-30 is Awesome! (for making snow, that is…)Posted: December 19, 2008
The World Cup and NORAM racers and crews have packed up and left, and now that the course has been cleared, snowmaking has begun in earnest for the soon-to-be permanent home of Lake Louise’s terrain park on Easy St. And, as scary as the recent cold temperatures have been, they have allowed snowmaking in the park to progress quickly, and large whales (mounds of new man-made snow) are popping up overnight.
An incredible amount of snow is required to build a park, and now that jumps are being re-introduced, the amount required has shot up even more. It’s fortunate that we have snowmaking equipment that is able to perform well in these frigid temperatures, and no time is wasted making as much as we can as quickly as possible.
The observant skier will have noticed that Lake Louise employs a few different types of snow guns, from the squat and noisy air/water guns to the large and quieter fan guns. Each gun has its own optimal operating environment, and these cold temperatures are perfect for some guns, less so for others. All guns use a mixture of air and water, and while all water is supplied to guns via in-ground pipes and above-ground hoses, the air is supplied differently depending on the gun – fan guns use their fans to propel ambient air through the gun, and all other guns use air supplied just as the water is, through pipes and hoses.
Air serves two purposes in the making of snow – it atomizes the water into tiny droplets that freeze into flakes, and propels the droplets into the air so that they have more time to freeze before they hit the ground. Fan guns are an exception to this, as they only use air to propel the droplets – the atomization of the water occurs as the water exits the many tiny nozzles that ring the output end of the gun. Fan guns require electricity to turn the fans, so you’ll always see an electrical cable alongside the hose supplying the water. All other guns use pressure in the air and water systems and therefore do not need power, and these guns always have two hoses running between them and the pairs of hydrants supplying them. The photos below show a fan gun and an air/water gun at work in the terrain park:
One of the great things about using high-pressure air/water guns is that it is theoretically possible to make snow when the temperature is above freezing, though in practice it can be difficult to get good quality snow, so you won’t see this happen often. This is a result of the complicated relationship between temperature and humidity, with humid conditions making it more difficult to produce snow at warmer temperatures.
Additional cooling can be provided by the energy released when the compressed air returns to ambient pressure. If you remember your high-school physics, temperature is directly related to pressure, and a substance will decrease in temperature as the pressure is decreased. So, when compressed air exits the nozzle of a gun and returns to ambient pressure, some of the heat energy is transformed into kinetic energy which propels the water vapour skyward, and the release of heat energy quickly cools the water vapour as well.
In order to achieve good quality manmade snow, all guns must receive the right mixture of air and water, and the correct mixture can depend on up to twenty-two factors; things like supply air temperature, supply water pressure, ambient air humidity, angle and duration of sunlight, type of gun, and terrain characteristics. The snowmaker will perform the tried-and-true sleeve test, where they stand in the fallout area and let the snow land on their sleeve. If it bounces off it’s dry, and if it sticks it’s wet. The snowmaker can then adjust the air/water mixture to achieve the desired type of snow.
There are all sorts of facts and figures that illustrate the scope of Lake Louise’s snowmaking system, but if there’s one fact that best sums it up, it’s that we can convert 2600 gallons of water per minute into snow – enough to cover a football field, including end zones, with 1.56 feet of snow in one hour! The amount of snow we aim to make in any given area varies; we’ll make more on high-traffic runs on the lower mountain to ensure they last well into spring, when otherwise all snow would have melted away long before we closed for the season. We’ll also make lots where the terrain is uneven in order to make a smoother run.