 Poster: A snowHead
|
The webcam on: www.valthorens.com is showing snow but its manmade, they must be testing the snow cannons I guess.
If they keep it up should be ok for EOSB 
|
|
|
|
|
|
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
|
Don't worry mate, there'll be plenty of the white stuff by the time we get there 
|
|
|
|
|
|
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
|
|
|
|
You need to Login to know who's really who.
You need to Login to know who's really who.
|
|
It's very, very early days, of course, and I don't want to tempt fate, but it may look already like a repeat of the last few seasons. We are seeing some early snow in Austria and the Pyrenees, but the French Alps are looking relatively dry.
|
|
|
|
|
|
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
|
|
On no its that time of year again
|
|
|
|
|
|
You'll need to Register first of course.
You'll need to Register first of course.
|
Forgive me if I'm wrong, but snow cannons just spray droplets of water into the air, which then due to the temperature fall as ice/snow.
So that said it must be cold enough for snow to fall when it arrives.
When I was in Soll, Austria in March they were taking the snow cannons away, they said they would not work due to the air temp is too high and the
spray would just fall as rain/water.
Hopefully this is just something they do to test they are working.
|
|
|
|
|
|
brian
brian
Guest
|
|
blytht, what makes you think they're just testing and not actually trying to lay down a base ?
|
|
|
|
|
|
|
|
|
blytht, IIRC if the RH is low enough, then snow cannons can work at temperatures higher than 0C, which is the temperature traditionally associated with snow making.
|
|
|
|
|
|
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
|
|
The weather gauges at Val Thorens are currently showing temperatures ranging from 6.5C to -13C...
|
|
|
|
|
|
|
|
| skanky wrote: |
| blytht, IIRC if the RH is low enough, then snow cannons can work at temperatures higher than 0C, which is the temperature traditionally associated with snow making. |
Umm they can? Normally temperatures need to be well below freezing.
|
|
|
|
|
|
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
|
|
davidof, I don't have time to look it up, but my recollection was that they partially rely on evaporation cooling to help freeze the droplets. If the rh is low enough (a simplified explanation), then the evaporation can be high enough to freeze the droplets even if it's a bit warmer. This is the same way that rainfall can turn to snow as it cools the air. It requires some very defined circumstances. However, I did read about this a couple of years ago and haven't looked into it since so reader beware.
|
|
|
|
|
|
And love to help out and answer questions and of course, read each other's snow reports.
And love to help out and answer questions and of course, read each other's snow reports.
|
brian, Do you think they would use Snow cannons to lay a base? Or should I say do they use snow cannons to lay a base?
Seems hell of a lot of energy to do natures work.
|
|
|
|
|
|
|
|
|
I wouldn't be surprised if they're trying to build a base - they're due to open in just over two weeks (Nov 18th). Last year they had only artificial snow when they opened. Mind you, they seemed capable of building a piste in just a few days.
|
|
|
|
|
|
You know it makes sense.
|
Val Thorens and Val d'Isere are both blasting a base, so they can be among the first to open at end-November. They did the same last year, leaving a crest-whitestrip on a brown mountain!
It is not uncommon for canons to blast manmade snow at temps slightly above 0c, as long as the humidity is at a suitable level. Compressed air, and perhaps chemical additives, chill the water to the point where it is crystallized upon exiting the nozzle.
Separately, I believe at least one company has recently invented a prototype gun that will make artificial snow at temps well into the 10c to 20c range. Compressed air and chemical additives seem to be the technology behind it.
|
|
|
|
|
|
Otherwise you'll just go on seeing the one name:
Otherwise you'll just go on seeing the one name:
|
Whitegold, picture of VT's Plein Sud piste on opening day last year - as you described:
|
|
|
|
|
|
Poster: A snowHead
|
|
Sorry I don't know how to do quotes but all Precipitation actually starts as snow its only as it defrosts moving down towards the ground it defrosts and becomes horrible rain !
|
|
|
|
|
|
Obviously A snowHead isn't a real person
Obviously A snowHead isn't a real person
|
skanky, there are two types of snow cannon, the ones which appear to be a simple pole and the ones with a fan. The fan type cool the water by evaporation only. The other type have a compressed air supply which gives additional cooling as the air expands from a nozzle.
