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OK, a typical mine hoist is about 10 metric tons. 10 metric tons descending at 1m/sec is very close to 100KW. So a 1000 meter deep hole can deliver 100KW for 1000 seconds, or 27 KWH. That's about $3 worth of electricity, and about 1/3 of the battery capacity of a Tesla Model S with the large batter option.

Numbers not looking reasonable for this concept.

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I don't know how heavy are the planned weights, but it sure as hell will be heavier than 10 tons.

Even if it was 1000 tons, it would still only be about $300 worth of power.

Depends on the spot price of power. Power on the open market (where utilities have to buy it to provide to customers) changes every minute. Its usually cheap at night until the early morning, starts to increase, and then spikes around 3-4pm (+_30-60 minutes, depending on the country).

If you delivered power when it was most expensive (ie high demand) and consumed it in the middle of the night, the arbitrage may work out.

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