Complexity of building electricity grid based on #renewables is probably best illustrated on days like this in #Germany[^1]:

instantaneous electricity consumption is 67 GW
Germany has 66 GW in wind, but it’s merely potential output if there was wind - and there’s now enough wind to produce 3.8 GW satisfying 5.67% of the demand
Germany also has 69 GW in PV, but same story here - there’s enough light to produce 5.3 GW (7.74%)

Note that each of these, wind and PV, have installed capacity alone exceeding the current demand! But installed capacity isn’t much worth when it doesn’t produce any electricity. Statistically that’s the case with wind and PV _most of the time (capacity factor <50%)🤷 I think this gives you some idea about the feasibility of postulates such as “we just need to build more renewables!”

Now let’s factor in time. Watt is the unit of instantaneous power, how much the country uses electricity right now. At this load (66 GW) to survive one hour Germany needs 66 GWh (unit of amount of electricity). Lower than that, and you need to start switching off factories, electricity supply to houses, trains, hospitals etc.

Germany, like most of us, is not ready for these consequences of variability. And this is the sole reason why it runs on gas and coal, including lignite, the dirtiest form of coal: these can be switched on and off whenever needed (they are dispatchable).

Of course, there are other dispatchable sources of electricity which are also as safe and low-carbon as renewables, such as #nuclear (see #France for comparison)[^2]. However, Germany governments in the course of #Energiewende decided that 0.03 deaths/1 TWh (nuclear)[^3] is too much and instead chose to switch to 24.6 deaths/1 TWh (coal) as the dispatchable source.[^4]

Of course, there are days when wind and PV perform much better so would electricity storage help? Let’s take the 66 GWh hourly consumption: there was much talk about how battery storage is going to fix the whole variability of renewables. ElectricityMaps doesn’t show the total capacity (GWh) of available batteries directly, but it can be somewhat estimated from 30 days average (at the bottom)[^1].

Over the last 30 days German batteries supplied 1 TWh to the grid, which makes ~53 GWh per day, which makes ~2 GWh per hour. While we don’t know their total capacity to estimate maximum period they could keep the country running, that’s still 30x less than the hourly consumption. A very rough guess, the battery farms built in Germany in over a decade (Energiewende started in 2011) could power the country for around 2 minutes.

I guess from now on you can make your extrapolations and assess the feasibility of statements like “we just need to build some more storage!”

[^1]: https://app.electricitymaps.com/zone/DE

[^2]: https://app.electricitymaps.com/zone/FR

[^3]: https://ourworldindata.org/safest-sources-of-energy

[^4]: https://write.as/arcadian/ideological-origins-of-energiewende