Atmospheric water generator

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State-of-the-art AWG for home use. Yeti AC-12 atmospheric water generator.jpg
State-of-the-art AWG for home use.

An atmospheric water generator (AWG), is a device that extracts water from humid ambient air, producing potable water. Water vapor in the air can be extracted either by condensation - cooling the air below its dew point, exposing the air to desiccants, using membranes that only pass water vapor, collecting fog, [1] or pressurizing the air. AWGs are useful where potable water is difficult to obtain, because water is always present in ambient air.

Contents

AWG may require significant energy inputs, or operate passively, relying on natural temperature differences. Biomimicry studies found that the Onymacris unguicularis beetle has the ability to perform this task. [2]

One study reported that AWGs could help provide potable water to one billion people. [3] [4] [5]

History

"Atrapanieblas" or fog collection in Alto Patache, Atacama Desert, Chile. Atrapanieblas en Alto Patache.jpg
"Atrapanieblas" or fog collection in Alto Patache, Atacama Desert, Chile.

Incas were able to sustain their culture above the rain line by collecting dew and channeling it to cisterns. [6] Records indicate that they used water-collecting fog fences. These traditional methods were passive, employing no external energy source and relying on naturally occurring temperature variations.[ citation needed ]

An emergency survival device existed as the Armbrust cup that converts condensation from breath into drinking water—for use in emergency landings at sea. [7] [8] [9]

In 2022 brine-based extraction technology was contracted by the US Army and the US Navy from Terralab and the Federal Emergency Management Agency (FEMA). [10]

DARPA's Atmospheric Water Extraction program aims to develop a device that can provide water for 150 soldiers and be carried by four people. In February 2021 General Electric was awarded 14 million dollars to continue development of their device. [11]

In 2022, a cellulose/konjac gum-based desiccant was demonstrated that produced 13 L/kg/day (1.56 US gal/lb/day) of water at 30% humidity, and 6 L/kg/day (0.72 US gal/lb/day) at 15% humidity. The dessicant releases the water when heated to 60 °C (140 °F). [12] [10]

In 2024 researchers announced a device that used vertical fins spaced 2 mm (0.08 in) apart. The fins are copper sheets, enveloped in copper foams coated with a zeolite. The water is released when the copper sheets are heated to 184 °C (363 °F). The fins become saturated in air with 30% humidity once per hour. Heated hourly, the harvester can produce 5.8 L (1.5 gal)/day per kilogram (2.2 lb) of material. [6] [11]

Technologies

Cooling-based systems are the most common, while hygroscopic systems are showing promise. Hybrid systems combine adsorption, refrigeration and condensation. [13] [14] Air wells are another way to passively collect moisture.

Cooling condensation

Example of cooling-condensation process. Atmospheric Water Generator diagram.svg
Example of cooling-condensation process.

Condensing systems are the most common approach. They use a compressor to circulate refrigerant through a condenser and an evaporator coil to cool the surrounding air. Once the air reaches its dew point, water condenses into the collector. A fan pushes filtered air over the coil. A purification/filtration system removes contaminants and reduces the risk posed by ambient microorganisms. [15]

The rate of water production depends on the ambient temperature, humidity, the volume of air passing over the coil, and the machine's cooling capacity. AWGs become more effective as relative humidity and air temperature increase. As a rule of thumb, cooling condensation AWGs do not work efficiently when the ambient temperature falls below 65 °F (18 °C) or the relative humidity drops below 30%.

The Peltier effect of semiconducting materials offer an alternative condensation system in which one side of the semi-conducting material heats while the other side cools. In this approach, the air is sent over the cooling fans on the cooling side, which lowers the air temperature. Solid-state semiconductors are convenient for portable units, but this is offset by low efficiency and high power consumption. [16]

Generation can be enhanced in low humidity conditions by using an evaporative cooler with a brackish water supply to increase humidity. Greenhouses are a special case because the interior air is hotter and more humid. Examples include the seawater greenhouse in Oman and the IBTS Greenhouse.

Dehumidifying air conditioners produce non-potable water. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air.

When powered by coal-based electricity it has one of the worst carbon footprints of any water source (exceeding reverse osmosis seawater desalination by three orders of magnitude) and demands more than four times as much water up the supply chain than it delivers to the user. [17]

Hygroscopy

Hygroscopic techniques pull water from the air via absorption or adsorption, which desiccate the air. Desiccants may be liquid ("wet") or solid. They need to be regenerated (typically thermally) to recover the water.

