing a technique where the vapor is below ambient temperature, we create new research possibilities for exploring alternatives to high-temperature steam generation.”
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