It seems like it’s best use case would be in conjunction with nearby buildings. Where the waste heat can be used for heating.

You can fight a lot of that with bigger batteries. Surface area goes up by r^2, but volume goes up by r^3.

More expensive batteries will also warrant better insulation.

Combine those and sand batteries make decent sense.

Most people could probably never even break even in the cost of energy that it takes to produce one of these things.