The most efficient and sustainable method is to use an adsorption refrigerator powered by solar thermal, which outperforms photovoltaic-powered systems. [18] Such systems can use waste heat, e.g. for pumping or for overnight operation, when humidity tends to rise.

In 2024 a sorption-based atmospheric water harvesting technology using a fin-array adsorption bed powered by high-density waste heat demonstrated 5.8 liters per kg of sorbent per day at 30% humidity via a 1 l adsorbent bed and commercial adsorbents. [19]

Wet desiccants

Examples of liquid desiccants include lithium chloride, lithium bromide, [20] calcium chloride, magnesium chloride, potassium formate, triethylene glycol, and [EMIM][OAc]. [21]

Concentrated brine can serve as a desiccant. The brine absorbs water, which is then extracted and purified. Some versions produce 5 gallons of water per gallon of fuel. [22] Concentrated brine, streamed down the outside of towers, absorbs water vapor. The brine then enters a chamber, under a partial vacuum and is heated, releasing water vapor that is condensed and collected. As the condensed water is removed from the system using gravity, it creates a vacuum which lowers the brine's boiling point. The system can be powered by passive solar energy. [23]

Hydrogels can capture moisture (e.g. at night in a desert) to cool solar panels [24] or produce fresh water. [25] [26] One application is to irrigate crops locating the hydrogel next to [27] [28] solar panel integrated systems or beneath the panels. [29] [30] [31] [32] [33] [34]

Solid desiccants

Silica gel and zeolite desiccate pressurized air. [35] One device consumes 310 watt-hours (1,100 kJ) per liter of water. It uses a zirconium/organic metal-organic framework on a porous copper base, attached to a graphite substrate. The sun heats the graphite, releasing the water, which then cools the graphite. [36]

Fuel cells

A hydrogen fuel cell car generates one liter of potable water for every 8 miles (12.87 kilometers) traveled by combining hydrogen with ambient oxygen. [37]

Hydropanel

Potable water can be generated by rooftop solar hydropanels using solar power and solar heat. [38] [39] [40]

The minimum energy for atmospheric water harvesting Least work AWH.png
The minimum energy for atmospheric water harvesting

Energy

Unless the air is super-saturated with moisture, energy is required to harvest water from the atmosphere. The energy required is a function of the humidity and temperature. It can be calculated using Gibbs free energy.

See also

Related Research Articles

<span class="mw-page-title-main">Evaporation</span> Vaporization of a liquid from its surface

Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidity affects rate of evaporation of water. When the molecules of the liquid collide, they transfer energy to each other based on how they collide. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.

<span class="mw-page-title-main">Condensation</span> Change of state of matter from a gas phase into a liquid phase

Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition.

<span class="mw-page-title-main">Humidity</span> Concentration of water vapour in the air

Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.

<span class="mw-page-title-main">Dew</span> Water in the form of droplets that appears on thin, exposed objects in the morning or evening

Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets.

Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor is transparent, like most constituents of the atmosphere. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than most of the other constituents of air and triggers convection currents that can lead to clouds and fog.

<span class="mw-page-title-main">Dehumidifier</span> Device which reduces humidity

A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses.

<span class="mw-page-title-main">Desiccant</span> Substance used to induce or sustain dryness

A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccants for specialized purposes may be in forms other than solid, and may work through other principles, such as chemical bonding of water molecules. They are commonly encountered in foods to retain crispness. Industrially, desiccants are widely used to control the level of water in gas streams.

<span class="mw-page-title-main">Clothes dryer</span> Appliance used for drying wet clothes

A clothes dryer is a powered household appliance that is used to remove moisture from a load of clothing, bedding and other textiles, usually after they are washed in the washing machine.

<span class="mw-page-title-main">Evaporative cooler</span> Device that cools air through the evaporation of water

An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.

<span class="mw-page-title-main">Heat recovery ventilation</span> Method of reusing thermal energy in a building

Heat recovery ventilation (HRV), also known as mechanical ventilation heat recovery (MVHR) is a ventilation system that recovers energy by operating between two air sources at different temperatures. It is used to reduce the heating and cooling demands of buildings.

<span class="mw-page-title-main">Solar still</span> Water distillation and purification system using solar energy

A solar still distills water with substances dissolved in it by using the heat of the Sun to evaporate water so that it may be cooled and collected, thereby purifying it. They are used in areas where drinking water is unavailable, so that clean water is obtained from dirty water or from plants by exposing them to sunlight.

