🔋 Finland's 'sand battery' survived its first brutal winter.
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Finland's 'sand battery' survived its first brutal winter. But the viral story gets one big thing wrong.What's real:
- Polar Night Energy built a commercial thermal battery in Pornainen, Finland (5,000 people)
- 2,000 tons of crushed soapstone heated to 500-600C
- 1 MW power, 100 MWh capacity
- 100% oil reduction (literally zero oil used now)
- 70% CO2 emissions cut, 60% less wood chip combustion
- Survived winter 2025-2026 without interruption
- 5 projects across Finland, 9M euros fundingWhat's misleading:
1) It stores HEAT, not electricity. The 100 MWh is thermal energy. It can't power your lights or EV - it heats buildings via district heating. 'Store electricity in sand' implies grid-scale electrical storage, which this isn't.
2) It's not sand - it's crushed soapstone (a byproduct from Finnish fireplace manufacturing). Better heat capacity and density than plain sand. 'Sand battery' is branding.
3) The 80-90% round-trip efficiency is company-claimed, not independently verified. And it's electricity-to-heat-to-heat, not electricity-to-electricity. Comparing it to lithium-ion (90-95%) is apples-to-oranges.
4) The underlying tech (packed-bed thermal storage) is decades old. What's new is the application, branding, and business model.
The sand battery isn't competing with your Powerwall. It's competing with oil boilers - and it's already winning.
Full fact-check: https://hermez.prose.sh/finland-sand-battery-survived-winter
#science #energy #renewable #Finland #engineering #CleanEnergy
@jcrabapple Really good analysis! Thanks
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Finland's 'sand battery' survived its first brutal winter. But the viral story gets one big thing wrong.
What's real:
- Polar Night Energy built a commercial thermal battery in Pornainen, Finland (5,000 people)
- 2,000 tons of crushed soapstone heated to 500-600C
- 1 MW power, 100 MWh capacity
- 100% oil reduction (literally zero oil used now)
- 70% CO2 emissions cut, 60% less wood chip combustion
- Survived winter 2025-2026 without interruption
- 5 projects across Finland, 9M euros fundingWhat's misleading:
1) It stores HEAT, not electricity. The 100 MWh is thermal energy. It can't power your lights or EV - it heats buildings via district heating. 'Store electricity in sand' implies grid-scale electrical storage, which this isn't.
2) It's not sand - it's crushed soapstone (a byproduct from Finnish fireplace manufacturing). Better heat capacity and density than plain sand. 'Sand battery' is branding.
3) The 80-90% round-trip efficiency is company-claimed, not independently verified. And it's electricity-to-heat-to-heat, not electricity-to-electricity. Comparing it to lithium-ion (90-95%) is apples-to-oranges.
4) The underlying tech (packed-bed thermal storage) is decades old. What's new is the application, branding, and business model.
The sand battery isn't competing with your Powerwall. It's competing with oil boilers - and it's already winning.
Full fact-check: https://hermez.prose.sh/finland-sand-battery-survived-winter
#science #energy #renewable #Finland #engineering #CleanEnergy
@jcrabapple And how many fireplaces could possibly be built to scale this business model?
And then how much CO2 would be released from the use of all these fireplaces?
I like the project, but I'm not sure it can reasonably scale.
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@jcrabapple And how many fireplaces could possibly be built to scale this business model?
And then how much CO2 would be released from the use of all these fireplaces?
I like the project, but I'm not sure it can reasonably scale.
@newstik those are very good questions! A lot of these types of innovations work great for small communities but don't work at scale, or just don't make sense at scale.
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Finland's 'sand battery' survived its first brutal winter. But the viral story gets one big thing wrong.
What's real:
- Polar Night Energy built a commercial thermal battery in Pornainen, Finland (5,000 people)
- 2,000 tons of crushed soapstone heated to 500-600C
- 1 MW power, 100 MWh capacity
- 100% oil reduction (literally zero oil used now)
- 70% CO2 emissions cut, 60% less wood chip combustion
- Survived winter 2025-2026 without interruption
- 5 projects across Finland, 9M euros fundingWhat's misleading:
1) It stores HEAT, not electricity. The 100 MWh is thermal energy. It can't power your lights or EV - it heats buildings via district heating. 'Store electricity in sand' implies grid-scale electrical storage, which this isn't.
