Dumbest idea I've even heard in my life

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The discussion centers around a proposed concept for heated roads designed to melt snow using solar energy. Participants express skepticism about the practicality and viability of this idea, highlighting several key concerns. The high costs associated with the materials and technology required for construction are a primary point of contention. Concerns are raised about the efficiency of solar panels when covered by snow, the brittleness of glass as a road material, and the challenges of maintaining and repairing such roads. Critics argue that the energy needed to melt snow far exceeds what could be realistically generated by solar panels, especially during winter conditions. They suggest that traditional methods, such as snow plowing and using salt, are more effective and economical. Some participants propose alternative solutions, such as Teflon-coated roads to allow snow to slide off, or simply improving vehicle capabilities for winter driving. Overall, while there is recognition of the innovative aspect of the idea, the consensus leans towards it being impractical and overly complicated compared to existing snow management methods.
  • #51
Just to back up Jimmy's calcs, I made a similar calculation a little more than a year ago when someone posted asking about a heated road infrastructure to replace snowplows: https://www.physicsforums.com/showthread.php?t=351186&highlight=snow

Basically the power requirements to melt snow which is exactly 0*C and falling at a rate of 1 in/hr is about 190 W/m^2. Problem is, 1) there's no sunlight when it's snowing! and 2) solar irradiance would have to be on the order of a sunny day to keep up with melting the snow. So unless this magical road has magical energy storage, give it up. You're better off with a dark colored road, snowplows, and salt/deicer. Then when the sun does come out, the dark colored road absorbs the solar energy and melts the snow.

Mech_Engineer said:
Well I've got a good reason why it can't completely replace snow plows: power requirements for a snow storm.

Say for example you have a 1-mile stretch of 2-lane road you want to keep snow free even during a fairly slow snowfall of 1 in/hr (heavier storms can be 6 in/hr). We will say the road is 7.5m (24.6 feet) wide, the snow falling has a density 8% that of water, and the snow falling is excatly 0 degrees C which means we only have to deal with water's enthalpy of fusion.

1 in/hr of snowfall correlates to 311 m^3/hr over a 1-mile stretch of road, or 25,000 kg/hr of snow. If we want all of this snow to melt right away and not accumulate, we need to put enough power through the heating coils to melt the snow as it falls. Given that water's enthalpy of fusion is 333.5 kJ/kg, that equates to a necessary power throughput of 2.3 MW for a single mile of 2-lane highway. Obviously the power requirements are substantial, at about 1.4 kW/m for 1 in/hr snowfall.

So say hypothetically tiny town X wants to completely get rid of their snow plow fleet and replace it with heated roads that are powered by wind turbines. They have a total of 5 miles of road, all 7.5m wide 2-lanes, that they want to be able to handle a maximum of 4 in/hr of snow. That would mean they would need a total power input of 46.1 MW to heat the entire road system during heavy storms (4 in/hr), and 11.5 MW during light storms (1 in/hr).

That sounds like a pretty significant wind farm/battery bank to me, especially for only 5 miles of road. It's obvious how this would scale up for larger areas, and shows why from a power standpoint a heated road infrastructure system just isn't practical.
 
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  • #52
Mech_Engineer said:
Just to back up Jimmy's calcs, I made a similar calculation a little more than a year ago when someone posted asking about a heated road infrastructure to replace snowplows: https://www.physicsforums.com/showthread.php?t=351186&highlight=snow

Basically the power requirements to melt snow which is exactly 0*C and falling at a rate of 1 in/hr is about 190 W/m^2. Problem is, 1) there's no sunlight when it's snowing! and 2) solar irradiance would have to be on the order of a sunny day to keep up with melting the snow. So unless this magical road has magical energy storage, give it up. You're better off with a dark colored road, snowplows, and salt/deicer. Then when the sun does come out, the dark colored road absorbs the solar energy and melts the snow.

You're making the same faulty assumptions that I pointed out about Jimmy's post.
 
  • #53
I can't vouch for the accuracy of these figures, there is a huge range of answers online. The figure of 1.4kW/m^3 crops up more than once for the amount of solar energy hitting Earth's surface, I have no idea how much of that is usuable by a solar cell, whether it is the average over a day, or peak during a sunny day. Assuming you stored it in batterys when conditions were good, and some hyper efficient solar cells.

If the numbers are good, ss this not at least possible without using external cells, ie only the ones under the road? I agree with the consensus this certainly isn't the best idea ever, but for a feat of "because we can" engineering, is it not at least feasable? Respect to the guys who actually crunched the numbers by the way.

