Snowmaking is the production of snow by forcing water and pressurized air through a "snow gun", also known as a "snow cannon". 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 from late autumn to early spring. Indoor ski slopes use snowmaking. They can generally do so year-round as they have climate-controlled environments. The use of snowmaking machines has become more common as changing weather patterns and the popularity of indoor ski resorts create a demand for snow beyond that which is provided by nature. Snowmaking machines have addressed the shortage in the supply of snow; however, there are significant environmental costs associated with the artificial production of snow. According to the European Environment Agency, the length of snow seasons in the northern hemisphere has decreased by five days each decade since the 1970s, thus increasing the demand for the production of artificial snow. Some ski resorts use artificial snow to extend their ski seasons and augment natural snowfall; however, there are some resorts that rely almost entirely upon artificial snow production. Artificial snow was used extensively at the 2014 Winter Olympics in Sochi, the 2018 Winter Olympics in Pyeongchang and the 2022 Winter Olympics in Beijing to supplement natural snowfall and provide the best possible conditions for competition. 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. The bulb temperature is always below the outside temperature. The damper the air, the less moisture it can absorb. The higher the atmospheric humidity, the colder it must be to turn the small water droplets into snow crystals. Examples:
0 °C (32 °F) dry temperature and a humidity of 90% are equal to a wet-bulb temperature of −0.6 °C (30.9 °F) 0 °C (32 °F) dry temperature and a humidity of 30% are equal to a wet-bulb temperature of −4.3 °C (24.3 °F) +2.0 °C (35.6 °F) dry temperature and a humidity of 90% are equal to a wet-bulb temperature of +1.5 °C (34.7 °F) +2.0 °C (35.6 °F) dry temperature and a humidity of 30% are equal to a wet-bulb temperature of −2.8 °C (27.0 °F) To start a snowmaking system, a wet-bulb temperature of −2.5 °C (27.5 °F) is required. If the atmospheric humidity is very low, this level can be reached at temperatures slightly above 0 °C (32 °F), but if the air humidity is high, colder temperatures are required. Temperatures around freezing point are referred to as borderline temperatures or limit temperatures. If the wet-bulb temperature drops, more snow can be produced faster and more efficiently. Snowmaking is an energy-intense process, and has environmental impacts, both of which inherently limit its use.
History
The first artificial snowflake was created by Ukichiro Nakaya in 1936, three years after his first attempt. Americans Art Hunt, Dave Richey, and Wayne Pierce invented the snow cannon in 1950, but secured a patent sometime later. In 1952, Grossinger's Catskill Resort Hotel became the first in the world to use artificial snow. Snowmaking began to be used extensively in the early 1970s. Many ski resorts depend heavily upon snowmaking. Snowmaking has achieved greater efficiency with increasing complexity. Traditionally, snowmaking quality depended upon the skill of the equipment operator. Today, computer control supplements that skill with greater precision, such that a snow gun operates only when snowmaking is optimal.
Operation
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 sometimes air compressors when using lances – that are both large and expensive. The energy required to make artificial snow is about 0.6–0.7 kW h/m3 for lances and 1–2 kW h/m3 for fan guns. The density of artificial snow is between 400 and 500 kg/m3 and the water consumption for producing snow is roughly equal to that number. Snowmaking begins with a water supply such as a river or reservoir. Water is pumped 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. Most 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. However, 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.
Ice nucleation-active proteins 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.
Infrastructure
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