  A new scenario for extracting energy from a Kerr black hole is proposed. With
magnetic field lines connecting plasma particles inside the ergosphere with
remote loads, the frame dragging twists the field lines so that energy and
angular momentum are extracted from the plasma particles. If the magnetic field
is strong enough, the energy extracted from the particles can be so large that
the particles have negative energy as they fall into the black hole. So
effectively the energy is extracted from the black hole.
  The particles inside the ergosphere can be continuously replenished with
accretion from a disk surrounding the black hole, so a transition region with
sufficient amount of plasma is formed between the black hole's horizon and the
inner edge of the disk. Thus the energy can be continuously extracted from the
black hole through the transition region. This may be the most efficient way
for extracting energy from a Kerr black hole: in principle almost all of the
rotational energy (up to $\approx 29%$ of the total energy of the black hole)
can be extracted.
