I cannot find any country using solid hydrogen on a large scale connecting it to a power grid (maybe someone can check further). First time I saw a country doing this so posting it.
Solid-state hydrogen storage is a key technology for breaking thru into hydrogen-based energy production.
TW Province media nicely explains the physics behind it and shows the huge potential once the hydrogen storage is mastered.
https://youtu.be/i0tMj-exy8Q