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Finnish City Inaugurates 1 MW/100 MWh Sand Battery

(cleantechnica.com)
190 points erwinmatijsen | 3 comments | 03 Sep 25 06:00 UTC | HN request time: 0s | source
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Cthulhu_ ◴[03 Sep 25 08:02 UTC] No.45113336[source]▶
So why a surface sand silo instead of going down and using the soil/clay/bedrock/whatever is there? Ease of installation and maintenance?
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whimsicalism ◴[03 Sep 25 08:08 UTC] No.45113364[source]▶
presumably you need the insulation from the air, otherwise it would just sort of dissipate through the ground
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IshKebab ◴[03 Sep 25 09:19 UTC] No.45113779[source]▶
Open air is not a good insulator; that's why we wear coats! In contrast the ground is actually a pretty good insulator - that's why the London underground is so hot; the heat is all stuck in the ground.

It'll just be cheaper to build it on the ground than to dig a big hole and then build it in the hole.

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1. whimsicalism ◴[03 Sep 25 09:46 UTC] No.45113936[source]▶
i don’t really know what to say, i wasn’t suggesting that the ground is very conductive of heat - but it is certainly much more conductive than the air is. just search.

the reason we wear coats has more to do with convection than the heat conduction of air

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2. IshKebab ◴[03 Sep 25 12:40 UTC] No.45115014[source]▶
I said open air.
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3. whimsicalism ◴[03 Sep 25 13:07 UTC] No.45115273[source]▶
convection is orthogonal to conduction/insulation properties and this sand pit is in a silo. i don’t understand how your point is related to the notion that heat would diffuse if we just were heating up the ground