A novel sand-based battery in western Finland is providing a potential solution to one of renewable energy's biggest challenges: storing power for months at a time. Located at the Vatajankoski power plant in Kankaanpää, about 270 km north-west of Helsinki, the world's first commercial-scale sand battery uses 100 tonnes of low-grade builders' sand to store thermal energy.
The battery, enclosed in a 7-metre-high steel container, is heated to 600°C using electricity from wind turbines and solar panels. A resistance heater warms the air inside, which is then circulated through heat exchange pipes by a fan. Thick insulation ensures the sand retains heat even in freezing winter temperatures, which average below 0°C in the region.
With a capacity of 8 MWh, the battery discharges about 200 kW of thermal power when needed, providing heating and hot water for around 100 homes and a local public swimming pool. The system is charged overnight when electricity prices are lower, and it requires minimal maintenance, as the sand and pipes experience no wear and tear; the fan is the only moving part.
The sand battery was developed by four Finnish engineers—Tommi Eronen, Markku Ylönen, Liisa Naskali, and Ville Kivioja—who were childhood friends and athletes. Their concern over climate change, evidenced by diminishing ice cover on Lake Näsijärvi, drove them to find a sustainable storage solution. Eronen's inspiration came from traditional Finnish fireplaces, leading him to consider solid materials like sand for energy storage.
Experts highlight the importance of such innovations. Yulong Ding, director of the Birmingham Centre for Energy Storage, notes that storing renewables is critical to achieving net-zero CO2 emissions by 2050, a target set by the IPCC to limit global warming to 1.5°C. The sand battery's use of cheap, low-quality sand—rejected by builders—also avoids contributing to the global shortage of high-quality river sand.
