Efficient Extraction of Energy Using a Black Hole Warren MorningstarDecember 18, 2017 Submitted as coursework for PH240, Stanford University, Fall 2016Fig. AccretionWhen a black hole siphons gas off of a star (usually one that is orbiting a black hole, as illustrated in Fig. This radiation escapes the gravitational pull of the black hole and thus the energy is liberated from its gravitational bonds. In order to increase the binding energy of a system, you have to extract energy from the system.  This efficiency is different for a rotating black hole depending on how rapidly the black hole is spinning, but it can be as high as 42 percent.