Air humidity as a strategic source for water production

Roberto Natali - September 5, 2023

* L’immagine di copertina di questo paper è stata presa dal seguente link: https://www.wallpaperflare.com/united-states-middleburg-trees-heat-sweat-fog-humidity-wallpaper-emyax

That water is a precious universal resource is an incontrovertible fact. What is not yet universal is the perception of this value, which varies inversely to the scarcity of the so-called "blue gold". The AB AQUA Hydrostrategic Studies Center insists on this essential concept, with the aim of spreading awareness that in a growing number of areas of the world the unavailability of water in sufficient quantity and quality for the life and development of the people who live there is taking on an objectively dramatic dimension.

The issue is certainly under the attention of the International Community which, through meetings, analyses, conferences and agreements, is working to identify possible solutions, in the context of a more general commitment to environmental conservation. However, it is important that in the face of the great phenomena of environmental degradation that characterize current events, from the melting of glaciers to the incessant advance of desert areas, from the difficulty of guaranteeing agricultural products to the rise in sea levels, everyone who has the possibility reflects and acts. In this context, it is necessary to strongly emphasize that water scarcity is a central issue. According to data from the World Water Forum, one in nine people does not have access to safe drinking water and it is estimated that by 2050 almost half of the world's population will suffer from water scarcity, both due to climate change and global population growth. Ultimately, if the water problem is not resolved as a priority, it appears difficult to reach solutions on other issues that concern humanity, including conflicts that, very often, arise precisely from water scarcity.

In addition to the study of the dynamics of hydro-diplomacy, in the context of international relations, AB AQUA follows some lines of investigation and commitment on the specific aspect of contributing to the search for solutions to increase the availability of water in regions where it is scarce. These include the construction of wells, canalization for agricultural purposes, the desalination of sea water, the construction of urban drinking water plants, the use of solar-powered hydraulic pumps to increase fertile surfaces along the edges of rivers, the extraction of water from air humidity. This last topic is the subject of this paper.

A fascinating physical phenomenon

We know that the water of the globe is kept in circulation thanks to the perennial cycle of evaporation and subsequent condensation: it evaporates from rivers, lakes, seas, ponds, basins and puddles. Furthermore, it transpires from the soil, from the leaves of plants, from the respiration of animals. During evaporation, water molecules abandon their liquid environment to mix with other components of the air. This form assumed by water molecules is called water vapor, a dimension invisible to the naked eye. The water vapor content in the atmosphere is the most variable component, ranging from 1% to 5%.

Fig. 1: Il fenomeno dell’evaporazione atmosferica su un bacino idrico
https://www.britannica.com/video/163379/process-water-vapour-atmosphere-video

The strong heat of the sun (as well as the wind) evidently accelerates the evaporation of water, which is retained in the atmosphere up to the saturation limit, beyond which the water condenses again to return to a liquid state in the form of rain (or solid in the case of hail and snow). Where the humidity level of the air is already particularly high, as, for example, in tropical forests, rainfall occurs with high frequency. The quantity of water that is dispersed into the atmosphere in these regions, thanks to the presence of plants, is particularly high, but in general it is estimated that the water dispersed into the Earth's atmosphere reaches an average of 12/13,000 cubic kilometers.

Fig. 2: Umidità in uno scorcio di foresta tropicale
https://ivaldisergio1960.altervista.org/foresta-tropicale-nebbiosa-cloud-forest/

The saturation limit increases with the increase in air temperature: the warmer an air mass is, the greater the capacity of water vapor it can contain. This also explains the phenomenon of summer heat and the feeling of discomfort that is felt in tropical climates, where it becomes difficult to cool the body through sweating because sweat does not evaporate, since the relative humidity of the air is significantly higher.

It should be noted that the hydrological cycle also constitutes a natural system for purifying water, because at the moment of evaporation, impure substances (dust, various residues) do not pass into a gaseous state and the water that falls in the form of rain, snow, dew and hail is in principle uncontaminated. Condensation, the reverse process of evaporation, returns water to a liquid state. In this regard, it is appropriate to cite a well-known case. We all have the experience of fogged-up window panes in winter, due to the temperature difference between the inside and outside of the house. Well, the possibility of inducing the humidity in the air to transform back into water is one of the elements of study of various academic institutions and research centers, with the aim of allowing the populations of arid regions to have access to the precious liquid, without having to spend a good part of their days looking for distant water sources for the daily supply of this essential natural substance.

