Polar Night Energy and Lahti Energia to Build World's Largest Sand Battery in Finland

Polar Night Energy and Lahti Energia will construct the world's largest sand-based thermal energy storage system in Vääksy, Finland, with a heating capacity of 2 MW and storage capacity of 250 MWh. Construction begins in early 2026 and is expected to be completed by summer 2027. The system will reduce fossil-based emissions in the district heating network by approximately 60% and will enable participation in grid balancing markets. The project is supported by Business Finland.

Published Mar 29, 2026

Polar Night Energy and Lahti Energia are set to build the world's largest sand-based thermal energy storage system in Vääksy, Finland. This system will have a heating capacity of 2 MW and a storage capacity of 250 MWh, directly connecting to Lahti Energia's district heating network.

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Construction will start in early 2026 and is expected to finish by summer 2027. The Sand Battery will use renewable electricity to heat 2,400 tons of natural sand, reducing fossil-based emissions by about 60% annually and allowing participation in Fingrid's grid balancing markets. The project is receiving funding from Business Finland.