There have been some interesting inventions since dawn, but this one surely takes the cake. Who would have thought that a sand battery would even be possible? Well, for Polar Night Energy, this was a challenge they were willing to take on, and they conquered it.
This massive sand battery uses thousands of tonnes of crushed soapstone to store surplus energy from solar and wind sources as heat, which can then be released on demand. Could this be the change in renewable energy we’ve been waiting for all these years?
How the Sand Battery Works
This remarkable sand battery works as a high-temperature thermal energy storage system that uses sand or sand-like materials to capture and retain heat generated from surplus renewable electricity, like solar or wind power. During the charging phase, clean electricity is used to heat air via electrical resistors, which are then circulated through a network of pipes embedded in the sand, raising the temperature of the sand to as high as 1,112°F. This heat can be stored for days or even months thanks to the sand’s impressive thermal retention and the battery’s robust insulation.
“There’s really nothing fancy there,” said Markku Ylönen, one of the founders. “The complex part happens on the computer; we need to know how the energy, or heat, moves inside the storage so that we know all the time how much is available and at what rate we can discharge and charge.”
The Remarkable Scale and Capacity
Located in Pornainen, Finland, this isn’t your average battery that fits in your back pocket. The sand battery towers a shocking 43 feet high and spans 49 feet wide. If that wasn’t shocking enough, this battery is filled with around 2,000 tonnes of crushed soapstone and has a storage capacity of 100 megawatt-hours.
That makes this battery ten times larger than Polar Night Energy’s earlier prototype in Kankaanpää. With the ability to deliver 1 megawatt of thermal power, the battery can supply enough heat to meet the town’s entire demand for nearly a week during the frigid Finnish winter or up to a month in the summer.
Charging and Discharging Process
What makes this battery so remarkable is that it works pretty straightforward while being very efficient, making the potential of application worldwide so much more plausible. When clean electricity is abundant, the system uses this surplus to heat air via electrical resistors. This hot air is circulated through a closed-loop heat transfer system embedded in the sand or crushed soapstone, raising its temperature to between 752°F and 1,112°F.
When heat is needed, cool air is blown through the hot sand, absorbing the stored energy. This heated air is then transferred via a heat exchanger to produce hot water, steam, or hot air, which is distributed through the district heating network.
The Problem of Renewable Energy Storage
Renewable energy is great, but it’s not perfect and certainly has some serious flaws that need to be dealt with. Unlike fossil fuels, renewables generate electricity unpredictably. Solar panels lie idle at night and during cloudy weather, while wind turbines stall in calm conditions. These silent periods force grids to either waste surplus energy during peak generation or rely on fossil fuels when demand is stronger than supply.
Efforts in trying to solve this problem have been lithium-ion batteries, which have high costs, limited energy density, and short lifespans. These batteries generally have 10–12 hours of backup and degrade significantly over time, raising environmental and supply-chain concerns. That’s exactly why this battery can potentially change renewable energy for good!
Environmental Impact
The sand battery isn’t just impressive in its design and capabilities; as a bonus, it leaves little to no environmental footprint, which is exactly what researchers are going for. Its operation releases no pollutants into the surrounding air, and its robust, well-insulated design ensures efficient energy storage without harmful emissions.
The sand battery’s integration into district heating networks, such as in Pornainen, Finland, has already eliminated oil-based heating and reduced emissions by nearly 70 percent, dramatically cutting reliance on fossil fuels and lowering carbon output.
“Our goal is to be climate neutral by 2035, and the Sand Battery is a major step toward that,” said Mikko Paajanen, CEO of Loviisan Lämpö. “Combustion is not a sustainable option for the climate or the environment. This project is a powerful example that effective solutions for mitigating climate change do exist,” added Liisa Naskali, Chief Operating Officer of Polar Night Energy.
Economic Advantages
Sand batteries are incredibly affordable compared to other energy-saving options that have been used. The cost to store energy in sand batteries is estimated at just $4 to $10 per kilowatt-hour, which is significantly lower than pumped hydropower (about $60/kWh), compressed air energy storage ($150–$300/kWh), and lithium-ion batteries (around $300/kWh).
To give you a rough idea of how much we’ll save, the cost to build a sand battery capable of storing 8 megawatt-hours is roughly $200,000, compared to at least $1.6 million for a lithium-ion battery with the same capacity.
Integration with District Heating
This remarkable sand battery is seamlessly integrated into the town’s district heating network, helping the town stay warm and eco-friendly. This integration allows the sand battery to serve as the primary production plant for the district heating system, with the existing biomass boiler remaining as a backup for peak demand.
“Pornainen wants to be a front runner in sustainable energy solutions, and we welcome all innovations that support that goal. One of the key targets in our municipal strategy is carbon neutrality, and the sand battery plays an important role in achieving it,” said Mayor of Pornainen Antti Kuusela.
Global Scalability and Future Plans
This project is a blueprint for global energy transformation, giving the world an environmentally friendly, low-cost option for running the world. While sand batteries are ideally paired with district heating networks, common in Northern and Eastern Europe, the concept can be tailored to fit local resources and infrastructure.
The global sand battery market is projected to grow rapidly, from $1.38 billion in 2025 to nearly $4.86 billion by 2034. Companies like Polar Night Energy are already planning next-generation pilots, including projects that will convert stored heat into electricity, further expanding the technology’s applications and efficiency.
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