Key facts
- Finland's Polar Night Energy has launched the world's largest commercial sand battery.
- The battery stores 100 MWh of renewable energy using 2,000 tons of crushed soapstone.
- It heats the soapstone to 400°C-600°C, retaining energy for weeks or months.
- The stored heat is used to produce hot water for the Pornainen district heating network.
- The system is automated and uses AI to optimize charging based on electricity prices.
- The sand battery is estimated to reduce greenhouse gas emissions by nearly 70%.
Modern power grids face instability due to the intermittent nature of renewable energy sources like wind and solar. To address this, Finland has deployed the world's largest commercial sand battery, a novel thermal energy storage solution developed by Polar Night Energy. Located in Pornainen, Southern Finland, the 100 MWh system utilizes 2,000 metric tons of crushed soapstone within a 13-meter-tall silo.
The battery operates by using electricity to heat air to temperatures between 400°C and 600°C, which is then circulated through the soapstone. This stored thermal energy can be retained for extended periods with minimal loss. When energy is needed, cool air is blown through the system to extract heat, which is converted into hot water via a heat exchanger. This hot water is then supplied to the local district heating network, providing warmth for homes, schools, and public buildings.
The entire operation is automated, with AI monitoring live electricity prices to charge the battery during periods of low cost and discharge it during peak demand. Polar Night Energy estimates this system has reduced greenhouse gas emissions by nearly 70% and decreased wood chip usage by approximately 60% compared to traditional methods.
Unlike conventional lithium-ion batteries, sand batteries do not degrade over time, do not rely on rare-earth materials, and offer a sustainable, low-cost solution for long-duration energy storage. Polar Night Energy has previously developed a smaller pilot project and is planning larger systems in the future, indicating growing commercial interest in thermal storage technologies as grids integrate more renewables.