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World’s largest sand battery enters operation in Finland
18/6/2025
News
Loviisan Lämpö has commissioned the world’s largest sand battery, a high-temperature thermal energy storage system. Developed by Polar Night Energy, the industrial-scale sand battery now serves as the main production facility for the district heating network in Pornainen, Finland.
The battery delivers 1 MW of thermal power and offers a storage capacity of 100 MWh, making it 10 times larger than the unit launched in Kankaanpää in 2022, reports Polar Night Energy. It is expected to reduce annual CO2-equivalent emissions from the local heating network by around 160 tonnes, cutting climate emissions in Pornainen’s district heating by nearly 70%.
‘Our goal is to be climate neutral by 2035, and the sand battery is a major step toward that,’ comments Mikko Paajanen, CEO of Loviisan Lämpö.
The launch of the sand battery means the use of oil in the Pornainen’s heating network will be completely phased out, and the consumption of wood chips will decrease by approximately 60%. The existing biomass boiler will continue to serve as a backup and will generate power during peak demand periods.
The Loviisan Lämpö sand battery stands about 13 metres tall and 15 metres wide, and uses approximately 2,000 tonnes of crushed soapstone as its thermal storage medium. In summer, the battery can cover almost a month’s heat demand in Pornainen, and in winter, close to a week.
A key part of the sand battery’s profitability lies in optimising its operation according to electricity prices and Finland’s grid operator Fingrid’s reserve markets, according to the project partners. In doing so, the battery also supports power grid stability. The optimisation is handled by Elisa, a Finnish telecommunications and digital software services company, which uses its AI-driven solution to automatically identify the most economically viable moments to charge or discharge the sand battery.
The crushed soapstone used as the thermal storage medium is a by-product from the production of Tulikivi’s heat-retaining fireplaces. ‘Finland aims to become a carbon-neutral circular economy by 2035. To reach this we need new cross-sectoral solutions to use resources more efficiently and turn the circular economy into practical reality across more industries,' comments Heikki Vauhkonen, CEO of Tulikivi.
Earlier this spring, Polar Night Energy announced a pilot in Valkeakoski, Finland, to explore the conversion of stored thermal energy back into electricity a process known as power-to-heat-to-power (P2H2P). Construction is set to begin in autumn 2025.