Edit, one more thought, one the snow had melted, it would need to stay melted. If the panels gave up the ghost, all that would be acheived is to have made a huge ice-rink.
 
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  • #54
speaking of dumb, how about a truck with a big magnifying glass held out front to concentrate the sun's rays and evaporate the snow?
 
  • #55
Kawakaze said:
Edit, one more thought, one the snow had melted, it would need to stay melted. If the panels gave up the ghost, all that would be acheived is to have made a huge ice-rink.

Any sort of drainage (holes, slope, etc.) would solve this problem.
 
  • #56
NeoDevin said:
Any sort of drainage (holes, slope, etc.) would solve this problem.

Then the drains would need heating.

Whenever we get heavy rain, the first things to get overwhelmed are the drains. Long before the rivers and streams around us hit capacity. We get light flooding because the drains can't cope.

I also noted over the last few weeks of cold weather, that one of the first things to freeze over are the drains. Some rather interesting ice formations on the grids.
 
  • #57
NeoDevin said:
You're making the same faulty assumptions that I pointed out about Jimmy's post.

I'll answer them.

NeoDevin said:
You are assuming that snow falls at an average rate of 1 inch per hour, and/or that no energy can be stored during times of less snowfall.

The calculations make no assumptions about where the energy comes from, I specifically pointed out the "road" would need energy storage in my post (remember? I called it magical). Problem is, periods between snowfall would need to be sunny for a "solar road" to store energy in the first place.

NeoDevin said:
While 1 inch per hour may not be uncommon, I sincerely doubt anywhere gets 1 inch per hour averaged over the entire winter (assuming winter lasts 3 months, that's ~185 feet of snow, imagine shoveling that!).

The average over the winter isn't important, it's the total output during the storm that matters, and how long the output has to kept up. For a 6 hour storm at 1 in/hr, you would need to store 8.4 kWh per meter of road length (EDIT- this also assumes all stored energy is going into melting snow, not conducting into the ground as well). The amount of energy storage you're proposing is truly fantastic (basically 7 large deep-cycle car batteries every meter of road length). Keep in mind the storage also has to maintain capacity in sub-freezing conditions, not an easy task...

It's yet another thing that makes this proposal ridiculous compared to snow plows, or even putting a roof over the entire road!
 
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  • #58
NeoDevin said:
Any sort of drainage (holes, slope, etc.) would solve this problem.

In theory yeah, but I can tell you, my driveway is about 10 degrees inclined, i spread normal salt (stupidly not rock salt) over it to get the ice off in winter, the water did drain, but it hit -10 at night and the thin layer of ice that formed was enough to put me flat on my arse when I stepped onto it! :D
 
  • #59
Kawakaze said:
The figure of 1.4kW/m^3 crops up more than once for the amount of solar energy hitting Earth's surface, I have no idea how much of that is usuable by a solar cell, whether it is the average over a day, or peak during a sunny day.

For what it's worth, that is probably peak solar irradiance on a sunny day in summer at sea level. Average over the course of a year (day and night) is something like 100-150 W/m^2.
 
  • #60
Kawakaze said:
In theory yeah, but I can tell you, my driveway is about 10 degrees inclined, i spread normal salt (stupidly not rock salt) over it to get the ice off in winter, the water did drain, but it hit -10 at night and the thin layer of ice that formed was enough to put me flat on my arse when I stepped onto it! :D

I think salt is only effective to about 0*F, the freezing point of heavily salted water...
 
  • #61
Kawakaze said:
In theory yeah, but I can tell you, my driveway is about 10 degrees inclined, i spread normal salt (stupidly not rock salt) over it to get the ice off in winter, the water did drain, but it hit -10 at night and the thin layer of ice that formed was enough to put me flat on my arse when I stepped onto it! :D

We've got drainage on our driveway. Didn't do nothing though. Just got clogged and froze over.

It got so cold that the groundwater underneath froze solid. I know this because our 6 inch thick concrete drive (about 5m3 of concrete) rose 3 inches and cracked in half.
 
  • #62
@Mech yeah you're right there, but the point I making is that even a thin film of water is enough to be dangerous. I know I sure felt it!

@Jared Scary! Fascinating how something as innocuous as water can bring down rock faces and destroy concrete structures.
 
  • #63
Mech_Engineer said:
It's yet another thing that makes this proposal ridiculous compared to snow plows, or even putting a roof over the entire road!

How much energy is required to plow the snow?
 
  • #64
Whatever it is, it wouldn't differ much if they plowed an inch of snow or a foot. Can the same be said of a heated road?
 
