Located in Pornainen, the sand battery, nearly 13 meters tall and 15 meters wide, uses approximately 2,000 tons of crushed soapstone, to store thermal energy. This makes it 10 times larger than the first commercial sand battery launched in Kankaanpää in 2022. The Pornainen system serves as the primary heat source for the local district heating network, meeting nearly a month’s heating needs in summer and about a week’s demand in winter.
The sand battery is projected to reduce annual CO2-equivalent emissions by around 160 tons, lowering Pornainen’s district heating emissions by nearly 70%. It eliminates the need for oil in the heating network and cuts wood chip consumption by approximately 60%, supporting sustainable energy goals. “The sand battery is a major step toward [achieving climate neutrality by 2035],” said Mikko Paajanen, CEO of Loviisan Lämpö.
Announced in March, 2024, the project underwent testing in November, 2024, involved around 40 subcontractors and over 100 workers during construction. Polar Night Energy’s Chief Operating Officer, Liisa Naskali, stated: “This is a solid foundation for scaling sand battery technology to even larger capacities, and across new industrial sectors.” The company is actively engaging with Finnish and international partners to explore further sand battery projects.
In May, 2025, Polar Night Energy revealed plans to develop a pilot plant in southern Finland, to test its power-to-heat-to-power sand battery technology, which converts stored thermal energy back into electricity. The startup also secured €7.6 million ($8.6 million) in seed funding in 2024, to support its growth and innovation efforts.
This project highlights Finland’s commitment to advancing renewable energy solutions, and sustainable heating systems. The Pornainen sand battery demonstrates the potential for scalable, eco-friendly technology to transform local energy systems while reducing environmental impact.
