How was Olivia powering the collision of the universes?

In the season 4 finale, we find out that

Since the Bridge has been deactivated, he has been using Olivia as a power source.

Or perhaps that was his plan all along.

WILLIAM BELL: (...) Olivia is a living uncertainty engine. Every breath she takes brings us closer to Nirvana. Every beat of her heart tears the world from its hinges. She is The Redeemer. (...)

_{Fringe, S4E22, "Brave New World, Part 2"}

But how does this work? Is it merely Olivia's existence that does this? If the process somehow feeds of her energy, how?