Alternative is to store heat in the subsoil at much lower temperature, a few degrees (like a ground source heatpump does). That needs a much bigger volume of soil, so long and expensive heat absorber pipes or boreholes. Better match for individual buildings, than for this 2MW district heat network.

April 10, 2026 - 08:59 UTC

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Yes I've spoken to Polar Night before - they insulate the tanks really well and they store at a high temp. It is possible to charge the ground with heat during summer that you use in winter, though! Has some ecological risks, possibly. Nowhere near the same density of energy storage.
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Polar night are focused on storage for a few days or a week, so balancing between windy and calm periods.

That means they need enough heat pipes to recharge and empty the store that quickly, which would become very expensive if the store were a larger volume at low temperature difference.
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