Finnish startup Polar Night Energy has announced its industrial-scale sand battery in Pornainen, southern Finland, is now operational following commissioning by district heating company Loviisan Lämpö.
The Pornainen sand battery delivers 1 MW of thermal power and offers a storage capacity of 100 MWh, making it 10 times larger than the world’s first commercial sand-based, high-temperature heat storage system launched in Kankaanpää in 2022 and the largest in the world to date.
Standing at almost 13 meters tall and 15 meters wide, it uses approximately 2,000 tons of crushed soapstone as its thermal storage medium.
It will serve as the main production facility for the district heating network in Pornainen, capable of covering almost a month’s heat demand in the municipality during summer and close to a week’s demand in winter.
The sand battery is expected to reduce annual CO2-equivalent emissions from the local heating network by around 160 tons, cutting climate emissions in Pornainen’s district heating by nearly 70%. It will also allow the use of oil in the municipality’s heating network to be completely phased out and reduce the consumption of wood chips by around 60%.
Mikko Paajanen, CEO of Loviisan Lämpö, said the municipality is aiming to be climate neutral by 2035 and “the sand battery is a major step toward that.”
The project was first announced in March 2024 before testing began in November 2024. Construction involved around 40 subcontractors and over 100 workers.
“This is a solid foundation for scaling sand battery technology to even larger capacities, and across new industrial sectors,” said Polar Night Energy Chief Operating Officer Liisa Naskali.
The company also revealed it is in “active discussions” with Finnish and international partners about new sand battery projects.
In May, Polar Night Energy announced plans to build a pilot plant in southern Finland that will test its power-to-heat-to-power sand battery technology, otherwise known as the conversion of stored thermal energy back into electricity. The company also secured €7.6 million ($8.2 million) in seed funding last year.
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