One of the largest problems in South Africa is ensuring the delivery of clean, potable water to a wide variety of rural communities. A new invention, inspired by the Japanese art of paper folding, origami, may however make that marginally easier for those who live within walking distance of the ocean.
According to a report in ACS Applied Materials & Interfaces, researchers have recently devised a solar steam generator that sets a new bar and approaches 100 percent efficiency for the production of clean water from salt water sources.
Solar steam generators produce clean water by converting energy from the sun into heat, which evaporates seawater, leaving salts and other impurities behind. The steam is then collected and condensed into clean water. Current solar steam generators contain a flat photothermal material, which produces heat from absorbed light. Although these devices are somewhat efficient, they tend to lose energy by heat dissipation from the material into the air.
Peng Wang and colleagues have now improved on energy efficiency by designing a three-dimensional photothermal material based on the Miura fold of origami, which consists of interlocking parallelograms that form “mountains” and “valleys” within the 3D structure.
The researchers made their solar steam generator by depositing a light-absorbing nanocarbon composite onto a cellulose membrane that was patterned with the Miura fold. They found that their 3D device had a 50 percent higher evaporation rate than a flat 2D device. In addition, the efficiency of the 3D structure approached 100 percent, compared with 71 percent for the 2D material.
The researchers say that, compared to a flat surface, origami “valleys” capture the sunlight better so that less is lost to reflection. In addition, heat can flow from the valleys toward the cooler “mountains,” evaporating water along the way instead of being lost to the air.