this achievement should come naturally if you are playing thru the campaing, you should have it by around the end of the first campaing(whichever faction you choose). if not you will definetely get it before you finish your second faction.
another way to get this is simply by setting up a skirmish game set the ai to normal, cripple it so it cannot do anything and build as many energy reactors you can, it may take a hour or 2 with some level 3 reactors to get it to pop.