My question is more about expectations of scale. If currently renewable energy (not just electricity - heating etc matters a lot) is something like 10% or 12% of total energy; and we need to go to something of 300% or even much more (to cover energy spent not on current needs but solely to cover the "unburning" the excess of previous century, "repaying the debt" much quicker than we accumulated it), then that extreme growth of renewable energy generation doesn't seem plausible to achieve in the timeframe you suggest.

It's been a while since I ran through the napkin math, and I'm on mobile and can't pull up the backing links, unfortunately, but I believe we are just barely on track to replace all energy use with renewables in 15-20 years. After which we should have spare production capacity, assuming there is wind/solar close enough to the carbon sequestration points.

The gist is that if you look at the exponential curves of growth of both wind and solar deployments, and assume that we don't back off from those, you get X amount of TWh/year in 2040. Combine that with conversion of heating and transport to electrification, which provides huge efficiency boosts and requires only 1/3 to 1/4 the energy (most fossil fuel energy is just wasted). Then add in all the parts of the developing world which will increase their energy use to EU/China standards, and we are just barely there.

However I think we are likely to see big gains in production capacity as the developing world ups their game. They will be consuming more electricity, but also be immensely more productive.

Consider that we didn't spend 100 years using electricity at current rates. There was was an s-curve growth that only recently flattened in developed countries.