Polar Night Energy, which in 2022 implemented the world’s first commercial sand-based, high-temperature heat storage system in the Finnish city of Kankaanpää, is now planning the largest such system to be built. An industrial-scale thermal energy storage unit for Lahti Energia’s district heating network in Vääksy, Finland, will deliver 2 MW of thermal output and 250 MWh of storage capacity.

The 14 m-tall system will supply heat to the Vääksy district heating network and is expected to lower fossil-based emissions by approximately 60% annually, primarily through an estimated 80% reduction in natural gas consumption and reduced reliance on wood chips. The energy storage medium will be approximately 2,400 tons of locally available natural sand, which is well suited for this purpose and enables storage temperatures above 500° C.

[See also: What is a 'sand battery'? And what does it mean?]

A recently activated sand battery, built for Loviisan Lämpö in Pornainen, stands nearly 13 m tall and delivers 1 MW of thermal power, provides 100 MWh of storage and contains approximately 2,000 tons of crushed soapstone as the storage medium. According to Polar Night Energy, the system “has been operating for half a year and has demonstrated strong, reliable performance in real-world operation.”