The battery stores 8 MWh of thermal energy when full. When energy demand rises, the battery discharges about 200 kW of power through the heat-exchange pipes: that's enough to provide heating and hot water for about 100 homes and a public swimming pool in Kankaanpää, supplementing power from the grid. The battery is charged overnight when the electricity prices are lower.
It's reported to be a low-maintenance system. The company uses cheap, low-quality sand that's been rejected by builders instead of high quality river-sand which is used in vast quantities for construction.
https://www.bbc.com/future/article/20221102-how-a-sand-battery-could-transform-clean-energy