https://www.indiegogo.com/projects/solar-roadways
But do they really think they could melt all the snow and ice from a Wisconsin winter?! Our army of snow plows wouldn't even be as effective.
Solar Roadways
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fuzzylunkin1
fuzzylunkin1 wrote:QUOTE (fuzzylunkin1 @ May 19 2014, 12:17 AM) I'm not here to say this is good or bad, that's a job for MrChaos.
https://www.indiegogo.com/projects/solar-roadways
But do they really think they could melt all the snow and ice from a Wisconsin winter?! Our army of snow plows wouldn't even be as effective.
The sun is already shining on the snow and it doesn't melt fast enough now. Not to be even more obvious but with the snow will be covering the panels so no energy wil get generated so the only way to power those heating elements via batteries or the grid. Either way the amount of energy neessary is way way way way way way higher than simply plowing it out of the way and if your goal is to lower the carbon footprint melting it off the roads is not the way to go. You can run the numbers yourself Fuzz (as in it is not that hard and your a smart cookie) to see how much energy it will take to melt a 100ft by 500ft parking lot with an inch of snow on the ground and a ground temperature of errrmm 25F.
I mean there is the possiblity I've missed something glaringly obvious here but my intial reaction is *facepalm* silly hippies
They are covering the surface in glass.... *sigh* thermal expansion and contraction is an issue. Freeze and thaw will be an issue once it gets between the cracks. Road level, tilt, grade, and no more road crowning to get the water off the pavement now so you are going to have to do something about standing water on those roads you gre up on Fuzz. ok it can bear a load at 72F but what about -10F or 110F. What about the dust, dirt, road grime, oil how do they plan on cleaning that off their road. It is a neat idea with some application Im sure but they need to tone done their claims quite a bit here including the snow removal stuff.
Actually Raveen is way more informed on that kind of stuff given his RL job!
Last edited by MrChaos on Mon May 19, 2014 5:12 am, edited 1 time in total.
Ssssh
Ok I'll do it *scratches his arm nervously*
There is all kinds of snow and how it is packed effects not only the mass but also the heat transfer... *happy sigh*
Here is an ASHRAE paper on the subject
QUOTE qo = qs + qm + Ar (qe + qh)
where
qs = sensible heat transferred to the snow (Btu/h.ft2)
qm = heat of fusion (Btu/h.ft2)
Ar = ratio of snow-free area to total area (dimensionless)
qe = heat of evaporation (Btu/h.ft2)
qh = heat transfer by convection and radiation (Btu/h.ft2)[/quote]
QUOTE During the summer period approximately 20% of the incident solar radiation on the activated road surface can be collected, corresponding to 150,000 kWh (512 million Btu). Losses amount to approximately 35% of this quantity, the remaining energy being available to keep the bridge surface free of ice during the winter period.[/quote]
150,000 - 150,000*.35 = 97,500 kw of heat energy from a system of pipes (they used mechanical heat transfer (a higher efficiency btw rather than solar panels) but no matter this is cards stacked in favor of the new system.... ok so we have a grand total of 100,000 lw of heat
You can now figure out how many inches of snow (based on some bassic assumptions of course) you can melt on the road surface that is 14,000 ft^2.
We need to get the values for heat flux to those in the paper Btu/h*ft^2
You have the conversion factor for Kw to Btu/hr and the total kw -> 341214200 Btu/hr
Now divide by the area for the heat flux -> 24372 BTU/hr*ft^2
So let's get calculating!
QUOTE qs = s cp ? (32 - ta) / c1
where
qs = sensible heat transferred to the snow (Btu/h.ft2)
s = rate of snowfall (inches of water equivalent per hour)
cp = specific heat of snow (0.5 Btu/lb.oF)
? = density of water equivalent of snow (62.4 lbs/ft3)
ta = air temperature (oF)
c1 = conversion factor (12 in./ft).[/quote]
An important point of the discussion is how much is the ambient air effecting the melt. Let's make it 32F to simply things and please note that temperatures colder than 32F mean some of the total heat availible goes to just warming the ambient air in contact with the snow
qs = s * cp * (32-32)/ c1 -> this equals 0 because 32-32 = 0
s = unknown (total inches we could melt of the road)
qs = 0
QUOTE qm = s hf ? / c1
where
hf = enthalpy of fusion for water (143.5 Btu/lb).
