Snow cannon

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Snow gun in action
Ski slope with artificial snow, Savognin (Switzerland)

With snow cannons , Beschneier or snow producer is using zugeliefertem water by means of an air stream snow produced technically. In technical parlance, the term snow gun is often used for a snow cannon , even if snow lance (or snow lance ) is also assigned to this term.

The snow-making system is the entirety of the components of a technical snow-making system for the mechanical production of snow. The components of a snowmaking system are water storage tanks, pumps, compressors, water / air / electricity supply lines and snow guns.

They are used in winter sports areas when the snow depth is insufficient for winter sports such as skiing and snowboarding due to insufficient snowfall or thaw . This is intended to increase the snow reliability and thus the profitability of the operation of ski areas in view of the climatic changes .

The colloquial term “artificial snow” has now been replaced by the term “technical snow” in the industry. This term arose from the consideration that the technically produced snow does not contain anything artificial, but rather was produced with technical aids. Snow made of plastic and styrofoam is called artificial snow .

In Austria , a nationwide uniform guideline for the water law administrative procedure for snowmaking systems has been published.

Technical procedures

Ice cannon
Water is either frozen into blocks of ice, which are then crushed, or splashed onto a rotating, chilled drum and scraped off. The “snow” can be distributed in a targeted manner using compressed air and a hose line. This is the simplest principle, regardless of the outside temperature; however, the "snow" here consists of ice splinters, not snowflakes, and is poorly suited for skiing. This procedure is mainly used in the event and promotion area or for city ​​contests .

The following processes mimic the natural formation of snow, in which small water droplets slowly crystallize and thus develop the characteristic shape of the snow crystals:

Compressed air cannon
A water-compressed air mixture emerges from a nozzle at a pressure of 5–10  bar ; when expanding under normal pressure, the air-water mixture cools down so that the water droplets can freeze. Compressed air cannons deliver comparatively good snow performance in the limit temperature range (around 0 ° C), with a very high energy consumption for the air compression for cold generation. The method has a low sensitivity to wind. The sound power levels of compressed air cannons are high compared to other methods.
The compressed air cannon is incorrectly referred to as a high pressure system.
Propeller cannon
The central element is a propeller that generates a strong air flow. The nozzle assembly with mostly several rings is located around the pipe outlet. The outer nozzles are mostly designed as mixing nozzles (water and compressed air) for the production of snow cores, the inner ones mostly as pure water nozzles. The mixing or nucleator nozzles produce small ice crystals as crystallization nuclei, similar to the principle of the compressed air cannon (see above).
The amount of water droplets must be adapted to the external weather conditions such as temperature and humidity as well as the throwing distance in order to achieve optimal properties of the technical snow. The water droplets contained in the air flow emerging from the propeller cannon partially evaporate in the dry winter air, whereby the droplets cool down. When the freezing point is reached, they crystallize on the crystal nuclei. The drier the ambient air, the better the cooling process works. This procedure works with a relative humidity of 30% at 1 ° C above zero, at 80% relative humidity , however, below -3 ° C are required.
The propeller cannon is the most frequently used principle, but it has a very high power consumption - due to the fan - and, uninsulated, results in a high noise level. Propeller cannons can best be regulated (working pressure approx. 8–40 bar).
Obsolete, it is also known as the low-pressure system.
Snow lance
At the tip of an aluminum tube up to 12 meters long, which is set up vertically or at an angle, there are water, air and nucleator nozzles . Air is blown into the water that is atomized when it emerges from the water nozzle. The previously compressed air expands and thereby cools down, creating ice nuclei on which the atomized water crystallizes. Due to the altitude and the slow rate of descent, there is enough time for this process. The process is comparatively energy-efficient, but compared to the propeller gun it provides a small range and snow performance and is more sensitive to wind.
Advantages compared to propeller guns: lower investment (only piping system with air and water connections, central compressor station), much quieter, half the energy consumption per amount of snow. Low maintenance and low wear. Regulation possible in principle. Working pressure from 15–60 bar. There are now also small mobile systems for home users that are operated on the garden connection (HomeSnow; Snow at Home) .
Cryo cannon
Water and compressed air are applied mixed with liquid nitrogen (LN). LN is delivered cold and almost pressureless in the semi-trailer tank and cools the surrounding media water and air by boiling and "dissolving into air" in the process. Due to the low boiling point of nitrogen, high doses can produce snow even at temperatures far above the ice point. In accordance with the high costs, the process is only used selectively in the event and promotion area.
Vacuum snow gun
In the "Vacuum Ice Machine" water is exposed to a high vacuum. This vacuum evaporates part of the water, while the rest of the water freezes to a water-ice mixture, which is pumped from the “freezer” into a “snow separator”.
Due to its size, the generator can only be moved by means of a low loader and requires a comparatively high amount of energy. For this, 'spring snow' can be produced with chilled water and a considerable amount of cooling water even at summer temperatures. The suitability for commercial snow-making on the slopes is rather doubtful, since a usable snow quality cannot be achieved at warm outside or ground temperatures, whereas at lower temperatures a much higher efficiency is given by propeller or lance systems.