The experiments already underway

For some time, various military survival courses have taught how to obtain water, even in desert areas, through simple mechanisms that exploit the temperature range between day and night to favor the condensation of the water vapor contained in the air and produce water. But the most recent critical issues due to visible climate changes have imposed the search for solutions on a larger scale that allow at least to reduce the negative effects of the increasingly frequent droughts in various areas of the world.

In this sense, AB AQUA considers the process of extracting water from the atmosphere of extreme interest and believes that it is a path worth pursuing, in which to invest intelligence and economic resources. Climate change is accelerating rapidly, leading humanity to have to adapt to new living conditions, especially in the most extreme areas of the planet. Despite the institutional efforts made at an international level by governments (including the Paris Agreement on climate change, the continuous Conferences of Parties, the strong commitment of the various actors of Development Cooperation), unfortunately we are still very far from solving the problem. Water, in particular, is lacking in many areas of the world and the construction of wells (even if extremely useful) cannot always be an adequate or sufficient solution. Let's see some ideas on extracting water from the atmosphere, born from the intuition and technical knowledge of private individuals or study centers in various countries around the world.

1. Veiga Method. During a long period of drought in southern Spain in the 1990s, the Spanish entrepreneur-engineer Enrique Veiga, owner of the company Aquaer, developed the idea of ​​extracting water from the air, also setting himself the goal of reaching places such as refugee camps where there is no drinking water. In essence, electricity cools the air, which in turn condenses and turns into water (a process similar to that of air conditioning systems). This tool works up to 40 °C and to extract water, air humidity of between 10 and 15% is sufficient, which allows water to be obtained even in the most desert areas of the world. The result is quite surprising: consider that the machine, based on its size, can produce from 75 liters per day (the smallest) to 5,000 liters (the largest). It is clear that, since electricity is needed to cool the air, the next step is to use solar panels, which are also useful for reducing the impact on the environment and can be used in the most extreme areas of the globe. Various communities in Namibia and a refugee camp in Lebanon are already successfully using Veiga's project.

Fig. 3: Enrique Veiga, ideatore del cosiddetto “Metodo Veiga”
https://aquaer.com/it/news/

2. Another project of extreme interest was carried out in the United States by researchers at MIT (Massachusetts Institute of Technology) and the University of California Berkeley, who developed a mechanism capable of extracting water from the air even in conditions of low humidity (around 10%) and, above all, without consuming electricity. These advantages mean that the device can also be used in desert areas, considering that traditional devices are not able to extract water when the humidity of the air is less than 50% and that they require high energy consumption. The tests were carried out in May 2017 in the city of Tempe, Arizona, and the results of the experiment were recently published in Nature.

The most important aspect of this device concerns the use of a metal-organic structure, the MOF (Metal-Organic Framework), made up of molecules that create an extremely porous surface. The MOF can be made using different materials, including some that are particularly hydrophilic and able to easily attract water present in the air, even if in small quantities.

Fig. 4: Immagine estremamente piccola di un MOF
https://it.wikipedia.org/wiki/Metal_organic_frameworks

By varying the organic material used, it is possible to modify the size of the pores that will retain the liquid, while the type of metal used affects the type of fluid that will be attracted to the structure. This means that it is possible to customize the MOF to suit the use that is intended; at the moment, over 30 different variants of MOF are being tested, some of which also have the power to retain dangerous gases.

The MOF used in the experiment is intended to attract water. During the test, it was verified that the material does not interfere with the properties of the liquid and does not pose any risk of contamination. The water is absorbed during the night and in the morning the sun's rays favor the condensation of the retained liquid, allowing it to be collected easily. Understandably, research is currently underway to try to make the system increasingly efficient, in order to improve the ratio of retained water in relation to the volume of the MOF. The practical applications of this discovery are countless, but the main goal is to create systems that can allow the rapid extraction of water in the main desert areas of the world, in order to help populations forced to live in conditions of continuous lack of water resources.

Subsequently, MIT researchers improved the device by perfecting a machine capable of extracting drinking water from the air, even in arid regions, using only solar energy. This is thanks to the replacement of the MOF with a kind of mineral "crystalline sponge", which uses the temperature difference to allow the adsorbent material to collect the liquid on its surface and capture humidity during the night. When, the next day, sunlight heats the material, the temperature difference causes the absorbed droplets to be released and condense on a collection plate.

