Snowmaking is the production of snow by forcing water and pressurized air through a "snow gun" or "snow cannon", on ski slopes. 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 increases as humidity decreases. Wet bulb temperature is used as a metric since it takes air temperature and relative humidity into account. Snowmaking is a relatively expensive process in its energy use; thereby limiting its use.
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The snow cannon was invented by Art Hunt, Dave Richey and Wayne Pierce in 1950,[1][2] who went on to patent it.[3] In 1952, Grossinger's Catskill Resort Hotel earned a place in the history of skiing as the first in the world to use artificial snow.[4] 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, so as 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. Recently, all weather snowmakers have been developed by IDE.[5]
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. It takes about 200,000 US gallons (757kL) of water to cover an acre to a depth of 1-foot (0.30 m).
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 ice crystals. The products are non-toxic and biodegradable.
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. Many fan-type snow guns have on-board electric air compressors, which allows for cheaper, and more compact operation. A ski area may have the required high-output water pumps, but not an air pump. Onboard compressors are cheaper and easier than having a dedicated pumping house. 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.
The water is sometimes mixed with ina (ice nucleation-active) proteins from the bacterium Pseudomonas syringae. These proteins serve as effective nuclei to initiate the formation of ice crystals at relatively high temperatures, so that the droplets will turn into ice before falling to the ground. The bacterium itself uses these ina proteins in order to injure plants.[6]
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 11⁄2"–2" pressure resistant hoses are connected similar to fire hoses with camlocks to the snow machine.
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.
Smaller versions of the snow machines found at ski resorts exist, scaled down to run off household size air and water supplies. Home snowmakers receive their water supply either from a garden hose or from a pressure washer, which makes more snow per hour. Plans also exist for do-it-yourself snowmaking machines made out of plumbing fittings and special nozzles.
Volumes of snow output by home snowmakers depend on the air/water mixture, temperature, wind variations, pumping capacity, water supply, air supply, and other factors.