  • #65
Is the cost of replacing the roads / installing required infrastructure (energy storage etc) along with maintaining said technology more or less than plowing it?
 
  • #66
I think I have a compromise. Most places where this technology would be useful are remote and sparsely populated. I propose we use the money to buy every household a half-track with fitted plough, or use it to forcefully evict them. If they want to live in a frozen hell, with 2 people per square kilometer they can pay to defrost their own damn roads! I don't see why I should subsidise someone who wants to live in a snowglobe. :)
 
  • #67
Jasongreat said:
Whatever it is, it wouldn't differ much if they plowed an inch of snow or a foot. Can the same be said of a heated road?

Nope, but without a number to compare it to, that statement isn't much use.
 
  • #68
NeoDevin said:
Nope, but without a number to compare it to, that statement isn't much use.

The plow would use around 880 joules(1/4 gallon of diesel fuel) of energy to plow a 8+ft wide swath one mile long. The driver would expend around 2 calories worth of energy at the same time, so just over 880 joules.
 
  • #69
NeoDevin said:
You are assuming that snow falls at an average rate of 1 inch per hour, and/or that no energy can be stored during times of less snowfall.

Asphalt roads are always storing solar energy, whenever there is solar energy to store. They're the last to freeze, and the first to thaw.
 
  • #70
mugaliens said:
Asphalt roads are always storing solar energy, whenever there is solar energy to store. They're the last to freeze, and the first to thaw.

They don't store it very well, or for very long.
 
  • #71
people who think this is a good idea don't know what solar cells are, and have no clue how money works, and are also clueless about materials science.

in other words, ignorant on all levels
 
  • #72
I have thought for awhile that I'd like to get ahold of a couple of spent fuel rods from my local electric provider, grind 'em up and mix the grind into asphalt, and use that to pave my driveway. I'm paying the guy down the road $40 bucks everytime he plows the drive, what do you think my payback time would be? Do you think they would *give* me the rods, to, you know, take them off their hands?
 
  • #73
I always wondered why we couldn't build solar cell awnings along/over most of the interstate system, at current efficiencies, assuming no significant improvements in the tech, we could provide the power needed for the US with a similar scale construction project to the interstate system.
 
  • #74
Max™ said:
I always wondered why we couldn't build solar cell awnings along/over most of the interstate system, at current efficiencies, assuming no significant improvements in the tech, we could provide the power needed for the US with a similar scale construction project to the interstate system.

Sure, just place these on the sides of the road along with a few tables to relax at. :smile:
 

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  • #75
Max™ said:
I always wondered why we couldn't build solar cell awnings along/over most of the interstate system, at current efficiencies, assuming no significant improvements in the tech, we could provide the power needed for the US with a similar scale construction project to the interstate system.

And no-one would steal them?
 
  • #76
Furthermore, to meet even basic D.O.T. standards, the awnings would have to be at least as sturdy as an over-highway pedestrian crossing.
The cost per mile under those safety conditions would be enormous.
 
  • #77
pallidin said:
Furthermore, to meet even basic D.O.T. standards, the awnings would have to be at least as sturdy as an over-highway pedestrian crossing.
The cost per mile under those safety conditions would be enormous.

And furthermore, the added costs of an expansion of the roadway would be enormous as well.
 
  • #78
pallidin said:
And no-one would steal them?

Oh, no - because everyone in the whole world is nice, polite, kind, and would never stoop to something as low as "stealing."

Yeah. http://en.wikipedia.org/wiki/Bill_the_Cat" !
 
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  • #79
For what it's worth, he does say that the road will act as a network. I suppose he's thinking something lofty like maybe one part of the road might be snow covered but another portion may not. I guess he thinks he can transfer the energy or something. I don't know where he gets that idea because when it snows, all roads everywhere in the word are instantly covered by the exact same amount of snow at once.

Meh, stupid idea from an ignorant man with a POS prototype--someone should tell him to get back in his box.




https://www.youtube.com/watch?v=Ep4L18zOEYI
 
  • #80
Amy G. Dala said:
For what it's worth, he does say that the road will act as a network. I suppose he's thinking something lofty like maybe one part of the road might be snow covered but another portion may not. I guess he thinks he can transfer the energy or something. I don't know where he gets that idea because when it snows, all roads everywhere in the word are instantly covered by the exact same amount of snow at once.

Meh, stupid idea from an ignorant man with a POS prototype--someone should tell him to get back in his box.

