Why not capture carbon from air with surplus energy? Build few capture plants and buy energy to keep price positive, then sell carbon cerificates on european market.
[edit] though frankly it’s probably even easier for Germans to just pay their domestic coal producers not to produce.
But I still think that we (as a world) should start capture carbon actively during this decade. Last summer in Europe was hottest yet and with such hot winter we are for even hotter summer this year. Keeping energy prices up would be just added benefit.