The science behind snowmaking
October 7, 2012
It is every ski town’s worst nightmare: A winter with no snow. Not only do locals and visitors get grumpy, the local economy suffers. Luckily snowmaking science has equipped local ski areas with the ability to keep mountains covered with fresh snow throughout the season.
The science behind snowmaking though brings many factors into play, but snowmaking officials base their operations mostly on temperature and humidity, a combination that provides them with a “wet-bulb temperature.”
“The drier the air, the more likely it is to be cooler,” said Mike Looney, snowmaking manager for Copper Mountain Resort. “We start at about a 28 degree wet-bulb temperature – that can be anywhere from 28 degrees and 100 percent humidity or as much as 35 degrees and 10 to 20 percent humidity.”
“The drier the air is. The more apt the water molecules are to freezing,” Looney said.
“Our best temperatures are about 10 to 15 degrees all wet-bulb driven. Anytime it gets colder than that everything starts freezing up and its a lot harder to work,” he said. “At 10 degrees you can really move a lot of water, make a lot of snow and still maintain the equipment from freezing.”
The ideal conditions for snowmaking fall between a wet-bulb temperature of 10 and 20 degrees with consistent winds of approximately 10 miles per hour, according to Looney.
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“There’s a chart that we use – there are multiple wet-bulb charts out there that give you 30 degrees through zero with 10 percent through 90 – it gives you a grid style chart,” he said.
The formula for the wet-bulb temperature is based on humidity and temperature. Temperatures vary as humidity increases or decreases but typically it’s about one degree per 10 percent humidity, Looney said.
Copper Mountain uses water from Ten Mile and West Ten Mile Creeks for its snowmaking operations. The naturally cold water is ideal for sustaining operations through the season, Looney says.
“It is relatively cold to begin with,” he said. “We’re lucky to be pulling water from a high-quality alpine source, the value of the water definitely comes out in our snowmaking product.”
As the water is cooled and comes out of snowmaking guns, the compression of the water paired with compressed air creates a smaller water molecule that freezes as it’s expelled from the nozzle.
Looney uses this example to describe the effect:
“Have you ever cleaned your keyboard with the compressed air and realized how cold that feels? That is the rabid expansion of the air. Water goes blasting out of a hydrant and as it expands it will physically frost the end of the hydrant because of that expansion that occurs.
Rapid expansion also creates the snowmaking properties of the water in the air mix. When the water reacts with the compression, it turns into a smaller molecule with a better chance of freezing once contacting outside temperatures.
Copper Mountain’s snowmaking product includes an additive called SnowMax made up of live cultures that serve as an ingredient for the water to cling onto.
“That additive gives the water something to stick to, it creates the nucleus to allow it to freeze easier,” Looney explained.
The rate of snowmaking is also reliant on outside temperatures. Snow guns in peak conditions for snowmaking can transform upwards of 2000-3000 gallons of water per minute into man-made snow.
Whether the ski season experiences a heavy snow year or a light snow year, like last year that caused a 12 percent decrease in profits at local ski resorts, snowmaking is an integral part of sustaining an attractive and suitable mountain for recreation.
“We make snow until about mid- to late December,” Looney said. “Even with a great snow year we still make snow because it can dry up and not snow again and you still have to have that base layer. Sometimes we make more, sometimes we make less, but we rely heavily on natural snowfall as well.”
A short explanation to that would be natural snow is better than man-made snow but, with snowmaking technology, ski resorts are getting closer to making a product comparable to Mother Nature’s.
“Man-made snow is getting way better with technology,” Looney said. “Our snowmaking crews are extremely conscientious about the product we put out. They are constantly checking the snow while the guns are running and if it’s too dense, too wet or too heavy, they make adjustments.”
Education has become a part of training new snowmaking crew members.
“We’re very adamant about teaching the crews snow science and how to create the best product that will last the longest period of time,” Looney said.
Man-made snow though, has an initial density that is already a heavier product than natural snow because of the size of the water molecule.
“Man-made snow its already a smaller particle and it can quickly pack into a pretty dense product, even right out of the gun,” Looney said. “There’s not much room for air and lightness to the product because of its molecule size.”