A revolutionary leap in renewable energy storage has just been realized in Finland’s Pornainen municipality—home to what is now the world’s largest “sand battery.” Developed by Polar Night Energy for Loviisan Lämpö, this towering 13‑meter structure packed with around 2,000 tonnes of crushed soapstone can store up to 100 MWh of thermal energy—enough heat to run a district network for weeks in summer and about a week during winter. Charged using surplus power from wind and solar through resistive heating, the sand captures and retains heat at around 500 °C, with only about a 10 % loss over extended periods.

This sand battery facility is more than a remarkable engineering feat—it’s a bold step toward eliminating fossil fuels from local heating systems. By supplying one megawatt of thermal power to the district grid, it enables Loviisan Lämpö to phase out oil and cut down wood-chip burning by 60 %, reducing carbon emissions by approximately 160 tons annually—nearly a 70 % drop. Leveraging industrial by‑products like crushed soapstone from fireplace production, the project also champions circular economy principles by avoiding virgin materials.

Beyond these environmental benefits, the project supports grid stability and smart energy dynamics. By participating in reserve electricity markets and toggling charge/discharge cycles in response to price signals, the sand battery ensures efficient energy usage across seasons. In summer, it can supply almost a month’s worth of heat; in winter, up to a week—showcasing its potential as a scalable, cost‑effective alternative to lithium batteries for long‑duration thermal storage. With expansion and power-to-heat-to-power pilots already on the horizon, this innovation positions sand—often overlooked—as a cornerstone in the global shift to clean, sustainable energy.