Mist condensation

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Trade wind clouds in front of El Hierro , La Palma , La Gomera , Tenerife and Gran Canaria (from west to east)
Trade wind clouds over the Cumbre Nueva (1,400 m), La Palma

Fog condensation occurs when air that is already saturated with moisture is cooled further by falling below the dew point .

The term also describes the production of drinking water through the targeted condensation of water vapor in places where there is hardly any precipitation, but where fog formation occurs regularly .

When cold ocean currents come to the surface of the sea off the coast, the humidity transported by the onshore winds condenses there because the dew point is below the dew point and rains down. In extreme cases, the air masses reaching the country are so dry that deserts such as the Namib desert of South-West Africa and the Atacama desert of South America develop directly on the coast . If fog frequently occurs due to regional climatic features, fog deserts and cloud forests form in subtropical and tropical mountains .

Use by plants

Fog plants are those plants that use their surface structure to comb out fog droplets from fog or promote the formation of dew (through the formation of condensation germs ), for example Tillandsia , some Crassula species, beard lichens hanging on tree branches or Oxalis gigantea . The effect should not be confused with the excretion of water from leaves (so-called guttation ). Further examples:

Canary pine

Canary pine, Caldera de Taburiente , La Palma.
Dew drops on pine needles in the fog in Puntagorda, La Palma.

The Canary Pine ( Pinus canariensis ) native to the Canary Islands Gran Canaria , Tenerife , La Palma , El Hierro and La Gomera is an endemic plant and occurs predominantly at altitudes of 700 meters to 2,000 meters. On the northern slopes of the islands, they are exposed to the constant, cloudy trade winds and comb the wetness out of the trade clouds with their up to 30 cm long, fine needles. The water condensed on the needles drips off as precipitation and is called "horizontal rain" ( la lluvia horizontal ) in contrast to "vertical rain" ( la lluvia vertical ). It doubles or triples the amount of local precipitation and is of great importance for groundwater extraction . The pines only need about a third of the amount.

The effect of the "horizontal rain" is easy to observe. Drops of water constantly fall to the ground beneath the fog-shrouded pine tree and moisten it. On the other hand, just a few meters away, where no tree covers the ground, the ground is dry and dusty.

The daily amount of water that a 30 meter high Canarian pine can comb out of the fog has been determined based on experimental and empirical studies to be 50 l / m².

The annual rainfall in the various regions on the islands makes the great differences in water extraction clear. On La Palma, the most wooded island in the Canary Islands with 40% of the forest area, the pine population makes a significant contribution to the island's total water balance. In the north, facing the Passat, there are 1,000 l / m² and 1,500 l / m² per year, whereas in the south facing away from the Passat, only 250 l / m² are collected per year.

The contrasts are correspondingly great in Tenerife. While there is hardly more than 195 l / m² per year in the south of the island, in the north ( El Sauzal ) it is 870 l / m² per year.

The altitude of the Canary Islands and the trade winds flowing towards the islands with its water-rich clouds are the conditions for the evolutionary form of the Canary Pine with its long needles, with which the tree secures its own water supply through fog condensation.

The needles of the Canary Pine differ significantly in their uptake of mist droplets compared to other pine species, such as those of the Scots pine ( Pinus sylvestris ). Many individual drops collect along their needles, while in the Scots pine a drop only forms at the end of the needle. Microscopic images of the needle of the Canary Island pine show pronounced barbs on their surface - in contrast to the needles of other pine species - which act as condensation nuclei for the mist droplets. The significantly higher fog yield of the Canary Pine compared to other types of pine results from the special type of drop formation along the needle and the length of the needles (maximum 30 cm), the needle of the Scots pine, on the other hand, is 4 to 7 cm long.

