Polar Night Energy and Lahti Energia have agreed on the construction of an industrial-scale thermal energy storage for Lahti Energia’s district heating network in Vääksy, Finland. The new Sand Battery will have a heating power of 2 MW and a storage capacity of 250 MWh, making it the world’s major sand-based thermal energy storage system once completed.
The Sand Battery will supply heat to Lahti Energia’s Vääksy district heating network. The goal is to provide local customers with energy that is as low-emission and cost-efficient as possible.
The Sand Battery will cut fossil-based emissions in the Vääksy district heating network by around 60% each year, driven by an approximately 80% reduction in natural gas use and a notable decrease in wood chip consumption.
A Sand Battery is a high-temperature thermal energy storage system that uses sand or a similar solid material to store renewable energy.
Polar Night Energy will act as the main contractor for the construction project. On-site work will begin in early 2026, and the Sand Battery will be completed in summer 2027.