Water is perhaps the most valuable resource our planet has to deal with. Despite covering 70% of our planet, freshwater, the water we use to drink, take a bath, or irrigate our farmlands, is scarce. Only 3% of the world’s water is freshwater. Moreover, two-thirds of that 3% dwells in frozen glaciers or is unavailable for use.
The outcome of water scarcity is something that is reflected worldwide. Globally, close to 1.1 billion people lack access to water. A total of 2.7 billion people in the world suffer from the scarcity of water for at least one month of the year.
Shortage of water also leads to many other problems, such as inadequate sanitation, a problem for 2.4 billion people who get vulnerable and exposed to diseases like cholera and typhoid, and many other fatal diarrheal diseases.
The growing population and the ever-expanding demand for water have always been at loggerheads. The more populated our planet has become, the more stressed its water systems have become.
Rising pollution levels have taken a toll on the planet’s rivers, lakes, and aquifers. What appears even more distressing is that over half of the world’s wetlands have disappeared.
If the scientific community fails to evolve with time and offer solutions to combat the menace of disappearing water, our agriculture systems won’t have enough water soon, leading to food insecurity and much more.
However, fortunately, the scientific community is up to the challenge worldwide. Today, we shall discuss one such breakthrough solution in the coming segment and then delve deeper.
Device Extracts Water from the Air Using Nothing More than Gravity
A team of international researchers, led by KAUST Professor Qiaoqiang Gan, has designed a device that can potentially run with no electricity and extract water from the air with the help of nothing but gravity. The device, already free from the need for a costly energy supply, can be made with cheap and readily available materials.
The experiment paper, titled ‘Lubricated Surface in a Vertical Double-Sided Architecture for Radiative Cooling and Atmospheric Water Harvesting’, seeks to make atmospheric water harvesting more efficient.
The water harvesting process improves significantly in radiative cooling. Radiative cooling works by significantly lowering condenser temperatures below ambient levels and making atmospheric water harvesting possible without additional energy.
One issue that radiative cooling systems face is the challenge of traditional sky-facing condensers having low cooling power density, and water droplets remaining pinned on the surface, requiring active condensate collection.
The research has proposed a solution to this problem: a lubricated surface (LS) coating—consisting of highly scalable polydimethylsiloxane elastomer lubricated with silicone oil applied on the condenser side in a vertical double-sided architecture.
The benefits of the design are several. For one, it effectively doubles the local cooling power.
Secondly, eliminates contact-line pinning, enabling passive, gravity-driven collection of water. The result is pumped up AWH capacity from a 0 × 30 cm2 sample in outdoor environments, which was under no artificial flow of humidified air.
The passive water collection rate of the lubricated surface (LS) coating reached 21 g m−2 h−1, double that on a superhydrophobic surface, 10 g m−2 h−1. The performance was even better in an indoor setting, where the system could achieve a condensation rate of up to 87% of the theoretical limit with up to 90% of the total condensate passively collected.
Benefits of Atmospheric Water Harvesting Done Correctly
The atmosphere has six times more water than all the earth’s rivers’ freshwater combined. According to Professor Gan:
“This water can be collected by atmospheric water harvesting technologies.”
And when the process is done efficiently with the solution mentioned above, it becomes all the more profitable for its adopters. While elaborating on the benefits of the system, Professor Dan Daniel, one of the post-doctorates in Professor Gan’s research group, had the following to say,
“The system doesn’t consume any electricity, leading to energy savings. Moreover, it doesn’t rely on any mechanical parts like compressors or fans, reducing the maintenance over traditional systems, leading to further savings.”
To Dan Daniel’s observations, another post-doctorate of the team, Shakeel Ahmad, added:
“Our coating effectively eliminated pinning, enabling true passive water collection driven by water.”
Altogether, the system enhances the quality of atmospheric water harvesting by a significant margin, making AWH a true blue solution in this world of increasingly scarce water resources.
Click here to learn how solar energy could do more than just provide clean energy.
Advances in Atmospheric Water Harvesting Systems
In October 2023, an article published in the scientific journal named Energy conducted a comprehensive review of techniques, performance, renewable energy solutions, and feasibility relating to the method of AWH. The review highlighted Atmospheric Water Harvesting as something that could be a vast source of freshwater at 12,900 km3.
It said:
“Atmospheric water harvesting systems have gained popularity in recent years as they offer a sustainable water source in dry regions.”
In the segments to come, we will look into some of these advances, including dehumidifying, condensing, vapor compression refrigeration cycles (VCRCs), thermoelectric coolers (TECs), air conditioning units, fuel cells, and integrated systems.
Dehumidifying Condensing
Dehumidification water harvesting technologies draw power from solar, wind, or electric sources. The technologies could be compressor/refrigerant-based or desiccant-based.
The first types operate via dew point condensation and provide a cold surface upon which water vapor can condense, while the second ones saturate water vapor using a sorbent that is then heated, and the supersaturated water vapor condenses on a surface when interacting with cooler ambient process air.
Vapor Compression Refrigeration Cycles (VCRCs)
This process refers to a mechanism where vapor is compressed, then condensed with water or air, and expanded to low pressure and correspondingly low temperature through a valve or an engine with power takeoff.
Thermoelectric Coolers
In 2023, the International Information and Engineering Technology Association (IIETA) published a study on harvesting atmospheric water using thermoelectric cooling technology.
