Ahhh... *nods* *grins* Well, you see, if you had Gallifreyan technology, then you'd be able to harness the energy. *continues on* Basically... *looks around the cafe, grabs a mug and a coffee carafe from a nearby table* So, basically, let's say the mug is the TARDIS and the coffee is energy... *trails off, brow furrowed a bit* And, the space in here... *gestures vaguely in front of them, coffee sloshing in the carafe* ...is the Space-Time Vortex.
Now, the Heart of the TARDIS... *holds up the mug* ...is a massive energy collector. In the past as long as we were traveling in the Space-Time Vortex... *begins "flying" the TARDIS-mug around in front of them* ...we'd be connected to the Eye of Harmony -- our power source -- and the Heart would be soaking all that Artron energy in... *starts pouring coffee into the mug while continuing to move it about* ...but that was before... *pauses, lowering the mug and the coffee* Well, before the end of Gallifrey. *clears his throat* So, nowadays, the only places we can collect fuel are temporal instabilities, like the Cardiff Rift. *place the carafe on the table, then the attempts to balance the mug on the carafe, eventually gives up and place the mug on the table* I just park the TARDIS on top of it, it uses Chronon Transduction to soak the energy up and in a day or two we're all filled up and ready to travel again. *grins at Ianto* Stores enough to keep us going for a little while. And... *adds quickly* Generally it's less messy than... this... *gestures vaguely to the coffee he's spilled in the process of demonstrating*