If you are a fan of stargate, you will understand, or if you dont know what is it, read this first:
http://stargate.wikia.com/wiki/Zero_Point_Module
In my opinion can be very good to add other energy sources, even sci-fi, (obviously without total free energy of entropy inverters)
1.The first thing is the ZPM, something very difficult to craft, but it can store a LOT of energy, and it is mono-use, the recipe can be something like:
When it is crafted, it goes at full charge, like 1.21 B EU
= Mass Fabricator
2.Dyson artificial SUN
The second idea pop up when i saw Spiderman 2, and when i read about the Dyson Sphere: http://en.wikipedia.org/wiki/Dyson_sphere
Something like an artificial sun on the Overworld, with a restraint shield, it will emit a LOT of energy, and it needs fuel like water (hydrogen and oxygen)
Video idea: http://www.youtube.com/watch?f…page&v=iwk8I7HS4ag#t=187s