For the first time I spent Christmas in the Alps; the plan was a week of skiing but it turned out to be rather warm. So although we skied, often it was on artificial snow…. which got me thinking about snow cannons and how they work. From a bit of reading around, most snow guns/cannons/lances need three things: water, electricity and air. However, just spraying water in the air will not necessarily result in snow, the water needs to fall a long way (or it must be very cold) in order for it to freeze. Instead, many snow machines push the water and compressed air through nozzles to create fine droplets. Compressing the air creates particulates which act as a nucleation site for small icy crystals to form. These ice crystals are then combined with a second stream of fine water droplets; as the air expands it cools the water and it also atomises it; all of which make it easier for the water to freeze and form snow as it falls to the ground. A lower air temperature allows the manufacture of more snow, so night time operation is often preferential and comes with the added bonus that there are less people about to soak! The final result might be a bit icy, but after some piste bashing, you end up with snow to ski on. So I just need a cold night, modified garden hose and some compressed air to create my own winter wonderland…..
On a side note: During our holiday I was very grateful for the hard work of the resort staff and the snow cannons, without them my skis may have stayed in the boot room. However, whilst I was messing around in the (partially artificial) snow covered mountain, the resort was facing criticism for using (allegedly) 200 trucks to move snow for a World Championship competition. According to Wikipedia, it takes 1 – 2 kWh/m³ for fan guns to make artificial snow, typically with an end snow density of 450 kg/m³. For comparison I checked out some standard kitchen appliances: A++ fridge uses 0.02 kW/h, a microwave 0.95 kW/h and the dishwasher 1.07 kW/h (ref: http://www.t2c.org.uk/saving-energy/electricity-usage/). The huge Three Valleys ski resort has 2100 snow cannons. My conclusion, snow making – although great for the resort – comes at a fairly significant energy cost.