A watermaker is a device used to obtain potable water by reverse osmosis of seawater. In boating and yachting circles, desalinators are often referred to as "watermakers".

<span class="mw-page-title-main">Ground-coupled heat exchanger</span> Underground heat exchanger loop that can capture or dissipate heat to or from the ground

A ground-coupled heat exchanger is an underground heat exchanger that can capture heat from and/or dissipate heat to the ground. They use the Earth's near constant subterranean temperature to warm or cool air or other fluids for residential, agricultural or industrial uses. If building air is blown through the heat exchanger for heat recovery ventilation, they are called earth tubes.

Solar air conditioning, or "solar-powered air conditioning", refers to any air conditioning (cooling) system that uses solar power.

Moisture analysis covers a variety of methods for measuring the moisture content in solids, liquids, or gases. For example, moisture is a common specification in commercial food production. There are many applications where trace moisture measurements are necessary for manufacturing and process quality assurance. Trace moisture in solids must be known in processes involving plastics, pharmaceuticals and heat treatment. Fields that require moisture measurement in gasses or liquids include hydrocarbon processing, pure semiconductor gases, bulk pure or mixed gases, dielectric gases such as those in transformers and power plants, and natural gas pipeline transport. Moisture content measurements can be reported in multiple units, such as: parts per million, pounds of water per million standard cubic feet of gas, mass of water vapor per unit volume or mass of water vapor per unit mass of dry gas.

A solar-powered desalination unit produces potable water from saline water through direct or indirect methods of desalination powered by sunlight. Solar energy is the most promising renewable energy source due to its ability to drive the more popular thermal desalination systems directly through solar collectors and to drive physical and chemical desalination systems indirectly through photovoltaic cells.

<span class="mw-page-title-main">Air well (condenser)</span> A building or device used to collect water by condensing the water vapor present in the air

An air well or aerial well is a structure or device that collects water by promoting the condensation of moisture from air. Designs for air wells are many and varied, but the simplest designs are completely passive, require no external energy source and have few, if any, moving parts.

<span class="mw-page-title-main">Thermal wheel</span> Type of energy recovery heat exchanger

A thermal wheel, also known as a rotary heat exchanger, or rotary air-to-air enthalpy wheel, energy recovery wheel, or heat recovery wheel, is a type of energy recovery heat exchanger positioned within the supply and exhaust air streams of air-handling units or rooftop units or in the exhaust gases of an industrial process, in order to recover the heat energy. Other variants include enthalpy wheels and desiccant wheels. A cooling-specific thermal wheel is sometimes referred to as a Kyoto wheel.

Compressed air dryers are special types of filter systems that are specifically designed to remove the water that is inherent in compressed air. The compression of air raises its temperature and concentrates atmospheric contaminants, primarily water vapor, as resulting in air with elevated temperature and 100% relative humidity. As the compressed air cools down, water vapor condenses into the tank(s), pipes, hoses and tools connected downstream from the compressor which may be damaging. Therefore water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes.

<span class="mw-page-title-main">Passive daytime radiative cooling</span> Management strategy for global warming

Passive daytime radiative cooling (PDRC) is the use of unpowered, reflective/thermally-emissive surfaces to lower the temperature of a building or other object.

