Climate change: 'Sand battery' could solve green energy's big problem (bbc.com)

The nice thing about this is they can use the sort of sand that's not useful for concrete.

Would be interested to know how this compares to other forms of thermal energy storage:

https://en.wikipedia.org/wiki/Thermal_energy_storage

This technology was used by a German entrepreneur approximately 15 years ago. He collected waste heat from industrial sites by storing it in trucks loaded with sand and then shuttled it to public swimming pools for heating.