this works in principle. heating dirt to store energy is cheap, the material costs almost nothing and the physics are solid. if the output needed is heat then it can beat batteries by a mile on cost.

the problem is scale. the dirt is free but heaters, piping, controls, permits, and contractors are not. balance of system costs creep up fast and thats where most cheap energy ideas collapse.

the market fit is narrow too. industrial heat or maybe district heating could work. coal plant conversion sounds good in headlines but takes forever to line up politics and utilities. daily cycling wont compete with batteries, only long slow seasonal storage makes sense.

execution decides if this survives. if they can keep real projects near the claimed cost then it has a shot, otherwise it stays as a cool demo.