Methods 

Today there are three main methods of providing snow for a ski area without being dependent on natural snowfall: 

  • Traditional snow production in below freezing temperatures (a)
  • Temperature independent snow production in above freezing temperatures (b)
  • Storage of snow (over the summer) of natural- og artificial snow (c)

In addition to these three methods, it is also possible to cool down a production area (tent, garage, snow tunnel etc) by using liquid nitrogen or electricity such that traditional snowmaking can take place.

Traditional snow production systems 

Description and equipment 

Traditional snow production systems have been around for many years, and work only in specific weather conditions; production can only take place if the wetbulb temperature is ca -2 C or colderWetbulb temperature is a combination of air temperature and humidity

The ratio between injected water and produced snow varies from 1.7 – 2.5 parts snow per 1 part water (1 m3 injected water will produce 1.7 – 2.5 m3 snow), depending on wind, temperature, the quality of the snow (dry or more humid) and other factors

  • It has been shown that between 15 – 40 % of the water that is injected in snow production systems either evaporates, blows off the course/hill or disappears in other ways.

The systems can be both stationary or mobile. Mobile systems may be suited for community venues, small ski jumps or small Cross-Country/Biathlon venues, but are very labour intensive.



Mobile systems are powered by a large generator (usually placed on a trailer or tractor) and have portable pumps and snow fans. In this example the generator on a trailer is moved around in the terrain together with the snow fan. The only external connection needed is water with relatively low pressure (2 – 7 bar). 1 bar is 14.5 PSI. This can come from nearby creeks or municipal water lines.

New snow production systems are normally designed and sold as half-automatic or automatic systems, but we still use the terms manual, half-automatic and automatic systems. 

Manual systems require that the operator must manually start/stop, as well as adjust the pumps and fan guns. The number of nozzles and/or amount of water added to each fan gun must be adjusted manually to produce the best possible snow quality. To achieve a good result, the snow maker must be very skilled. It is labour intensive to operate manual systems, and supervison is needed every 1 – 2 hours both night and day. Since the automation is in the fan gun itself, it is possible to install an automatic fan gun together with other manual ffan guns in a manual system. Manual system are recommended mostly for smaller ski venues, but can also be recommended for sites with cold, stable temperatures and with relatively limited snowmaking needs.

For half-automatic systems some of the adjustments are simplified such that a fast start- and stop procedure can be done for multiple fan guns simultaneously. This is done by pre-installing air and water intakes on the fan guns. The fan guns will start up when the main pump station adds air and water to the pipe system. The disadvantage with this system is that it provides for poor quality control. For a sfan gun it means, for example, that the startup temperature must be adjusted manually while the fan gun itself adjusts the amount of injected water relative to this set temperature. The advantage with a half-automatic system is that it is less expensive than an automatic system and have minimum maintenance. These systems are suitable for larger venues and at sites with little wind and cold conditions.

All larger alpine venues have automatic systems, and these systems are more and more common also in smaller alpine venues and in larger Cross-Country/Biathlon venues. Pumps, compressors og fan guns start and stop based on pre-set values and parameters such as air temprature, humidity, water temperature and the time of day. These systems produce up to 20 – 40 % more snow compared to equivalent manual systems. The fan guns need limited supervision during operation and saves labour. The automation will work with all types of fan guns and snow lances, and the snowmakers can monitor a large number of units from either a PC, web cam or smart phone. The disadvantage with such a system is the high initial cost and that maintenance is complicated.

