The benefits of exploring a large scenario space for future energy systems

Energy scenario analysis with optimization approaches rarely goes beyond a small number of scenarios. Disadvantages include limited coverage of uncertainties and assumptions, and a limited ability to provide robust policy advice. We present an approach that enables the multi-criterial evaluation of more than 11,000 scenarios and demonstrate it for the German power system. We vary both a wide range of input parameters and method choices. The resulting scenarios are assessed through a number of indicators on affordability, supply-security and sustainability. The most significant impacts on the results stem from considering multiple weather years. Furthermore, we estimate the number of runs required for robust energy systems analyses - well over 100 scenarios are needed. Nevertheless, fewer scenarios may be sufficient for limited scopes. Our analysis also underlines a challenge for future energy system design: cost-efficient decarbonization while conserving natural resources.