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they melt your snow

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they melt your snow

Postby Nick Berigan » Sat Jan 09, 2010 1:34 pm

Going by CUNA on Rosa this morning I noticed a big plume of steam rising from the parking lot. Looked closer and there was a truck making noise that was emblazoned "www.meltyoursnow.com".

That seems nuts to me. Pile it somewhere and let it melt in March. How much energy must it take to do that?
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Re: they melt your snow

Postby Galoot » Sat Jan 09, 2010 2:02 pm

Their website is under construction, but they do have a claim that the whole thing is "green". Riiiiiight. Using what must be the equivalent of a few tanks of gasoline, just to turn the snow into water that will freeze out in the street? This is the opposite of "green".

I see no good reason not to just ban something like that.
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Re: they melt your snow

Postby Dairylander » Sun Jan 10, 2010 11:36 am

When there's too much snow and nowhere to push it, it must be loaded into dump trucks and hauled away.
The city does this every year, and chances are you've seen their dumping sites around town. The West High football field on Regent and Grand is one such location.
Melting snow is not by any stretch a "green" option, but it does use less diesel than loading and hauling and dumping.
CUNA, however, has acres of land and lawn. I can't imagine why they would need to melt.
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Re: they melt your snow

Postby gargantua » Sun Jan 10, 2010 12:23 pm

So, someone wants to "just ban it". Based on what FACTS? So far, I have not seen anyone provide any facts as to how much energy is involved in snow melt, and how that compares to the energy usage involved in other snow removal techniques.

My snow removal technique for my residence is shoveling the snow. That uses less fossil fuel than my snowblower-wielding neighbors, but I'd never even thought to call for a ban on snowblowers.

At least bring some facts if you want to start banning things.
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Re: they melt your snow

Postby Galoot » Sun Jan 10, 2010 12:58 pm

Facts? You want facts? Maybe you don't remember that it takes far more energy to melt a gram of ice, than it does to just raise the temperature a few degrees?

Going through a few calculations, using the latent heat of fusion for water/ice, it would require five hundred and twenty eight gallons of gasoline to melt an acre of snow, assuming there was 20" of snow on that acre.

You can drive a large truck a LONG way on 528 gallons of gas. And merely plowing the stuff into a pile somewhere would obviously require even less gas.
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Re: they melt your snow

Postby Ducatista » Sun Jan 10, 2010 1:38 pm

Galoot wrote:Going through a few calculations, using the latent heat of fusion for water/ice, it would require five hundred and twenty eight gallons of gasoline to melt an acre of snow, assuming there was 20" of snow on that acre.

I'm guessing they don't just wave a flame at the snow, but who knows.

The City of Toronto has used a snow melter for years. Don't know how their method compares to Melt Your Snow's method, but apparently Toronto has found a workable process.
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Re: they melt your snow

Postby Average Joe » Sun Jan 10, 2010 1:40 pm

There was a segment on one of the local TV news stations recently about this operation, they are demoing their product to the city. They mentioned they filter out the salt, sand and other contaminants before they return the melted snow, now water, into the drainage system. That is probably their "green" slant. Now only if they could figure out a way to heat their hot water that melts the snow with a solar powered battery cell instead of diesel they might be on to something. Another idea would be to capture and use the discharge steam from the MG&E power plant to melt snow, filter it and return it to the water table.
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Re: they melt your snow

Postby ArturoBandini » Sun Jan 10, 2010 2:03 pm

Galoot,
I love doing back-of-envelope calculations like this. I calculate your quantity like this:
-1 acre is roughly 4000 sq. m.
-50cm of snow on that acre would mean 2000 cu. m of snow
-snow is roughly 10% as dense as water, so 200 cu. m of (liquid ice)
--For simplicity, ignore the fact that ice and liquid water have slightly different densities (why ice floats)
-density of water is 1.0 g/cu. cm = 100^3 g/cu. m
-heat of fusion of water is = 333 J/g
-total heat required to melt 200 cu. m of snow = 200*100^3*333 = 6.66e4 MJ (MegaJoules)
-gasoline energy density = 32 MJ/L
-thus, 2082 liters of gasoline are required
-equivalent to 550 gallons of gasoline - surprisingly close to your value!

