I would like somebody to explain his "replace batteries every 2-3 years" comment. I think this is true of small scale Lead-Acid based UPS, but Neoen scale Li-Ion stacks come with a battery management system which I believe offers better than 80% effective battery energy density over a longer life: 5+ years. Certainly the assumptive economics behind grid-scale battery models from Tesla is, a far longer working life than this. And, the evidence of full cycle life on Tesla car batteries and even Prius, is better than 2-3 years of useful life.
This may be because they over-provision so "rated" energy is met by replacement from a 110% sold capacity-type model.
I think the rest of the article is great. Fascinating.
Grid scale compressed air storage is a thing, and may have low energy efficiency, but so does PHES. The thing is, they can be huge, and they can sustain power for long periods. The heat loss story, I am confused by because usually this gets better with scale: you can exploit a lot of lower grade energy in heat/cool cycles, either to retain it in system eg heat transfer to another form of heat energy storage, or, for adjunct purpose like building heating or cooling.
Fan, not expert, experts can put me right!