Finland’s radical answer to renewable energy’s biggest headache: The world’s largest sand battery

Yes it is. The heat from the sand battery can be used throughout the winter. All you need is good insulation.

I think of it as a simpler alternative to pumped hydro when all you need is heat. It kind of dumb to waste the great pumped hydro resources that can store electricity on heating stuff. So, this can cover their heating needs during bad weather, and they can used pumped hydro for the rest.

Removing industrial and transportation, heating represents is more than half of the energy use in Finland. Being able to store it and use later - particularly in district heating applications - is definitely a long-term solution

IIRC it can store heat for months.