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| An '''atmospheric water generator''' (often abbreviated as '''AWG'''), is a device that extracts water from ] ambient air. Water vapor in the air is ] by cooling the air below its ], exposing the air to ]s, or pressurizing the air. An atmospheric water generator is very useful in locations where pure drinking water is difficult or impossible to obtain, as there is almost always a small amount of water in the air. The two primary techniques in use are cooling and desiccants. | |||
| An '''Atmospheric water generator''' (AWG), is a device that extracts water from ] ambient air. An AWG operates in a manner very similar to that of a ]: air is passed over a cooled coil, causing water to condense. The rate of water production depends on the ambient temperature, humidity, the volume of air passing over the coil, and the machine's capacity to cool the coil. An AWG is very useful for locations where pure drinking water is difficult to obtain or impossible to have, as there is almost always a small amount of water in the air. It is estimated that 12,900 cubic kilometers (or 0.04%) of the ]'s total supply of fresh water is contained in the atmosphere, mostly as water vapor.<ref>Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823</ref> | |||
| == History == | == History == | ||
| Collecting water from the air has been a practice for some 2,000 years, in the form of ] in Middle Eastern deserts, and later in Europe. Around the 1400s, history records water-collecting ], and later ]. | |||
| <ref name=pugsley>{{cite book | |||
| | last = Pugsley | | last = Pugsley | ||
| | first = Alfred J | | first = Alfred J | ||
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| | doi = | | doi = | ||
| | id = | | id = | ||
| | isbn = }}</ref><ref>'']'': dew-pond</ref> | | isbn = }}</ref> | ||
| <ref>'']'': dew-pond</ref> | |||
| == Principle of operation == | |||
| ==Modern technologies== | |||
| The AWG is essentially a conventional dehumidifier that condenses water from air. A ] circulates ] through a condenser coil. A controlled-speed fan pushes filtered air over the coil which creates an artificial ] causing water to condense. This water is then passed into a holding tank with purification and filtration system to keep the water pure. AWG features vary depending on the manufacturer. In order to meet stringent FDA standards and NSF, most systems are coupled to one or more advanced filter systems.<ref>http://everestwater.com/purification.htm</ref> | |||
| Many atmospheric water generator's operate in a manner very similar to that of a ]: air is passed over a cooled coil, causing water to condense. The rate of water production depends on the ambient temperature, humidity, the volume of air passing over the coil, and the machine's capacity to cool the coil. These systems reduce air temperature, which in turn reduces the air's capacity to carry water vapor. This is the most common technology. | |||
| ] | |||
| An alternative technology uses desiccants.<ref>. New York Times. July 2, 2001</ref> One technique combines the use of solid desiccants with pressure condensation. Desiccants used for such applications include ] and ]. Some liquid desiccants, such as ] or ] are also in use. Although liquid desiccants have better adsorption capacity, the interface between gas and liquid creates technical issues and the liquid desiccants themselves are very toxic. Moreover, liquid desiccants easily become polluted by air contaminants, while solid desiccant are almost unaffected by pollution.{{Citation needed|date=October 2009}} | |||
| ⚫ | The rate at which water can be produced depends on ] and ambient air temperature and size of the compressor. AWGs become more effective as relative humidity and air temperature increase. As a rule of thumb, AWGs do not work efficiently when the temperature falls below (65°F), the relative humidity drops below 30%. The cost-effectiveness of an atmospheric water generator depends on the capacity of the machine, local humidity and temperature conditions and the cost to power the unit. | ||
| === Cooling condensation === | |||
| In a cooling condensation based atmospheric water generator, a ] circulates ] through a condenser coil which cools the air surrounding it, lowering the air's ] and causing water to condense. A controlled-speed fan pushes filtered air over the coil. The resulting water is then passed into a holding tank with purification and filtration system to keep the water pure.<ref>. Atlanta Journal Constitution.</ref> | |||
| ⚫ | == External links == | ||
| ⚫ | The rate at which water can be produced depends on ] and ambient air temperature and size of the compressor. |
||
| ⚫ | * {{dmoz|Business/Food_and_Related_Products/Beverages/Water/Tools_and_Equipment/Atmospheric_Water_Generators/|Links to Atmospheric Water Generators}} - lists commercial sites | ||
| === Dry desiccation with pressure condensation === | |||
| Atmospheric water generators using desiccation with pressure technology are effective from as little as 20% of relative humidity and in temperatures ranging from 4°C to 45°C. A key advantage of dry desiccation is that no air filtration is required and micro-organisms or air pollutants cannot contaminate the produced water - so no filtering or purification of the water is needed. Because the water is pure, trace amounts of calcium and magnesium have to be added to make the water drinkable. | |||
