It was called an "energizer" and those are tied to power generation in TOS/TOS Movies so it makes sense that the energizer room here used the crystals to charge and discharge to power the ship.
Or then we can decide that the term is not related to power generation, but purely to the "priming" of dilithium, either in a separate dilithium hospital or then in situ. The term is only loosely related to things such as warp power, after all. Say, in "Doomsday Machine", main energizers fail (among other things), but Decker doesn't think that this would mean loss of capabilities such as warp power or weapons power; he has to be separately informed of that.
The loss of two plus two crystals goes
unnoticed at first. Surely power loss, no matter how slight, would be observed on various consoles and applications across the ship. But the keyword with the events at this energizer is "unnoticed"... Even the lack of personnel other than the two specialists speaks of a special facility unrelated to Scotty's usual line of work.
The episode calls out that the crystals could be used to detect physical warps in space from the antimatter universe (and also charged up to open a doorway thru to crossover).
Indeed - for a given value of "antimatter" which I want to carefully separate from the usual one, as the "antimatter" Lazarus certainly didn't blow up when walking on the matter decks of the
Enterprise!
...to regenerate power by providing more antimatter than put in. Funny enough, this was what happened in TNG's "Booby Trap".
Hmh? "Extending the matter-antimatter energy supplies" doesn't necessarily mean getting more antimatter, or matter. What LaForge seems to be doing is getting more
energy out of the existing matter and antimatter supplies, even if by spending more of it per time unit (that is, getting more power, but also more efficiently). This gives him the ability to sustain shields, which appears to be the key to maintaining energy (as opposed to having it be sucked out).
Providing/creating antimatter doesn't appear in explicit Trek dialogue. Even reactivating deactivated antimatter happens to other people: in "DDM", the
Enterprise is never said to lose her antimatter potency (even if the failure to use photon torpedoes or warp might hint in that direction), unlike the
Constellation.
Naturally, Starfleet gets antimatter from somewhere, and any encounter with a natural supply takes our heroes by surprise, so there would appear to be a clever machine involved. Does any of the starships have one aboard? One'd think this would have been discussed in VOY "Deadlock", but it very much was not.
Timo Saloniemi