  • Close-up of a mobile snow cannon

  • Rear view looking towards the fan

  • Nozzles of a snow cannon

  • Snow lance

  • Side view of a snow cannon, Nassfeld 2012

Properties of engineered snow

The properties of snow depend largely on the shape of the snow crystals, the temperature and the liquid water content. The shape of the crystals is determined by the meteorological environmental conditions during crystallization , both with natural and technical snow. The environmental conditions include above all temperature and humidity , but also air pressure .

Technical snow differs in its structure (30–350 micrometers, spherical shape) quite significantly from new snow (50–100 micrometers, hexagonal shapes). Depending on the external conditions, the density of artificially produced snow is 300–500 kg / m³ (natural snow: 10 -80 kg / m³). These differences have a significant effect on the albedo (measure of the reflectivity) and the thermal conductivity of the snow cover. In addition to the spherical shape, liquid water inclusions can be observed in the ice spheres immediately after the snow has been made.

The differences between the two ice forms can be found in the following parameters:

Technical snow differs from natural snow in:

In practice, the following properties are typical:

  • higher heat resistance due to higher density (technical snow melts more slowly than natural snow)
  • more compact / harder texture and consequently less rapid formation of bumps

Energy and water consumption

Water storage for the Hochjoch ski area in Schruns , Montafon

Resource balance using the example of a propeller cannon with 24 kW: (1)

  • A water throughput of 1 liter / second at -3 ° C results in a snow output of 9 m³ / hour (snow weight 400 kg / m³), ​​which corresponds to about 3 kWh / m³ of snow.
  • At –10 ° C you can get around 7 liters / second, whereby the energy requirement of the snow cannon remains unchanged, but the pump energy increases linearly.

This means that the efficiency of a snow-making system increases linearly with falling temperature (calculation without pump energy). (2)

No additional energy needs to be used for a high-pressure pump for water supply, provided the storage pond is higher than the location of the snow cannon. For the withdrawal of water from a reservoir z. B. a submersible pump is required.

Energy balance of a propeller cannon with aliquot inclusion of the pump energy: (2)

  • –3 ° C: 9 m³ snow / h, corresponds to approx. 5 kWh / m³ snow
  • –10 ° C: 60 m³ snow / h, corresponds to approx. 1 kWh / m³ snow

Characteristics:

(1) Propeller cannon: fan 15 kW, compressor 4 kW, heating 4 kW, other 1 kW
(2)Pump output in kW: mean value P = 1 ⁄ 7  ·  v  ·  p , with v  … volume flow in liters / second, p  … pressure in bar.

In the summer of 2008, a snow-making system was put into operation in Rauris, Austria , which is also equipped with a small hydroelectric power station. At the upper end of the riser there is a pond from which both the snow-making system and the small power plant are fed. The pond is fed by a torrent. When - as in summer - there is no snowmaking, the small power plant is used to feed electricity into the grid. The operator hopes to use only as much electricity for snowmaking in this way as is produced by the company itself.

Wet bulb temperature

Not only does the air temperature play a role in making snow, but also the relative humidity. Experts speak of the so-called wet bulb temperature . It is made up of the ratio of air temperature and relative humidity and is always below the outside temperature. The more humid the air, the less moisture it can absorb. This means that when the air humidity is higher, lower temperatures (called dry bulb temperature) are necessary so that water droplets can freeze out to form snow crystals.