| Most of the energy involved is thermal, electricity being needed only to operate the air blowers and some auxiliary motors. This technology has a positive energy balance that allows to recover about 90% of the latent heat involved in the water production process.{{Citation needed|date=October 2009}} Solar heat can be integrated as a complementary heat source. The condensation process utilizes the latent heat released upon adsorption, and the heat formed by applying pressure is recovered and returned to the process. The system reuses energy through heat transfers and storage in a heat reservoir, so incremental thermal energy can be provided by almost any heat source (such as residual heat from power generators, cooling towers, waste incineration, or solar thermal panels). | |||
| A typical machine using this technology produces fresh liquid water as follows: | |||
| * Stage 1 – Door opens, air blow through and released dry. | |||
| * Stage 2 – Door closes, lower blower turns off, heat exchanger valve opens and the chamber is heated to 85c, filling with steam | |||
| * Stage 3 – Steam valve opens and the steam is sucked out by a piston and pressed into the condensation container. | |||
| * Stage 4 – Steam is condensed in the condensation container and pumped out as water. | |||
| * Stage 5 – Latent and pressure heat is returned to the heat storage tank. | |||
| * Stage 6 – Heating and steam valves are closed, followed by door opening. | |||
| ===Wet desiccant=== | |||
| One form of wet desiccant water generation involves the use of salt. ] is streamed down the side of towers, where it absorbs water. The brine is then placed in a vacuum and heated. The vacuum significantly lowers the boiling point of the brine, so the boiling process requires only a small amount of energy. The steam is collected and condensed, while the remaining brine is recirculated through the system. As the condensed water is removed from the system using gravity, it creates the vacuum which lowers the boiling point of the brine.<ref>. ScienceDaily (June 8, 2009)</ref> | |||
| == References == | == References == | ||
| {{Reflist}} | {{Reflist}} | ||
| ⚫ | == External links == | ||
| ⚫ | * {{dmoz|Business/Food_and_Related_Products/Beverages/Water/Tools_and_Equipment/Atmospheric_Water_Generators/|Links to Atmospheric Water Generators}} - lists commercial sites | ||
| {{DEFAULTSORT:Atmospheric Water Generator}} | {{DEFAULTSORT:Atmospheric Water Generator}} | ||
| ] | ] | ||
| ] | ] | ||
| ] | |||
Revision as of 07:30, 21 October 2009
An Atmospheric water generator (AWG), is a device that extracts water from humid ambient air. An AWG operates in a manner very similar to that of a dehumidifier: air is passed over a cooled coil, causing water to condense. The rate of water production depends on the ambient temperature, humidity, the volume of air passing over the coil, and the machine's capacity to cool the coil. An AWG is very useful for locations where pure drinking water is difficult to obtain or impossible to have, as there is almost always a small amount of water in the air. It is estimated that 12,900 cubic kilometers (or 0.04%) of the earth's total supply of fresh water is contained in the atmosphere, mostly as water vapor.
History
Collecting water from the air has been a practice for some 2,000 years, in the form of air wells in Middle Eastern deserts, and later in Europe. Around the 1400s, history records water-collecting dew ponds, and later fog fences.
Principle of operation
The AWG is essentially a conventional dehumidifier that condenses water from air. A compressor circulates refrigerant through a condenser coil. A controlled-speed fan pushes filtered air over the coil which creates an artificial dew point causing water to condense. This water is then passed into a holding tank with purification and filtration system to keep the water pure. AWG features vary depending on the manufacturer. In order to meet stringent FDA standards and NSF, most systems are coupled to one or more advanced filter systems.
The rate at which water can be produced depends on relative humidity and ambient air temperature and size of the compressor. AWGs become more effective as relative humidity and air temperature increase. As a rule of thumb, AWGs do not work efficiently when the temperature falls below (65°F), the relative humidity drops below 30%. The cost-effectiveness of an atmospheric water generator depends on the capacity of the machine, local humidity and temperature conditions and the cost to power the unit.
External links
- Template:Dmoz - lists commercial sites
References
- Gleick, P. H., 1996: Water resources. In Encyclopedia of Climate and Weather, ed. by S. H. Schneider, Oxford University Press, New York, vol. 2, pp.817-823
- Pugsley, Alfred J (1939). Dewponds in Fable and Fact. London: Country Life Ltd.
{{cite book}}: Cite has empty unknown parameter:|coauthors=(help) - Oxford English Dictionary: dew-pond
- http://everestwater.com/purification.htm