A bit about zero point energy.
Many systems in the world have a ground state energy > zero. So at ‘rest’ the system has a little energy in it. This is pretty common.
‘Zero point energy’ is a term that refers to using this energy to do stuff.
So suppose a system in the ground state has half an eV. That’s a low but not atypical energy level. That energy does exist, but it can’t be used.
But Matt, you say, isn’t the literal definition of energy the ability to do work? Doesn’t that violate the nature of what energy is?
Fantasic question. The short answer is, it sounds like it, doesn’t it?
Perhaps, but perhaps not. Suppose there are barriers to enter or exit a system. If those barriers are 1/2 eV ‘tall’ then a ground state of 1/2 eV might not be usable as the system is constructed. I have no idea if this exists, and it would probably be specific system dependent.
Now a lot of people have concocted ideas to use this ground state energy to do stuff. As yet, none have proved useful. (There are a few where people discovered the ground state could be changed, and that is useful to know. It’s not useful from an energy generation or more accurately, energy harnessing, perspective.) I’m ignoring systems doing things that the system would do by itself anyway.
So zero point energy isn’t the same as ground state energy, even though they sound like the same thing.