Dune grass

The dune grass ( Stipagrostis sabulicola ) is an endemic species of the central Namib Desert that grows on extremely dry dunes . With about 1 meter long blades of grass, it is an effective mist collector. On the upright stalks, the water harvested from the mist flows over the stalks directly to the roots of the plant. The plant is able to collect approx. 4 liters of water per night of fog.

The special features of the stalk for collecting fog droplets consist of furrows running parallel to the longitudinal axis of the stalk and fine spiked hairs that cover the surface of the stalk. The furrows on the stalk offer a guided descent of the water droplets directly to the roots of the plant. The spiky hair prevents premature detachment and a descent to small drops.

The droplet formation process, as it has been observed under natural conditions and in the laboratory, is described as follows: Small droplets tend to accumulate along the furrows of the vertical stalk. The droplets get bigger as the mist continues to flow. As soon as a drop has reached a critical size, it rolls down the stalk and takes with it the other droplets that are in the furrow on the lower stalk.

This harvest of fog contributes significantly to the increase in soil moisture and thus provides protection and food for various other organisms such as ants and lizards. This is of great importance for the ecosystem of the Namib dunes.

Usage in the animal world

Mist Drinker Beetle

Fog condensation is also used for survival in the animal world, such as the dark beetle , gecko and sand viper . In the arid Namib Desert, which stretches over 2000 km, the animals gain their water balance through humidification from the fog that rises every day.

The dark beetle ( mist drinker beetle ), approx. 2 cm long, has noticeably long legs to protect itself from the hot desert sand. It is endemic to the Namib Desert. To absorb water from the fog, he stands with his head bowed against the fog and picks up the condensing water droplets on the inclined body. When the drops that have accumulated on its back have reached a size of about 5 mm, they flood the body and the water runs down the gutters on the back to the beetle's mouthparts. The water absorbed corresponds to about 40% of his body weight.

Application by humans

Atrapanieblas in Alto Patache, Chile

Fog catchers in Chile and Peru (Atrapaniebla)

Chilean research institutions in the period from 1967 to 1988 in various coastal regions in Chile and Peru (Las Cuchillas), at altitudes of 400 to 1000 meters networks for sustainable production of drinking water installed, the fog collection are called (from atrapar / catch and niebla / Fog ).

Fog catchers made of nylon or polypropylene nets with 0.1 mm fine threads and 1 mm mesh size were used, which achieved average fog yields of 3–9 l / (m² · d) in the regions examined. The most abundant haul of fog takes place in spring and summer. The annual fog season varied between 365 and 210 days. The technology is easy to implement, use and maintain, which limits the cost of installation and maintenance. The pipeline distribution system accounts for the highest amount. In kiwi and wine plantations, the large-scale mist catchers also serve as wind protection.

In 1987, in the Chilean fishing village of Chungungo in the Atacama Desert (in the 4th region 73 km north of the city ​​of La Serena ), 75 nets made of polypropylene were made there at approx. 750 meters above sea level with financial support from the European Union and the Canadian government each 2 meters long and 4 meters wide. The coastal fog (camanchaca) meets the nets perpendicular to the dominant wind direction on a ridge of the coastal cordillera called El Tofo at a height of around 900 m.

Depending on the location of the fog, between 10 and 100 m³ of good quality water was collected per day, which was led to the village via pipes. Each of the 330 residents had an average of 35 liters of water available. The cost of the fog water system was $ 65,000.

Before this time, the water had to be brought to the village by truck, whereby a resident had to get by on 14 liters a day (in Germany the consumption of drinking water is 122 liters per person per day, as of 2011). Since 2002 the village has been supplied with tank trucks again.

In 2003, another system was put into operation in Chañaral with the support of the Australian Embassy in Chile .

Mist catcher in the Namib Desert

In a research project of the BMBF for the development of innovative textile materials for extracting drinking water from fog, field tests were carried out in the Namib from 2008 to 2010 with 1 m² and 16 m² nets made of different textiles. The water production in fog ranged from 1 l / (m² · d) to 14 l / (m² · d) (on average 3.3 l / (m² · d)). The annual average was 1 l / (m² · d) with 105 foggy days per year. The water droplets reach sizes between 1 µm and 40 µm. The quality of the collected water was almost always better than that of the groundwater.

