A giant “sand battery” that can store enough cheap renewable energy to heat 100 homes for a fortnight has been constructed in Finland.
The system relies on about 100 tonnes of ordinary builders’ sand, held in a silo that stands about 22ft high. When more solar and wind power is being generated than can be used, the surplus is used to run a kind of oversized electrical toaster.
This warms air which is blown through a system of pipes that runs through the sand, heating it to about 500°C.
This heat can be stored for months at a time. When the wind stops blowing and the sun does not shine, cold air can be fed through the same pipes. Once heated, it can be funnelled into homes and offices to warm them. The device, designed to help smooth the peaks and troughs of renewable energy production, has been built by researchers near the city of Jyvaskyla.
The company behind it, Polar Night Energy, said it is the first sand battery in commercial service in the world, and that it could be scaled up for large housing developments.
