If we're to believe https://www.technologyreview.com/s/601514/germany-runs-up-ag... then the Germans didn't quite "have to [...] start building coal fired plants", but they have trouble stopping people from building more coal fired plants, because that is still economically lucrative.
No. They have to have fossil plants because electricity cannot be stored effectively, except in very mountainous countries with enough hydroelectric dams, like Norway or Costa Rica. Since electricity cannot be stored, it has to be manufactured when required. People require electricity at night or on calm days when the wind is not blowing, and they often don't require as much electricity as can be produced at the right time. Since the Germans turned off their nuclear plants, to make that electricity, they had to build more fossil plants.
So sell the solar generated energy to Norway via the existing DC link and upgrade the link as necessary. Also upgrade the east-west electricity distribution system and sell the energy to neighbours who are in the dark.
> 'Since electricity cannot currently be cost effectively stored," It is a matter of economics not natural law.
What I meant should be obvious to someone who read my entire reply. Selectively quoting part of it and then making a counter-claim using the quote as a strawman argument shows that you are not a person to be taken seriously.