Polar Night Energy has entered into an agreement with Lahti Energia to build an industrial-scale sand battery, which will integrate into Lahti Energia’s district heating network in Vääksy, Finland.
The project will deliver the world’s largest sand-based thermal energy storage once completed, with a heating power of 2MW and a storage capacity of 250MWh.
The Sand Battery will supply heat to the Vääksy district heating network, aiming to provide customers with energy that is both low-emission and cost-efficient. Fossil-based emissions are expected to fall by around 60% annually, driven by an 80% reduction in natural gas use and a significant decrease in wood chip consumption.
“We want to offer our customers affordable district heating and make use of renewable energy in our heat production,” said Jouni Haikarainen, CEO of Lahti Energia. “The scale of this Sand Battery also enables us to participate in Fingrid’s reserve and grid balancing markets. As the share of weather-dependent energy grows in the grid, the Sand Battery will contribute to balancing electricity supply and demand.”
Polar Night Energy will act as the main contractor, with construction beginning in early 2026 and completion scheduled for summer 2027. The system will use approximately 2,400 tonnes of locally sourced sand, capable of storing heat at over 500°C. Once finished, the installation will stand 14m high and 15m wide, alongside a dedicated technical building.
The company’s earlier Sand Battery in Pornainen is already said to be demonstrating reliable performance.