A snow production system consists of the following elements: 

  • A water source (reservoar, lake, river/creek or municipal water lines)
  • Possibly a cooling tower (if the water is warmer than 3 – 4 degrees Celcius during the snow production period).
    • A cooling tower should be considered if it is known that the water temperature is too high, and is especially useful for snow production in marginal temperatures (will improve the efficiency of the snow fans)
    • Along it way down the tower, the water is circulated through pipes while a strong fan blows cold air over it.  The water will decrease in temperature both due to the contact with the colder air and the cold steel, which cause evaporation (release of heat) from the water droplets.  The colder water is collected at the bottom of the tank and further use in the snowmaking process.
    • If a reservoir is built as part of the snowmaking system, a bubble system can instead or in addition be installed to move water and increase the cooling effect by the air on the surface.  The speed of the pump in the bubble-system regulates the cooling effect (be careful not to cause ice build-up).
    • Cooling towers come in many sizes, can be delivered as a unit or built in place by available components. It is a relatively simple construction
  • If desirable, water additives that are mixed into the snowmaking water through a separate pump, for eksempel Snomax (snomax.com) or Drift (aquatrols.com/drift ), and that in most cases will increase the amount of snow produced
  • A system of pipes and hydrants that distributes water and air to the fan guns and snow lances.
    • Water pipes used for snow making are constructed in galvanized steel or cast iron (steel is also used for air pipes), and must withstand 30 – 80 bar from the high pressure water pumps, depending on the elevation the water needs to be lifted.
      • The pipes should optinmally be buried below freezing level in the ground such that they can be filled with water that is immediatelly available for snowmaking  
      • The pipes can alternatively be buried shallow (or even laid on top of the ground) but must then be drained every time the system is stopped (to avoid freezing). Additionally, each endpoint must be open such that water is always flowing in the pipes.
      • Both methods have pros and cons:
        • Pipes on top of the ground:
          Pros: Lower cost, easy to inspect, can be cooled by cold air, easy to service
          Cons: Looks ugly, often requires extra safety for skiers, needs special anchoring due to the possible jolting when the high pressure water pump starts up
        • Buried pipes:
          Pros: Not visible, less prone to freezing, not in the way of course layouts or grooming
          Cons: Higher investment costs, eventual leaks are difficult to identify, no cooling effect by cold air
    • Hydrants are installed above ground or in pits every 20 – 80 meters around the course or in a few central locations. The fan guns or snow lances are connected to the hydrant with a cam lock using a snowmaking hose (usually 20 meter long). Larger fan guns or snow lances are connected directly to the hydrant without using a hose (or by using a stiff, self-draining hose). Multiple hoses can be connected to each other, with an equally long power cable. 
  • Pumps
    • A separate “feed pump” brings the water from the water source to the high pressure pump that pumps the water out into the pipe system. Depending on the water source, an intermediate cleaning reservoir or tank may be required. It is important to install filters such that dirt- or sand particles do not block the on-boards filters on the fan guns or wear the pumps uneccessary.  
    • A pump house with one or more high pressure pumps must be built solidly with a proper concrete foundation/floor and be insulated to withstand the weight, wet weather, cold temperatures etc.
      •  For snowmaking systems regular sentrifugal pumps are used. These are delivered in different sizes depending on the required capacity. The pumps should be dimentioned concervatively (for possible future expansion).
    • If the water source is located at elevations high above where it is used, the gravity will provide parts of the required water pressure, such that the size and power needs for the pumps can be reduced (or even eliminated in some cases). It can be estimated that a 300 ft difference in elevation will provide almost 10 bar of water pressure when connected by a pipe.
    • Usually the snow production system provider is helpful in calculating the size and number of pumps required for the amount of water and required water pressure.
      • The range of the water pressure for snow lances is 15 – 50 bar
      • The range of the water pressure for fan guns is 8 – 40 bar, depending on the model
      • The required pressure will depend on the elevation change of the pipes
    • Mobile pumps can be delivered in small containers. These are handy when several sites share production units, or when the snowmaking needs are irregular or infrequent.

