>The battery stores 8 MWh of thermal energy when full. When energy demand rises, the battery discharges about 200 kW of power through the heat-exchange pipes: that's enough to provide heating and hot water for about 100 homes

Cool, so we just need three million of these to take care of Europe.

If you look up Kankanpää on a map, you will find that it is a very small town in the middle of nowhere. And I haven't looked this up, but I'm suspecting it's got abundant sand production/shipping nearby from the Baltic. In those conditions, this sand-thermal storage might work well. But for most of the world, the space requirement, low energy efficiency, and costs associated with building large projects (and digging deep holes) in places where people actually, you know, live, will basically rule this out.