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Interesting. Does anyone know what source of electricity is going to be used for this ? Probably solar but it might be also useful with coal plants or wind farm

Interesting. Does anyone know what source of electricity is going to be used for this ? Probably solar but it might be also useful with coal plants or wind farms that produce even when there is not enough demand. How are they moving the heat ?

whizzter 10mo ago
See my other comment about Nordic power balancing.
crishoj 10mo ago
It's a heat battery for district heating. Could be other sources than electricity, e.g. municipal garbage incineration plant.
- Maxion 10mo ago
  No, these generally use excess power during the night and windy days to store heat. There's not that much CHP production that there'd be excess, plus they can adjust those plants well enough that there's no unnecessary burning going on.
- fulafel 10mo ago
  There's water based heat batteries (aka thermal storage caverns) that are supplied with district heat in use in other places, but this is not one of them. The article says "Polar Night Energy’s technology works by heating a sand or a similar solid material using electricity"
perihelions 10mo ago
Natural gas and wood chips, > "The installation will supply heat to the Vääksy district heating network and is expected to lower fossil-based emissions by approximately 60% annually, primarily through an estimated 80% reduction in natural gas consumption and reduced reliance on wood chips." https://www.pv-magazine.com/2025/11/25/finlands-polar-night-to-build-250-mwh-sand-battery-for-district-heating-provider/ https://www.pv-magazine.com/2025/11/25/finlands-polar-night-...
- jonners00 10mo ago
  Those are the energy sources they're replacing with this tech - according to <https://reneweconomy.com.au/new-worlds-largest-sand-battery-to-double-the-size-of-current-record-holder/ https://reneweconomy.com.au/new-worlds-largest-sand-battery-...> it's surplus energy from renewables that will 'charge' the battery (so likely wind, hydro and solar that is produced but surplus to the grid's requirements)
Hamuko 10mo ago
Most likely not solar since there’s almost no solar during the winter months. Sun comes up at 0900 and goes down at 1500 in the south. In the north it’s worse. It's currently noon in Finland and solar accounts for 6 MW in the grid. That's about 0.05% of the total production. Nuclear is 3863 MW (~31%) and wind is 6281 MW (~50%). What might be plentiful is wind, especially during the nights.
anttisalmela 10mo ago
Wind in practice. There's only few hours of sunlight in the winter during the day. There has been a surge of electric boiler buildup by district heating companies in the last few years to exploit the periods of high wind and resulting very low electricity prices. Heat is transferred using disctrict heating networks where 65-120 C water is circulated.

whizzter 10mo ago

See my other comment about Nordic power balancing.

crishoj 10mo ago

It's a heat battery for district heating. Could be other sources than electricity, e.g. municipal garbage incineration plant.

Maxion 10mo ago
No, these generally use excess power during the night and windy days to store heat. There's not that much CHP production that there'd be excess, plus they can adjust those plants well enough that there's no unnecessary burning going on.
fulafel 10mo ago
There's water based heat batteries (aka thermal storage caverns) that are supplied with district heat in use in other places, but this is not one of them. The article says "Polar Night Energy’s technology works by heating a sand or a similar solid material using electricity"

perihelions 10mo ago

Natural gas and wood chips, > "The installation will supply heat to the Vääksy district heating network and is expected to lower fossil-based emissions by approximately 60% annually, primarily through an estimated 80% reduction in natural gas consumption and reduced reliance on wood chips." https://www.pv-magazine.com/2025/11/25/finlands-polar-night-to-build-250-mwh-sand-battery-for-district-heating-provider/ https://www.pv-magazine.com/2025/11/25/finlands-polar-night-...

jonners00 10mo ago
Those are the energy sources they're replacing with this tech - according to <https://reneweconomy.com.au/new-worlds-largest-sand-battery-to-double-the-size-of-current-record-holder/ https://reneweconomy.com.au/new-worlds-largest-sand-battery-...> it's surplus energy from renewables that will 'charge' the battery (so likely wind, hydro and solar that is produced but surplus to the grid's requirements)

Hamuko 10mo ago

Most likely not solar since there’s almost no solar during the winter months. Sun comes up at 0900 and goes down at 1500 in the south. In the north it’s worse. It's currently noon in Finland and solar accounts for 6 MW in the grid. That's about 0.05% of the total production. Nuclear is 3863 MW (~31%) and wind is 6281 MW (~50%). What might be plentiful is wind, especially during the nights.

anttisalmela 10mo ago

Wind in practice. There's only few hours of sunlight in the winter during the day. There has been a surge of electric boiler buildup by district heating companies in the last few years to exploit the periods of high wind and resulting very low electricity prices. Heat is transferred using disctrict heating networks where 65-120 C water is circulated.