.png)
.png)
Finland has successfully implemented the first fully functional sand battery, a groundbreaking technology designed to store renewable heat energy for long durations—making it ideal for keeping homes warm during the harsh winter months. This system works by using renewable electricity, such as solar or wind power, to heat 100 tonnes of sand.
The innovation comes from Polar Night Energy, a company that specializes in seasonal thermal storage solutions. According to the company, this technology has the potential to scale up the use of solar and wind energy to meet 100% of a community’s heating and electricity needs. At the heart of their system is a patented, large-scale, high-temperature thermal storage method.
The process involves converting electrical energy into heat, which is then stored within sand. Sand is chosen for its safety, environmental compatibility, affordability, and its ability to withstand extreme temperatures—up to 1,000°C or more. Inside the storage unit, an internal heat transfer system is used to efficiently move energy into and out of the sand. High-quality insulation surrounding the system minimizes heat loss, allowing energy to be stored for months.
Polar Night Energy has installed its first commercial sand-based heat storage unit at Vatajankoski, an energy utility in western Finland. This facility will support the district heating system in Kankaanpää. The unit has a heating capacity of 100 kW and an energy storage capacity of 8 megawatt-hours (MWh). Full operations were expected to begin in 2022.
According to Ville Kivioja, the company's lead scientist, the sand deep in the silo retains heat extremely well, even over several days or weeks. However, sand closer to the outer walls of the steel container loses heat more quickly due to proximity to the boundary, though this only represents a small portion of the total volume.
What Is a Sand Battery?
A sand battery is a type of high-temperature thermal energy storage system that uses sand or similar materials to hold heat. Its main purpose is to store surplus energy generated by renewable sources like wind and solar in the form of heat. This stored energy can then be used to warm buildings and serve other heating needs, making it an efficient and sustainable solution for managing intermittent renewable energy.