Solar powered water purification dates back to Ancient Egypt in between the third and fourth century BC. Now, using activated carbon dipped paper folded in to a v shape scientists have broken record speeds for purification via the sun. Activated carbon is really just another word for highly processed charcoal dust. Not surprisingly, charcoal was one of these more ancient methods of purification.
We use charcoal to purify because of it’s high micro-porosity. Which means that microscopic pores around molecules of carbon dust are so small that almost all contaminants can be filtered out of smaller water molecules flowing through.
The theoretical upper limit for conventional purification is 1.68 litres per square metre. However, because of the upside V shaped geometry the slope allows one side to remain cool until the sun passes a critical angle. This allows the evaporation process to “reset” half way through, preventing over-evaporation via loss of water in to atmosphere. The result is 31% more than the theoretical upper limit or 2.2 litres of water per square metre.
other unique forms of evaporation based purification include the more transparent floating solar ball which is more of a 360 degree conical design.
Ancient Sanskrit and Egyptian writings depict a civilisation that also understood evaporation in the same way using it to filter their water. Now scientists have added an extra dose of processed carbon bridging over two millenniums of knowledge saving many future lives from poverty as a result.
The article was published in the journal Advanced Science on May 3rd
Lead Researcher Qiaogiang Gan from the University of Buffalo explains that
“Our technique is able to produce drinking water at a faster pace than is theoretically calculated under natural sunlight,” says lead researcher Qiaoqiang Gan, PhD, associate professor of electrical engineering in the University at Buffalo School of Engineering and Applied Sciences.
In a collaboration between MB Fudan University in China and the University of Wisconsin-Madison.
The project was funded by the National Science Foundation. Researchers Gan and Song have launched a startup called Sunny Clean Water that brings the invention to people who need it most. The Small Business Innovation Research program is going to help test a prototype of the solar still – a sun power water purifier.
cover photo: Huaxiu Chen