Atmospheric water generator

File:Atrapanieblas en Alto Patache.jpg 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.{{cite web |title=Water II |url=https://www.foresightfordevelopment.org/featured/water-ii |website=foresightfordevelopment.org |publisher=Foresight For Development |access-date=29 March 2022}} 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|date=June 2015}}

An emergency survival device existed as the Armbrust cup that converts condensation from breath into drinking water—for use in emergency landings at sea.https://airandspace.si.edu/collection-objects/armbrust-cup-lockheed-sirius-tingmissartoq-lindbergh/nasm_A20030072000https://www.smithsonianmag.com/air-space-magazine/fly-powered-planes-and-other-oddities-103154316/https://pioneersofflight.si.edu/content/armbrust-cup

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).{{Cite web |last=Totty |first=Michael |date=September 24, 2007 |title=Innovations for Life : Awards |url=https://www.wsj.com/ad/article/acurainnovations-071030.html |access-date=2022-05-24 |website=www.wsj.com}}

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.{{cite web |last1=Tucker |first1=Patrick |title=The Military Wants To Produce Water From Air. Here's the Science Behind It |url=https://www.defenseone.com/technology/2021/02/military-wants-produce-water-air-heres-science-behind-it/171932/ |website=www.defenseone.com |date=8 February 2021 |publisher=Defense One |access-date=13 February 2021}}

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 {{Convert|60|C}}.{{Cite web

| last = Irving

| first = Michael

| title = Cheap gel film pulls buckets of drinking water per day from thin air

| url = https://newatlas.com/materials/drinking-water-harvester-air-gel-film/

| date = 2022-05-24

| access-date = 2022-06-04

| website = New Atlas

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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.

Cooling-based systems are the most common, while hygroscopic systems are showing promise. Hybrid systems combine adsorption, refrigeration and condensation.[http://www.igb.fraunhofer.de/content/dam/igb/en/documents/sheets/pt/1510_PB-pt_wasserausluft_en.pdf Fraunhofer]. Fraunhofer (2014) {{Webarchive|url=https://web.archive.org/web/20161012161339/http://www.igb.fraunhofer.de/content/dam/igb/en/documents/sheets/pt/1510_PB-pt_wasserausluft_en.pdf |date=2016-10-12 }}{{cite web |date=April 25, 2016 |title=Innovation Making Waves Pulling Water From Air |url=https://www.sfu.ca/sfunews/stories/2016/innovation-making-waves-pulling-water-from-air.html |publisher=Simon Fraser University}} Air wells are another way to passively collect moisture.

File:Atmospheric Water Generator diagram.svg

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.[http://www.ajc.com/homefinder/content/shared/money/stories/2008/10/WILLIE_WATER_1015_COX.html Latest Willie Nelson venture: Water from Air]. Atlanta Journal-Constitution.

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 {{Convert|65|F|abbr=on}} 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.{{Cite web |title=Solid State Detectors - an overview {{!}} ScienceDirect Topics |url=https://www.sciencedirect.com/topics/mathematics/solid-state-detectors |access-date=2022-06-02 |website=www.sciencedirect.com}}

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.{{Cite journal |last1=Peters |first1=Greg M. |last2=Blackburn |first2=Naomi J. |last3=Armedion |first3=Michael |date=June 2013 |title=Environmental assessment of air to water machines—triangulation to manage scope uncertainty |url=http://link.springer.com/10.1007/s11367-013-0568-2 |journal=The International Journal of Life Cycle Assessment |language=en |volume=18 |issue=5 |pages=1149–1157 |doi=10.1007/s11367-013-0568-2 |bibcode=2013IJLCA..18.1149P |s2cid=111347244 |issn=0948-3349}}

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.{{cite journal | last1=Alobaid | first1=Mohammad | last2=Hughes | first2=Ben | last3=Calautit | first3=John Kaiser | last4=O’Connor | first4=Dominic | last5=Heyes | first5=Andrew | title=A review of solar driven absorption cooling with photovoltaic thermal systems | journal=Renewable and Sustainable Energy Reviews | volume=76 | date=2017 | doi=10.1016/j.rser.2017.03.081 | pages=728–742| url=https://strathprints.strath.ac.uk/64185/1/Alobaid_etal_RSER_2017_A_review_of_solar_driven_absorption_cooling_with_photovoltaic.pdf }} Such systems can use waste heat, e.g. for pumping or for overnight operation, when humidity tends to rise.