For hot water (hydronic) systems, the above reduces
to:
qm = 746 s[/quote]
nothing more to do here
QUOTE Ar = ratio of snow-free area to total area (dimensionless)[/quote]
Once all the snow has melted how much is still on the road? The new road system is not zero but lets say it is
QUOTE Ar (qe + qh)[/quote]
so if we assune 100% of the water drains off the road... obviously horse poop but I'm lazy as heck
nothing more to do here either
therefore qo = qs + qm + Ar (qe + qh)
wittles down to (if we neglact everything but just what is needed to melt the snow):
24372 BTU/hr*ft^2 = 746 BTU/hr*ft^2 * s inch/hr
32.6 in of snow could be melted in total IF
the ambient temperature was always 32F when it snowed, the water always completely drained off (including any film) the road, snow density was light, the efficiency of the solar cells approached the mechanical system, 100% of the energy was used to melt snow, and there where no other loses.
So Fuzz my man the answer is a resounding no for your old stomping grounds
There is all kinds of snow and how it is packed effects not only the mass but also the heat transfer... *happy sigh*
Here is an ASHRAE paper on the subject
QUOTE qo = qs + qm + Ar (qe + qh)
where
qs = sensible heat transferred to the snow (Btu/h.ft2)
qm = heat of fusion (Btu/h.ft2)
Ar = ratio of snow-free area to total area (dimensionless)
qe = heat of evaporation (Btu/h.ft2)
qh = heat transfer by convection and radiation (Btu/h.ft2)[/quote]
QUOTE During the summer period approximately 20% of the incident solar radiation on the activated road surface can be collected, corresponding to 150,000 kWh (512 million Btu). Losses amount to approximately 35% of this quantity, the remaining energy being available to keep the bridge surface free of ice during the winter period.[/quote]
150,000 - 150,000*.35 = 97,500 kw of heat energy from a system of pipes (they used mechanical heat transfer (a higher efficiency btw rather than solar panels) but no matter this is cards stacked in favor of the new system.... ok so we have a grand total of 100,000 lw of heat
You can now figure out how many inches of snow (based on some bassic assumptions of course) you can melt on the road surface that is 14,000 ft^2.
We need to get the values for heat flux to those in the paper Btu/h*ft^2
You have the conversion factor for Kw to Btu/hr and the total kw -> 341214200 Btu/hr
Now divide by the area for the heat flux -> 24372 BTU/hr*ft^2
So let's get calculating!
QUOTE qs = s cp ? (32 - ta) / c1
where
qs = sensible heat transferred to the snow (Btu/h.ft2)
s = rate of snowfall (inches of water equivalent per hour)
cp = specific heat of snow (0.5 Btu/lb.oF)
? = density of water equivalent of snow (62.4 lbs/ft3)
ta = air temperature (oF)
c1 = conversion factor (12 in./ft).[/quote]
An important point of the discussion is how much is the ambient air effecting the melt. Let's make it 32F to simply things and please note that temperatures colder than 32F mean some of the total heat availible goes to just warming the ambient air in contact with the snow
qs = s * cp * (32-32)/ c1 -> this equals 0 because 32-32 = 0
s = unknown (total inches we could melt of the road)
qs = 0
QUOTE qm = s hf ? / c1
where
hf = enthalpy of fusion for water (143.5 Btu/lb).
For hot water (hydronic) systems, the above reduces
to:
qm = 746 s[/quote]
nothing more to do here
QUOTE Ar = ratio of snow-free area to total area (dimensionless)[/quote]
Once all the snow has melted how much is still on the road? The new road system is not zero but lets say it is
QUOTE Ar (qe + qh)[/quote]
so if we assune 100% of the water drains off the road... obviously horse poop but I'm lazy as heck
nothing more to do here either
therefore qo = qs + qm + Ar (qe + qh)
wittles down to (if we neglact everything but just what is needed to melt the snow):
24372 BTU/hr*ft^2 = 746 BTU/hr*ft^2 * s inch/hr
32.6 in of snow could be melted in total IF
the ambient temperature was always 32F when it snowed, the water always completely drained off (including any film) the road, snow density was light, the efficiency of the solar cells approached the mechanical system, 100% of the energy was used to melt snow, and there where no other loses.
