I think it could scale. If you can directly transfer mechanical stress from the cable to the earth, with no concerns over vacuum or thermal insulation, the econ

I think it could scale. If you can directly transfer mechanical stress from the cable to the earth, with no concerns over vacuum or thermal insulation, the economics might work. Even if you can only store ~1 Wh per kg of enclosed rock, it seems possible to enclose millions of kgs of granite in a solenoid.