In 2024 a sorbent-based atmospheric water harvesting (SAWH) 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.{{Cite journal |last=Li |first=Xiangyu |last2=El Fil |first2=Bachir |last3=Li |first3=Buxuan |last4=Graeber |first4=Gustav |last5=Li |first5=Adela C. |last6=Zhong |first6=Yang |last7=Alshrah |first7=Mohammed |last8=Wilson |first8=Chad T. |last9=Lin |first9=Emily |date=2024-07-12 |title=Design of a Compact Multicyclic High-Performance Atmospheric Water Harvester for Arid Environments |url=https://pubs.acs.org/doi/10.1021/acsenergylett.4c01061 |journal=ACS Energy Letters |language=en |volume=9 |issue=7 |pages=3391–3399 |doi=10.1021/acsenergylett.4c01061 |issn=2380-8195 |pmc=11250079 |pmid=39022669}}

Examples of liquid desiccants include lithium chloride, lithium bromide,{{Cite news |last=Chartrand |first=Sabra |date=2001-07-02 |title=Patents; Draw water from air, measure how much water you drink and be kind to the fish you catch. |language=en-US |work=The New York Times |url=https://www.nytimes.com/2001/07/02/business/patents-draw-water-air-measure-much-water-you-drink-be-kind-fish-you-catch.html |access-date=2022-05-24 |issn=0362-4331}} calcium chloride, magnesium chloride, potassium formate, triethylene glycol, and [EMIM][OAc]. {{cite journal |last1=Su |first1=Wei |last2=Lu |first2=Zhifei |last3=She |first3=Xiaohui |last4=Zhou |first4=Junming |last5=Wang |first5=Feng |last6=Sun |first6=Bo |last7=Zhang |first7=Xiaosong |title=Liquid desiccant regeneration for advanced air conditioning: A comprehensive review on desiccant materials, regenerators, systems and improvement technologies |journal=Applied Energy |date=February 2022 |volume=308 |pages=118394 |doi=10.1016/j.apenergy.2021.118394|bibcode=2022ApEn..30818394S }}

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.{{Cite news |last=Greenfieldboyce |first=Nell |date=October 19, 2006 |title=Water Extracted from the Air for Disaster Relief |language=en |work=NPR.org |url=https://www.npr.org/templates/story/story.php?storyId=6326050 |access-date=May 5, 2022}} 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.{{Cite web |author=Fraunhofer-Gesellschaft |date=June 8, 2009 |title=Drinking Water From Air Humidity |url=https://www.sciencedaily.com/releases/2009/06/090605091856.htm |access-date=May 5, 2022 |website=ScienceDaily |language=en}}

Hydrogels can capture moisture (e.g. at night in a desert) to cool solar panels{{cite news |date=12 June 2020 |title=Hydrogel helps make self-cooling solar panels |url=https://physicsworld.com/a/hydrogel-helps-make-self-cooling-solar-panels/ |access-date=28 April 2022 |work=Physics World}} or produce fresh water.{{cite journal |author1=Youhong Guo |author2=W. Guan |author3=C. Lei |author4=H. Lu |author5=W. Shi |author6=Guihua Yu |year=2022 |title=Scalable super hygroscopic polymer films for sustainable moisture harvesting in arid environments |journal=Nature Communications |volume=13 |issue=1 |pages=2761 |bibcode=2022NatCo..13.2761G |doi=10.1038/s41467-022-30505-2 |pmc=9120194 |pmid=35589809 |s2cid=248917548}}{{cite journal |last1=Shi |first1=Ye |last2=Ilic |first2=Ognjen |last3=Atwater |first3=Harry A. |last4=Greer |first4=Julia R. |date=14 May 2021 |title=All-day fresh water harvesting by microstructured hydrogel membranes |journal=Nature Communications |language=en |volume=12 |issue=1 |pages=2797 |bibcode=2021NatCo..12.2797S |doi=10.1038/s41467-021-23174-0 |issn=2041-1723 |pmc=8121874 |pmid=33990601 |s2cid=234596800}} One application is to irrigate crops locating the hydrogel next to{{cite news |date=15 April 2021 |title=Self-contained SmartFarm grows plants using water drawn from the air |url=https://newatlas.com/good-thinking/smartfarm-plants-hydrogel-water/ |access-date=28 April 2022 |work=New Atlas}}{{cite journal |last1=Yang |first1=Jiachen |last2=Zhang |first2=Xueping |last3=Qu |first3=Hao |last4=Yu |first4=Zhi Gen |last5=Zhang |first5=Yaoxin |last6=Eey |first6=Tze Jie |last7=Zhang |first7=Yong-Wei |last8=Tan |first8=Swee Ching |date=October 2020 |title=A Moisture-Hungry Copper Complex Harvesting Air Moisture for Potable Water and Autonomous Urban Agriculture |journal=Advanced Materials |language=en |volume=32 |issue=39 |pages=2002936 |bibcode=2020AdM....3202936Y |doi=10.1002/adma.202002936 |issn=0935-9648 |pmid=32743963 |s2cid=220946177}} solar panel integrated systems or beneath the panels.{{cite news |title=These solar panels pull in water vapor to grow crops in the desert |url=https://techxplore.com/news/2022-03-solar-panels-vapor-crops.html |access-date=18 April 2022 |work=Cell Press |language=en}}{{cite news |last1=Ravisetti |first1=Monisha |title=New Solar Panel Design Uses Wasted Energy to Make Water From Air |url=https://www.cnet.com/home/energy-and-utilities/new-solar-panel-design-uses-wasted-energy-to-make-water-from-air/ |access-date=28 April 2022 |work=CNET |language=en}}{{cite news |date=2 March 2022 |title=Strom und Wasser aus Sonne und Wüstenluft |url=https://www.scinexx.de/news/technik/strom-und-wasser-aus-sonne-und-wuestenluft/ |access-date=28 April 2022 |work=scinexx {{!}} Das Wissensmagazin |language=de-DE}}{{cite news |date=1 March 2022 |title=Hybrid system produces electricity and irrigation water in the desert |url=https://newatlas.com/good-thinking/wec2p-water-electricity-desert/ |access-date=28 April 2022 |work=New Atlas}}{{cite news |last1=Schank |first1=Eric |date=8 March 2022 |title=Turning the desert green: this solar panel system makes water (and grows food) out of thin air |url=https://www.salon.com/2022/03/08/turning-the-desert-green-this-solar-panel-system-makes-water-and-grows-food-out-of-thin-air/ |access-date=28 April 2022 |work=Salon |language=en}}{{cite journal |last1=Li |first1=Renyuan |last2=Wu |first2=Mengchun |last3=Aleid |first3=Sara |last4=Zhang |first4=Chenlin |last5=Wang |first5=Wenbin |last6=Wang |first6=Peng |date=16 March 2022 |title=An integrated solar-driven system produces electricity with fresh water and crops in arid regions |journal=Cell Reports Physical Science |language=en |volume=3 |issue=3 |pages=100781 |bibcode=2022CRPS....300781L |doi=10.1016/j.xcrp.2022.100781 |issn=2666-3864 |s2cid=247211013 |hdl-access=free |hdl=10754/676557}}