Textiles with different mesh sizes and fabric shapes (knob, pore and honeycomb structures) were used to examine suitable materials for the mist catchers. A particular subject of investigation was the ability of the different fabrics to absorb the water droplets from the mist and to release the water from the fabric. In terms of the type of wetting by the mist droplets , a distinction is made between water-repellent ( hydrophobic , large contact angle between the water droplet and the tissue, lotus effect ) and water-attracting ( hydrophilic , high moistening, small contact angle with the tissue).

The physical process of water absorption and re-release is explained as follows: Small mist droplets attach to the tissue and are enlarged by the mist droplets that constantly follow (the surface of the droplet formed is smaller than the sum of the surfaces of the individual droplets / coalescence ) until they are large that lead to the drainage of the drops. A process similar to the one described for the black beetle.

The ability of the (cheapest) textile types used to absorb and release water, which was determined in the field tests, showed only minor differences. The physical properties of the networks to give up or release more or less water remained unclear. There is no theoretical model that describes the adhesion and dripping behavior in tissues.

Mist catcher in Spain

On the Spanish Mediterranean coast, in the region of Valencia , investigations into the extraction of water from fog were carried out from 2004 to 2009. For this purpose, five fog collectors were used in the - up to 1839 meters high - mountain area at 428 meters and 845 meters and approx. 7 km from the coast. The most productive time for water production was in summer, during the evening and night.

In 2007, studies were carried out in the same region to improve water extraction through fog condensation in order to support the reforestation of the forest area destroyed by fire. For this purpose, cylindrical fog collectors and 18 m² flat plate collectors (6.4 × 2.8 meters) were installed at 8 locations. The cylindrical fog collectors achieved an average water volume of 3.3 liters / m² day. In contrast, the yield from rain was 1.4 liters / m² day. The comparison of the water yield from fog and rain over the course of the year showed that the fog yielded significantly higher yields than rain except for the months of September and October (roughly the same yields).

Canary Islands

Coat of arms of the island of El Hierro

The first reported use of fog condensation by humans came from the indigenous people, the Bimbaches of El Hierro , before the island was conquered by the Spanish in the 15th century. The Garoé , a laurel tree that condenses and drips water out of the fog with its foliage, supplied the indigenous people with drinking water. The Garoé, the sacred tree (Arbol Santo) of the indigenous people, is today the symbol of El Hierro. The island's coat of arms shows the Garoé tree with a cloud in its crown and a water surface at the foot of the tree.

In a study on Tenerife from 1996 to 2003, the use of water extraction through fog for agriculture, livestock, forestry and humans was examined. The fire fighting benefits were also of particular importance, as the forest areas of the Canary Islands suffer from severe erosion and constant fire hazard. Three cloudy peaks on Tenerife were selected as locations, in the northwest (Teno, Erjos, 1,010 m), northeast (Anaga, 864 m) and in the center (El Gaitero, Pedro Gil 1,747 m). The average fog yield at the three locations differs considerably and fluctuates in the time of year and day. In the Teno area the average water yields from fog were 5 l / m²d in summer and autumn and 4 l / m²d in winter and spring. The maximum yield was 51 l / m²d. The highest values ​​were measured in Anaga with 156 l / m²d.

Fog condensation was first used commercially on Gran Canaria to produce mineral water. In 2012, 30 mist traps were installed on the 1,600 meter high ridge of Las Cumbres in the municipality of Valleseco on an area of ​​350 m². The structure of the fog catcher used is box-shaped and differs from the earlier design of the fog catcher, which was flat like a billboard and was first used in Chile in the 1960s. It shows the result of more than 50 years of development of the mist catcher. With changing wind directions, it has a more effective fog yield and less water loss via the collecting tray than the flat version. The fog catcher is more stable against the wind pressure and does not require any additional tensioners to fasten it to the ground. The construction is also easier to transport and install in generally inaccessible terrain.

