Scientists at the King Abdullah University of Science and Technology in Saudi Arabia have discovered a way to make a more efficient solar water purifier. Is that important? If you live in the Arabian peninsular where desert is the primary geological feature and fresh water is at a premium, it certainly is.
Desalinization is vital to life in that part of the world, where schemes to obtain more fresh water by towing icebergs to the area have been actively considered for generations. The hitch is, large scale desalinization requires lots of energy. If the sun is harnessed to provide the needed energy, fresh water can be obtained without spewing carbon emissions into the atmosphere.
Desalinization usually takes place in one of two ways. Either the source water is pushed through a membrane that allows water molecules to pass through but not larger molecules — a process often known as reverse osmosis — or the source water is heated until it evaporates. Collect the steam, let it condense, and you have pure water. That process is called distillation.
The solar powered distillers in use today use a two-dimensional device to absorb heat from sunlight. Some of that heat is lost to the surrounding air. The researchers reasoned that making the part of the device that absorbs sunlight three dimensional — thereby increasing its surface area — would boost efficiency.
They were right. Using the interlocking parallelograms found in origami art, they created a 3D structure from cellulose with the peaks and valleys that are common to origami. Then they covered it with a light absorbing nanocarbon composite made from graphene oxide and carbon nanotubes. Their new 3D heat absorber turned out to be 50% more efficient than the 2D devices used in conventional solar powered desalinization equipment. In fact, the new water purifier is nearly 100% efficient.
The researchers say the valleys in the origami-derived structure do a better job of capturing heat from the sun partly because less of the sunlight is reflected away from the heating element. The heat collected flows from the valleys toward the cooler peaks, evaporating water along the way instead of being lost to the surrounding air.
Humans cannot exist without access to clean water. Less than 1% of all the water on Earth is available for human consumption. The rest is either in the oceans or locked up in glaciers and snowfalls. The ability to create abundant fresh water from sunshine could prove vital to millions of people as warmer average temperatures lead to increased desertification in more parts of the world.
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