This is not correct. I didn't miss your point; I was explaining why your point was wrong. Now I will do that again, even though you discourteously didn't answer the question in my comment: does that mean you agree with Robotbeat's calculations? The combination of apparently refusing to clarify your position with basing your arguments on easily checkable falsehoods, while accusing me of basing mine on "intuition", reduces my willingness to extend good faith to you. Please, do better.
China's growth in either solar or wind generation capacity in 02020 was bigger than their growth in coal generation capacity. I haven't seen the 02021 numbers yet but I expect that their coal generation capacity growth in 02021 will turn out to have been actually negative, i.e., not growth but shrinkage, quite aside from the lower-capacity-factor crises resulting from their feud with Australia, their main coal supplier.
Quoting from my notes in Dernocua (http://canonical.org/~kragen/dernocua):
> Specifically, in 02020, the People’s Republic of China installed 71.7 GW of new wind capacity, 48.2 GW of new solar capacity (which was already larger than the rest of the world combined), and 38.4 GW(e) of coal capacity. Assuming typical capacity factors of 40% for wind, 25% for solar, and 60% for coal, that would add up to 23 GW average new coal, 29 GW average new wind, and 12 GW average new solar. (But China’s capacity factors are lower; see below.) New solar installations worldwide double on average every three years, which has slowed down from every two years in the 02010s. ...
> But China is a larger country than Germany. Chinese marketed energy consumption was 28 PWh/year (3.2 TW) in 02010, of which 3.9 PWh/year (440 GW) was electric. In 02019 they produced 7330 TWh electric calculated as (+ 4554 233 148 349 1270 32 405 224 113) rounded to three places. That’s 836 GW. (The 32 TWh of pumped-storage hydro may be double-counted.) In 02019 224 TWh/year (26 GW) was produced from solar and 405 TWh/year (46 GW) from wind, using 204 GW of solar capacity (capacity factor 13%) and 209 GW of wind capacity (capacity factor 22%). Also the 4554 TWh/year from coal (519.5 GW) is on a 1.041 TW basis, so their capacity factor is only 50.0%. Hopefully they’ll start installing their energy plants in more propitious places, like the Gobi, and the capacity factor will go up.
> So probably last year’s new installations of 38.4 GW (coal), 71.7 GW (wind), and 48.2 GW (solar) will produce on average 19.2 GW (coal), 16 GW (wind), and 6.3 GW (solar). The resulting 22 GW (average) of renewable energy added last year amounts to 2.6% of the total current electric energy use of China. If we assume that China’s total energy use has increased by 90% since 02010, just as their electrical energy use did by 02019, it would now be 6.1 TW, and 22 GW is 0.36% of it.
Solar energy (127 PW at Earth's surface) is far more abundant than fossil-fuel energy consumption, which has never reached more than 15 TW, 0.012% of solar energy. Historically the big problem has been that solar energy, though abundant, was expensive to gather; that problem has now been solved, and solar panels are now cheaper in the world market than either fossil fuels or fossil-fuel plants, let alone the sum of the two.
> Both of these conditions are false, but even your reasoning here is assuming these are true.
No, my reasoning is based on evidence that says it is feasible and economical to expand power generation using renewable energy. It is not assuming either "unlimited fossil fuels" or "no serious externalities with fossil fuel usage."
> We haven't even come close to really solving just replacing our current energy demands with entirely renewable energy (which, even assuming perfect battery solutions, also requires growing the overall output of our grid by a factor proportional to intermittent power needs), let alone additional energy requirements that start popping up all over the place once you start removing fossil fuels.
Let's take these one by one.
First, current renewable energy production is about 12% of world total primary energy consumption (https://en.wikipedia.org/wiki/World_energy_supply_and_consum...). More than half of this is hydro, which is, roughly speaking, not growing. The other half is solar and wind, which is growing 14% per year, which puts it on track to replace all of world total primary energy consumption in 02043.
Wind is currently much larger, and already supplies most electricity in countries like Denmark, but solar is growing about 23% per year and has now reached about 1 TW peak, 150 GW average. That means that it is currently supplying about 0.8% of total marketed energy consumption, 1/128. (Since this is all electric, the percentage for electrical energy is higher.)
Of course, when exponential growth is involved, prediction is very difficult, because sooner or later the exponential trend must stop, at which point the trend line diverges from reality by orders of magnitude. Even a small misprediction of the exponential growth rate results in misprediction by an order of magnitude after a few orders of magnitude of growth. https://en.wikipedia.org/wiki/Solar_power#/media/File:PV_cum... shows that the exponential trend was a fairly consistent 36% per year over the last 30 years, so it seems to be slowing down, but it's unlikely to stop anytime soon. I've investigated the fundamentals and can't find any resource limitation or demand limitation that would prevent it.
Solar is currently on track to surpass wind around 02030, so probably we'll move to a majority-renewables energy system before the 02043 you get from extrapolating the overall non-hydro renewables growth rate.
As for the intermittency question, it doesn't affect hydrogen electrolysis (a gasometer full of hydrogen is a perfectly reasonable way to store excess energy for up to a month or two) and to the extent that intermittency is managed at the peripheries of the grid rather than the center, it doesn't require additional transmission or distribution capacity as you say either. Moreover, even needing to double transmission or distribution capacity would not be a civilization-destroying crisis; as I said, PRC has done that three times over the last ten years, and to generation capacity too.
Finally, the additional energy requirements that start popping up are basically only fixing nitrogen into ammonia, smelting steel, and plastics. All three of these are small compared to the use of fossil fuels as fuels.
This is indeed a problem that has been well studied for years, but until five years ago, we didn't know how we could scale up PV production; there was the concern that it might be physically possible but out of our technological reach, like fusion energy. That problem has now been solved, and that is why, for example, Peabody Coal went bankrupt and coal-fired power generation is globally in decline.
Our current way of life is unsustainable in many ways, but needing a lot of energy isn't one of them. We can increase our energy usage by two orders of magnitude before it starts to be a sustainability problem.