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Ground-Source Thermosyphon Road Markers

Use free low-grade heat to melt road markings into snow
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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 and 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 & salt/gritting equipment, there is always a time lag between when it snows and when the road can be treated. 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 piles.

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 this we use geothermal energy. The ground gets warmer as you dig down <link>. In most parts of the US as least, 2ft/60cm 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 a 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 thermal 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 alignment. 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 at the bottom, counterproductive.

bs0u0155, Oct 05 2020

Ground temp by depth: Fig 2 https://igws.indian...eothermal/HeatPumps
[bs0u0155, Oct 05 2020]

[link]






       Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha Ha (ask me why?)
xenzag, Oct 05 2020
  

       There's a massive nitrous oxide leak at you current location ?
8th of 7, Oct 05 2020
  

       It certainly would make one of xenzag's recent ideas more energy efficient. Although there's some question if it's meant to be practical or just artistic.
kdf, Oct 05 2020
  

       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.
wjt, Oct 07 2020
  

       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.
sanman, Oct 07 2020
  

       // 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 alloying bonds.//   

       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.
bs0u0155, Oct 07 2020
  

       //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?
wjt, Oct 07 2020
  

       // 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 hole 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 road 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.
bs0u0155, Oct 07 2020
  

       Why not just build a roof ?
8th of 7, Oct 07 2020
  
      
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