Finland has inaugurated an industrial-scale sand battery this week in the southern town of Pornainen, where it'll take over heating duties from an old woodchip power plant for the municipality. It's set to reduce carbon emissions from the local heating network by as much as 70%, and is the largest…
Why build it so high above the ground, where it needs these strong walls of steel? Wouldn’t it be cheaper to dig a hole in the ground and put the sand in there?
Then you’d end up making strong walls to keep the surrounding soil out when the bin is empty
I got interested in this tech a while back myself (thinking I should build one myself, how hard can it be?) and I made some simulations (because who wouldn’t). The thermal gradient in sand is actually quite steep, even with very high temps around the core where the resistors are, the temps fall off pretty quickly. Then when you are at a point where the surface temp is reasonable, you switch to a conventional thermal insulator. Putting it underground would cause all sorts of issues in eg. maintaining the resistors, insulation etc. so it’s probably just easier to do it like this.
The ground is… 4C or something? Would it lose more heat more easily to the solid ground, than to the air?
Its probably easier to keep it dry above ground too.
Maintenance? Might be easier above ground, but I know nothing of the tech, so I could be completely wrong 😞
More likely construction cost. Deep excavations are expensive, it’s much cheaper to just install a concrete pad and land things on top of it.
Construction costs are a one-time expense, though.
Is it cheaper to maintain over the course of the unit’s lifespan above or below ground?