1. Forschungszentrum Jülich, Institute for Energy and Climate Research—Energy Systems Engineering (IEK-10) 1 , 52428 Jülich, Germany
2. Forschungszentrum Jülich, Institute for Energy and Climate Research—Systems Analysis and Technology Evaluation (IEK-STE) 2 , 52428 Jülich, Germany
3. Institute for Theoretical Physics, University of Cologne 3 , 50937 Köln, Germany