"There is zero chance of 100% replacement of fossil fuels with renewables. Zero. Without a Thanos solution."
is utter nonsense. I mean, it's as if you're asking me what's wrong with a statement that the Earth is flat.
Developing societies such as Africa, India and China are increasing their consumption for the next few decades at least, radically accelerating the demand for hydrocarbons. India expects a quintupling of coal use in the next 4 decades. Airline miles will quintuple in much shorter period of time (like ten-twenty years). There is no shortage of hydrocarbons to naturally limit these demands. Politically there is no way to restrain newly developing nations. Technologically there is no net-positive energy generation source that competes on a density basis with fossil fuels. Again, the numbers tell the story.
I sincerely appreciate your frustration and hope for something different/better, but you need to come up with contrary data to argue these points. A hope in technical improvements year-over-year is all you've pointed to, and the trendline of capacity and efficiency improvements doesn't back that up. Further cost paid for a solar panel is not a benchmark. Energy intensity of its emplacement to bring it online is what its output needs to be balanced against. Its output, limited by useful life and useful operating hours really hamstrings its total lifecycle cost after the fossil fuel intense journey it takes.
That renewables are still a fairly small percentage of global energy demand is a good thing. It means that these experience effects still have room to kick in. Extrapolating the demonstrated experience curve gives that resistive heat from PV will be cheaper than heat from burning any form of fossil fuel, by the time PV has expanded fully.
The investment required to go 100% renewable will be many trillions of dollars. But the world GDP is $87 trillion, and the world spends about 10% of that on energy each year. There is enormous capacity to invest in energy infrastructure -- which is good, because enormous investment will be needed, regardless of what that infrastructure is.
Certainly they must be competitive in terms of energy density otherwise how can they substantially displace another energy source? Today renewable tech is not energy dense enough.
> Once renewables are sufficiently cheap
..cheap in total lifecycle cost (not end user cost of panel), carbon negative and sufficiently energy dense (transportable at light weight/low volume relative to stored energy)
> it's just building more of them.
For all of this, please remember we're talking global scale for electricity generation (<30% of fossil fuel use today), plus transportation, and manufacturing, not just electric use at my house or even a small country.
Straight cost - you mention taxes and regulation. This implies regulatory disincentives to produce and consume fossil fuels. It's relevant to note that at no time in recorded human history have humans backed off the consumption of an energy source unless a better replacement (more dense) was found. We nearly deforested the US east coast and almost killed off a whale species until coal came along and saved both (true story). Now we couldn't go back if we wanted to because civilization assumes a certain amount of energy input. Reducing it would have huge humanitarian impacts. Stabilizing it would be good, but this unfairly puts a huge burden on developing regions who would likely not tolerate it anyway.
Technology improvement - Look in the graph below at where diesel is relative to a Li-Ion battery. That's the gap it needs to make up at 5% efficiency gain per year (many orders of magnitude). It's beyond optimistic to say that would be covered any time soon barring a miracle (the track record shows that Moore's law doesn't apply to solar cells and batteries).
https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...
Even if you doubled the rate of efficiency improvements to 10% annualized, it's still an unrealistically wide gap to make up in my lifetime at least.
Fundamentally, for your position to be true you have to assume a miraculous leap forward in technology. And/or you have to assume some global-scale rational decision making (or force) to reduce consumption voluntarily (or involuntarily :/), in contrast with the whole of historic human behavior regarding energy consumption. Seems like there's a lot of hope involved there.