Mist catcher on the Cumbre Nueva

The type NRP 3.0 mist catcher has an inner and outer network with dimensions of 2000 mm × 800 mm and 2000 mm × 800 mm × 240 mm, which is made of polyester reinforced with glass fiber. The box-shaped structure of the fog catcher stands on a rectangular metal bowl in which the condensation water is collected and from there drained into a collecting container. The single mist catcher on Gran Canaria can collect more than 500 liters of water in a day, with the average amount being 180 to 230 l / d. The best conditions for exploiting fog water are found at wind speeds of 30 to 35 kilometers per hour.

In 2013, six NRP 3.0 type fog collectors were installed on El Hierro in the regions of Binto, Malpaso and Ajonce - with the same objectives as on Tenerife.

Since 2006 there have been fog collectors on the Cumbre Nueva of La Palma at an altitude of 1,425 m to extract water from the trade winds. The system of fog traps, pipelines and water tanks, which was set up with € 200,000, is intended to supply passing hiking tourists with drinking water and to provide fire-fighting water, but its use is limited due to insufficient maintenance to keep the fog traps clean.

Morocco

In June 2006 , a project to obtain drinking water from fog started in the south of Morocco , near the coastal town of Sidi Ifni (south of Agadir ). In the arid area (with 112 mm of precipitation per year) 14 villages, in which 161 families (897 people) live, are to be supplied with drinking water. Their average water consumption is 15 liters per person and day (a German uses 122 liters / day). The 1225 m high mountain Boutmezguida was chosen as the location for the mist catchers. The first fog catchers had to be replaced by more stable technologies soon after they were erected, as they could not withstand the wind speeds of up to 120 km / h. The 1,590 m² area of ​​the mist catcher provides an average of 8.7 l / m² per day with around 112 fog days / year (in 2007), which is fed to the villages via 6.9 km of water pipes. This means that each family member has 18 liters of water per day.

Fog yield on the island of Maui

Ohia Tree, Maui, Waihee Ridge Trail

The importance of water extraction through fog for the ecosystem was researched in an American research project on the island of Maui , Hawaii from 2001 to 2003.

Two study sites were selected, the windward, forested east side (at 1950 meters) of the 3055 meter high Haleakalā volcano on Maui and the windward, deforested west side (at 1220 meters). It is assumed that before 1800 the west side was also forested and got its water balance from the fog.

In order to differentiate between the precipitation from rain and fog, tree sap samples were taken monthly by pruning the branches of the ohia tree and their isotope compositions ( 16 O / 18 O and H 2 O / D 2 O ) were determined.

The ohia is the predominant plant in the cloud forest of Maui, it grows slowly and reaches a trunk diameter of 1.8 meters in 400–500 years.

One result of the study is that on the wooded windward side of the Haleakala volcano, the amount of water collected by fog is higher than rain by a factor of 1.26 to 3.67.

Other countries

The application of the mist collector technology for the rural population takes place in other countries such as Namibia , Nepal , Guatemala , Ethiopia , Eritrea , Haiti , Yemen and Croatia . The maximum yield is between 3 l / (m² · d) and 55 l / (m² · d).

Bionics

The research and use of fog condensation is now part of the scientific discipline of bionics , which deals with the technical implementation and application of constructions, processes and development principles of biological systems.

The MIT in Cambridge developed for the extraction of water from the air, a porous metal-organic material (MOF), which already at 20% humidity is effective. 2.8 liters of water can be extracted from one kilogram of MOF in one day. The water absorbed from the air in the MOF is evaporated, condensed and captured by natural solar radiation.

