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I am wondering why this does not exist:

After substrate, before laying a concrete or asphalt driveway, drive 9'+ lengths of aluminum rebar with large plates at the head (imagine a very long nail) into the earth, with the head plates floating an inch above the substrate, positioning them mid-way in the material. In theory, given enough of these spikes, wouldn't a passive geothermal heatsink effect result in a driveway that keeps slightly cooler in the summer and much more importantly, raises the median temperature of the driveway enough benefit in the winter through less snow/ice accumulation?

I realize heated driveways exist, but they are extremely expensive to operate. With enough spikes driven deep into the earth would this result in a meaningful, passive, partial solution?

user162124
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  • So have you calculated the heat gain / loss from the surface? what about the amount of heat that can be conducted by each "spike"? Then how many would be needed to achieve a given temperature? – Solar Mike Feb 12 '22 at 16:19
  • I assume you got your info from here: https://lisbdnet.com/what-is-the-temperature-6-feet-underground/ which states 10 feet below surface level the temperature is relatively constant year round and a 10C difference could be expected. But heat would be lost to the surroundings during the transmission and ground unless you insulated it. I don't know about you but I'm not sure my hand would feel any warmer in winter touching a 10 foot long aluminum rod when the opposite end is 10C warmer. Rebar, by form, has high surface area to volume which is not good for heat loss. – DKNguyen Feb 12 '22 at 18:12
  • Steel rebar is only 0.5% to 3% of the volume of concrete. And for something like a driveway it's on the low end. And vertical rebar does not contribute to the strength of the driveway. I imagine a passive heat pipe solution not only be more effective but cheaper, but those seem as if they would not be terribly robust. – DKNguyen Feb 12 '22 at 18:15

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