  • Compressor station
    • An air compressor system for snow lances is based on supply of high pressure air from a centrally located compressor. The capacity of the compressor determines the capacity of the snowmaking system. Compressors are noisy, and it is important that sound-insulation is used in the compressor house.
      • This type of snow production has two pipe systems, one for air and one for water. Other important parts are a condensor and a cooling system for the air. The air must have a pressure of ca. 7 – 8 bar, and the temperature should be 4 – 8 degrees C.
    • There are mainly two types of air compressors used in snow production systems.
      • A piston compressor is often purchased used. The compressor can not be loaded more than 80%.
        • a worn compressor may leak oil
      • A rotary screw compressor is a more modern compressor that can be loaded 100% when operating continuosly. The total capacity can therfore be reduced by 20% compared to a piston compressor
  • Production units
    • Fan gun for systems based on water and electricity, and a single system of pipes
      • Uses water only (has on-board compressor) 
      • Has a large capacity (up to 90 m3 of snow per hour for the largest models) 
      • Can easily be adjusted and angled according to the wind direction 
      • Can “throw” snow up to 80 meters (in piles or “whales” along the hill or course) 
      • Needs electricity 
      • Is relatively expensive (ca. 30 000 EUR per fan gun) 
      • Energy consumption per m3 snow is between 1 – 2 kWh in cold temperatures (colder thaan -8 C) but can be as high as 8 kWh at marginal temperatures
      • Is typically lifted and moved from hydrant to hydrant using the grooming machine’s front blade (is usually pulled by a tractor, truck or ATV for the initial pre-season setup). Is also installed permanently on towers for alpine and ski jumping venues

    • Snow lance for systems based on supply of compressed air from a central compressor and water from a central pump
      • Uses both water and air (which is mixed externally, or internally inside the lance’s head by a nucleator nozzle)  
      • Comes in many sizes, both stationary and portable types
      • Needs two sets of pipes and hydrants for distributing the air and the water
      • Has less capacity than fan guns (see graph below)
      • Can, depending on the model, be adjusted in 1 – 4 (or more) positions according to the wind direction
      • Will normally produce snow in a cone-shaped pile underneath the snow lance, but can throw 10 – 30 meters  
      • Does not need power unless it is part of an automated system 
      • Is reasonably priced (~3 000-5000 EUR)  
      • The energy consumption per m3 snow is between 0.5 – 1 kWh in cold temperatures (below -6 C) but can be as high as 6 kWh in marginal temperatures
      • Is normally installed permanently for alpine and ski jump venues, but portable models are often used for Cross-Country
  • A source of electricity with power for pumps, air compressors, automation and production units
    • The power requirement must be estimated and investigated before planning and establishing a snow production system, including the possibilities and conditions for bringing in and installing transformers. The providers of snow making system production units are usually helpful in determining the required power dimensions.  
    • Manual or non-automated snow lances do not need power, but electricity for fan guns must be installed in cabinets or in pits together with the water hydrants
      • Most of the larger fan guns need 400V 63 A, while smaller models need 400 V 32 A.
    • Power cables for the fan guns must be purchased (especially extra long ones when using multiple hose lengths)
Picture: Norwegian Ski Federation

Production capacity

  • The snow production capacity for a fan gun or a snow lance depends on the wetbulb temperaturecombination of air temprature and humidity – see table below
  • The average wetbulb temperature almost anywhere in the World can be found at the web site Climatemps.com
  • A fan gun or snow lance can produce much more snow at low temperatures and in dry air.  The capacity for a standard fan gun and snow lance relative to the wetbulb temperature is shown below (from Bernhard Vagle, master thesis). The graph shows that the snow production capacity doubles from -7 to -14 degrees C. 

By using information from the mentioned web site, the table and graph above (local wetbulb temperature and capacity for fan gun and snow lance), it is possible to estimate the capacity for snow production anywhere (see example showing how to do this later in this section). 

It is however important to be aware of that local crosswinds and evaporation may reduce the capacity or cause loss. For a narrow Cross-Country course this loss can be as high as 40 – 60%, for a ski jump hill 20 – 40%, and for an alpine slope 10 – 20%.  Evaporation of up to 10% can also happen during very cold temperatures or when very small nozzles are being used. 

Temperature independent snow production

Description

The most cost- and energy efficient snow production technology is still traditional production in cold tempeatures (artificial or man-made snow production will use from 0.5 – 6 kWh energy per cubic meter snow).  It is also quite normal to use shaved ice from hockey- or ice skating arenas to supplement artificial snow during warm temperatures, especially for skiing events in or near cities. 

