Can ordinary sand solve the global energy crisis?

Lithium runs out. Batteries degrade. But sand? It lasts billions of years.

In this episode of Lexicon, Interesting Engineering sits down with Annette Haglund-Dones (CCO at Polar Night Energy) to reveal how they turned ordinary sand into a massive thermal battery—and survived one of Finland’s coldest winters on record.

Here is what you’ll discover:

• Zero Degradation: Why sand beats lithium for long-duration heat storage.

• The Scaling Surprise: What happened when they built a battery 20x larger than the prototype.

• Industrial Decarbonization: How 250°C heat stored in sand can replace fossil boilers.

Listen now to discover why the future of clean energy might be beneath our feet.

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