Only three months after inaugurating the world’s largest ‘sand battery’, a large-scale and high-temperature thermal energy storage system, Finnish company Polar Night Energy has agreed to build an even larger battery to supply district heating to the village of Vääksy.
Polar Night Energy announced this week that it would partner with Finnish renewable energy company Lahti Energia on the construction of an industrial-scale sand battery which will have a heating power of 2 megawatts (MW) and storage capacity of 250 megawatt-hours (MWh).
Sand batteries made by Polar Night Energy use sand or similar materials as a storage medium and can be used to provide hot water for district heating and other heating systems, hot air for space heating and other industrial processes, and steam.
Polar Night Energy also hopes to soon be able to use its sand battery technology to convert stored energy back into electricity.
Polar Night Energy’s sand battery stores energy in sand as heat, acting as a high-power and high-capacity reservoir for excess renewable energy.
According to Polar Night Energy, sand batteries serve three primary functions – storing excess renewable energy, participating in reserve markets to balance the frequency of the grid, and producing heat and power without combustion.
The sand battery will provide thermal energy storage for Lahti Energia’s district heating network in the Finnish village of Vääksy.
Once completed and operational, the sand battery will cut fossil-based emissions in the heating network by around 60 per cent each year thanks to an approximately 80 per cent reduction in natural gas usage and a reduction 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.”
Image Credit: Polar Night Energy
Polar Night Energy inaugurated what is currently the world’s largest sand battery in August, which provides heating power of 1 MW and capacity of 100 MWh. Built for Loviisan Lämpö, a Finnish energy company, the battery is located in Pornainen, Finland, and serves as the primary production plant of the local heating network.
Construction on the new sand battery in Vääksy is expected to begin in early 2026 and completed by the middle of 2027. The storage medium for the new battery will be approximately 2,400 tons of locally available natural sand, stored in a silo measuring around 14 metres high and 15 metres wide.
“We are truly proud to collaborate with a major energy company like Lahti Energia,” said Tommi Eronen, CEO of Polar Night Energy.
“This project is not only an important reference for us but also another step toward cleaner heat production in demanding high-temperature applications.
“It is incredible to once again build the world’s largest Sand Battery. This represents a major step forward for both organizations toward achieving our emission-reduction goals.”
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