Examples:

  • 0 ° C dry bulb temperature corresponds to a wet bulb temperature of −0.6 at 90% humidity
  • A dry bulb temperature of 0 ° C corresponds to a wet bulb temperature of −4.3 at 30% humidity
  • +2 ° C dry bulb temperature corresponds to a wet bulb temperature of +1.5 at 90% humidity
  • +2 ° C dry bulb temperature corresponds to a wet bulb temperature of −2.8 at 30% humidity

A wet bulb temperature of −2.5 is necessary for snowmaking. When the humidity is low, the snowmaking works even at slight plus degrees, with high humidity, minus degrees are necessary. Temperatures around freezing point are referred to as marginal or limit temperatures.

Chemical auxiliaries

So-called snow inducers are proteins that are added to the water by snowmaking systems in order to increase the nucleation temperature.

The Snomax snow inducer, manufactured by a US company, has been used in the USA since 1987, and Snomax is also approved for use in Canada , Norway , Japan , Sweden , Switzerland , Finland , Chile and Australia .

In Germany and Austria , the use is discussed very controversially. In 2002 an environmental impact assessment was carried out. Snomax is very controversial as pseudomonads are used to make the protein. Since the bacterium Pseudomonas syringae 31R is only killed and not removed, these inactive bacteria are also brought into nature with the water. Therefore, the use in Bavaria is prohibited.

Critics fear that these will have a negative impact on fauna and flora as soon as the snow melts in spring and this pollution remains on the fields. The headline also circulated in the media: bacterial snow poisons drinking water .

In a survey of Swiss cable car companies in 2007, around 14 percent of the areas that produce artificial snow stated that they use additives such as Snomax.

In August 2018, the Tyrolean regional administrative court allowed a field test in Seefeld with killed bacteria as an additive. Politicians from various parties and the majority of cable car operators, on the other hand, want to stick to pure water.

invention

The basic principle was discovered by chance in Canada at the end of the 1940s, when a team of researchers led by the Canadian Raymond T. Ringer sprayed water in a wind tunnel at low temperatures to investigate the icing of jet engines - which resulted in unwanted snow. The first compressed air snow cannon was invented in 1950 by Art Hunt, Dave Richey and Wayne Pierce of the American ski manufacturer Tey Manufacturing in response to a winter without snow and granted a patent in 1954 - which was later annulled due to earlier research. In 1958 the American Alden Hanson applied for a patent for the first propeller snow cannon, which was granted in 1961. The invention of a complete snow-making system with a lance system (October 1970) goes back to Herman K. Dupré, for this reason such systems are usually referred to as HKD systems. (US Patent 3,706,414)

The first European low-pressure snow cannon was designed by Fritz Jakob from Linde in 1968 .

criticism

Snowmaking lance in autumn

When using snow guns, the demands of winter sports enthusiasts for the "good" snow possible are offset by the high technical effort and high economic and ecological costs. The OECD criticizes the enormous use of water and energy and the associated long-term damage to the environment, even if appropriate water reservoirs are built.

The roughly 19,000 snow cannons in Austria (as of February 2013) use around six million liters of water per hectare and a total of 260,000 MWh of electricity. The snow cannons in Europe use as much energy as a city with 150,000 inhabitants and as much water as a large city like Hamburg. This water is missing in the waters during the winter months: Researchers have found that up to 70 percent less water has flowed into streams and rivers in the French Alps since the introduction of the snow cannons. However, especially in the Alps, a large part of the electricity is generated by renewable energies, for example 72% in Austria.

Short-term environmental damage can also be observed when special storage ponds are built for snowmaking systems in previously untouched mountain areas and unique ecosystems are destroyed to enable people to ski.

Law

Austria

The guideline for the water law official procedure for snowmaking systems is intended to provide a nationwide uniform orientation for authorities, experts, planners and operators for the water law official procedure for snowmaking systems, without pre-empting the individual assessment. The aim is to ensure planning security for new permits and upcoming reassignments.

