How can a Stargate draw power from a black hole?

In "Beachhead" (SG-1 season 9), Col. Carter notes that the only thing in the Universe powerful enough to power an Ori Supergate is a black hole, and indeed the Ori manage to collapse an entire planet in order to create one (the gate's completion was thwarted, however).

In a later episode, Camelot, they succeed in deploying a Supergate near another artificially-created singularity, allowing an Ori fleet to enter our galaxy.

My question is, how can a Stargate harness energy from a black hole?

Answer

The mechanism is never explained in-universe. And the current understanding of physics is that any energy generated inside the event horizon cannot be harnessed. Even the energy generated by matter in the accretion disk cannot be harnessed because the harnessing device itself will eventually fall into the black hole. But there may be two other possible mechanisms:

1. 
   

   If massive quantum fluctuations can be forced at the boundary of the black hole (which may not be totally beyond the ability of the Ancients or the Ori), one half of the virtual particle pairs being generated will fall into the black hole and the others will escape with positive energy. This could power the stargate. (see: http://en.wikipedia.org/wiki/Hawking_radiation)

   
   



2. 
   

   Black holes may contain traversable wormholes, which are basically the same phenomenon used by stargates. Perhaps the stargate wormhole can draw energy flowing through another wormhole in its proximity.