References

  1. 1 2 Rao, Akshay K.; Fix, Andrew J.; Yang, Yun Chi; Warsinger, David M. (2022). "Thermodynamic limits of atmospheric water harvesting". Energy & Environmental Science. 15 (10). Royal Society of Chemistry (RSC): 4025–4037. doi:10.1039/d2ee01071b. ISSN   1754-5692. S2CID   252252878.
  2. ↑ Nørgaard, Thomas; Dacke, Marie (2010-07-16). "Fog-basking behaviour and water collection efficiency in Namib Desert Darkling beetles". Frontiers in Zoology. 7 (1): 23. doi: 10.1186/1742-9994-7-23 . ISSN   1742-9994. PMC   2918599 . PMID   20637085.
  3. ↑ Yirka, Bob. "Model suggests a billion people could get safe drinking water from hypothetical harvesting device". Tech Xplore. Retrieved 15 November 2021.
  4. ↑ "Solar-powered harvesters could produce clean water for one billion people". Physics World. 13 November 2021. Retrieved 15 November 2021.
  5. ↑ Lord, Jackson; Thomas, Ashley; Treat, Neil; Forkin, Matthew; Bain, Robert; Dulac, Pierre; Behroozi, Cyrus H.; Mamutov, Tilek; Fongheiser, Jillia; Kobilansky, Nicole; Washburn, Shane; Truesdell, Claudia; Lee, Clare; Schmaelzle, Philipp H. (October 2021). "Global potential for harvesting drinking water from air using solar energy". Nature. 598 (7882): 611–617. Bibcode:2021Natur.598..611L. doi:10.1038/s41586-021-03900-w. ISSN   1476-4687. PMC   8550973 . PMID   34707305. S2CID   238014057.
  6. 1 2 "Water II". foresightfordevelopment.org. Foresight For Development. Retrieved 29 March 2022.
  7. ↑ https://airandspace.si.edu/collection-objects/armbrust-cup-lockheed-sirius-tingmissartoq-lindbergh/nasm_A20030072000
  8. ↑ https://www.smithsonianmag.com/air-space-magazine/fly-powered-planes-and-other-oddities-103154316/
  9. ↑ https://pioneersofflight.si.edu/content/armbrust-cup
  10. 1 2 Totty, Michael (September 24, 2007). "Innovations for Life : Awards". www.wsj.com. Retrieved 2022-05-24.
  11. 1 2 Tucker, Patrick (8 February 2021). "The Military Wants To Produce Water From Air. Here's the Science Behind It". www.defenseone.com. Defense One. Retrieved 13 February 2021.
  12. ↑ Irving, Michael (2022-05-24). "Cheap gel film pulls buckets of drinking water per day from thin air". New Atlas. Retrieved 2022-06-04.
  13. ↑ Fraunhofer. Fraunhofer (2014) Archived 2016-10-12 at the Wayback Machine
  14. ↑ "Innovation Making Waves Pulling Water From Air". Simon Fraser University. April 25, 2016.
  15. ↑ Latest Willie Nelson venture: Water from Air. Atlanta Journal-Constitution.
  16. ↑ "Solid State Detectors - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2022-06-02.
  17. ↑ Peters, Greg M.; Blackburn, Naomi J.; Armedion, Michael (June 2013). "Environmental assessment of air to water machines—triangulation to manage scope uncertainty". The International Journal of Life Cycle Assessment. 18 (5): 1149–1157. Bibcode:2013IJLCA..18.1149P. doi:10.1007/s11367-013-0568-2. ISSN   0948-3349. S2CID   111347244.
  18. ↑ Alobaid, Mohammad; Hughes, Ben; Calautit, John Kaiser; O’Connor, Dominic; Heyes, Andrew (2017). "A review of solar driven absorption cooling with photovoltaic thermal systems" (PDF). Renewable and Sustainable Energy Reviews. 76: 728–742. doi:10.1016/j.rser.2017.03.081.
  19. ↑ Li, Xiangyu; El Fil, Bachir; Li, Buxuan; Graeber, Gustav; Li, Adela C.; Zhong, Yang; Alshrah, Mohammed; Wilson, Chad T.; Lin, Emily (2024-07-12). "Design of a Compact Multicyclic High-Performance Atmospheric Water Harvester for Arid Environments". ACS Energy Letters. 9 (7): 3391–3399. doi:10.1021/acsenergylett.4c01061. ISSN   2380-8195. PMC   11250079 . PMID   39022669.
  20. ↑ Chartrand, Sabra (2001-07-02). "Patents; Draw water from air, measure how much water you drink and be kind to the fish you catch". The New York Times. ISSN   0362-4331 . Retrieved 2022-05-24.
