By Joshua S. Hill | Renew Economy | November 27, 2025
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.
