A new industrial-scale 'sand battery' has been announced for Finland, which packs 1 MW of power and a capacity of up to 100 MWh of thermal energy for use during those cold polar winters. The new battery will be about 10 times bigger than a pilot plant that’s been running since 2022.
They’re using heat exchangers to add it to the municipal heating loop. No electricity involved on that side.
I saw that, but they said it could be converted to heat with a loss.