The more I think about the Solar Harvester as a science fiction concept the worse it gets. Unless the very first Transformer took two steps with no energy, figured out how to build the Harvester with no energy and then flew out into space with no energy then how did the Transformers evolve before they mastered space flight that would get them where they needed to go quickly enough to have a source of energy? It's kind of like saying life depends on the iPhone even though life on Earth has done just fine before the iPhone. It really feels like a case of the writer needed a doomsday weapon without thinking the whole concept out. As to war and resources, every war is about some sort of resource. We just like to noble up the whole thing because it sounds better than saying you are sending people out to die over who gets to claim a spot of land, oil, gold, a food source, a trade route or whatever we happen to be fighting over at the moment.