[cesarb]

> > > The Germans have switched from nuclear to coal.

> > No, they did not.

> There have been several recent stories about the increase in coal usage this year.

But was there any closure of nuclear power plants in Germany this year? If not, you cannot say that this increase was because they have switched from nuclear to coal; they must have switched from something else.

> https://www.dw.com/en/germany-coal-tops-wind-as-primary-elec...

That story implies that Germany this year switched from wind to coal (due to weaker winds), not from nuclear.

[melling]

So they switched from nuclear to wind to coal?

Coal in the primary source of electricity. If they hadn’t reduced nuclear, coal could almost be gone?

“ Nuclear power in Germany accounted for 11.63% of electricity supply in 2017[3] compared to 22.4% in 2010”

https://en.m.wikipedia.org/wiki/Nuclear_power_in_Germany

[jhgb]

No, if they hadn't reduced nuclear production, the relative changes between coal and renewables would have exactly been the same, only coal would have had the same uptick from a lower 2020 value. "The increase in coal usage" would have been exactly the same regardless of whether they shut down some nuclear power plants or not. That should be obvious to you. Since this inter-annual change would have happened regardless of nuclear generation levels (unless you for some reason assume that the number of nuclear power plants operating in Germany affects German inter-annual weather changes), you can't use the nuclear generation levels to make this argument.

[gdavisson]

Why would that be the case? Shutting down nuclear plants doesn't increase the production capacity from renewables. For a given renewable production capacity, there's a fixed amount that has to be made up from non-renewable sources; since coal is pretty clearly the worst of those, you use things other than coal -- anything other than coal -- first, and kill off coal as fast as possible.

If you have a way to increase the renewable capacity to make up for a decrease in nuclear production, why not do that anyway, and shut down more coal production instead of nuclear?

[jhgb]

Yes, the situation is that whatever you don't source from renewables, you have to source from something else. Assuming that in both alternative scenarios (some nuclear plants shut down vs. all existing plants kept in operation), the nuclear generation levels are approximately constant, this means that any decrease from renewables has to be compensated by an equal increase from non-nuclear sources (since the nuclear contribution is constant from year to year in both scenarios, assuming no Chernobyl/Fukushima like situation where a nuclear source suddenly goes away permanently).

For sake of a simple example, let's say you have nuclear, renewable, and coal power plants, and you have 600 TWh of electricity consumption in a year and you have 200 TWh of nuclear power contribution and 200 TWh of renewable power contribution. You then need to burn coal worth 200 TWh to compensate for the rest. The next year the nuclear power contribution is the same at 200 TWh, since it's weather-independent, but weather variations allow you to generate only 150 TWh of renewable electricity. You now need to burn 250 TWh worth of coal; 50 TWh worth of coal more than the last year.

Let's assume that you shut down 100 TWh/y worth of nuclear plants a few years ago. Your energy needs today are the same. You have 600 TWh of electricity consumption in a year and you have only 100 TWh of nuclear power contribution in this scenario, and 200 TWh of renewable power contribution. You then need to burn coal worth 300 TWh to compensate for the rest. The next year the nuclear power contribution is the same at the decreased level of 100 TWh, since it's weather-independent, but weather variations allow you to generate only 150 TWh of renewable electricity. You now need to burn 350 TWh worth of coal; 50 TWh worth of coal more than the last year.

See how in both scenarios you need 50 TWh worth of coal more in the latter year because of weather variability? The argument was that the nuclear shutdowns changed the coal uptick. The shutdowns clearly didn't cause the uptick, or even affect its size, unless they happened inter-annually (which to my knowledge they didn't).

As for increasing RE contribution, that is happening in Germany regardless. In fact shutting down the most expensive-to-run old nuclear plants might liberate some money for extra renewables expansion, although I'd have to check on the exact numbers.

[talolard]

Could you elaborate, im interested in understanding your perspective but couldn’t follow it. In my mind , uptick in coal usage was directly caused by a decrease in wind power production. I understand that if Germany had chosen nuclear over wind, that decline would not happen and thus the usage of coal would not increase. Is that not true ?

[jhgb]

> I understand that if Germany had chosen nuclear over wind, that decline would not happen

This doesn't make sense unless nuclear power plants blow additional wind. See my other comment for a simple example. Keeping nuclear plants alive vs. not keeping them alive doesn't change the picture of inter-annual generation changes unless those shutdowns happened exactly between those two years.