Design And Research On Interfacial Solar-thermal Atmospheric Water Harvesting

Water is an important basic resource for human survival and development.Two-thirds of the population of world lives at least one month a year under moderate water shortages.Not only that,but more than 500 million people face extreme water shortages throughout the year.According to EPA?U.S.Environmental Protection Agency?data,the global total water resources are approximately 1,386,000,000 km³,and fresh water accounts for only 3%.The freshwater resources?river water,freshwater lake water and shallow groundwater?that are easily utilized for humans account for only 0.3%of the total freshwater resources,which is equivalent to 0.007%of the global total water storage.It is worth noting that the amount of water resources in the atmosphere,which is often overlooked,is actually substantial enough to meet the needs of every human being.It is estimated that the atmosphere contains more than 12.9×10¹² m³ of freshwater,equivalently one-eighth of the total freshwater resources of rivers and lakes.At present,the most common system of atmospheric water harvesting is based on traditional passive water harvesting or active electric-driven water harvesting technology.These two types of technology are limited by climatic geography or need to consume a large amount of electrical energy and cannot be applied in most areas of the world.Therefore,it is important to meet human demand for freshwater by further utilizing the treasure trove of atmospheric water resources.At the historic moment,solar-driven sorbent-based atmospheric water harvesting technology emerged.This type of technology consists of a hygroscopic sorbent as the basis,which can be applied to a wider range of scenarios,and the recycling of the entire system is driven by solar energy.Based on these characteristics,this technology is regarded as an emerging development goal with great application value and environmental protection.However,in the widely used intermittent liquid hygroscopic water harvesting systems:due to the poor photo-thermal conversion performance of the liquid hygroscopic agent,the water in the hygroscopic sorbents cannot be fully evaporated and desorbed during the desorption process,resulting in lower water production.In addition,the intermittent water harvesting system is open at night and absorbs water in the air by the hygroscopic sorbents.The water is desorbed and collected by sunlight during the day.Because the atmospheric water that can be collected by this type of system is ultimately limited by the amount of water absorbed at night.Thus,during daylight desorption time,as the water content in the sorbent continues to decrease,the rate of water desorption decreases sharply,resulting in low efficiency of solar energy and water production.Therefore,in this work we designed a new type of continuous diffusion water harvesting device.It enhances the adsorbed and desorbed performance of the whole system by using[EMIM][Ac]ionic liquid as a liquid sorbent and combined with interfacial heating technology.The device can not only absorb atmospheric water at night;while generating water during the day,it can also continuously absorb water in the air to maintain a higher water content in the sorbents,thereby improving the final water collection and energy utilization of the overall device.Moreover,when under 1sun light intensity in lab,the water desorption rate has reached about 0.5 L m^-2 h^-1,and in a long-term cycle experiment of 18 hours,the entire system shows extremely high stability.The total amount of water collected on a day of outdoor experiments was as high as 2.8 L m^-2.As this approach can be generalized for various liquid sorbent and corresponding interfacial solar absorbers,it is expected that this concept provides a promising pathway for the future development of harvesting water from air.