The device, which contains 100 tons of low-quality sand, is filled with heat made from cheap electricity from the sun or wind.
The developer said it could solve the supply problem all year round,
In the city of Tampere in western Finland, a pump pushes hot air into a large container filled with building sand.
This coarse, ready-to-use grain is highly effective at retaining heat, keeping it at extremely high temperatures for months.
This sand-based technology aims to address one of the biggest challenges facing renewable energy – what do you do when the wind isn't blowing and the sun isn't shining?
