Re: blasting smallish tunnels in hard rock

Sodium-ion batteries might be cheap enough.  Promising for static
applications (Li-ion for mobile applications).
Pump-storage hydro. schemes are viable where you have togography.

Nuclear fission power has to way improve.
In the USA you can have inland water-cooled-reactors - PWR's (and BWR's)
- because you have continental-sized rivers to take away the
abundant!
waste heat.

Can see nuclear reactor operating temperature has to go way way up to
increase efficiency.  Then power plants can be small (mass-produced so
cheap) and located inland - much less waste heat to disperse.
Distributed, for energy security.

Reach I think it's 1060C and you can produce hydrogen no electric
intermediary.  So you could make electricity all day and hydrogen all
night.  100% loading on the plant.