The world’s largest sand battery in Pornainen, Finland was commissioned by Polar Night Energy and district heating provider Loviisan Lampo in June 2025. The facility has a capacity of approximately 1 MW of thermal power and stores around 100 MWh of heat, using about 2,000 tonnes of crushed soapstone as the storage medium.
The sand battery storage system uses surplus renewable electricity to heat soapstone to high temperatures, and then releases this energy into the district heating network when it is needed.
Finland is also developing the world’s largest heat storage project, named Varanto, in Vantaa in the Greater Helsinki metropolitan area. The project has a 90 GWh storage capacity.
The World’s Largest Sand Battery Goes Live in Finland, First of its Kind
Reported August 28, 2025 – Finland has inaugurated the world’s largest sand battery this week in the southern town of Pornainen, first of its kind. The project is expected to take over heating duties from an old woodchip power plant for the municipality. Moreover, it is set to reduce carbon emissions from the local heating network by as much as 70%, the largest of its kind. The battery was developed by Finnish Firm Polar Night Energy, which proved to be stellar in delivering such projects.
Few years ago, the company also built the world’s first commercial sand battery. The current battery is about 42 feet tall and 50 feet wide. It serves as a storage medium for up to 100 MWh with a round trip efficiency of 90%. This makes it about 10 times larger than the first-ever sand battery. Furthermore, it is capable of storing enough heat for the whole town to use for a week. The use of battery energy storage as means of storing energy is one that is gaining traction around the world. Projects such as the world’s largest BESS project is a clear indication of this. Furthermore, Africa’s largest BESS project in South Africa also underscores this commitment to develop bess projects around the world.
Project Factsheet for the World’s Largest Sand Battery in Pornainen, Finland
Project Name: Pornainen Sand Battery
Location: Pornainen, Uusimaa region, Finland
Developer: Polar Night Energy
Partner/Operator: Loviisan Lampo
Technology Use: High-temperature thermal energy storage using sand.
Thermal Output Capacity: 1 MW
Energy Storage Capacity: 100 MWh of thermal energy
Storage Medium: 2,000 tonnes of crushed soapstone and sand mixture.
Operating Temperature: 400 to 600 degrees Celsius
Height and Diameter: 13 m high by 15 m wide
AI Optimization Partner: Elisa Industriq for energy-flexibility and operational optimization.
Environmental Impact:
- 70% reduction in CO2 emissions for Pornainen’s district heating network
- Estimated annual CO2 reduction of about 160 tonnes
Project Status: Fully commissioned and operational
Project Timeline
2021: Polar Night Energy and Loviisan Lampo begin technical discussions on scaling sand-battery technology from Tampere pilot.
2022: Polar Night Energy’s first commercial sand-battery pilot in Kankaanpaa, Finland.
2023-2024: Design and permitting stages for the Pornainen installation.
January 2025: Polar Night Energy partners with Elisa Industriq to integrate an AI-based optimization platform for system flexibility and participation in electricity reserve markets.
June 2025: Project officially commissioned. The world’s largest sand battery goes online in Pornainen.
October 2025: System starts operations. Replaces most of the town’s fossil-based heating sources.
Significance of the World’s Largest Sand Battery in Finland
The implementation of the world’s largest battery in Finland is a critical tool for such places which intermittently generate vast quantities of wind and solar but also face variations in energy demand and supply. The project will facilitate this as charges up battery when electricity is cheaply available and can hold a charge for months. Through this, it helps balance the energy grid during periods of high demand.
This battery has actually been in operation since June, and the company says it has already exceeded its efficiency targets in the early days of optimizing its functions. Many of Pornainen’s buildings, including its town hall, are currently heated by the new TES. In the coming years, it will play a major role in helping the town achieve carbon neutrality. Moreover, it might inspire more municipalities in regions with similar climate and energy sources to adopt these giant batteries.
