It’s not very visible, but Finland recently flipped the switch on the world’s largest sand-based battery.
Yes, sand.
Sand batteries are a type of thermal energy storage system that uses sand or crushed rock to store heat. Electricity – Electricity from renewable sources is usually used to heat sand. The stored heat can be used later on various edges, including warm buildings.
Economics is persuasive and it is difficult to get cheaper than the soapstones now crushed into insulated silos in the small town of Pornen. Soapstones are essentially garbage and were dumped by a Finnish fireplace manufacturer.
While it may not be as impressive as the large lithium-ion battery pack, the 2,000-meter crushed rock within a 49-foot-wide silo promises to reduce Pornen’s carbon emissions and helps eliminate expensive oil that will help the town strengthen its district heating network now.
Like many Scandinavian towns, Pornen operates a central boiler that heats water for homes and buildings around the town. The sand battery, brought to life by the Finnish company Polar Night Energy, can store 1,000 megawatt-hour heat for a week. From storage to recovery, only about 10% to 15% of the heat is lost, with the outlet temperature up to 400°C.
According to Polar Night, the town’s district heating system also relies on burning wood chips, and sand batteries reduce its consumption by about 60%. Heat from the battery can also generate electricity, but the process sacrifices some efficiency.
As renewable energy gets cheaper, interest in thermal batteries is growing. Beyond Polar Night, many startups are pursuing thermal batteries. Based in Scotland, Sunamp builds something that relies on the same ingredients that taste salt and poisonous potato chips. Selectified Thermal Solutions, TechCrunch’s Startup Battlefield 2023 runner-up, has created a kind of brick that can produce heat that approaches 2,000°C. The fourth power creates a graphite block that stores electricity as 2,400°C heat.
Pornainen’s batteries are charged using electricity from the grid, and their large storage capacity allows operators to draw power when they are at their lowest. The Finland grid is primarily renewable energy (43%) and nuclear energy (26%). In other words, the electricity is pretty clean. It is also the cheapest in Europe, with just under 0.08 euros per kilowatt-hour, less than half the EU average.
Polar Night did not disclose the cost of the project, but the raw materials are cheap and the structure itself is not particularly complicated. The much smaller prototype built several years ago would cost around $25 per kilowatt-hour storage, the company estimated at the time. The newer version is probably cheaper. Lithium-ion batteries cost around $115 per kilowatt-hour.
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