Use in agriculture

Recently a water curtain has been used to dehumidify greenhouse air. The water droplets serve as heat sinks , condensation nuclei and a means of transport for condensation water and fog droplets ( Novarbo system and Watergy system ). Even with fog nets, the already captured water droplets act as condensation nuclei in the steam- oversaturated, mist-containing air, with nets that cool down at night, similar to parked cars, the dew point falls below the dew point and, in addition to the fog trap, condensation of water vapor occurs (see also dew point ).

Web links

Commons : Fog collectors  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b M. M. Bollmann, F. Herwig: Alternatives to conventional drinking water production. ( PowerPoint presentation ( Memento from April 18, 2014 in the Internet Archive )).
  2. ↑ Jörg S. Pfadenhauer, Frank A. Klötzli: Vegetation of the earth. Basics, ecology, distribution. 2014, ISBN 978-3-642-41950-8 , pp. 220ff.
  3. ↑ La Palma - Guía del turismo tranquilo - Guide for peaceful tourism. ( limited preview in Google Book search)
  4. ↑ JCS Cerezal, JN Borges: Ingeniería forestal y ambiental en medios insulares. Técnicas y Experiencias en las Islas Canarias. Tenerife 2013, ISBN 978-84-616-3859-8 . ( PDF ( Memento of April 13, 2014 in the Internet Archive )).
  5. ↑ JJB Ruiz: Aproximación al cálculo de la lluvia horizontal ya su incidencia de la recarga del sistema de Tenerife Aquifer. In: Theme B: Hidrología y Gestión del Agua. ( PDF ( Memento of April 16, 2014 in the Internet Archive )).
  6. ↑ R. Goetz: La Palma, active vacation on the greenest of the Canary Islands. (= Peter Meyer travel guide ). 5th edition. Frankfurt am Main 2000.
  7. ↑ a b c T. Stegmaier: Development of innovative textile materials for obtaining drinking water from fog. BMBF research project (PDF)
  8. ^ A. Roth-Nebelsick, M. Ebner, T. Miranda: Efficient fog harvesting by Stipagrostis sabulicola (Namib dune bushman grass). In: Journal of Arid Environments. 75, 2011, pp. 524-531. doi: 10.1016 / j.jaridenv.2011.01.004 (full text source at researchgate.net)
  9. ^ Animal or Plant: Which Is the Better Fog Water Collector? In: PLOS-one. April 3, 2012. (plosone.org)
  10. ^ A. Roth-Nebelsick: Leaf surface structures enable the endemic Namib desert grass Stipagrostis sabulicola to irrigate itself with fog water. In: Journal of the Royal Society Interface. (rsif.royalsocietypublishing.org)
  11. ^ A b W. Nachtigall: Bionics: Basics and examples for engineers and scientists, Technology & Engineering. Water extraction through fog condensation, 2002, p. 337 ( limited preview in the Google book search).
  12. ^ W. Nachtigall, A. Wisser: Bionics in examples. 2013, p. 63 ( limited preview in Google Book search).
  13. ^ Fog harvesting. In: Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean. UNEP - International Environmental Technology Center United Nations Environment Program, Washington, DC, 1997. In: Website of the Organization of American States
  14. ^ Construcciones, Atrapanieblas ( Memento of December 21, 2016 in the Internet Archive ), Jung, September 18, 2013.
  15. ↑ K. Kramer: Nebelfischer. ( Memento from July 19, 2012 in the Internet Archive ) In: Mare. No. 45, August 2004.
  16. ↑ Milking fog: The new way of obtaining drinking water. In: Tagesanzeiger. July 23, 2010. (tagesanzeiger.ch)
  17. ↑ C. Azorin, D. Corell, MJ Estrela, JA Valiente: Fog water collection under sea breeze conditions in the western Mediterranean basin (Valencia region, Spain). In: 5th International Conference on Fog, Fog Collection and Dew, Münster, Germany, 25–30 July 2010. P. 65. (meetings.copernicus.org)
