Finland warms up the world’s largest sand battery, and the economics look appealing

In a remarkable feat of innovation, Finland has activated the world's largest sand-based battery, a groundbreaking energy storage solution that utilizes sand to store thermal energy. This unique system harnesses electricity, primarily generated from renewable sources, to heat sand or crushed rock, which can later be used for a variety of applications, including heating residential and commercial buildings. Located in the small town of Pornainen, this sand battery, filled with 2,000 metric tons of crushed soapstone—previously considered waste from a local fireplace manufacturer—promises to dramatically reduce the town's carbon footprint. While it may not have the sleek appearance of conventional lithium-ion battery packs, the insulated silo, measuring 49 feet in diameter, is set to replace the costly oil currently used to power the town’s district heating network. Pornainen, like many Scandinavian communities, relies on a central boiler system to provide hot water to homes and businesses. The Polar Night battery is capable of storing a staggering 1,000 megawatt-hours of heat for extended periods, sufficient to meet heating demands for an entire week during the harsh Finnish winters. Impressively, only 10% to 15% of the heat is lost during storage, with outlet temperatures reaching up to 400 degrees Celsius. Moreover, the integration of this sand battery is expected to cut wood chip consumption by approximately 60%, further enhancing the sustainability of the town’s energy systems. While the heat generated from the battery could potentially be converted back into electricity, this would come at the cost of some efficiency. The growing trend towards thermal batteries has attracted the attention of various startups, with Scotland's Sunamp developing a similar system that uses materials reminiscent of the flavoring in salt-and-vinegar chips. Additionally, Electrified Thermal Solutions, a runner-up at TechCrunch’s Startup Battlefield 2023, has innovated a type of brick capable of reaching temperatures near 2,000 degrees Celsius. Another company, Fourth Power, is working on graphite blocks that can store energy as heat at an astonishing 2,400 degrees Celsius. Finland’s energy grid, primarily powered by renewables at 43% and nuclear at 26%, offers some of the cleanest electricity in Europe, priced at just under €0.08 per kilowatt-hour—significantly lower than the EU average. Although Polar Night has not disclosed the exact costs of the sand battery project, the affordability of its raw materials and the simplicity of its design suggest a cost-effective solution, potentially cheaper than the previously estimated $25 per kilowatt-hour for a smaller prototype, especially when compared to lithium-ion batteries, which are around $115 per kilowatt-hour.