Silica gel and zeolite desiccate pressurized air.{{Cite web |title=Solar-Powered Device Pulls Water Out of Thin (And Pretty Dry) Air |first=Prachi |last=Patel|website=IEEE|url=https://spectrum.ieee.org/solarpowered-device-pulls-water-out-of-thin-and-pretty-dry-air |access-date=13 April 2017}} One device consumes {{Convert|310|Wh}} 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.{{Cite web |last=Hamilton |first=Anita |date=April 24, 2014 |title=This Gadget Makes Gallons of Drinking Water Out of Air |url=https://time.com/75612/atmospheric-water-generator-watergen/ |access-date=2022-05-24 |website=Time |language=en}}

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.{{cite web |title=2016 Toyota Mirai Fuel-Cell Sedan |url=http://www.caranddriver.com/toyota/mirai |access-date=28 August 2016}}

Potable water can be generated by rooftop solar hydropanels using solar power and solar heat.{{cite web |date=29 November 2017 |title=New rooftop solar hydro panels harvest drinking water and energy at the same time |url=https://inhabitat.com/new-rooftop-solar-hydropanels-harvest-drinking-water-and-energy-at-the-same-time/ |access-date=2017-11-30}}{{cite journal |last1=LaPotin |first1=Alina |last2=Zhong |first2=Yang |last3=Zhang |first3=Lenan |last4=Zhao |first4=Lin |last5=Leroy |first5=Arny |last6=Kim |first6=Hyunho |last7=Rao |first7=Sameer R. |last8=Wang |first8=Evelyn N. |date=20 January 2021 |title=Dual-Stage Atmospheric Water Harvesting Device for Scalable Solar-Driven Water Production |journal=Joule |language=English |volume=5 |issue=1 |pages=166–182 |doi=10.1016/j.joule.2020.09.008 |issn=2542-4785 |s2cid=225118164 |doi-access=free}}
News article: {{cite news |title=Solar-powered system extracts drinkable water from 'dry' air |url=https://techxplore.com/news/2020-10-solar-powered-drinkable-air.html |access-date=28 April 2022 |work=Massachusetts Institute of Technology |language=en}}{{cite web |title=Rain fed solar-powered water purification systems. |url=http://www.windpowerengineering.com/environmental/wind-solar-powered-offgridbox-useful-hurricane-passes/ |access-date=21 October 2017}}File:Least work AWH.png

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.

{{Portal|Water}}

• {{annotated link|Air well (condenser)}}
• {{annotated link|Dehumidifier}}
• {{annotated link|Desalination}}
• {{annotated link|Dew pond}}
• {{annotated link|Fog collection}}
• {{annotated link|Rainwater harvesting}}
• {{annotated link|Solar chimney}}
• {{annotated link|Solar still}}
• {{annotated link|Watergen}}
• {{annotated link|Watermaker}}
• {{annotated link|Water scarcity}}

{{Reflist}}

{{DEFAULTSORT:Atmospheric Water Generator}}

Category:Drinking water

Category:Water supply

Category:Water and the environment