So Fuzz my man the answer is a resounding no for your old stomping grounds
Ssssh
After thinking about the paper I think they are leaving out a number of effects
Sunload
Heat lose into the Earth
etc etc
*shrug* maybe I'm making harder than I need to but Im tempted go find the details of the snowfall on the main surfae road right by my house and really go for it (snowfall amount/rate, temperature across time, windspeed across time, etc). I am now really curious how much actual snow the road will melt... I think they give the w/m^2 numbers. Tbt I've been noodling some ideas on this one myself now. Fuzz
Sunload
Heat lose into the Earth
etc etc
*shrug* maybe I'm making harder than I need to but Im tempted go find the details of the snowfall on the main surfae road right by my house and really go for it (snowfall amount/rate, temperature across time, windspeed across time, etc). I am now really curious how much actual snow the road will melt... I think they give the w/m^2 numbers. Tbt I've been noodling some ideas on this one myself now. Fuzz
Ssssh
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fuzzylunkin1
I figured that brain of yours need some exercisingannexedbyBlake420 wrote:QUOTE (annexedbyBlake420 @ May 19 2014, 11:30 PM) After thinking about the paper I think they are leaving out a number of effects
Sunload
Heat lose into the Earth
etc etc
*shrug* maybe I'm making harder than I need to but Im tempted go find the details of the snowfall on the main surfae road right by my house and really go for it (snowfall amount/rate, temperature across time, windspeed across time, etc). I am now really curious how much actual snow the road will melt... I think they give the w/m^2 numbers. Tbt I've been noodling some ideas on this one myself now. Fuzz
.Surely vegas would still have to worry about dust, etc? Regardless, they aren't going to cover the entire country and get the numbers they advertised.Viscur wrote:QUOTE (Viscur @ May 19 2014, 11:40 PM) Ok, so it wouldn't work for you.
What about vegas?
My concern with this was the practicality: Are you going to get the grip and wear out of these that you get from bitmac?
Blacktop is a fantastic material, it's grippy (and you can easily modulate how grippy through aggregate choice), easily maintained (saw cut, excavate and patch or overlay or plane and patch) and extremely hard wearing. At junctions where HGVs are making 90 degree+ turns you get a lot of screwing over the surface which, assuming your surface isn't slippy (and it shouldn't be or it's far too lethal), means that there's a lot of sheer force exerted which will pull the surface apart or, in the case of bitmac, pull the aggregate out of the bitumen matrix.
A new road surface on a moderately busy road should have a design life of 25 years with appropriate maintenance. If you choose to overlay with 6-12mm of aggregate and tar you can extend that by 10 years or so. I honestly would be amazed if these panels can match that for the same price.
If they were to be used I would suggest that they go in quieter, residential roads or possibly car parking areas (although a car park that's parked on during the day rather defeats the point...) where the loading is lower overall and there's less wear. I can see these being useful on private drives to offer residential electricity along with solar roof panels and so on.
From my POV as a drainage engineer it would be good in they were manufactured in such a way that water can drain between the panels into a permeable stone layer and then either into the ground or at least filter through to a sustainable drainage system. That kind of arrangement could help with the build up of dust as this would be washed into the stone layer.
Blacktop is a fantastic material, it's grippy (and you can easily modulate how grippy through aggregate choice), easily maintained (saw cut, excavate and patch or overlay or plane and patch) and extremely hard wearing. At junctions where HGVs are making 90 degree+ turns you get a lot of screwing over the surface which, assuming your surface isn't slippy (and it shouldn't be or it's far too lethal), means that there's a lot of sheer force exerted which will pull the surface apart or, in the case of bitmac, pull the aggregate out of the bitumen matrix.
A new road surface on a moderately busy road should have a design life of 25 years with appropriate maintenance. If you choose to overlay with 6-12mm of aggregate and tar you can extend that by 10 years or so. I honestly would be amazed if these panels can match that for the same price.
If they were to be used I would suggest that they go in quieter, residential roads or possibly car parking areas (although a car park that's parked on during the day rather defeats the point...) where the loading is lower overall and there's less wear. I can see these being useful on private drives to offer residential electricity along with solar roof panels and so on.
From my POV as a drainage engineer it would be good in they were manufactured in such a way that water can drain between the panels into a permeable stone layer and then either into the ground or at least filter through to a sustainable drainage system. That kind of arrangement could help with the build up of dust as this would be washed into the stone layer.
Spidey: Can't think of a reason I'd need to know anything
Hmm, a quick look at the video (and I'll watch it all later) suggests that there's a lot of concrete in the construction. Concrete is a horribly polluting material (really useful and essential for construction but the CO2 footprint is a bitch) which is going to take some overcoming. Ideally a lower carbon alternative to the crawlspace in the video could be built as standard, using uPVC ducting most likely. And of course the standard ducting can't contain drainage because that needs to fall to it's outfall (watercourse or treatment works depending on whether it's foul or surface water, oh and you need to have separate systems for both and the foul sewer should be deeper so that leaks don't cause cross contamination).
Spidey: Can't think of a reason I'd need to know anything
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