Integrated renewable energy systems for Germany–A model-based exploration of the decision space

There is a rising need for decision makers to understand the trade-offs between different possible future energy systems and to discuss their respective plausibility in the face of uncertainty. Only then, policy makers can identify compromise solutions and necessary regulatory changes. This process can be facilitated by the interactive exploration of the near-optimal decision space generated by an energy system optimisation model. The purpose of this paper is to illustrate and exemplify the steps involved in the generation of such a decision space of energy systems and its visual presentation to stakeholders. We focus on a sector coupled energy system model of Germany subject to the 95% emission reduction target. The outlined procedure involves methods to calculate, visualize, and analyse over one thousand energy system alternatives. Based on our findings, we can state that specific technology expansions vary a lot across the computed alternative energy systems. Thus, the decision space of alternatives should be discussed in public debates more often to generate insights, support the formation of consensus and the setting of policy goals or regulation.