Siemens currently has turbines that can burn up to 75% hydrogen and is targeting 100% hydrogen by 2030:
https://www.siemens-energy.com/global/en/priorities/future-t...
General Electric has a variety of gas turbines, accepting 50% to 100% hydrogen in the fuel blend:
https://www.ge.com/gas-power/future-of-energy/hydrogen-fuele...
Eg. the Hybrit project produces iron sponge with electrolyzed hydrogen. So the process becomes
> (electricity + H2O) + Fe3O4 [iron ore] => Fe + H2O
instead of the usual
> C [coke] + Fe3O4 => Fe + CO2
What compressed gas storage does is (aside from combustion energy of a fuel gas) to provide not a store of energy, but a store of reduced entropy, enabling otherwise unusable amounts of heat to be converted to work.
Hydroelectric, compressed air and batteries have round trip efficiency of ~80%.
https://www.sciencedirect.com/topics/engineering/compressed-...
The facility you linked produces and stores chemical fuel, and can't even convert it back into electricity. It is really easy to store insane quantity of fuel, just like we can store loads of oil.
The kicker is that production of Hydrogen and other e-fuelds is less than 50% efficient, and converting them back to electricity is another 50% loss. Compression for storage and transportation mean further losses. So the overall round-trip efficiency is expected to be about 25% or lower.
It is probably possible to build an economy based on e-fuels, and that's what many oil companies are pushing for. They are probably the only viable way to achieve seasonal storage. It's a different set of tradeoffs.
No, the project includes using Mitsubishi M501JAC combined-cycle gas turbines to turn the hydrogen back into electricity:
https://www.powermag.com/aces-deltas-giant-utah-salt-cavern-...
https://power.mhi.com/products/gasturbines/lineup/m501j
This turbine has a rated combined-cycle efficiency of 64%.
Production of hydrogen is more than 70% efficient in the best current commercial electrolyzers:
https://www.nrel.gov/docs/fy04osti/36705.pdf
Round-trip efficiency is much lower than 80%, but not as low as you have written here.
1: https://www.sciencedirect.com/science/article/pii/S019689041...
Electrolysis efficiency and expense are entirely sufficient to requirements.
If it makes more financial sense and uses less resources to overbuild solar 3x and curtail 60% of the energy than paying for fuel, then you have 2 units of energy you have already paid for spread out over 6-8hrs/day.
As long as using your $300/kw electrolyser at reduced duty cycle is cheaper and less resource intensive than mining and shipping gas, you do it.
https://en.wikipedia.org/wiki/Grand_Coulee_Dam#Irrigation
However it seems that the pumped storage I recall hearing about as a kid has an extremely low storage capacity and is more focused on irrigation.
The largest pumped storage station in the US has a storage capacity of 24,000 MWh:
https://en.wikipedia.org/wiki/Bath_County_Pumped_Storage_Sta...
There's an underground hydrogen storage project underway in Delta, Utah with a capacity of 300,000 MWh:
https://www.powermag.com/massive-utah-hydrogen-storage-proje...
It would take 22 Deltas to overtake the world's largest pumped storage plant, a massive Chinese installation with 6.6 terawatt hours of storage capacity:
https://www.pv-magazine.com/2022/01/04/state-grid-of-china-s...
Still, potential underground hydrogen capacity is tremendous, amounting to thousands of terawatt hours in Europe alone:
https://www.preprints.org/manuscript/201910.0187/v1