> we'd need to be consuming millions of times more energy in order to match what's currently being captured by our CO2 emissions
With backpack reactors, we'd have that. Our CO2 production would dwindle (fossil fuels are so 2015) and now everyone has a personal energy generator AND one in their car and their house, maybe one for the garage, etc.
> Energy: I don't see any evidence that it's energy limiting population growth:
Energy is always the limiting factor in a population. For most creatures, this is in the form of limited food sources, but for humanity it's about distribution, expressed by socioeconomics. I believe the population decline is combination of things. As modern humans have a rising standard of living (thanks to better information dissemination and distribution methods), they are increasingly reluctant to split resources with offspring, as it's a competitive disadvantage and the educated humans recognize it (children at half the fun or my high end lifestyle at 100% fun like those people I see on TV). The humans that are multiplying the fastest are generally not far above the poverty level and those beneath are pragmatically unable to afford it. So I totally agree on the basic premise. It's possible that humanity has had a unique response that mirrors the "beautiful ones" of the John Calhoun's utopian mouse experiments leading to this sub-replacement fertility effect. For the most part, we're capable of keeping our standard of living above barbaric levels, so some people just preen themselves in their niche. These are just casual beliefs from a white male, of course.
Back to energy theorycrafting....if I could generate useful energy (potential to kinetic) at will, I can move any resource anywhere. Price of milk and fuel would dwindle to nothing. It would wreck all types of havoc, economically. I can ignore friction and timescales by laterally scaling production, limited by the ability to automate with...power. Water in death valley, no problem? Let's just pump a river over there from our thousands of desalinization plants that we can setup with pocket generators. Waste production would require Mr Fusion style solutions.
> And assuming your ship, robots, corpsicles, reactor, etc,etc,etc can survive inert for thousands of years, why would you assume solar panels and capacitors would not?
Poor corpsicles. Currently, our energy storages are quite fragile, that I know about. At high velocity, almost any dust from say, a long dead rogue planetoid or comet, would shred most terrestrial materials in transit. I guess wrapping it all up in a tungsten steel alloy ball or rock (like an asteroid) wold work if we could get it to open after being frozen solid and semi-thawed in a couple thousand years, but your (whatever)engine that started up the transit will probably be non-functional. This is why I mentioned the nebulous "Durable" energy storages. You'll have to have the ship float around a start for awhile to store up enough for a landing routine or have an internal generator. Maybe a trick using fissionable material that brings 2 chemicals together after a 5k year halflife would suffice for restart. As long as the rest of the internals were properly shielded and I don't know how feasible that is as it would take a LOT of energy to move an asteroid at any reasonable velocity. I've never heard of aneutronic fusion so I'll have to look into that. It may change my thinking.
I may be wrong on a number of assumptions, but limitations are what I imagine based on my experiences. I'm no space geek, but I do watch a lot of TV and remember a time before the first space shuttle.