Hailing from Queens, NY

[AeneasWalks]

Hello all, I'm working up my post count so I can add pictures to me garage build thread.

I'm also interested in radiant heat for a commercial parking lot application. I understand radiant heat has been discussed ad nauseam so I will try my best not to beat a dead horse.

I operate a small parking garage located in an urban area and was inspired by seeing municipal snow-melting operations. The cost of these machines is astronomical and don't make economic sense for my business. However, it occurred to me I could dedicate a small portion of our lot for snow melting, as long as we direct all of our plowing to that area. I'm interested in researching the pros and cons of electric vs. hydronic, and maybe even running it off the condominium's boiler, in which case it would only be turned on for snow events.

Looking forward to all the wealth of knowledge on this forum.

 

[nadogail]

Welcome to the Forum from Southwestern California. In my city we have no experience with Snow.

 

[AeneasWalks]

Welcome to the Forum from Southwestern California. In my city we have no experience with Snow.

Thank you, I've been to San Diego before, it's a lovely place. That library at UCSD is something. Coincidentally, I've been looking online for upholsterers in Tijuana to re-wrap a steering wheel. No dice yet.

 

[Is this thing on]

Hello all, I'm working up my post count so I can add pictures to me garage build thread.

I'm also interested in radiant heat for a commercial parking lot application. I understand radiant heat has been discussed ad nauseam so I will try my best not to beat a dead horse.

I operate a small parking garage located in an urban area and was inspired by seeing municipal snow-melting operations. The cost of these machines is astronomical and don't make economic sense for my business. However, it occurred to me I could dedicate a small portion of our lot for snow melting, as long as we direct all of our plowing to that area. I'm interested in researching the pros and cons of electric vs. hydronic, and maybe even running it off the condominium's boiler, in which case it would only be turned on for snow events.

Looking forward to all the wealth of knowledge on this forum.

Waiting 5 years to post in the welcome thread seems odd.
Welcome, belated I guess.

 

[rlitman]

...I operate a small parking garage located in an urban area and was inspired by seeing municipal snow-melting operations. The cost of these machines is astronomical and don't make economic sense for my business. However, it occurred to me I could dedicate a small portion of our lot for snow melting, as long as we direct all of our plowing to that area. I'm interested in researching the pros and cons of electric vs. hydronic, and maybe even running it off the condominium's boiler, in which case it would only be turned on for snow events...

Welcome to the forum.

Your snow melting pad idea is interesting, but unlikely to work out for you. Commercial snow melting systems are designed to put out enough heat to melt snow as fast as it falls from the sky. In this region (and the requirements can vary regionally), that is around 50 watts/sq-ft. That's enough heat only if the entire snow covered space is heated. So, for S&G, figure out how many square feet of plowed area you have, multiply by 50, and that's roughly the amount of watts of heat you'll need to concentrate into your melting machine. That's going to be an astronomical number FYI, which is why the price of such systems is astronomical.

And keep in mind there's the issue of heat transmission. You can coil hydronic loops in concrete to provide SOME heat, but concrete is too insulating to allow that much heat to be transferred in such a small space. That sort of system needs large surface areas to work.

Are you simply plowing, or using something like a skid steer with a bucket that can also lift the snow? The city uses buckets to dump snow into their melters.

Do you have access to natural gas and a machine with a bucket that can dump snow? And also a spot you can use with sufficient drainage (don't forget this important detail!)?

If so, what I'd suggest is getting a natural gas pool heater, plumbing it through an exposed loop of pipe sitting on your melt zone circulating propylene glycol, that's protected by a cover of bar grating. Dump the snow on the grating, and it falls through making direct contact with the pipe, so you get good thermal transfer. Of course, PEX pipe won't last that long outdoors, and metal pipe is both expensive and will have corrosion issues, so good luck with that. My guess is that the City's commercial melters either use stainless or possibly even titanium tubes for their heat exchangers. They're likely burning fuel oil, but NG is going to be a lot more economical in the long run.

 

[AeneasWalks]

Waiting 5 years to post in the welcome thread seems odd.
Welcome, belated I guess.

Thank you. I'm a long time lurker, I confess.

Are you simply plowing, or using something like a skid steer with a bucket that can also lift the snow? The city uses buckets to dump snow into their melters.

Do you have access to natural gas and a machine with a bucket that can dump snow? And also a spot you can use with sufficient drainage (don't forget this important detail!)?

If so, what I'd suggest is getting a natural gas pool heater, plumbing it through an exposed loop of pipe sitting on your melt zone circulating propylene glycol, that's protected by a cover of bar grating. Dump the snow on the grating, and it falls through making direct contact with the pipe, so you get good thermal transfer. Of course, PEX pipe won't last that long outdoors, and metal pipe is both expensive and will have corrosion issues, so good luck with that. My guess is that the City's commercial melters either use stainless or possibly even titanium tubes for their heat exchangers. They're likely burning fuel oil, but NG is going to be a lot more economical in the long run.

These are very interesting ideas. To answer your questions I only have a plow, no skid steer. I would like to make do with the equipment we already have and I'm wary of training my guys to operate a skid-steer properly - let alone the insurance implications. It might seem odd that I'm weighing a hydronic system yet am skittish over a skid-steer, but that's because I'm in the process of planning for concrete repair.