Trucking would certainly take much less energy than onsite melting. A semi trailer hold about 110 cubic meters of stuff. So, roughly two trucks would be required to hold our canonical parking-lot full of snow. With 225 gallons in the tank, you could go a good distance - probably anywhere in the midwest. So, for the sake of the environment, I think we should forgo melting the snow in favor of trucking it to Illinois.
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Re: they melt your snow

Postby Scotty » Sun Jan 10, 2010 2:46 pm

chevy chase.jpg
chevy chase.jpg (12.02 KiB) Viewed 2351 times


"It was my understanding that there would be no math."
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Re: they melt your snow

Postby Nick Berigan » Sun Jan 10, 2010 9:12 pm

the snow was presumably at most 16 degrees having been exposed the previous night to subzero temps and it was 10 am. does it take more energy to bring it to the melting point then too just melt it.

there was a huge plume of steam going up into the air. should that be happening in an efficient system?
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Re: they melt your snow

Postby Dairylander » Sun Jan 10, 2010 9:24 pm

A company that manufactures the machines has some different numbers:
"Typically, one ton of snow requires 1.5 gallons of diesel to melt."

http://www.anticosnowremoval.com/snow_m ... trecan.htm
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Re: they melt your snow

Postby Galoot » Sun Jan 10, 2010 10:23 pm

Even at perfect efficiency, they can't achieve that--theory says that it takes about 1.9 gallons of diesel to melt a ton of snow. And achieving theoretical efficiency is pretty much impossible. As Nick B pointed out, you'll always have to bring the snow up to the melting point first.
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Re: they melt your snow

Postby ArturoBandini » Sun Jan 10, 2010 10:24 pm

Dairylander wrote:A company that manufactures the machines has some different numbers:
"Typically, one ton of snow requires 1.5 gallons of diesel to melt."

http://www.anticosnowremoval.com/snow_m ... trecan.htm

I get 2.35 gallons required:
1 ton of snow = 240 gallons = 908 L = 908 kg of water
**Latent heat of fusion of water = 333 kJ/kg
908 kg water * 333 kJ/kg = approx. 300,000 MJ required to melt 1 ton
**Energy density of diesel fuel = 33.7 MJ/L = 37,300 kJ/L
300,000kJ / 37,300 kJ/L = 8.9 L of diesel fuel required
8.9 L = 2.35 gallons of diesel fuel

I wonder why their reported number is lower... My number would be for ideal melting efficiency (all fuel energy is turned into thermal energy of the H2O, none is lost to the surrounding environment, no fuel is left un-burned). Maybe these ice melters have some energy coming in from another source? (e.g. the mechanical mixing of the snow might come from a different motor)

Nick B: Heating snow from 16 F to 32 F takes roughly 1/18 the amount of energy required to melt the same amount of snow. Converting some snow to steam sounds like an inefficiency for sure, but in reality it might not have been that much water - condensed water vapor might just look like 'a lot'.
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Re: they melt your snow

Postby Galoot » Mon Jan 11, 2010 9:53 am

Good calculations, Arturo!

To compare to the meltyoursnow.com method, how much energy does it take to just move the snow out of the way? The vast majority of the energy is expended in lifting the snow up, as anybody who has shoveled snow will agree.

Let's assume, to be generous, that the snow is lifted over 6 feet, or 2 meters. Using Arturo's numbers, a ton of snow has a mass of 908 kg. The energy to lift something is given by E= m*g*h, where m is the mass, g is around 10 Newtons per kg, and we're assuming h, the height, is 2 meters.

This means that it takes 18,160 Joules to lift that ton of snow out of the way. How much diesel fuel is this equivalent to? Diesel has about 146 MJ/gallon, so this means that lifting that ton of snow requires a bit over 0.0001 gallons of diesel.

Assuming perfect theoretical efficiency, that means the snow melting approach uses about 19 thousand times more energy than just shoveling it out of the way.

Arturo, I'd appreciate it if you'd doublecheck my calculations. I knew it would require vastly more energy to melt the snow, but 19,000 times more? That almost seems ridiculous.
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Re: they melt your snow

Postby ArturoBandini » Mon Jan 11, 2010 12:03 pm

I get essentially the same number you do, Galoot. Good work. Gravitational potential energy pales in comparison with intramolecular potential energy (in the case of ice - hydrogen bonding). The energy you put into lifting that shovelfull of snow 2m is the same amount that the snow lost when it fell from that same distance (lost in thermal vibrations of the air, other snowflakes etc.).
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