Massive sand battery heats district in Finland
A large-scale Sand Battery has been launched in Finland, as part of a district heating system.
Published on June 16, 2025
Team IO+ selects and features the most important news stories on innovation and technology, carefully curated by our editors.
A large-scale Sand Battery has been launched in Pornainen, Finland, as part of Loviisan Lämpö’s district heating system. Developed by Polar Night Energy, this installation provides 1 MW of thermal power and stores up to 100 MWh of energy, making it ten times bigger than the company’s earlier pilot.
Sand Battery: way more sustainable
By replacing fossil fuels with renewable heat storage, the Sand Battery is expected to lower annual CO₂-equivalent emissions from the local heating network by about 160 tons. That’s nearly a 70% reduction in climate impact for the area.
The system allows Pornainen to completely eliminate oil from its heating supply and reduce the use of wood chips by roughly 60%. The existing biomass boiler remains in place as a backup for peak demand.
How the Sand Battery works
The Sand Battery works by storing electricity as heat in crushed stone, such as soapstone. This stored heat can then be released on demand to warm homes and buildings. It's a robust, high-temperature storage solution that supports both municipal heating and industrial use.
100 workers
Polar Night Energy led the construction and delivered the battery as a turnkey project. The build took about a year, involving over 40 subcontractors and 100 workers.
2,000 tonnes of crushed stone
Standing 13 meters tall and 15 meters wide, the battery contains around 2,000 tonnes of crushed soapstone. In summer, it can meet almost a full month of heating needs for Pornainen; in winter, nearly a week.
