A sand battery in Finland is transforming sustainable heating

From housing to businesses and a municipal swimming pool, this battery is slowly changing the game for Finland's district heating.
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A split-screen shows a photograph of the sand battery from the outside (left) and an illustration stripping down the same building's walls to show how it works on the inside (right)
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By 2050, more than 68 percent of humanity is expected to live in urban areas. But are our cities prepared for all the challenges this entails? This Mashable series explores how our cities can become more sustainable and equitable homes to their human and non-human inhabitants.


Heating Finland's cities is becoming more sustainable thanks to sand. Finnish startup Polar Night Energy has developed a battery that uses sand to trap and store energy from solar and wind electricity. The battery is a high-energy storage facility located in Kankaanpää and is fed power from the grid whenever excess electricity is available. Warming up to 600℃, the system traps the heat until it's needed, when it can be released as either hot water, steam, or air.

Sand is the second most exploited natural resource after water and its emissions-heavy mining is highly damaging to local ecosystems. Polar Night Energy has stated that it uses high-density sand, which is only sourced from abundant areas and cannot be used in construction.

So far, the sand battery is providing a local district heating network, heating homes and businesses, as well as a municipal swimming pool. Scaling up, a similar sand battery will be installed in the city of Pornaien in a recent agreement between Polar Night Energy and district heating company Loviisan Lämpö.

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Teodosia Dobriyanova
Video Producer

Teodosia is a video producer at Mashable UK, focussing on stories about climate resilience, urban development, and social good.


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