  • Volume 1 includes: Approval and review of new systems
  • Volume 2 includes: re-granting procedures for existing water rights, recurring reviews, precautions in the event of the expiry of water usage rights

The documents were prepared under the direction of Thomas Eistert, State of Salzburg  - Water Department, in cooperation with all the federal states concerned, the Ministry of Life (Supreme Water Rights Authority , Reservoir Commission , torrent and avalanche control ) and with the support of external experts. The professional association of cable cars and the chamber of architects and engineering consultants were involved as interest representatives.

Bavaria

The construction and operation of snow-making systems are subject to approval in accordance with Article 35 of the Bavarian Water Act.

Snow farming

If snow in one winter is prefabricated for the next winter season, this is known as snow farming. The coldest days possible in winter are used to generate snow, which is stored covered above in an insulated manner in order to preserve it over the summer and harvest it in late autumn. In Ramsau am Dachstein 2013, this method for some time used in Switzerland was the first time: In the cold January 5000 m³ of snow about 10 were piled high m, approximately 1 m thick with wood chips , fabric and covered film and in early November from the summer A cross-country ski run on the green meadow created a long-term amount of 4000 m³, a few weeks before the night temperatures would have allowed the production of fresh snow. The storage of snow and ice - for cooling beer and meat - in ice cellars actually goes back to the 18th century. The word ice box or ice cabinet, which was also used by those born around 1900/1920 for the modern household refrigerator with cooling machine , goes back to the time when the ice cream man brought the ice into the streets, which was chopped and filled into the freezer made of soldered zinc sheet and so the compartment below cooled.

literature

Individual evidence

  1. ↑ Snow cannon system as a power plant. In: ORF news archive. August 13, 2008. Retrieved August 17, 2008 .
  2. ^ Heinz Bayer: Electricity from the snow-making system . In: Salzburger Nachrichten, regional section from town and country . August 14, 2008, p. 1, 11 .
  3. ↑ a b Frequently asked questions about TechnoAlpin and technical snowmaking. Retrieved October 1, 2019 .
  4. ↑ UmweltWissen - Bavarian State Office for the Environment; Snow-making systems and artificial snow (PDF; 280 kB). ( Memento from November 7, 2014 in the Internet Archive )
  5. ↑ "Ecology of Snow Systems " on das-hoechste.de
  6. ↑ "Snow at any price?" On salzburg.com ( Memento from February 6, 2007 in the Internet Archive )
  7. ↑ Controversial additions are prohibited in the canton of Bern In: Der Bund , December 20, 2015, accessed on February 4, 2018.
  8. ↑ Court allows additive at artificial snow orf.at, August 14, 2018, accessed August 14, 2018.
  9. ↑ Mr. Holle and the snow of tomorrow , weltbildung.com
  10. ↑ US Patent 2,676,471
  11. ↑ US Patent 2968164
  12. ^ Making Snow , About.com
  13. ^ The technology behind the snow cannon , Spectrum of Science, December 9, 2006
  14. ↑ http://www.seilbahn.net/aktuell/wintermuseum/wintersportmuseum.htm ( Memento from January 23, 2009 in the Internet Archive )
  15. ^ OECD: Climate Change in the European Alps: Adapting Winter Tourism and Natural Hazards Management . Ed .: OECD Publishing. Paris 2007, ISBN 978-92-64-03169-2 , pp. 46-48 , doi : 10.1787 / 9789264031692-en .
  16. ↑ David Krutzler: Snow guarantee through 19,000 cannons . derStandard.at. February 28, 2013. Retrieved May 18, 2013.
  17. ↑ How much does snow cost . In: Capital, January 18, 2007, p. 16.
  18. ↑ https://oesterreichsenergie.at/daten-ffekten-zur-stromerzeugung.html
  19. ↑ Guide for snow-making systems , State of Salzburg, Water Department
  20. ↑ [1] , BayWG, Bavarian Water Act
  21. ↑ http://steiermark.orf.at/news/stories/2613996/ Ramsau relies on yesterday's snow, ORF.at from November 10, 2013

Web links

Commons : Snow cannon  - album with pictures, videos and audio files
Wiktionary: Snow cannon  - explanations of meanings, word origins, synonyms, translations