It’s an interesting question, let’s break it apart
Net energy produced requires a net reaction; even if an ‘AC Battery’ could be instantiated you’d still need a net reaction to produce energy.
Imagine a ball rolling up and down a hill. Our hill has no friction, and our atmosphere provides no resistance.
Sean: there still needs to be a demonstrative chemical difference between the beginning state and the end state. The _mechanism_ they ascribe does not have any chemical difference between states.
To be clear: I am not saying their system violates the first law. That is impossible. What I am saying is their analysis violates…