In the small Finnish town of Kankaanpää, engineers have built the world’s first commercial ‘sand battery’ that stores clean energy as heat — and it’s turning heads across the globe. The system heats sand to around 500°C using surplus wind and solar power, then releases that stored heat months later when energy demand spikes.
The innovation, developed by startup Polar Night Energy, is simple yet groundbreaking. Instead of using rare and expensive materials like lithium, it relies on regular construction sand — abundant, cheap, and recyclable — to hold vast amounts of thermal energy efficiently.
“It’s a simple, sustainable, and scalable solution for seasonal energy storage,” said Polar Night Energy’s co-founder Markku Ylönen.
Experts say this technology could transform renewable energy infrastructure worldwide. Because sand doesn’t degrade, the system can last for decades with minimal maintenance. One installation already supplies heat to the local district grid, enough to power a small town for a week during Finland’s harsh winters.
The concept could help solve one of the biggest challenges in renewable power — storing excess energy for when the sun doesn’t shine or the wind doesn’t blow. If scaled globally, sand batteries could help nations cut fossil fuel reliance while keeping energy costs low. Sometimes, the simplest materials really do hold the most powerful answers.
