Granite Geek: The Science Behind Snowmaking

Nov 25, 2014

David Brooks says nearly all of New Hampshire ski areas use snowmaking machines, such as fan guns, to ensure the slopes are ready for skiers all winter long.
Credit Leo-setä via Flickr/CC - http://ow.ly/ETla1

Mother Nature looks ready to unleash some snow on New Hampshire ahead of Thanksgiving. That's not great news for travelers, but it would be good news for New Hampshire ski areas - though, of course, they already have the technology to make their own snow no matter what’s coming down from the sky.

David Brooks writes the weekly Granite Geek science column for the Nashua Telegraph and Granite Geek.org. He’s been looking into the snowmaking process, and he joined All Things Considered with some of what he found.

Ski areas cover a fair bit of ground – how much effort does it take to make enough snow for a day on the slopes?

I'm a skier - I've skied through, occasionally, as the fan guns are blowing, but I didn't realize quite how much it was until I talked to Pats Peak. Over the course of an entire season they can use as much as 50 million gallons of water to make snow, which is amazing. Pats is not a huge mountain by any means - we're not talking about Cannon Mountain, or Sunday River, or Killington, or some of those monster places. And that's a whole lot of water.

And what exactly do those fan guns do?

You make snow, basically, by throwing water into the air when it's cold, and the water crystallizes. Obviously it's much more complicated than that - getting the air and water mix seems to be the most important thing, and that is dependent on the conditions outside, what they call the wet bulb temperature, a mix of the air temperature and the humidity.

There are the sticks, that spray out over the run - they require a lot of energy because you have to spray the water out with compressed air. The gold standard these days is the fan gun, which most anybody who skis has seen. They look like a mid-size turbine, usually up on a pole. They are energy-efficient because they don't require compressed air to shoot the water out into the air, they just shoot it out with a fan. Basically the fan turns and sucks up the water and spits it out into the air, and it freezes and falls down to Earth.

What's the sweet spot - when is it too warm, or even too cold, to put a good pack of snow down?

I was told by Kris Blomback, the general manager at Pats, that 29 degrees wet bulb temperature is the maximum you can be. The drier it is the better, so the less humidity is in the air, the water turns into the crystals you want at a higher temperature, whereas if it's really moist, the temperature has to be lower.

The lower the temperature the better, in general. It freezes faster and you produce more snow from a given volume of water and air. YOu don't use as much electricity and as much water to make the snow. You get down to 10 degrees, single digits, even down to zero, they're still good in theory, but what happens, he says, is then you have to worry about the water freezing in all the pipes, because obviously there are pipes crawling all over the mountain to take the water up to these guns. If it ever freezes in one of them, you're in trouble.

Snowmaking is becoming increasingly important for these ski areas, as the amount of natural snow coming down is not necessarily as predictable as it used to be.

Pretty much any mountain, any ski area bigger than a little tiny one, has 100 percent snowmaking these days. And the question now is, how good is your snowmaking? How fast can you make snow? So if there's a melt and a rain-off - rain is really the big problem. You get warm weather and rain, and that really can wipe out snow on the ground quickly. You need probably a couple of feet to handle most skiers.

The other thing they're fighting over now is electricity costs, which, as we know, are not low in New England and New Hampshire, and are getting higher this winter. They're trying to find more efficient ways to make snow - that's where fan guns and other equipment can help out.

If the snowmaking machines are up and about, and there's even some natural snow coming down across the state, are you just up the next morning with your equipment?

I'm not quite that frenzied - I'm not one of those people who lives to ski, partly because I'm pretty incompetent. But I definitely go about a half a dozen times a year at the minimum. One of the things you like about living here is that I can get to Pats, [to get] across it in literally half an hour. So I can go skiing in the morning and still make it back in time for the dump run.

That's New Hampshire defined right there.

You betcha, buddy.