Sand as battery: storing heat to return electricity

Published on May 24, 2026 | Translated from Spanish

A team of Finnish scientists has developed a prototype battery that stores surplus solar and wind energy as heat within sand. Then, using a Stirling engine, they convert that heat back into electricity. The idea is to have energy available when the sun isn't shining or the wind isn't blowing, although current efficiency is low.

Cross-section of a large industrial sand battery, glowing orange heat radiating from dark granular sand core, metal heat exchanger pipes embedded vertically, Stirling engine connected via insulated ducts, engineers in safety gear monitoring digital temperature display, action showing thermal energy transfer process, technical engineering visualization, photorealistic industrial lighting, reflective metallic surfaces, dust particles illuminated, detailed mechanical components, dramatic chiaroscuro contrast between hot core and cool exterior

From 4% to 31%: the leap the prototype needs 🔋

Initial tests yielded an efficiency of between 4 and 8%, modest figures for a storage system. However, the researchers' calculations indicate that with an improved design, up to 31% could be achieved. This would involve optimizing thermal insulation and the coupling with the Stirling engine. Further development is still needed for the technology to be commercially viable, but the low cost of sand makes it attractive.

Sand: the new tech diamond 🏖️

Finally, an application for sand other than building castles or complaining about it at the beach. The Finns have decided that a pile of hot sand is the solution to save the planet. And hey, if efficiency rises to 31%, maybe it's not such a bad idea. At least we don't need lithium, just a bucket and a shovel. Let's hope their invention doesn't cool down before winter arrives.