More hypothetical than theoretical. Not a naysayer myself, but there's far too many missing pieces in the theoretical aspect. Even if there weren't, it still remains little more than academic. Even with 100% efficiency, powering such a thing isn't even practical. Generally speaking, we aren't even within the ballpark of 25% energy efficiency. Thermal dynamics is kind of a b***h in that regard.
"Don't confuse facts with reality."
-Robert D. Ballard