Because of the climate changes, with fewer cold days and less natural snow in lower elevations, there is an increased interest in technologies that can produce snow or ice in warm temperatures.   This technology is not new; ice has been used for many decades in the fishing- and mining industry as a cooling element. It is today at least 3 – 4 commercial producers of ice/ice-slurry for ski venues, and the technology can be divided into three main systems and products:

  1. “Binary snow” using vacuum technology  
  2. Ice slurry technology 
  3. Flake ice technology 

All the technologies can produce snow or ice in temperatures up to over over +20 degrees Celcius.

Technologies

Vacuum technology 

The vacuum technology produces binary snow by injecting ca. 4 degrees C water into a vacuum chamber. The vacuum effect initiates an evaporation (vacuum evaporation), while the temperature in the rest of the water decreases, such that ice is generated at zero degrees Celcius. 20 % of this is fine ice crystals (binary snow) that is separated after it is pumped into a snow concentrator. The snow is then pushed out while the water is pumped back into the vacuum chamber such that the process can be repeated. Since water is used as the cooling element in the system, it depends on a cooling tower unless water is available from a cold mountain river or mountain lake.  

The vacuum machine can utilize the generated heat, but this is conditional on installing a heat pump that can lift the tempeature to a higher level, as well as run the external cooling tower separately from the snow production.  

Systems using the vacuum technology are installed in Zermatt, Switzerland, Pitzdal, Austria (alpine) and Lago di Tesero in Val Di Fiemme (Cross-Country).

Ice slurry technology 

There are several companies, both in Scandinavia and North-America that can deliver snow that has been separated from ice slurry, and that are using standard cooling technology. 

The technology, in simple terms, consists of a cooling system and an ice-slurry generator (liquid mixture of salt and water). After cooling (takes place by evaporation of a cooling medium) the snow is separated from the rest of the liquid in a snow/ice separator.  This system uses a pump that circulates the liquid. The ice/snow attach to the suraface of plates and is scrapes off by knives.  

A variation of the same technology consists of a rotating system and therefore eliminates the need for pumps, thus reducing the energy consumption by 30%.     

Torsby Ski tunnel, Anglagården ski hall in Sweden, and Kivikko ski hall in Finland uses ice-slurry systems. The system was also used during the 2014 Winter Olympic Games in Sochi on the Nordic Combined courses.

Flake ice technology

Flake ice technology is a standard technology that is used in many known cooling systems, such as production of ice and air conditioning.  Water is cooled by compressed gas or a liquid, ice is created on a surface and is then cut off in small pieces and collected. Many companies are delivering flake-ice systems.  

Geilo, Sjusjøen, Skiforeningen in Oslo, Norway, Idrefjell in Sweden, Lake Placid and North Star in the USA and several veneus in Germany uses flake ice systems.

New technologies

New technologies for temperature independent systems are being developed, using heat pumps, dry ice etc. With optimal water temperatures (as cold as +2 degrees Celcius) also these systems may reduce their energy demand to below 10 kWh per m3 snow.

Comparison of technologies 

Some of the temperature independent systems are using ammonia or freon as cooling elements, while others are using water or nitrogen. Most of them use about 1 – 2 liters/second of water (large vacuum technology machines use up to 6 – 7 liters/second), and the water pressure is between 2 – 5 bar. The table below shows approximate capacity, energy usage, size of the production units and an estimated cost of the system.

Technology Ice or snow Ca. capacity 
(m3 snow per 24 hrs) 
Ca, energy usage (kWh per m3)* Size in meter (l x w x h) Cost (EURO)  
Vacuum Snow 860 7 – 11 30 x 30 x 15 Up to ca. 3.5 mill 
Ice slush Snow 267 22 – 26 20 x 10 x 7 Ca. 1.5 mill 
Ice slush Snow250 18 – 20 20 x 10 x 10 Ca. 0.9 mill 
Flake iceIce 220 29 – 34 30 x 10 x 10 Ca. 0.7 mill 
Flake iceIce 450 29 – 34 40 x 10 x 10 Ca. 1.4 mill 
*is estimated theoretically (John Aalberg)

In addition to the costs listed in the table above, additional costs will likely occure, although those costs are quite similar for all the systems.

