1. Forschungszentrum Jülich, Institute of Energy and Climate Research—Systems Analysis and Technology Evaluation (IEK-STE) 1 , 52428 Jülich, Germany
2. German Aerospace Center (DLR), Institute of Networked Energy Systems 2 , 26129 Oldenburg, Germany
3. Institute for Theoretical Physics, University of Cologne 3 , 50937 Köln, Germany