Surviving Winter with Sand! The Impact of the World's Largest "Sand Battery" from Finland

Surviving Winter with Sand! The Impact of the World's Largest "Sand Battery" from Finland

2025年06月17日 20:48

Comprehensive Guide to the "World's Largest Sand Battery" from Finland


1. What is a Sand Battery?

A type of high-temperature thermal energy storage (HTTES) that heats sand or crushed rock to several hundred degrees and retrieves the stored heat as needed. This particular system was developed by the Finnish startup Polar Night Energy. It involves filling a steel silo approximately 15 meters in diameter and 13 meters high with 2,000 tons of soapstone, capable of storing up to 1 MW/100 MWh of heat.


2. Role in the Town of Kankaanpää

It is directly connected to the district heating system, which is common in the Nordic countries, and can provide heating for the entire town for about a week in winter and a month in summer. It is estimated to reduce the fuel usage of wood chip-fired boilers by 60% and reduce annual CO₂ emissions by about 70%.


3. Economic Viability—"Heat can be stored for a few cents per kWh"

  • The cost of a small prototype (8 MWh) is about $25/kWh, which is significantly cheaper compared to the average cost of Li-ion batteries at the same time ($115/kWh).

  • Charging is done during the negative price periods at night in the Finnish electricity market, and heat is released during high-price periods during the day (with a heat pump, the heat COP is greater than 1.0). On Hacker News, there was an estimation that "even if built for 1 M€, it could be recouped in 10 years with a power price difference of 2.3 c/kWh."


4. Key Technologies

ItemFigures/SpecificationsNotes
Heat Storage MediumSoapstone (Crushed Soapstone)Reuse of stone discarded as waste
Maximum Temperature500–600 ℃Heat loss 10–15 %/week
Heat Charging/Discharging MethodAir heater + duct circulationSteam power generation possible in the future
Expected Lifespan20–30 yearsAlmost no degradation of the medium


5. Reactions on SNS

| X (formerly Twitter) 🇯🇵 | "Seems like it could be adapted for regional heat supply in Hokkaido" "The decisiveness of not converting heat back to electricity is good" | Many welcoming voices from regions dependent on winter heating |
| Reddit /r/energy | "Best solution for cold regions" "Low material cost is a strength" | High evaluation of technological potentialreddit.com |
| Hacker News | "Cost structure is unclear" "Being heat-only, it thrives in urban concentrated areas" | Critical views on profitability and application conditionsnews.ycombinator.com |
| Japanese Tech Blogs※ | "The term 'sand battery' can be misleading" "The hybrid proposal with hot spring heat is interesting" | Focus on terminology clarification and feasibility of domestic productiongigazine.net |

※Aggregated from blog and bulletin board comment sections (as of 2025/6/17)


6. Impact on Japan

  1. Heat Demand Smoothing in Cold Regions – Can be directly connected to existing regional heat supply networks in Sapporo, Asahikawa, etc.

  2. Industrial Waste Heat Recycling – Store waste heat from paper and steel industries for nighttime steam use.

  3. Adjustment Capability of Renewable Energy – In northeastern Tohoku with a high wind power ratio, a system of "surplus→heat→regional heating" can be envisioned.

  4. Low-Cost Disaster Prevention Stock – Effective for heating shelters during disasters as it retains heat for several days even if electric heaters stop.


7. Implementation Challenges

  • Limited District Heating Networks: Only about 180 areas nationwide in Japan.

  • Site Selection: When placing 13-meter-class silos in urban areas, attention must be paid to landscape and fire regulations.

  • Electricity Pricing System: Without dynamic pricing, economic benefits diminish.

  • Policy Support: Subsidies for green growth strategies targeting heat utilization are needed.


8. Future Outlook

  • Polar Night Energy has announced the development of anext-generation 10 MW class.

  • Towards an era of material diversification with companies like Sunamp in Scotland (sodium chloride phase change material) and Electrified Thermal Solutions in the US (carbon block).techcrunch.com

  • In Japan, if hybrid projects like **"Geothermal + Sand Battery"** progress, it is expected to solve the waste heat problem in hot spring areas and serve as a tourism PR benefit.

Reference Articles

Finland Starts Operation of the World's Largest Sand Battery, Economically Appealing Outlook
Source: https://techcrunch.com/2025/06/16/finland-warms-up-the-worlds-largest-sand-battery-and-the-economics-look-appealing/

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