The study intended to explore the potential of atmospheric air as an alternative clean water source to mitigate water shortage in Indonesia, a country with an average atmospheric humidity of 75% to 85%.
The researchers deployed a thermoelectric cooler (TEC 1-12706), supplemented with a heatsink and fan on its hot side to enhance heat dissipation. A copper-made cooling coil served as both a heat absorber and a condenser for atmospheric air passing through it.
The cooling source for the coil (diameter=7.9mm; length=1000mm) was derived from a water block attached to the cooler’s cold side. The settings for the experiment included all possible environmental settings, including laboratory, residential area, and coastal area, with the airflow rate of the heatsink cooling fan varied.
Data was collected over a humidity range of 72.27%-83.01% and the results disclosed a direct correlation between the air mass flow rate of the heatsink cooling fan and the amount of water extractable from the air.
The experiment also offered interesting insights into the impact of the type of environment on the volume of air extracted, as more water could be extracted on the coast than in laboratories and residential areas.
More specifically, the air mass flow rate was 0.092 kg/s in the coastal areas, and the water that could be extracted was 7.75 ml/hour. In the laboratory setting, the performance dropped to 5.5 ml/hour, and in residential areas, it was 4.75 ml/hour. The researchers understood that they could augment water extraction by maximizing the contact surface between the air cooler and the coil surface.
Air Conditioning Units
In June 2024, a research paper published in the journal Case Studies in Chemical and Environmental Engineering assessed the probability of water production from air conditioning systems as an unconventional supply source.
More specifically, the study examined the physical and chemical properties of condensed water and investigated the presence of heavy metals in the collected condensate water samples produced by air conditioning systems.
The purpose of the evaluation was to ensure that the water quality met the criteria set by Jordanian standards for drinking water and FAO guidelines for irrigation purposes.
The study was carried out in Jordan which ranked among the most economically disadvantaged countries worldwide in terms of renewable freshwater resources, with a scanty per capita availability of around 61 cubic meters in 2021.
The test results indicated that the samples mostly complied with the allowed limits specified by both the drinking water guidelines (below 20 °C) and the criteria for treated water used in irrigation (below 25 °C). The temperature range of the samples was between 16 °C and 20 °C, with an average of 18 °C, while the pH values of the condensate water samples varied from 7.16 to 7.25, with an average of 7.20.
Fuel Cells
Another research, published in the December 2020 issue of Applied Energy proposed to reuse the electrochemical water of the fuel cell for the vapor compression cycle-based atmospheric water generator (VCC-AWG).
The solution mechanism leveraged the fuel cell flue gas that entered the VCC-AWG at a higher relative humidity than natural atmospheric air as it passed through an ambient heat exchanger to remove the electrochemical waste heat.
The scientists proposed that the higher relative humidity could increase the freshwater yield per energy input. The results showed that at a relative humidity of 0.75, adding a 2 Kilowatt fuel cell generated up to 3 kg/hr of fresh water, which was 50% higher than excluding the Fuel Cell.
With the specific energy consumption at 200 Wh/kg, the VCC-AWG could be integrated with small sacrifices to the FC power output.
Integrated Systems
Finally, several researchers have also proposed innovative integrated systems that combine desiccant wheels and evaporator coolers to deliver both cooled air and condensed water.
More importantly, these integrated systems have demonstrated outstanding water harvesting capabilities in arid settings. For instance, as per data obtained from one experiment, a one cubic meter dehumidifier system could provide a Qatari family with over 15 l of freshwater daily under relative humidity levels of 50–70 %.
While scientific communities across the world have consistently explored the possibilities of atmospheric water harvesting and pushed its boundaries, companies have come up with solutions that are fit for mass adoption. In the coming segments, we briefly look at a couple of such companies.
#1. Atoco
Source: Atoco
Atoco’s water harvesting technology is capable of capturing and generating pure water out of the atmosphere, even under dry conditions with relative humidity below 20%.
Like the research we started our discussions with, the Atoco solution can operate in passive mode without the use of electricity, enabling off-grid operations with zero carbon footprint.
The quality of the water that comes out as the result of Atoco’s use of novel reticular materials is extremely pure, requiring no additional filtration. It complies fully with global standards, including WHO and EPA standards in the case of drinking water and FAO water quality for agricultural purposes.
Founded by Prof. Omar Yaghi – the father of reticular chemistry – Atoco believes it can tackle both the cause and effect of climate change and address global warming and water scarcity by developing sustainable, resilient, and transformational solutions in the field of atmospheric water harvesting.
#2. Watergen
Watergen, a pioneering Israeli company and a global leader in the atmospheric drinking water devices (AWG) market, offers machines that create drinking water most effectively and economically possible. Its solutions are present in more than 65 countries around the world.
Its commercial Gen-L solution can produce up to 6,000 liters a day, while the small Genny solution offers 30 liters a day. It has solutions for every type of need between these two terminals.
In 2022, Watergen announced a strategic joint venture with SMV Jaipuria Group with a planned investment of more than USD 50 million in the next 2-3 years for bringing water-from-air technology products to India.
Concluding Words
Altogether, the world is ready to take water scarcity challenges head-on by skillfully utilizing another natural resource we have in abundance: the atmospheric air.
However, more work is to be done to expand the frontiers by bringing down the cost of production and making the processes environmentally sustainable with no or minimal use of energy.
Many of the water-scarce countries are low-income economies. They need to be supplied with solutions that are affordable to the masses and deployable in the most seamless way possible.
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