If you have 2 black holes rotating close to each other around each other,
there might be the possibility, that (by quantum effects)
engergy is beeing produced out of nothing!,
This is by seperating antimappter and matter quants.
These quants can emerge out of nothing, but anihilate right after they emerged.
The gravitational field could seperate this matter-antimatter couple,
creating energy(mass) out of nothing.

i am not totally shure about this thing,
but it would be the only way to create energy out of nothing,

Other ways of creating perpetuum-mobile do not exist.
it is all about transforming energy/mass to other forms.

The only thing that created big amounts of energy out of "nothing"
i know was the big bang.

A good way to produce energy is nuclear fusion,
melting hydrogen into helium.
Probably the energy source for the 2nd half og the 21rst centauri.