1. Ph.D. Student, Faculty of Economics, esp. Economics of Renewable Energies, Univ. Duisburg-Essen, Universitätsstr. 2, Essen 45141, Germany (corresponding author). ORCID: .
2. Professor, Faculty of Economics, esp. Economics of Renewable Energies, Univ. Duisburg-Essen, Universitätsstr. 2, Essen 45141, Germany. Email: .