Finland Launches the World’s Largest Sand Battery, Unveiling Positive Economic Potential

While it may look ordinary, Finland has recently launched the world’s largest sand-powered battery.

Yes, you read that right—sand.

A sand battery is an innovative thermal energy storage solution that uses sand or crushed rock to store heat. It harnesses electricity, typically sourced from renewable energy, to heat the sand, which can then be utilized for various applications, such as warming buildings.

Economically, it offers clear advantages, making it hard to find a more affordable resource than the crushed soapstone currently housed in an insulated silo in Pornainen. This soapstone was primarily waste material—discarded by a manufacturer of Finnish fireplaces.

Though it lacks the aesthetic charm of a large lithium-ion battery, the 2,000 metric tons of crushed rock inside the 49-foot-wide silo is set to dramatically lower Pornainen’s carbon emissions, helping the town transition away from the costly oil that sustains its district heating system.

Like many Scandinavian towns, Pornainen relies on a central boiler to heat water for local homes and buildings. The Polar Night battery can store 1,000 megawatt-hours of heat for several weeks, enough to keep the area warm through the harsh Finnish winter. During storage and recovery, only about 10% to 15% of the heat is lost, with outlet temperatures reaching up to 400°C.

Additionally, the district heating system relies on burning wood chips, and Polar Night estimates that the sand battery will reduce this consumption by roughly 60%. Furthermore, heat from the battery could potentially generate electricity, although that may reduce some efficiency.

As the costs of renewable energy continue to drop, interest in thermal batteries is growing. Beyond Polar Night, multiple startups are delving into thermal battery technology. For instance, Scotland-based Sunamp is working on a variant that uses the same ingredient that gives salt-and-vinegar potato chips their zing. Electrified Thermal Solutions, a runner-up in TechCrunch’s Startup Battlefield 2023, has developed a brick that can generate heat approaching 2,000°C. Fourth Power is crafting graphite blocks designed to store electricity as heat at 2,400°C.

The battery in Pornainen is charged using grid electricity, and its large storage capability allows for power to be accessed at reduced costs. Finland’s electricity grid is predominantly renewable (43%) and nuclear (26%), resulting in relatively clean energy. Additionally, Finland boasts the lowest electricity rates in Europe, at just under €0.08 per kilowatt-hour, which is less than half the EU average.

While Polar Night hasn’t disclosed the overall cost of the project, the raw materials are affordable, and the design is fairly straightforward. A smaller prototype developed a few years ago was estimated to cost around $25 per kilowatt-hour of storage, and it stands to reason that the newer version is even less expensive. For comparison, lithium-ion batteries are priced around $115 per kilowatt-hour.