Wednesday, December 27, 2017

The Cold Facts: Snowmaking

Frigid temperatures, pressurized air, and lots of water; all the things needed to produce snow when the weather is not cooperating. By forcing water and pressurized air through a "snow gun," or "snow cannon", ski slopes locally and around the world can be covered by man-made snow. Snowmaking is mainly used at ski resorts to supplement natural snow. This allows them to improve snow coverage on certain trails and to extend their season from late autumn to early spring.

The production of snow requires freezing temperatures. Wet bulb temperature (the lowest temperature that can be achieved by evaporative cooling of a water-wetted or even ice-covered, ventilated surface) is used as the standard since it takes air temperature and relative humidity into account. Some limitations do apply. Snowmaking is a relatively expensive process in its energy use, also water is in great demand and is usually pulled from run-off ponds. In drought years, it is not unusual to run out of water before the real snow arrives.

Snowmaking Invented

Art Hunt, Dave Richey, and Wayne Pierce invented the snow cannon in 1950. Wayne Pierce was a ski manufacturer in the 1940s, along with his two partners, Art Hunt and Dave Richey. All three formed the Tey Manufacturing Company of Milford, Connecticut in 1947 and sold a new ski design—an aluminum metal ski with a hollow interior and three layers of metal bonded together. Two years later, the company was hit hard by a winter without snow, which caused an obvious slump in ski sales.

With such a major problem at hand, Wayne Pierce came up with a solution. On March 14, 1950, he arrived at work and exclaimed, "I know how to make snow!". He had the idea to blow water droplets through freezing air, causing the water to turn into snowflakes. Using a paint spray compressor, a nozzle and some garden hose, Pierce, and his partners invented the machine that made snow.

In 1952, Mohawk Mountain Ski Area in Connecticut became the first in the world to use man-made snow by implementing Tey Manufacturing’s invention. The company didn’t make snow for long, however. The three partners sold Tey Manufacturing and the snowmaking machine's patent rights to the Emhart Corporation in 1956.

Today’s Machines

Since 1952, research and development of snowmaking technology have provided great strides in the industry. These are the machines in use today.

Internal mixing guns. Water and air are mixed together in a chamber and forced through jets into the air, descending as snow. These guns are typically low to the ground, on a stand and require a lot of air to compensate for the short time the water is airborne. Some newer versions are taller and use much less air because of the increased time to the ground. The amount of water flow determines the type of snow that is to be made and is controlled by an adjustable water valve.

External mixing guns spray water from a nozzle as a stream while other nozzles shoot air through the water stream to break it up into water particles. Internal nucleators help create a nucleus for the water droplets to bond to as they freeze. External mixing guns typically rely on a longer hang time to freeze the snow. This allows for much less air use. High water pressure is a necessity to operate this machinery correctly, so the water supply is opened completely, though in some the flow can be regulated by valves on the gun.

Fan Guns are different from all other snowmaking guns because they require a power supply to engage a fan as well as an onboard air compressor. Compressed air and water are forced out of the gun's drum through an array of nozzles (there are several different arrangements). Fan guns have anywhere from 12 to 360 water nozzles on a ring on the front of the gun's drum. The fan blows air through the drum to create a mist, which then crystalizes from its long hang time, due to the force of the fan. 

Snow Lances can be up to 12 meters long and are vertically inclined aluminum tubes. At the head of each lance is placed a water and/or air nucleator. Air is blown into the atomized water at the outlet from the water nozzle. The compressed air expands and cools, creating ice nuclei on which crystallization of the atomized water takes place. Due to height and the slow rate of descent, there is enough time to complete crystallization. This process uses less energy than a fan gun but has a smaller range and lower snow quality.

Snowmaking has achieved greater efficiency with increasing complexity. Traditionally, snowmaking quality depended upon the skill of the equipment operator. Today, computer control helps optimize that skill with greater precision, such that a snow gun only operates when snowmaking conditions are optimal.

Editor’s Note: At this writing, we are still looking for Mother Nature’s great holiday snow dump, and are total believers that we will be enjoying it by the time this article is in print!

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