Roaming into uncharted, dry and hot places requires extra supplies. It is quite unimaginable to go on an expedition without the auxiliary battery pack, extra tire, and of course, lots of food and water supply. While a human can survive weeks without food, water is so essential that the human body can hardly survive more than one day in harsh environmental conditions. As with many expeditions, some unforeseen consequences might interfere with plans, extending the period spent in the desert. In such cases, the food is not so high priority, as the sun and air with low relative humidity down to 10% pluck the remaining water out of the human body. Now imagine a little, portable device, that can harvest the water in the driest and hot places on earth, that could potentially save lives in emergency situations. Scientists and engineers at Shanghai Jiao Tong University have developed a low-cost and scalable hygroscopic material and deployed it into a portable water harvester for a stable water supply.

The hygroscopic material made of active carbon and hygroscopic salt can extract water vapor from the air in various regions and even in the desert, and then the trapped water molecules can be released and condensed to produce freshwater with mild heating. The atmospheric water is abundant and ubiquitous, making the extractionof atmospheric water as a practical approach to providing freshwater anytime, anywhere.

In the last few years, a myriad of lab-scale water harvesters has been introduced. However, the majority of these devices served the purpose to promote new materials, rather than show new advanced system designs that would promote this technology into practical applications. A wide gap has therefore been observed. “Our research was based on the recent advances in materials science, but we're thinking more about how we connect materials science to advanced thermal engineering science, realizing water production of hundred grams in real semi-arid areas.” said Ruzhu Wang, one of the corresponding authors and principal investigators. Wang is the leader of the Energy-Water-Air interdisciplinary innovation team (ITEWA) at Shanghai Jiao Tong University. “Such an exceptional water production highly relies on the novel water harvesting cycling strategy and the advanced thermal solutions of the water harvester,” he added.

The water harvester could be carried and operated easily by a single person, allowing millions of people to gain access to safely managed drinking water, especially in an expedition or other emergency. A piece of the new material made of sustainable recycled organic biomass materials only costs $1 in case of mass production, demonstrating the commercial and scalable potential.

Of course, several modifications to the proposed system could be done in the future. Currently, the device requires electrical power from the grid. However, the researchers calculated the required PV panel area for each month of the year, helping designers to build the actual emergency water harvester.

This work not only provided a vertical integration of materials development and advanced system designs, but also introduced several other aspects that are essential to make breakthroughs in the market: techno-economic analysis in the case of mass production of the device, PV panel requirements, and the feasibility study that showed the global potential of this water harvester to be deployed worldwide.  Wang said, “The developed material and the water harvester have bridged the gap between material science and thermal engineering science, paving the way to practical water production in emergency and real arid areas.”

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