That's great, but how do I take one of these underground caverns around with me? :P
More seriously, I'm sure hydrogen will make a valuable contribution to the stationary grid-level energy storage situation. I'm not convinced about other applications.
You don't, just as you don't take massive takes of compressed methane around with you (I know about CNG cars; they're not competitive with BEVs or liquid fueled cars.) Methane and hydrogen are competing in stationary applications.
More seriously, I'm sure hydrogen will make a valuable contribution to the stationary grid-level energy storage situation. I'm not convinced about other applications.