snowmaking

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Snow production at Camelback Ski Area, USA.

Snow making at Mount Hotham, Australia.

Snowmaking is the production of snow by forcing water and pressurized air through a "snow gun" or "snow cannon", on ski slopes. Many people consider this fake snow, as it does not fall from the sky, but it is essentially the same as real snow. Snowmaking is mainly used at ski resorts to supplement natural snow. This allows ski resorts to improve the reliability of their snow cover and to extend their ski seasons. Indoor ski slopes often use snowmaking. They are generally able to do so all year round as they have a climate-controlled environment.

The production of snow requires low temperatures. The threshold temperature for snowmaking decreases as humidity decreases. Snowmaking is an inefficient process in its energy and water use. This makes snow production costly thereby limiting its use to main ski trails.

History

Full blast snow cannon at The Nordic Centre, Canmore, Alberta, Canada

The snow cannon was invented by Art Hunt, Dave Richey and Wayne Pierce in 1950,^{[1] [2]} who went on to patent it.^[3] Snowmaking started to be used on a commercial scale in the early 1970s. Since then, many ski resorts have come to depend on snowmaking.

Snowmaking has become increasingly complex to achieve greater efficiency. Traditionally snowmaking relied on having a skilled snowmaker to operate the equipment. The addition of computer control means that snow making can be controlled with greater precision to ensure that snow guns only operate when conditions make snowmaking possible. However, the process is not fully automatic as computers only supplement human control^{[citation needed]}. Recently, all weather snowmakers have been developed by IDE ^[4].

Operation

If conditions are below the curve snow can be made.

The key considerations in snow production are increasing water and energy efficiency and increasing the environmental window in which snow can be made.

Snowmaking plants require water pumps and air compressors that are both very large and expensive. The production itself requires large amounts of energy (number in kilowatts?). It takes about 220,000 US gallons (815kL) of water to cover an acre to a depth of 1-foot (0.30 m)^{[citation needed]}.

Snowmaking begins with a water supply such as a river or reservoir. Water is pushed up a pipeline on the mountain using very large electric pumps in a pump house. This water is distributed through an intricate series of valves and pipes to any trails that require snowmaking. Many resorts also add a nucleating agent to ensure that as much water as possible freezes and turns into snow. These products are organic or inorganic materials that facilitate the water molecules to form the proper shape to freeze into an ice crystal. The products are non toxic and biodegradable

Pump House & Air Plant Combo

The next step in the snowmaking process is to add air using an air plant. This plant is often a building which contains electric or diesel industrial air compressors the size of a van or truck. Although in some instances air compression is provided using diesel powered portable trailer mounted compressors which can be added to the system.The air is generally cooled and excess moisture is removed before it is sent out of the plant.Some systems even cool the water before it enters the system.This improves the snowmaking process as the less heat in the air and water, the less heat must be dissipated to the atmosphere to freeze the water. From this plant the air travels up a separate pipeline following the same path as the water pipeline.

Infrastructure

Piping Diagram

The pipes following the trails are equipped with shelters containing hydrants, electrical power and optionally communication lines mounted. Whereas shelters for fan guns require only water, power and maybe communication, lance-shelters usually need air hydrants as well. Hybrid shelters allow maximum flexibility to connect each snow machine type as they have all supplies available. The typical distance for lance shelters is ~100-150 ft., for fan guns ~250-300 ft. From these hydrants 1 1/2"–2" pressure resistant hoses are connected similar to fire hoses with camlocks to the snow machine.

Snowmaking guns

Rear view of snow cannon at Mölltaler Gletscher, Austria, showing the powerful fan.

There are many different forms of snowmaking guns, however they all share the basic principle of combining air and water to form snow. For most guns you can change the type or "quality" of snow by regulating the amount of water you are adding to the mixture. For others they are simply on or off and the snow quality is determined by the air temperature and humidity.

In general there are three types of snowmaking guns: Internal Mixing, External Mixing and Fan Guns. These come in two main styles of makers: air water guns and fan guns.

