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Re:Nuclear is back on the table for a green future by ncmncm on Friday June 17, 2022 @12:10PM (#31780306)
(1) Rock is not very dense; pig iron density is 3x rock's. (2) A cube is not the only shape, for a weight. (3) Total capacity is not the only parameter of interest, for utility storage. (4) There is not only one mineshaft. (5) No utility is restricted to using only one kind of storage; different kinds favor different parameters, and we may expect utilities to use different kinds at the same time to maximize value and minimize cost.

Assuming utilities will do the stupid, expensive thing leads to failed analyses.

Re:Nuclear is back on the table for a green future by qsdf38100 on Friday June 17, 2022 @02:06PM (#31782016)
Rock is cheap. The shape is irrelevant. For grid scale, total capacity is what makes it grid scale. No amount of parameter tuning can change the fact that stored energy is at best mass * g * height. Adding more huge mineshafts is irrelevant. You can always add more units, it doesn’t make it more efficient.

Sounds like an Elon Musk solution. Make it bigger, taller, make more of it, and somehow it’ll bend basic physics facts to become the ground breaking disruptor technology of the next century.

Re:Nuclear is back on the table for a green future by ncmncm on Saturday June 18, 2022 @12:14AM (#31787215)
Efficiency doesn't matter nearly so much as is usually assumed. What matters is cost. Exactly, cost per Wh stored, and per W in and per W out.

Mineshaft storage is very, very efficient, but has an upper limit on energy per mineshaft determined by its depth and how much weight fits in it. The cost of the winch apparatus is amortized over that amount. More mineshafts means more total storage.

Pumped hydro has very, very low cost per Wh stored, but kinda high per W in and out. But thousands of pumped hydro systems were already built, almost, so seem free; they just needed pumps added.

Synthetic H2 and NH3 are very, very cheap per Wh stored. W out uses existing turbines, so seems cheap. W in depends on your electrolysers, which are improving fast.

In batteries, cost per Wh stored has been large, but is different in different chemistries. In a better chemistry it is lower. Flow batteries have lower cost per Wh stored, for any liquid chemistry, but higher per W in or out; and need plumbing and pumps.

Details matter. Numbers matter. Dumb choices make dumb designs. Dumb designs can be improved on.

Drawing conclusions based on dumb choices is just dumb.

Musk is dumb, but just barely smart enough to hire smart people and, sometimes, let them be smart. So, Hyperloop was just dumb, no matter who works on it. Starship is kinda smart, depending on what you can think of to do with it. Mars colonization is dumb. Starlink could possibly be smart, depending on a lot of details.

A wholly new capability, like radically cheaper mass to orbit, can often enable smart ideas. Super-expensive mass to orbit was good enough for weather satellites, planetary probes, and geosynch COMSATs.