Description of how snow is made
Want to learn the basics of how snow is made? Read on for a lesson in Snowmaking 101.
Marti Mayne, 207-846-6331;
Snowmaking technology allows ski resorts to extend the natural ski season as well as add to the naturally occurring snow all season long. With snowmaking systems, resorts can make the snow fall even when it's sunny. And often times when it's raining down in the valleys and cities, resorts are busy making snow at elevation. Here's how it works.
Essentially, snow is small particles of ice. So, the really old way of making snow, and the way they still do in the tropics and for special events, is to grind up blocks of ice. However, this is very expensive and labor intensive for larger scale requirements, so, if possible, machines that convert water into snow directly and on site are used.
These snowmaking machines make snow by breaking water into small particles, cooling the water by causing them to move through cold air, nucleating the water particles and distributing the resulting snow on a surface. Why don't people just sprinkle water to make snow? Water is a unique material, it expands when it freezes and it has high heat of fusion, thus your ice cubes float and last a long time.Heat of fusion means that one can cool a pound of water say from 65°F (18.3°C) to 64°F (17.8°C) or 34°F (1.1°C) to 33°F (.6°C) by removing 1 BTU. But to convert one pound of liquid water at 32°F (0°C) from a liquid to one pound of ice at 32°F (0°C) requires the removal of 144 BTUs. In summary, a large amount of heat removal (cooling) is required in snowmaking. Also, water can be cooled well below 32°F (0°C) and still stay a liquid unless it is nucleated. This phenomenon is called supercooling.
So a snowmaking machine (a) breaks the water into small particles, (b) cools the water to 32°F (0°C), (c) removes the heat of fusion, and (d) nucleates. Snowmaking requires relatively large quantities of water, for example, to cover an area of 200 feet (61 meters) by 200 feet (61 meters) with 6 inches (15 centimeters) of snow, one would need 20,000 cubic feet (566 cubic meters) of snow or 1,000 cubic feet -(283 cubic meters) of water. This is 82,000 gallons (310,000 liters) of water or 11 truck tankers full. Thus, an excellent water supply is needed and the water pressure should be at least 100 PSI (pounds per square inch) (7 Bar) or 230 feet TDH (total dynamic head).
Many ski areas can convert over 5,000 gallons (18,900 liters) per minute of water into snow. This is 20 tons per minute or 1,250 tons per hour. Or stated another way, a truckload every minute. Snowmaking, while usually used at ski areas, is also used for frost protection on construction projects, freeze protection of crops, automotive and aircraft testing, and sewage disposal. There are over thirty snowmaking companies around the world.
Source: SMI Snowmakers / http://www.snowmakers.com/