The Penrose process (Penrose mechanism) is a mechanism consistent with black hole models such that energy can be extracted from the rotation of a black hole. It involves an object entering the black hole's ergosphere (space frame dragged to rotate around the black hole), and having it split in such manner that part of it escapes. In theory, the object could be a space probe programmed to separate into two parts by means of an explosion. Given some specifics, the escaping object can have more total energy than the original object, the total energy between them maintained through a reduction in the black hole's rotation.
It is not clear this happens in nature to any significant degree. The later-devised Blandford-Znajek mechanism may be a common phenomenon.