This Ph.D. thesis proposes a novel model-based decision support approach for the energy transition in Germany that incorporates central contemporary multidisciplinary obstacles. A new system dynamics model was established to depict the development of the German electrical energy supply regarding its economic and ecological efficiency along with its reliability. One of the simulations studies shows that the most effective greenhouse gas (GHG) mitigation of about 40 percent can be achieved in Germany at lower costs through increasing wind and photovoltaic capacities of 200 gigawatt (GW), integrated load management, and through combining the SNG production capacity of 20 GW obtained using excess electricity from the wind and solar energy. The emissions trading is of great relevance for the estimation of the total costs of the energy transition for the consumer. It is considered to be one of the most efficient ways to harness the power of the market to mitigate income losses caused by the GHG emission reductions, and thus, to push the efforts addressing the global climate challenge. However, there are substantial economic, technological, and even institutional uncertainties each of which may influence the development of the emissions trading market.Within the energy transition, contracting has a significant impact on the efficiency of acquisition processes, especially in the context of so-called public-private partnership (PPP) projects. We used the model to analyze the effects of delay penalties on the duration of PPP projects. Finally, we applied our model to identify the potential contribution of the Nord.Link project, under real load conditions, to the future energy system of Germany, especially looking at the economic and the ecological aspects, as well as supply security.