An air water gun can be mounted on a tower or on a stand on the ground. It uses higher pressure water and air, while a fan gun uses a powerful axial fan to propel the water jet to a great distance.

A modern snow fan usually consists of one or more rings of nozzles which inject water into the fan air stream. A separate nozzle or small group of nozzles is fed with a mix of water and compressed air and produces the nucleation points for the snow crystals. The small droplets of water and the tiny ice crystals are then mixed and propelled out by a powerful fan, after which they further cool through evaporation in the surrounding air when they fall to the ground. The crystals of ice act as seeds to make the water droplets freeze at 0 °C (32 °F). Without these crystals water would supercool instead of freezing. This method can produce snow when the wet-bulb temperature of the air is as high as -2 °C (28.4 °F). The lower the air temperature is, the more and the better snow a cannon can make. This is the main reason snow cannons are usually operated in the night. The mix of all water and air streams and their relative pressures is crucial to the amount of snow made and its quality.

Modern snow cannons are fully computerized and can operate autonomously or be remotely controlled from a central location. Operational parameters are: starting and stopping time, quality of snow, max. wet-bulb temperature in which to operate, max. windspeed, horizontal and vertical orientation, sweeping angle to cover a wider area, sweeping may follow wind direction.

• Internal mixing guns have a chamber where the water and air get mixed together and violently forced out an opening or through holes and fall to the ground as snow. These guns are typically low to the ground on a frame or tripod and require a lot of air to compensate for the short hang time of the water. Some newer guns are built in a tower form and use much less air because of the increased hang time. The amount of water flow determines the type of snow that is to be made and is controlled by an adjustable water hydrant.

• External mixing guns have nozzles spraying water and air nozzles shooting air through the water stream to break it up into much smaller water particles. These guns are sometimes equipped with a set of internal mixing nozzles that are known a nucleators. These help create a nucleus for the water droplets to bond to. External mixing guns are typically tower guns and rely on a longer hang time to freeze the snow. This allows them to use much less air. External mixing guns are usually reliant on high water pressure to operate correctly so the water supply is opened completely and the flow can sometimes be regulated by valves on the gun.

• Fan Guns are much different than all other guns because they require electricity to power a fan and small compressor. The fans propel the water into the air to achieve the hang time and the compressor creates the air needed to operate the nucleator nozzles that are similar to the ones on the external mixing guns. The compressor also allows this gun to operate in an area that has no supply of air from an air plant. Fan guns have anywhere from 12 to 150 water nozzles on a ring that the fan blows through on the front of the gun. These nozzles are usually heated and are arranged in sets or banks. These banks can be shut on or off by valves. The valves are either manual, manual electric, or automatic electric (controlled by a computer).

Home Snowmaking

The same technology used to make snow at ski resorts is now available to the average homeowner looking to make snow at home. Using a smaller version of the snow machines found at ski resorts, home snowmakers are scaled down to run off household size air and water supplies.

A home snowmaker can receive its water supply from either a garden hose or pressure washer/high pressure pump. Home snowguns that receive water from a garden hose make much less snow per hour compared to snowguns that receive water from a pressure washer. This is because designs that use a pressure washer have multiple nozzles with higher flow rate nozzles to create more snow per hour. There are many home snowmaking companies that have snowmaking equipment available for homeowners looking to make their own snow. In addition to snowmakers available for purchase, there are many sites online that offer plans to build your own home snowmaking machine out of plumbing fittings and special nozzles.

Volumes of snow output by home snow makers vary depending on certain air/water mixtures, temperature, wind variations, pumping capacity, water supply, air supply, and other factors. Some snow enthusiasts have spent thousands of dollars to fully automate their own snow systems and design new forms of snowguns based on their needs.

See also

Wikimedia Commons has media related to: Snow cannon

• Artificial ski slopes
• Snow grooming
• Kern arc - one of optical displays caused by snowgun ice crystal clouds
• Air cannon

References