On coal-fired power stations:
Doesn't work like that. A coal-fired generating plant isn't a light bulb, you can't just switch it on and off as needed....we should keep a few open and just not use them except in very occassional situations, say if there happens to be very low wind and sun power, and at the same time unusual high demand....
And running them in a load-following mode adds to their wear and tear, already the big power operators are complaining.
The alternative is building more CCGT plants, running on expensive imported gas.
You seem to assume that a national electricity grid could run on 100% renewables.
This has never been achieved anywhere in the world. In fact baseline generation using conventional power sources is an absolute necessity to maintain a stable grid, be it from hydro, ff, or even nuclear power sources. That's where the hypothetical 50% decarbonization mentioned originally comes from.
Two more German examples. If the Germans can't get it right, who do you think can?...Chile?
https://www.telegraph.co.uk/comment/955 ... he-UK.html.....The more a country depends on such sources of energy, the more there will arise – as Germany is discovering – two massive technical problems. One is that it becomes incredibly difficult to maintain a consistent supply of power to the grid, when that wildly fluctuating renewable output has to be balanced by input from conventional power stations. The other is that, to keep that back-up constantly available can require fossil-fuel power plants to run much of the time very inefficiently and expensively (incidentally chucking out so much more “carbon” than normal that it negates any supposed CO2 savings from the wind).
And from 2018:
https://www.thegwpf.com/germany-risks-c ... ice-warns/The expenditure for the ecological restructuring of the energy supply is in a “blatant disproportion to the hitherto poor yield”, said President of the Court of Audit Kay Scheller in Berlin: “The Federal Government is at risk to fail with its once in a generation project of the Energiewende”.