The variability of renewables

Actually I think it is mainly wind, where this is an issue. Hydropower, biomass or geothermal are much like baseload or peaking power plant.

And solar is not nearly as problematic as one might think at first glance. It is largely quite predictable. At 3 in the morning it is always zero, and peak output is always around lunchtime. Seaonal differences are predictable, and after a few months of regularly looking at the daily output graphics provided by transparency EEX, I see that cloudiness also gets averaged out quite well even over an area as small as Germany.

On all days this summer solar has flattened out the load profile for conventional power plants, effectively it has been nearly like peaking power, and to me it is clear a lot more solar could be employed across Europe without requiring any storage.

For wind this is different, wind power I have seen at well above 10 GW in the middle of the night and at 200 MW during peak demand hours. There tends to be more wind in the winter than the summer, but with solar, you can rely on the output enough I think that conventional power plants can go into maintenance in June, while for wind that is not the case.