https://www.wired.com/2016/05/forget-elons-batteries-fix-gri...
> 9,600 tons of rock- and concrete-filled railcars up a 2,000-foot hill.
> $55 million
> The Nevada project has a power capacity of 50 megawatts and can produce 12.5 megawatt-hours of energy.
Using the 4 cents/kWh figure upstream, that's ... $500 of electricity per round trip.
Yeah, as-is, there's no way it can pay for itself. But how much room does this have to grow, and at what cost? If most the cost is down to laying the track and making these custom railroad cars, then maybe there are some economies of scale that could come into play. And then I assume that most of the equipment involved could easily last for decades.
Up-front cost for battery installations may be cheap, but don't lithium ion batteries typically only last a few years? That means you won't be able to amortize the cost of equipment over a very big stretch of time at all.
When it does, you might be able to use it to generate electricity. But I wouldn't be surprised if that isn't done simply because it wouldn't justify the added cost and complexity of building all that extra energy harvesting mechanism into the elevator.
Having lived in a 17-story building with Thyssen-Krupp "green elevators", they're terrible! An elevator would break down and require days of maintenance every couple months, greatly increasing queueing times.