I'd expect the compressed type to be able to operate at higher temperatures but don't take this as fact I'm no expert on this.
|
|
|
|
|
|
Well, the person's real but it's just a made up name, see?
Well, the person's real but it's just a made up name, see?
|
|
Yes, as I understand it, compressed air works best today. Compressed air freezes the water droplets at point of exit, while chemical additives retard the flake's thaw as it falls to the ground.
|
|
|
|
|
|
You need to Login to know who's really who.
You need to Login to know who's really who.
|
|
|
|
Anyway, snowHeads is much more fun if you do.
Anyway, snowHeads is much more fun if you do.
|
|
Yes, as I understand it, compressed air works best today. Compressed air freezes the water droplets at point of exit, while chemical additives retard the flake's thaw as it falls to the ground.
|
|
|
|
|
|
You'll need to Register first of course.
You'll need to Register first of course.
|
|
High temperature snow-making does seem to be possible according to this article.
|
|
|
|
|
|
|
|
I spoke to a number of manufacturers at the SAM event in Grenoble in April. They tell me you need temperatures of -2C to -4C to make snow if you are not relying on a prefreezing unit . For example the very widely deployed Borax guns which use compressed air need a wet bulb air temperature[1] of -2C in order to work even with Snomax.
One problem is that mountain water is heavily ionized and this affects the freezing point, at least for water droplets. Without additiives you may need temperatures in the -8C to -15C to make snow as the water has to lose a lot of energy in order to turn from a water droplet to an ice crystal on its short trip to the ground. Snomax is the normal additive used, this is protein that acts as a nucleat and allows snow making at the -2C to -4C temperatures mentioned. Snow making is very expensive to run in terms of energy and water resources. l'Alpe d'Huez uses more electricity for snow making than to run the lift system.
High temperature units exist but they are not practical for widespread snowmaking due to the cost of prefreezing the water supply. I believe there is only one unit in France in the Massif Central.
Personally it seems crazy to me that Val Tho wants to run its snowmaking at the moment when temperatures are set to rise in the next days but they are maybe just testing out the system prior to winter.
[1] This of course means that you can make snow at higher temperatures than -2C (dry bulb) given a dry atmosphere because the the water droplets are able to evaporate more water vapour as they fall to earth and so lose energy at a a faster rate. Pratically in France you need subzero temperatures to make snow although the air must get dryer the further inland you go so central China is probably ideal for snowmaking.
|
|
|
|
|
|
|
|
davidof, interesting, thanks. One question though.
| Quote: |
| [1] This of course means that you can make snow at higher temperatures than -2C (dry bulb) given a dry atmosphere because the the water droplets are able to evaporate more water vapour as they fall to earth and so lose energy at a a faster rate. Pratically in France you need subzero temperatures to make snow although the air must get dryer the further inland you go so central China is probably ideal for snowmaking. |
There's got to be a bit more to it than that as you can have a wet bulb of -2 with a dry bulb > 0 fairly easily, even in this country.
|
|
|
|
|
|
You'll get to see more forums and be part of the best ski club on the net.
You'll get to see more forums and be part of the best ski club on the net.
|
Val Thorens Webcam. Now looking a like a ski resort. Just about fully covered and still snowing by look of it. 
|
|
|
|
|
|
|
|
| skanky wrote: |
There's got to be a bit more to it than that as you can have a wet bulb of -2 with a dry bulb > 0 fairly easily, even in this country. |
The snow won't hang around if it is warm.
|
|
|
|
|
|
snowHeads are a friendly bunch.
snowHeads are a friendly bunch.
|
davidof, yes true. 
|
|
|
|
|
|
|
|
FAQ