3. There is another interesting device, designed by the Italian architects Arturo Vittori and Andreas Vogler, called Warka Water and which also uses the principle of condensation of water present in the air, but taking advantage of the day-night temperature range. It is, obviously, much larger than the systems used in military operations, mentioned above, since it is rather bulky, about ten meters high and weighs more than 50 kilos. Due to its characteristics, it is certainly very useful even in desert areas, with particular regard to the sunny African regions.

Fig. 5: Schema di funzionamento del Warka Water
https://www.bioecogeo.com/warka-water-lalbero-che-in-etiopia-produce-acqua/

The Warka Water captures dew, fog and tiny particles of humidity, transforming them into drinking water, through the bamboo frame and a polyester substructure. The collected water accumulates on the net and, dripping into a funnel, accumulates in a tank. The Warka – whose name derives from an Ethiopian word meaning “large fig tree” – was built for the first time on Ethiopian soil, thanks to the support of the Italian Cooperation, with a production capacity of up to 100 liters of fresh water per day and a cost between 500 and 1000 dollars. The structure has proven effective in meeting the needs of rural populations who, until then, had enormous difficulties in obtaining clean water, necessary for drinking and hygiene purposes.

4. Equally worthy of great attention is the Peltier Cooling Mechanism. When it is powered, the hot side starts to get hotter and the cold side colder, thus reaching the dew point temperature. The cold side of the thermoelectric device begins to cool the air that passes through an area equipped with a heat sink (or fan) and the water vapor begins to condense. In fact, a significant difference in temperature is produced - which reaches a maximum of 67 degrees Celsius (152.5 Fahrenheit) - capable of condensing the humidity present in the air. This condensation forms on the external surface of an aluminum cone connected to the colder side of the element, thus generating drops of water that can be collected.

5. A mechanism patented in Switzerland, called Water Service Provider by SEAS, has already been tested and is operational in Namibia, at a school. The system, also presented at Expo Milano in 2015, provides for obtaining water from humidity in the air thanks to a filter system at 30°C. The water produced is then mineralized and is ready to drink. The Water Service Provider installed in Namibia produces up to 2,500 liters of drinking water per day, but there are machines of different power, capable of providing water in differentiated quantities, ranging from 250 to 10,000 liters per day. The engines of the Water Service Providers are electric and use renewable sources for power, such as photovoltaic panels, wind systems, based on the various contexts in which they are installed. The usefulness of this type of system is immediately evident. In the case cited in Namibia, for example, around 600 students of the school use drinking water, but also over 3,000 people living in the village of Opuwo (Kunene region). The Water Service Provider device can be replicated in all arid areas where the lack of water is a serious problem. And for this reason it has also aroused the interest of the United Nations (in particular UNIDO, which deals with industrial development) which welcomes the multiplication of systems to be able to provide clean and drinkable water to thousands of people in arid areas of the world.

6. The machine, called Kumulus-1, is an AWG, or Atmospheric Water Generator, which can produce 20 to 30 liters of drinking water every day. Physically, it does not take up more than a cubic meter and can be powered by solar energy. Produced by the start-up Kumulus, the device, which transforms the humidity in the air into drinking water, is based on the principle of morning dew. In essence, the air full of humidity is captured by the machine which condenses it. It is a rather simple principle, but its usefulness has effects of absolute importance. In this case too, the mechanism was tested in a school, in a Tunisian village (Al Baidha) on the border with Algeria, in a particularly arid area, where it was also found that the possibility of providing clean and drinkable water in a school also produced a significant decrease in diseases resulting from polluted water.

Conclusions

In Europe, the United States and many other countries in the world, it is enough to open a tap to fill a glass of water, or open another to feel the water flowing over your body while taking a shower. But we are not all aware that clean, drinkable water is a real luxury. And although the United Nations reminds us that drinking water is a right for everyone, we must note that more than two billion human beings do not have access to it. And unfortunately, even animals find less and less sufficient pastures due to the growing shortage of water and agriculture is in a truly critical situation in many regions of the world. The AB AQUA Hydrostrategic Studies Center pays particular attention to this important aspect. In this article we wanted to present some projects of great innovative interest, some of which have already been successfully tested. But there are many energies that are being set in motion to address the emergency of the shortage of drinking water. If they were connected and shared information, they would certainly be strengthened and become more efficient and usable. The new frontier of the possibility of extracting water from the air, in fact, is linked to an idea that could revolutionize access to drinking water and that constitutes a real hope for all the regions of the world where blue gold is more gold than elsewhere.