Sand Batteries Are a Game Changer for Clean Energy
By Haley Zaremba - Jul 22, 2025, 4:00 PM CDT Finland has deployed the world's largest sand battery, which uses heated sand to store thermal energy for district heating and industrial use, significantly cutting emissions. Sand batteries offer a cost-effective and efficient alternative to lithium-ion batteries, capable of storing energy for weeks at a significantly lower price point and with fewer environmental concerns. This innovative thermal energy storage technology is gaining international attention, with other countries like the United States investing in pilot projects for its potential to provide long-term, sustainable energy solutions.

This month, Finland switched on the world’s biggest sand battery, which will “enable residents to eliminate oil from their district heating network, thereby cutting emissions by nearly 70 percent,” according to Euro News. And if it keeps running as cheaply and efficiently as it appears to be doing now, don’t be surprised if sand batteries start popping up around the world – even in your neck of the woods.

The battery, built by Finnish company Polar Night Energy, employs a form of thermal energy storage by using excess clean electricity to heat sand to searingly high temperatures. The sand holds onto this thermal energy, to be released back to the grid as needed to heat homes and provide energy for local industry. This isn’t Finland’s first sand battery, but it’s far and away its biggest. The groundbreaking model in Pornainen, Finland is an insulated silo measuring 13 meters tall and 15 meters across, and holds 2,000 tonnes of soapstone that has been crushed into sand. The sand is “remarkably efficient at maintaining its heat, losing only 10 percent to 15 percent from storage to recovery,” according to The Cool Down.

Altogether, the model can hold a whopping 100MWh of energy for weeks at a time, which would be enough to heat the entire town center even in the middle of a Nordic winter, according to a recent report from the World Economic Forum. When the heat from the battery is released, it can still be as hot as 400º Celsius (752º Fahrenheit).

Energy storage, and especially long-term energy storage is becoming increasingly necessary as global energy grids become more reliant on variable energy sources like wind and solar. Energy storage can capture excess energy when the sun is shining and the wind is blowing, and then feed that back into the energy grid when demand outstrips supply. Thermal energy storage could be an excellent way to accomplish this with relative simplicity.

While Finland’s newest sand battery was just fired up earlier this month, the cost-effectiveness and efficiency of the model are already turning heads. “Price-wise, it's hard to imagine a cheaper energy storage system,” reports The Cool Down. “The pulverized soapstone inside Pornainen's sand battery was discarded from a fireplace maker.” But as they say, one man’s trash is another man’s game-changing clean energy innovation.

TechCrunch estimates that the Finnish battery costs less than $25 per kilowatt-hour of storage. By comparison, the leading technology – lithium-ion batteries – cost approximately $115 per kilowatt-hour of storage. And lithium-ion batteries hold onto energy for a matter of hours, not days or weeks. Plus, since the incredibly low-tech sand battery technology relies on recycled materials, it doesn’t face the same supply-chain woes as lithium-ion battery storage. What is more, while lithium is associated with clean energy tech, lithium extraction can be extremely harmful to the environment. Using cast-off crushed rock is a cheaper, more eco-friendly, and more democratizing alternative, since it can be adopted in virtually any environment and does not rely on imports and vulnerable global supply chains.

Basically, sand batteries are looking like a win-win-win. “With high specific heat, low thermal conductivity, and no risk of fire, sand-based energy storage systems are gaining traction in grid-scale and industrial heating applications,” Interesting Engineering reported late last week in an article detailing why they think that the next big energy-storage device could be a 1000°C sand battery.

While Finland is leading the way in developing and deploying sand batteries, it’s not the only country investing in the technology. Last April, the United States Department of Energy (under the Biden Administration) announced that it would provide $4 million to fund a pilot sand battery project outside of Boulder, Colorado at the National Renewable Energy Laboratory (NREL)’s Flatiron campus. The NREL team has calculated that a commercial-scale system based on their model would be able to retain more than 95 percent of its heat for a minimum of five days. Moreover, the team reported that “a targeted levelized cost of storage of 5¢/kWh could be achieved under a variety of scenarios,” according to PV Magazine. However, the fate of this project is not entirely clear under the new administration.

Sand Batteries Are a Game Changer for Clean Energy

Finland has deployed the world's largest sand battery, using heated sand to store thermal energy for district heating and industrial use, reducing emissions by 70%. The technology, developed by Polar Night Energy, is cost-effective and eco-friendly, with a 100MWh storage capacity. The U.S. Department of Energy is funding a pilot project, and sand batteries are seen as a sustainable alternative to lithium-ion batteries due to lower costs and environmental benefits.