  21. ↑ Su, Wei; Lu, Zhifei; She, Xiaohui; Zhou, Junming; Wang, Feng; Sun, Bo; Zhang, Xiaosong (February 2022). "Liquid desiccant regeneration for advanced air conditioning: A comprehensive review on desiccant materials, regenerators, systems and improvement technologies". Applied Energy. 308: 118394. Bibcode:2022ApEn..30818394S. doi:10.1016/j.apenergy.2021.118394.
  22. ↑ Greenfieldboyce, Nell (October 19, 2006). "Water Extracted from the Air for Disaster Relief". NPR.org. Retrieved May 5, 2022.
  23. ↑ Fraunhofer-Gesellschaft (June 8, 2009). "Drinking Water From Air Humidity". ScienceDaily. Retrieved May 5, 2022.
  24. ↑ "Hydrogel helps make self-cooling solar panels". Physics World. 12 June 2020. Retrieved 28 April 2022.
  25. ↑ Youhong Guo; W. Guan; C. Lei; H. Lu; W. Shi; Guihua Yu (2022). "Scalable super hygroscopic polymer films for sustainable moisture harvesting in arid environments". Nature Communications. 13 (1): 2761. Bibcode:2022NatCo..13.2761G. doi:10.1038/s41467-022-30505-2. PMC   9120194 . PMID   35589809. S2CID   248917548.
  26. ↑ Shi, Ye; Ilic, Ognjen; Atwater, Harry A.; Greer, Julia R. (14 May 2021). "All-day fresh water harvesting by microstructured hydrogel membranes". Nature Communications. 12 (1): 2797. Bibcode:2021NatCo..12.2797S. doi:10.1038/s41467-021-23174-0. ISSN   2041-1723. PMC   8121874 . PMID   33990601. S2CID   234596800.
  27. ↑ "Self-contained SmartFarm grows plants using water drawn from the air". New Atlas. 15 April 2021. Retrieved 28 April 2022.
  28. ↑ Yang, Jiachen; Zhang, Xueping; Qu, Hao; Yu, Zhi Gen; Zhang, Yaoxin; Eey, Tze Jie; Zhang, Yong-Wei; Tan, Swee Ching (October 2020). "A Moisture-Hungry Copper Complex Harvesting Air Moisture for Potable Water and Autonomous Urban Agriculture". Advanced Materials. 32 (39): 2002936. Bibcode:2020AdM....3202936Y. doi:10.1002/adma.202002936. ISSN   0935-9648. PMID   32743963. S2CID   220946177.
  29. ↑ "These solar panels pull in water vapor to grow crops in the desert". Cell Press. Retrieved 18 April 2022.
  30. ↑ Ravisetti, Monisha. "New Solar Panel Design Uses Wasted Energy to Make Water From Air". CNET. Retrieved 28 April 2022.
  31. ↑ "Strom und Wasser aus Sonne und Wüstenluft". scinexx | Das Wissensmagazin (in German). 2 March 2022. Retrieved 28 April 2022.
  32. ↑ "Hybrid system produces electricity and irrigation water in the desert". New Atlas. 1 March 2022. Retrieved 28 April 2022.
  33. ↑ Schank, Eric (8 March 2022). "Turning the desert green: this solar panel system makes water (and grows food) out of thin air". Salon. Retrieved 28 April 2022.
  34. ↑ Li, Renyuan; Wu, Mengchun; Aleid, Sara; Zhang, Chenlin; Wang, Wenbin; Wang, Peng (16 March 2022). "An integrated solar-driven system produces electricity with fresh water and crops in arid regions". Cell Reports Physical Science. 3 (3): 100781. Bibcode:2022CRPS....300781L. doi:10.1016/j.xcrp.2022.100781. hdl: 10754/676557 . ISSN   2666-3864. S2CID   247211013.
  35. ↑ Patel, Prachi. "Solar-Powered Device Pulls Water Out of Thin (And Pretty Dry) Air". IEEE . Retrieved 13 April 2017.
  36. ↑ Hamilton, Anita (April 24, 2014). "This Gadget Makes Gallons of Drinking Water Out of Air". Time . Retrieved 2022-05-24.
  37. ↑ "2016 Toyota Mirai Fuel-Cell Sedan" . Retrieved 28 August 2016.
  38. ↑ "New rooftop solar hydro panels harvest drinking water and energy at the same time". 29 November 2017. Retrieved 2017-11-30.
  39. ↑ LaPotin, Alina; Zhong, Yang; Zhang, Lenan; Zhao, Lin; Leroy, Arny; Kim, Hyunho; Rao, Sameer R.; Wang, Evelyn N. (20 January 2021). "Dual-Stage Atmospheric Water Harvesting Device for Scalable Solar-Driven Water Production". Joule. 5 (1): 166–182. doi: 10.1016/j.joule.2020.09.008 . ISSN   2542-4785. S2CID   225118164.
    News article: "Solar-powered system extracts drinkable water from 'dry' air". Massachusetts Institute of Technology. Retrieved 28 April 2022.
  40. ↑ "Rain fed solar-powered water purification systems" . Retrieved 21 October 2017.
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