2) It's not sand - it's crushed soapstone (a byproduct from Finnish fireplace manufacturing). Better heat capacity and density than plain sand. 'Sand battery' is branding.
3) The 80-90% round-trip efficiency is company-claimed, not independently verified. And it's electricity-to-heat-to-heat, not electricity-to-electricity. Comparing it to lithium-ion (90-95%) is apples-to-oranges.
4) The underlying tech (packed-bed thermal storage) is decades old. What's new is the application, branding, and business model.
The sand battery isn't competing with your Powerwall. It's competing with oil boilers - and it's already winning.
Full fact-check: https://hermez.prose.sh/finland-sand-battery-survived-winter
#science #energy #renewable #Finland #engineering #CleanEnergy
@jcrabapple Just some small addition: As a geologic term, the word sand specifies only grain size and not composition. The sand battery could very well be filled with sand, provided the crushed soapstone has the correct grain size.
In everyday language, "sand" is obviously understood differently, but I think this should at least be noted in a fact-check. Giving physical properties for "sand" in a fact-check without specifying the material is not good, though "plain sand" probably means quartz. -
@bigblen from what I remember, Finland's system is pretty advanced. They were at like 75% carbon neutral production, I think.
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@bigblen @jcrabapple
Afaik district heating is common across the Nordics. But yeah, the heat has to generate somehow. iirc here in Stockholm a lot of it from burning trash. -
@jcrabapple And how many fireplaces could possibly be built to scale this business model?
And then how much CO2 would be released from the use of all these fireplaces?
I like the project, but I'm not sure it can reasonably scale.
@newstik @jcrabapple plain sand is not 3 times worse and can be used pretty fine. So your "what about" is just "what about".
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@jcrabapple Just some small addition: As a geologic term, the word sand specifies only grain size and not composition. The sand battery could very well be filled with sand, provided the crushed soapstone has the correct grain size.
In everyday language, "sand" is obviously understood differently, but I think this should at least be noted in a fact-check. Giving physical properties for "sand" in a fact-check without specifying the material is not good, though "plain sand" probably means quartz.@KathrinM @jcrabapple in fact check they used 0.80 J/kg for sand while in other places it's 0.83 J/kg
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@bigblen Distributed heating is very common here, but it is generally built around use of excess energy, so finding an alternative would not mean replacing oil. But, new ways to store energy for distributed heading could possibly mean it opens up to new locations.
The fact that it is so common here shows that it works well, we use water to carry heat, a great way to heat in winter. No dust burning, no risk of fire if covered, etc
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Finland's 'sand battery' survived its first brutal winter. But the viral story gets one big thing wrong.
What's real:
- Polar Night Energy built a commercial thermal battery in Pornainen, Finland (5,000 people)
- 2,000 tons of crushed soapstone heated to 500-600C
- 1 MW power, 100 MWh capacity
- 100% oil reduction (literally zero oil used now)
- 70% CO2 emissions cut, 60% less wood chip combustion
- Survived winter 2025-2026 without interruption
- 5 projects across Finland, 9M euros fundingWhat's misleading:
1) It stores HEAT, not electricity. The 100 MWh is thermal energy. It can't power your lights or EV - it heats buildings via district heating. 'Store electricity in sand' implies grid-scale electrical storage, which this isn't.
2) It's not sand - it's crushed soapstone (a byproduct from Finnish fireplace manufacturing). Better heat capacity and density than plain sand. 'Sand battery' is branding.
3) The 80-90% round-trip efficiency is company-claimed, not independently verified. And it's electricity-to-heat-to-heat, not electricity-to-electricity. Comparing it to lithium-ion (90-95%) is apples-to-oranges.
4) The underlying tech (packed-bed thermal storage) is decades old. What's new is the application, branding, and business model.
The sand battery isn't competing with your Powerwall. It's competing with oil boilers - and it's already winning.
Full fact-check: https://hermez.prose.sh/finland-sand-battery-survived-winter
#science #energy #renewable #Finland #engineering #CleanEnergy
@jcrabapple sand is defined by grain size, not composition.
That said, awesome stuff
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@bigblen @jcrabapple
Afaik district heating is common across the Nordics. But yeah, the heat has to generate somehow. iirc here in Stockholm a lot of it from burning trash.From the pdf available here: https://energia.fi/en/statistics/statistics-on-district-heating/
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