Tech news often focuses on tiny chips or sleek new phones. But sometimes, the biggest innovations are right under our noses – or, in this case, inside a giant pile of sand. Finland recently unveiled the world’s largest sand battery. This week, on August 28, 2025, it officially began its mission. It promises to drastically cut carbon pollution for local heating grids.
This industrial-scale sand battery is a game-changer for countries like Finland. They generate a lot of clean power from wind and sun. The problem is, sometimes there’s too much energy, and sometimes not enough. This new energy storage system helps balance that tricky supply and demand.
Standing about 13 meters tall and 15 meters wide, this new battery is truly massive. It was inaugurated just this week. Experts believe it will slash carbon emissions from the local heating network by up to 70%. Located in Pornainen, a town in southern Finland, the structure was built by Polar Night Energy, a Finnish company. They actually built the world’s first sand battery a few years ago. This new, larger system will take over heating duties from an old wood-fired power plant for the entire municipality.
This powerhouse can store up to 100 megawatt-hours (MWh) of energy. It boasts an impressive 90% efficiency rate. To put that in perspective, it’s roughly ten times bigger than Polar Night Energy’s first sand battery. It holds enough stored heat to warm the entire town for a whole week.
At its core, this industrial-scale sand battery is a thermal energy storage (TES) system. It’s a crucial tool for regions that depend heavily on intermittent renewable energy sources, like wind and solar. The goal is simple: charge the battery when electricity is cheap and plentiful. Then, hold that charge for months. This helps to stabilize the energy grid, especially during times of high demand.
How Finland’s Sand Battery Works
Polar Night Energy has made it clear: the sand battery doesn’t store or deliver electricity directly. Think of it as a giant, super-efficient thermos.
Here’s how it converts excess power into useful heat. Renewable electricity that isn’t immediately needed is used to heat the sand inside the battery’s insulated structure. This happens through a closed-loop air tube system. The sand can get incredibly hot, reaching temperatures up to 600 degrees Celsius (1112 degrees Fahrenheit). Once hot, the sand stays that way for a very long time, just like a battery holds a charge.
When heat is needed, cold air is pumped through the same tubes. As it travels, it absorbs the heat from the sand. This now-hot air, which can reach 400 degrees Celsius (752 degrees Fahrenheit), can then be used in a few ways. It can turn water into steam for industrial work. Or, it can heat water directly for homes and businesses. This transfer happens thanks to a device called a heat exchanger.
This Finnish battery has been running since June. According to reports from New Atlas, the company says it even exceeded its efficiency goals in its first days of operation. Today, many buildings in Pornainen, including the city hall, are already being warmed by this innovative new structure.
The impressive results in Finland highlight the power of this solution. Such a thermal energy storage system could easily inspire other cities. Especially those with similar climates and energy setups might look to adopt these massive, sand-based batteries.