Using flowing sand in a thermal battery is interesting. They’re flowing cold sand through an electric heater to heat it up and store that heat, then flowing the hot sand as one of the fluids through a heat exchanger with whatever you’re actually trying to heat, whether its air or water or oil, and then storing the now cold sand to be reheated.

I guess if you have some way of concentrating and dumping industrial heat into the sand, that could replace the electric heater and let it run off of some existing industrial process