let me try and articulate my thoughts on this more clearly. there isn't a direct link between energy supply and the current fiat currency controversey (latest ina long line since time immemorial), but:
- easy access to energy fuels real growth
- government and other bureaucracies tend to grow at 7% year-on-year, hence exponential growth
- a 7% year-on-year growth leads to a doubling in 12 years
- fiat currencies enable deficit spending and enable "unlimited" credit
- easy access to credit fuels fake growth
- fake growth continues to the point that it can no longer be supported by easy access to resources
- the quick fix of printing more money (increasing access to credit) hastens the collapse
Provided that there is real growth (which I tie back to easy access to energy), a semi-finite, long-lasting physical resource as reserve currency sets real limits on the pace and achievable level of growth.
Efficiency gains are a one-time way to flatten the demand curve, but they aren't cumulative.
"Easy access" to energy means that when you expend one source, you have to be bringing another onstream within a short space of time (the 12-year doubling). If your development time is 30 years, you have a problem - you will have a crash.
Wider out, there is another problem. You can all too easily lock yourself out from being able to access the plentiful energy because you couldn't afford the energy budget to get there.
Low-Earth orbit may be "halfway to the rest of the solar system" and resources are essentially unlimited. But we're at the bottom of a gravity well and access to those resources is not easy. The energy budget to LEO is well-known - you need to adjust deltaV of about 9500 m/s, which currently means rockets. To build a Ringworld or a Buckyball or a Dyson Sphere or even a space elevator to get there with electricity would take the resources of the planet with the gamble of accessing the resources of the solar system.
Let's say it took 100 years to build a space elevator or a GEO solar power plant. In that time, at 7% growth, there will have been 7 doublings in bureaucracy and 3 in population. If it took 20 years, that's one doubling, but you need to add 15TW in that time. A 4GW station is estimated to cost $11 billion.
Fiat currencies that fuel artificial credit are an illusion that serves only to hide the fact that we are not fast enough at supplying energy that would be required to support real growth at those levels. We're not running out of energy and we're not not smart enough to figure out and exploit new sources. But time is not on our side. Going back to a physical reserve currency does not solve the problem - it only slows it down. There will be a crunch.