I assume he's checked the amount of energy produced 'elsewhere' and how much of it can be transferred to the required areas (considering loses etc)? It usually snows over quite a large area and the nearest sunny location capable of producing the required energy levels is a fair bit away. Which means you need as many roads with this tech as possible, otherwise having it only locally is useless - unless you start drawing from the grid that is, meaning you need to recover that usage once the sun is back out.
 
  • #81
Curl said:
... Even if the industry can crank out solar polymers faster than humans crank out feces, it wouldn't be enough to do jack.
Well it will do jack and then some. Cover the tiny little squares in this graphic of the world with solar arrays and the energy produced w/ today's technology solar cells while the sun is shining is equivalent to the world's entire primary energy consumption, all of it - nuclear to coal to oil - day and night.
http://www.ez2c.de/ml/solar_land_area/
The trick yet to be mastered is in making and installing them economically and storing the energy, and having a transportation system that makes use of electric power somewhere in the loop.
 
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  • #82
Curl said:
ROFL, this idea is so retarded is sad.

2) Laying solar cells underneath? Really? That is just completely stupid...
Did you read the article? Cells are one option, solar thermal heating the other:

"Think about it, we have more than 3 million miles of highways exposed to sunlight, so if we can harness this energy, it's free, and you don't need photovoltaic solar cells," said Mallick
 
  • #83
Jasongreat said:
880 joules(1/4 gallon of diesel fuel)

Amy G. Dala said:
when it snows, all roads everywhere in the word are instantly covered by the exact same amount of snow at once

[URL]http://www.bpp.com.pl/IMG/faint.gif[/URL]
 
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  • #84
There are two reasons why this idea is "dumb": 1) ineffective hybridization, and 2) ineffective utilization.

1) People are often too quick to think that combining things offers some sort of savings. Why would you combine a solar panel with the road pavement material. This offers no savings. Roads are made of grippy and durable asphalt. Panels are made from delicate semiconductors...If you really want to use solar for this, why don't you just place the panels beside the road? Cheaper road, cheaper panels. Even still it would be a bad idea because:

2) Ineffective utilization: Convert solar electricity into HEAT to melt snow?! Anyone who knows anything about the second law would roll over in their grave at mention of this!

Oddly enough, asphalt is a fairly good solar absorber, and insulator on its own, try walking barefoot on a road on a sunny day.
 
  • #85
Sorry, if there was mention of solar thermal in the article, I may have overlooked it. I didn't read beyond mention of " super-strong glass, instead of conventional asphalt or concrete". But use of a thermal absorber and storage medium to increase the average pavement temperature is, I think, a good idea. Any use of photovoltaics in this application is ridiculous, and that comes from a PV engineer.
 
  • #86
This also reminds me of a CNN article I read about a car the runs on water...hehehehe...water.
 
  • #87
Borek said:
[PLAIN]http://www.bpp.com.pl/IMG/faint.gif[/QUOTE]

Sorry Borek, didnt mean to make you faint and hit your head. I don't have any idea how I came up with that number, I have tried repeatedly to come up with it again and I have not been even close to being successful.

Here goes my next try, a ten wheeler gets about 4-7mpg, taking the lower end, one quarter of a gallon will cover one mile, the energy density of diesel is 45.3 MJ/kg, one gallon of diesel weighs 3.402 kg so one quart would weigh .8505 kg, which would leave us at 38.53 MJ/mile(one pass around 9 foot wide). Is this close or have you just fainted again?

Assuming this try at math was successful, it would take 4 passes to completely clean a one mile section of 2 lane highway from shoulder to shoulder with the plow, which would make it 154.12 MJ of energy expended. According to Mech Engineer (post #51), to get the same area to melt one inch of snow it would take 2.3MW/h. 2.3 MW/h converts to 8280 MJ, so it would take 53.72 times more energy to melt the snow. If it takes pretty much the same energy to plow 1 foot as it does to plow 1 inch, the difference in energy expenditures between plowing and heating would be even more enormous(since it already is for an inch), and that's before we even discuss the added costs of building the heated roads, maintaining them and storage facilities for the energy they make.

As you probably already know, I'm no mathmatician nor a physicist or even a college graduate, so please correct me where it is needed. I am here to learn but fainting emoticons don't teach me much other than that I was wrong. If this thread is not the place to further this discussion, could you please PM me an explanation of where I went wrong. Thanks.
 
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  • #88
Jasongreat said:
the energy density of diesel is 45.3 MJ/kg

Without checking details - this is a correct ballpark figure. And you got it on your own, so me fainting was a correct approach.
 

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