EVs & Mobility

This article was published on July 7, 2022

What the hell is a ‘sand battery?’ And why am I so damn excited?

Using sand to heat local home and businesses


What the hell is a ‘sand battery?’ And why am I so damn excited?
Cate Lawrence
Story by

Cate Lawrence

Cate Lawrence is an Australian tech journo living in Berlin. She focuses on all things mobility: ebikes, autonomous vehicles, VTOL, smart ci Cate Lawrence is an Australian tech journo living in Berlin. She focuses on all things mobility: ebikes, autonomous vehicles, VTOL, smart cities, and the future of alternative energy sources like electric batteries, solar, and hydrogen.

When you think of energy solutions, you might not imagine 100 tonnes of builders’ sand piled inside a huge silo. But one company has actually found that sand can be the secret sauce to energy storage, as it can store heat for months. 

How does this work?

Finnish startup Polar Night Energy has developed a novel way to store heat. 

storing sand
Yep, it’s a giant silo full of sand!

A 4×7 meter steel container is filled with hundreds of tonnes of sand. The sand is then heated with wind or solar energy, and stored for use by a local energy provider to heat the local district. It’s effectively a giant sand battery. 

Why sand? 

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While wind and solar energy are extremely useful, they only offer intermittent power. Check out what this means in the video below:  

On the other hand, sand is durable and inexpensive, and can store a lot of heat without dissipation at a temperature of about 500–600 degrees Celsius.

This means that once heated,  the silo can stay hot for months with minimal intervention. 

sand FTWQ
The advantages of sand for energy storage. Credit: Polar Night Energy

Specifically, the system can discharge a maximum of 100kW of heat power and has a total energy capacity of 8MWh.

The company’s sand battery is currently heating the Kankaanpää district, keeping homes, offices, factories, and the local swimming pool warm. 

Not only a solution to a problem but commercially viable 

Polar Night Energy was founded in 2016 by two university graduates well versed in thermal energy. They’ve only raised 500k in seed funding

The challenge is that there’s no shortage of innovation in the renewable energy space with a slew of R&D in academia. But taking an idea from the hyperfocus University environment to real-world commercial applications is where many startups fail.  

But the company has succeeded in going hyper-local. They’ve partnered with energy provider Vatajankoski and gained local government traction to deliver district heating.

And they’ve hit at just the right time to solve a local problem. 

Many homes and businesses are facing fuel poverty due to rising gas prices. Russia cut Finland off from its gas supplies for refusing to pay in rubles. Not great news for Finland, a country that experiences long, cold winters. 

But through their successful partnership, Polar Night Energy represents a great example of how creativity can solve complex environmental and societal problems.  

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