  • installing electricity and water
  • preparing a flat and paved surface
  • buildings
  • general operations
  • maintenance (more for those with many mechanical components)
  • distribution of the produced snow (some systems can blow snow up to 200 meters through pipes)

The table shows that vacuum technology is the most effective, both in terms of capacity and energi usage (ca 10 kWh per m3 snow).  The product has higher quality (better snow to ski on) than for example flake ice. But, the technology is an expensive investment and may need a large space and shelter/building.

Ice slurry systems are quite energy demanding (ca 18 – 26 kWh/m3 snow), but the quality of the “snow” is similar to vacuum technology and is better than for flake ice systems. The system is often deliverd as a “plug and play” system (add water and electricity only) and is portable. The technology is still developing, but is used in many locations. 

Flake ice technology has the highest energy consumption per m3 snow/ice (over 30 kWh/m3).  Several companies deliver this technology. The injected water must be clean and from municipal water pipes. The produced ice must be crushedby grooming machines and mixed with natural snow or transformed by precipitation before providing an optimal skiing surface (venues are also exploring different methods). The system is relatively easy to operate, and comes in modular “plug and play” modules (capacity can be doubled by adding two modules together).

Investing in a temperature independent system 

Several questions should be consided before purchasing a temperature independent snow production system.

1. It must first be clarified if the main goal is to be able to promise a fixed, annual opening date for skiing (for example November 15). If this is not important,  the focus should rather be on improving an existing- or installing a traditional snow production system, and optimizing this such that large amount of snow can be produced in a short amount of time during cold temperatures. However, if it is desirable to guarantee early skiing independent of the weather, further clarification and decisions are needed.

2. The next question should be if it is possible or practical to store snow over the summer? It is in most cases cheaper to produce artifical snow (during the winter) and store this (with 15 – 35 % loss) than to produce snow or ice with temperature independent systems in the late summer or early fall. It is however difficult to store snow at low elevations (near sea level) in warm summer temperatures, or might even be impossible due to municipal restrictions inside city limits.

3. If it is not possible to store snow, it should next be clarified if a temperature independent system is locally accepted in today’s political climate discussion. All temperature independent snow- or ice production systems will use much more energy than a traditional cold temperature system (2 – 5 kWh versus 10 – 35 kWh per m³ snow).  

4. It is further important to decide how much snow to produce since this will determine the capacity of the system. For example, a 2 km long Cross-Country course needs minimum ca. 4000 m³ snow (for a ca. 6 meter wide course with ca. 30 cm depth).  A temperature independent system will loose about 10 % snow due to melting, so 4400 m³ should be produced. It is also important that the snow density is suitable, for Cross-Country skiing this should be at 400 – 450 kg/m³. A production system (for example a double module flake ice system) with capacity of 200 m³/24 hrs will need 23 days to produce enough snow (and will use about 100 000 kWh for an approximate electricity cost of NOK 115 00011 000 EURO (depending on the system and price of electricity). 

Decision matrix for considering temperature independent systems:

Is the goal to have a fixed opening date (ca 15. Nov)?
Yes
No
Nullstill matrisen

Using liquid Nitrogen or CO2 

Liguid nitrogen or CO2 is already used for many cooling purposes. It can also be used to cool down a tent such that it becomes suitable for a traditional snow production system – by spraying the liquid nitrogen/CO2 into the air. This may lower the temperature towards – 40 degrees Celcius inside the tent. Water droplets from a regular fan gun will rapidly freeze, and may produce 20 – 30 m3 snow per hour.  

This method was used for the August 2016 X-Games Big Air event at the Tøyen Park, Oslo, Norway (https://polareurope.com/). 

Big Air arena in Oslo where snow was produced in August using liquid nitrogen. This method is not commonly used due to the cost of the nitrogen and the safety aspects