  18. ↑ JA Valiente, MJ Estrela, D. Corell, D. Fuentes, A. Valdecantos: Fog water collection and reforestation at mountain locations in a western Mediterranean basin region. In: 5th International Conference on Fog, Fog Collection and Dew, Münster, Germany, 25–30 July 2010. P. 52. (meetings.copernicus.org)
  19. ↑ El Garoé
  20. ↑ Simbolos de canarias .
  21. ^ Maria Victoria Marzol Jaén: Fog water collection in a rural park in the Canary Islands. Geography Department, La Laguna University, Canary Islands, Spain. (sciencedirect.com)
  22. ^ Maria Victoria Marzol Jaén: Frecuencia y duración de la niebla en Tenerife con el fin de su aprovechamiento hidrológico. Department of Geography, Universidad de La Laguna, 2004. (tiempo.com)
  23. ↑ Depósitos para Captadores de nieblas, June 2012 ( Memento of January 10, 2017 in the Internet Archive )
  24. ↑ Alisios, Canarian Mist Water, Nuestro manantial está en el cielo (Trade in Canarian water mist, our source is in heaven) ( Memento of December 21, 2016 in the Internet Archive ), Alisios, Canarian Mist Water.
  25. ↑ Captadores NRP 3.0, La revolución en captación de agua de las nieblas (The revolution in water extraction from fog) ( Memento of December 22, 2016 in the Internet Archive ), Alisios, Canarian Mist Water.
  26. ↑ a b Captadores de niebla, rocío y precipitaciones conformarán el primer “huerto hídrico” con aparatos tridimensionales del mundo (mist catcher, dew and precipitation form the world's first "water garden" with three-dimensional devices) , Agua de Niebla Alisios, October 17, 2012 .
  27. ↑ Agua de niebla de Canarias
  28. ^ Fog collectors on the island of El Hierro. Agua de Niebla de Canarias SL 2013. (eng.aguadeniebla.com)
  29. ↑ Inaugurar y no mantener (initiate and not maintain) , La voz de La Palma, June 6, 2016.
  30. ↑ The CloudFisher, Developing and Providing Methods and Techniques for Water Harvesting, Water Foundation.
  31. ↑ Floating sources, installation of fog collectors in the Anti-Atlas Mountains in Morocco , water foundation.
  32. ↑ Boutmezguida: A Decade Long Engagement
  33. ↑ Quantifying the importance of fog drip to ecosystem hydrology and water resources in tropical montane cloud forests on East Maui , Hawaii, US Department of the Interior, US Geological Survey, Reston, VA, USA, August 20, 2004. (water.usgs. gov)
  34. ↑ Definitions: Stable isotope tracers , US Department of the Interior, US Geological Survey, Reston, VA, USA, 2002. (water.usgs.gov)
  35. ↑ Nathan Yuen: GIANT AGE-OLD OHIA TREES. 2008. ( hawaiianforest.com ( Memento from July 16, 2014 in the Internet Archive ))
  36. ↑ St. B. Gingerich, MA Scholl: The Contribution of Cloud Water to Recharge on the Volcanic Island Maui, Hawaii. Abstract for 2003 International Union of Geodesy and Geophysics meeting, Sapporo, Japan, US Department of the Interior, US Geological Survey, Reston, VA, USA, 2003. (water.usgs.gov)
  37. ^ 5th International Conference on Fog, Fog Collection and Dew , Münster, Germany, 25–30 July 2010. (fogconference.org)
  38. ↑ Manfred Lindinger: New water collector gets drinking water from desert air. In: FAZ. May 3, 2017. (A newly developed material can also produce drinking water from dry air) (faz.net)
  39. ^ Evelyn Wang et al.: Water harvesting from air with metal-organic frameworks powered by natural sunlight. In: Science. Vol. 356, No. 6336, April 13, 2017, pp. 430-434. (science.sciencemag.org)

See also