late to the game, there are villiage/town scale thermal batteries operating in northern scandinavia useing sand inside a conventinal style insulated silos, ever

late to the game, there are villiage/town scale thermal batteries operating in northern scandinavia useing sand inside a conventinal style insulated silos, everything is off the shelf civil engineering equipment. any company offering similar tech will need a sharp pencil. I live off grid and am considering adding thermal storage as part of my system to allow for unatended background heating while on the road in the winter, where 2500 liters of water will provide pre heat for domestic hot water, and as a semi passive thermal siphon for area heating