Finland’s Sand Battery: Storing Green Energy Beneath the Surface

by | Jul 24, 2025 | Ecofriendly, Fashion and Tech, Home | 0 comments

Finland’s Sand Battery: Storing Green Energy Beneath the Surface

Introduction

In a world racing to decarbonize, one of the greatest challenges remains unsolved: how to store green energy for when the sun isn’t shining and the wind isn’t blowing. While lithium-ion batteries have long dominated the energy storage conversation, Finland is quietly pioneering a radically different—and surprisingly simple—solution: sand.

In the town of Kankaanpää, western Finland, engineers have built the world’s first commercial-scale sand battery, using low-cost, abundant sand to store excess renewable energy as heat. Developed by a Finnish startup called Polar Night Energy, this innovative system offers a glimpse of the future—one where renewable energy is not just produced cleanly but stored sustainably.

“It’s simple, low-tech, and extremely efficient,” says Markku Ylönen, co-founder of Polar Night Energy. “We’re proving that sand can do what lithium can’t—store large amounts of energy affordably and without rare materials.”

How the Sand Battery Works

At the heart of the system is a 7-meter-tall steel silo filled with 100 tons of builder’s sand, connected to a district heating network. When wind or solar farms generate surplus electricity—often at night or during low-demand periods—this clean energy powers resistive heating elements embedded in the sand, raising its temperature to around 500–600°C (932–1,112°F).

Thanks to sand’s excellent thermal retention properties, the heat can be stored for days, even weeks, with minimal loss. When needed, the stored heat is transferred into the town’s water-based district heating system, which supplies warm water to homes, offices, and even saunas.

“Sand is an excellent medium for storing heat,” explains Dr. Emilia Järvinen, a materials engineer at Aalto University. “It’s cheap, non-toxic, and abundant—and at high temperatures, it holds energy for long periods without degradation.”

Why Heat Storage Matters

While much of the world’s focus is on electrical energy storage, such as grid-scale batteries, more than half of global energy consumption is for heating, not electricity. In cold climates like Finland, district heating networks supply hot water and warmth to urban buildings, and they need vast amounts of reliable energy—especially in winter.

The sand battery is designed specifically for this purpose. Instead of trying to convert electricity into heat at the last minute (a wasteful and expensive process), the system stores heat directly in a renewable, passive, and scalable way.

“Most energy storage technologies today are aimed at electricity,” says Laura Ahonen, energy systems analyst at VTT Technical Research Centre of Finland. “But thermal storage is equally crucial, especially in Nordic countries.”

Advantages Over Conventional Batteries

✅ Cost-Effective

Lithium-ion batteries rely on expensive, limited materials like lithium, cobalt, and nickel. In contrast, sand is cheap, widely available, and environmentally benign.

✅ Sustainable & Safe

There’s no risk of chemical leaks, thermal runaway, or resource extraction issues. Sand doesn’t degrade or pollute.

✅ Long Lifespan

The sand battery has virtually no moving parts, making it durable and low-maintenance, with an expected lifespan of decades.

✅ Large-Scale Storage

It’s ideal for storing hundreds of megawatt-hours of energy, much more than typical home or industrial batteries.

✅ Minimal Environmental Impact

There are no toxic waste concerns, no mining footprint, and the system can be built with recycled steel and local sand.

Real-World Impact in Kankaanpää

In Kankaanpää, a town of around 13,000 people, the sand battery is already proving itself. Connected to the local Vatajankoski district heating network, it supplements traditional energy sources and reduces the need for oil or biomass, especially during energy spikes in winter.

The system currently has a capacity of 8 megawatt-hours and peak heat output of 100 kilowatts, though plans are underway to scale up. Even at this size, it lowers emissions, cuts energy bills, and improves resilience to energy price shocks.

“In Finland, where winter temperatures can drop below -30°C, reliable heating is a matter of survival,” notes Janne Käpylä, energy manager at Vatajankoski. “The sand battery gives us flexibility and peace of mind.”

Scaling Up and Global Interest

Polar Night Energy believes the technology has global potential—especially in countries with district heating networks or industrial heat needs. Future models could store up to 1,000 MWh, making them suitable for entire cities, factories, or desalination plants.

Countries like Germany, Canada, and Japan have expressed interest in adapting the technology. With the rise of heat-as-a-service models, the demand for clean thermal storage is expected to grow rapidly.

“We’ve had inquiries from all over the world,” Ylönen confirms. “Anywhere there’s a need for sustainable heating, sand batteries can play a role.”

A Complement to Other Storage Technologies

The sand battery isn’t meant to replace lithium-ion or hydrogen storage but to complement them. While lithium excels at short-term electrical energy storage, sand is better suited to long-duration thermal storage, especially in cold climates.

This hybrid approach—pairing wind, solar, batteries, and sand—could help build a more resilient, diversified clean energy system.

“Energy storage is not one-size-fits-all,” says Dr. Järvinen. “We need a toolkit of solutions, and sand batteries fill a gap we’ve long ignored.”

Challenges and What’s Next

While promising, sand batteries are still early in their commercial journey. Key challenges include:

  • Public awareness: Many policymakers and utilities are unfamiliar with thermal storage.
  • Grid integration: In places without district heating, the application is less straightforward.
  • Scaling production: Larger units require significant investment and careful design.

Nevertheless, Finland’s success has opened the door. Polar Night Energy is now exploring industrial partnerships, modular units, and international pilots.

Conclusion: Simple Materials, Big Climate Potential

In an age dominated by high-tech climate solutions, Finland’s sand battery reminds us that sometimes the answers lie beneath our feet. With a humble material and clever design, engineers have created a powerful tool for clean energy storage—one that’s affordable, scalable, and sustainable.

As the energy transition accelerates, solutions like the sand battery will be crucial not just in storing electrons, but in keeping homes warm, industries powered, and emissions low—even in the darkest winters.

“The future of energy is not just smart—it’s surprisingly simple,” says Ylönen. “And it may just be made of sand.”

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