January 18, 2010
It's 6 a.m. On top of Wintergreen Mountain -- about 3,500 feet up -- the temperature reads 15 degrees.
One sound fills the air -- Wintergreen's $6 million computerized snowmaking system. It's one of the world's most sophisticated, and it all starts with water and air.
"It's pretty cold out here this morning, so it's running 30 to 40 gallons a minute, making really nice snow," said Scott Gunnell, Wintergreen's slope services manager.
Inside the compressor building, the heart of the snowmaking system, ambient air is compressed and cooled to around 55 degrees. At the same time, seven pumps move water from a lake at the base of the mountain to the slopes.
"The water pressure starts out at about 600psi down here," Gunnell said. "Up top, it's about 250, and down the bottom, it's almost 1,000."
About 40,000 feet of pipeline take the water and compressed air to the more than 400 snowguns along the slopes. The water and air travel separately until they are forced together in the last few inches of the snowgun. Then, high school chemistry takes over.
"Boyle's Law says as it rapidly expands, the temperature drops dramatically," Gunnell said. "In fact, it goes way below zero just outside the gun."
The cold air supercools the water and crystallizes it, almost instantly forming snow.
"[Snow is] the one thing you can't buy," Gunnell said. "Mother Nature -- while this year she's helped us a lot -- sometimes she's not such a big fan of ski areas in the South. But all we need is cold air, a little compressed air and water, and we can make it happen."