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Often, in winter at least, roads become covered in a kind
of low-density ice-air foam. This covers road markings
as a result road traffic can find it difficult to stay in the
appropriate lane or even the roadway as a whole.
While many authorities quickly mobilize ploughs &
equipment, there is always a time lag
between when it snows and when the road can be
Similarly, ploughs often move snow out of the main
roadway to the sides, in this scenario, the center of the
road may not be cleared and the edges covered in thick
So, to solve this we need to melt enough snow to make a
visible mark in the surface. We only need to raise the
temperature to above 0C and we are in business. To do
we use geothermal energy. The ground gets warmer as
dig down <link>. In most parts of the US as least,
is enough to ensure above-freezing temperatures all year
round, for the east coast where a good amount of the
traffic is, half this depth is fine. This fits well with road
structure since the first stage of building a road is to dig
long strip through the top 1-2ft/30-60cm anyway.
The device. This should be simple, rugged and mass-
producible. The basic design is a tube of corrosion-
resistant steel with a spike on the lower end. This should
be filed with a freeze-resistant corrosion-inhibiting
liquid. A crude low-grade alkane/alcohol mix seems
obvious*. The top should have a plate of road marking
width extending toward the flow of traffic, for
convenience this might be bolted on for ease of
Topmost, over the tube, it's a good idea to put a
conventional cats-eyes retroreflective marker.
Once installed, the liquid at the lower end will absorb
thermal energy from the warm ground around it, expand
and rise to the top. Here, in contact with snow, it will
cool, transferring energy to melt the snow before
contracting and sinking again to complete the cycle. On
top of the device, a steel plate just under the surface is
the main melting zone. This should extend toward traffic
from the cats-eyes marker. The length of this can be
chosen to take into account the angle from reflector to
driver's eye line given a typical snow depth.
Special versions of this may include an external auger to
allow simply screwing the device into the ground. A
thermocouple between top and bottom could provide
enough power for a ~1mA LED to embed in the reflector.
*Crucially, it shouldn't be water since water exhibits
utterly weird behavior around 4C, you'd get a situation
where the colder water rises and the warmer water sits
the bottom, counterproductive.
Ground temp by depth: Fig 2
[bs0u0155, Oct 05 2020]
||Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha (ask me why?)
||There's a massive nitrous oxide leak at you current location ?
||One for the road will have a different meaning. Especially if they unscrew.
||There's needed abilities, high heat conductivity in a needed direction, strength of material, they can't be cheap even if the micro electronics are.
Ultimately, does the mathematics of volume of melt from of the energy captured at 600mm minus transfer loss, work out to be viable? My gut says a inverted spike or cone seems a more viable but expensive shape.
||Strangely, I wondered whether an alloy could heat up when cooled because of it's structure. The two alloyed materials change shape differently under cooling and generate heat by the stress on the alloying bonds.
||Perhaps in snowy areas, the road paint needs to be of a color
that stands out from the white snow. I had thought about an
idea for using ground-loop heating to melt snow on your
driveway. Alternatively, there are already solutions involving
electric wires embedded just underneath the surface.
||// high heat conductivity in a needed direction,//
||Liquid convection solves heat conductivity, in this case
it's far from the limiting factor. What is a problem is
accidentally conducting the heat from the warmest lower
section to all of the middle sections before doing the
work at the top. So you'd need to insulate the middle
45cm or so.
||//strength of material, they can't be cheap even if the
micro electronics are// It HAS to be strong and cheap.
Road people think gravel and bitumen are expensive. So
mass production, standardization & steel are likely the
order of the day.
||Ultimately, does the mathematics of volume of melt from
of the energy captured at 600mm minus transfer loss,
work out to be viable?//
||Ball park, yes. If not, add length ~100mm more doubles
the power. There will be weather conditions that
overwhealm the melting. If it's -36 with 80mph winds the
heat delivery will never keep up, but this is extreme and
you'd design to the majority use conditions. Those are
likely in the -15C kind of range. Anywhere that routinely
gets colder than that for extended periods likely has
people who've already figured out how to navigate by
moose tracks or something.
//Strangely, I wondered whether an alloy could heat up
when cooled because of it's structure.//
||Oooh, that fires up some neurons, I see where you're
going, I think it happens, but here comes the boring "no"
part of the brain... heat generated as a by product of
cooling-induced shape change would just reach
equilibrium and inhibit shape change/temp change and
manifest as a slight perturbation of the cooling behavior.
||// The two alloyed materials change shape differently
under cooling and generate heat by the stress on the
||Using this the other way around we can input heat and
get shape change. The crudest implementation of this is
the bimetallic strip. Things have got a lot more
interesting recently however. Check out shape-memory
alloys and the derived shape memory actuators. They can
be used for all sorts of tiny things, but NASA is using them
to fold wings. They're very big on force density if not so
much range of motion. It's even conceivable to use them
as slower flight control surfaces - flaps and exotic wing
shape changes etc.
||//If not, add length ~100mm more doubles the power.// New roads then, else wouldn't it take more than double the power to shoot them into the road?
||// else wouldn't it take more than double the power to
shoot them into the road?//
||Ultimately it's putting a ~1m long object in a ~1m deep
in an environment surrounded by construction equipment.
You could even just place concrete sleeves on the graded
surface before backfilling the gravel layer. You'd plug the
holes with a bit of wood or something, lay most of your
surface, then just add them in and level them off at the
end. OR, install them first and use the long sequence as
straight-level markers of the middle of the road-to-be.
||Why not just build a roof ?