I like the bar grate idea. I'm concerned about whether the plow will catch on the grating, but I think that would very much come down to the grating itself and the transition from the rest of the lot. I will keep this in the back burner (pun intended). As far as the heat output required, it's acceptable to me that the snow mounds be melted over the course of days instead of hours. This is our largest mound from February 2nd. It is February 10th today and I'm guessing that mound is going to be there for another month if not longer. The drainage is a good consideration too. I was thinking that the water would just find its way to existing sewer drains, but that could lead to more slip-and-falls from overnight freeze. It will be a good idea to perimeter the melting pads with the grate, which would also serve as easy visual cues for where the pads are. Thank you for chiming in, rlitman. I did much of my growing up in Nassau County.

Here's a bonus pic of our 2002 Chevy Suburban LT 4WD. It has Bridgestone W965 winter tires on it which make me feel indestructible in the snow. I recently replaced the plow lights with LED units from Amazon. I'm pretty happy with the light output, except that lo-hi beams are reversed and I'm already getting condensation in them. She has about 90k miles and I'm sending her in for her first transmission + differential oil change, also installing a Merchant Auto transfer case pump rub kit.

 

[rlitman]

Ok, here's some engineering data.

The latent heat of fusion of water is 334kJ/kg. A 1500W heat blanket (the largest heater you will get with a single 15A plug), assuming that ALL of the heat goes into melting snow, and none is lost to the outside (it's unrealistic, but...), can melt almost 36lbs of snow per hour, at a cost of say 33 cents to Con Ed. That's what, two big plastic shovels full? But once you account for heat losses to the outside, figure on maybe half that efficiency. With an average parking space being 180sq-ft, figure on that 1500 watts taking over a week to melt the volume of a foot of (low density) snow from a single parking space, at a cost of $60. Plowed snow is much higher density, so triple that time and cost.

I'm able to run electric snow melting mats on an entrance staircase of mine off a single outlet. I've got mats for 5 treads and a landing at the top and bottom, and don't really have much headroom on the circuit for more power. It has no trouble staying ahead of a blizzard, but I also wouldn't consider pushing more snow onto it than what already falls on it from the sky.

 

[AeneasWalks]

So... what you're saying is that hydronic would be the way to go . My education background is in a useless soft science so it will take me some time to make sense (and make use) of your engineering calculations. I appreciate the lesson - something for me to sink my teeth into. For my own posterity, the surface of our lot is approximately 40,000 sf. It's fresh right now because I'm filling paperwork for a tax appeal. This is also some reading saved for later: Practical Snow Melt Design.

 

[AeneasWalks]

Givens
Area: 40,000 sf
Weight of average snow: 15lbs / cubic foot
Heat of fusion: 144 BTU
Specific heat of ice: .51 BTU / f
Average (Jan.) nightly low, NYC: 26f
Melt slab efficiency: 50%

Assuming we want to melt a 1' snowfall in 3 days:

Total snow = 40,000sf * 15lbs = 600,000lbs of snow
Bringing snow from to 26f to 32f = 600,000 * .51BTU * 6 = 1,836,000 BTU
Inducing phase change from ice to water = 600,000 * 144BTU = 86,400,000 BTU
Total BTU requirement = 88,236,000 BTU
Account for efficiency loss = 88,236,000 BTU / (.5) = 176,472,000 BTU
Required BTU output = 176,472,000 BTU / 72 hours = 2,400,000 BTU / hour or 2,400 MBH

Have I missed anything? My feeling is the slab efficiency should be higher than 50%. If the slab is completely covered in snow very little of it should be escaping into the atmosphere. Most of the heat should be lost to the surrounding pavement which could be mitigated by insulation. However, I have no idea how insulation would hold up in a commercial application.

 

[rlitman]

...Have I missed anything?...

Looks mostly reasonable to me as a good start.

I simply assumed the ice heating component as zero for two reasons. First, because it's negligible compared to the phase change heat, and second, because most snowfall here happens very close to 32F, with snowfall accumulations being very low when you drop into the 20's. So I would disregard this part and simplify the math.

Your earlier link was a good one. I don't recall if it was one of the places I found in my research before doing my hydronic steps, but that was around 10 years ago and memory fades. His point about differential heat waste across large areas is not relevant to you, since you are instead planning to plow snow into a melting machine. Such a concentrated area that is guaranteed to be covered deeply in snow also doesn't really have significant slab losses.

Instead, your problem with a snow melting machine is about thermal transfer efficiency. You're making a heat exchanger. Spread across a large slab, the surface area makes the low thermal conductivity of PEX and concrete good enough. Concentrated into a small space, you're going to need what amounts to a radiator. Fins might help, but at the very least, you need something where nothing but metal gets between the snow and the circulating heated fluid (antifreeze solution is a must). Then there will be ongoing corrosion issues, plus plowed snow isn't conducive to melting from below, because you will get ice damming. Commercial snow melting machines get around this by spraying warmed water over the melt pile as well as heating from beneath. Also, there's the issue about contamination other than snow being ingested by whatever you make. That will clog up the works, blocking areas from effective melting.

Stepping back from that for a sec, assuming 100% transfer efficiency (and not worrying about how long it takes), based on $1.64/therm for NG from Con Ed (what I found in a 2019 news article) you'd be using $1667 of natural gas just to melt that foot of snow. The good news is that that is about 1/3 of the price of melting with electricity. But because of the concentration of heat, snow melters run their water baths at around 70F, so figure on that heating as well (water has a specific heat of 1, rather than the 0.5 of ice as well).