Learn English – They wouldn’t/won’t come here if they didn’t/don’t like this place

Compare
(A) "If Anna was here, she would've known what to do."
(B) "If Anna had been here, she would've known what to do."

In (A), the speakers are currently considering what to do and lamenting that Anna isn't with them right now, because she would have been able to help them.

In (B), the speakers are discussing a past situation (we don't know how recent) where Anna's absence left them with no solution. The opportunity to do the right thing has now passed.

I think if you see the difference between the two, that will go a long way to helping you with similar constructs.

"If you (wear) a beard all the time, they (not recognize) you without it."

All the below are possible:
(A) If you wore a beard all the time, they would not recognize you without it.
(B) If you had worn a beard all the time, they would not have recognized you without it.
(C) If you were to wear a beard all the time, they would not recognize you without it.

(A) Can be used in a past sense, in a kind of confirmatory way: Given that you always wore a beard, then of course they wouldn't recognise you without it. But it can also be a suggestion for the future: if>then. (B) In the past period referred to, he wasn't in the habit of wearing a beard, and therefore had no chance to pass unrecognised by removing it.
(C) More specific than the second sense of (A). Making a hypothetical suggestion concerning a group of people currently unknown; implying that at the moment he doesn't wear a beard all the time (or at all).

In the first case, the first statement is hypothetical (using the conditional mood), so considers a hypothetical situation where the machines would need to work, and weren't going to work without energy.
The other is a basic true statement (using the future tense) that simply states that the machines won't work without energy. I should note that this statement doesn't mean they can't work without energy, only that they won't. This is more to do with the idea of free will: consider a person who is able to work without biscuits but refuses to.

The second case is a lot more fun. Saying a machine can't (or cannot) work without energy sort of states that the machine couldn't work without energy even if it wanted to. In this case, because machines aren't sentient, it is identical to saying they won't work without energy.

However, the first sentence in the second group is either conditional or imperfect. In the case where it is conditional, it talks about a hypothetical situation like before. If, however, the tense is imperfect, it implies that the machines, in the past, weren't able to work without energy, but now supposedly can.

Note 1: Machines need energy to work. Fact of physics.

Note 2: I have no way of knowing what tense 'couldn't' is in. Normally you'd need to use the context to work it out.