Optimal infrastructure investments for renewable energy integration in Germany

We analyze optimal infrastructure investments for the integration of variable renewables in the German electricity system. Using a combined dispatch, transmission, and investment model, we compare four scenarios with different investment options, including gas-fired power plants, pumped hydro storage and transmission lines. In a reference scenario of the year 2024, geographically optimized investments into gas-fired power plants dominate. However, system costs are only slightly higher in scenarios with increased investments into networks and storage. Considering additional system values of storage facilities that are not included in the optimization, additional pumped storage capacity in Germany appears to be beneficial. We also find that increased system flexibility may not only improve renewable integration, but also increase the utilization of emission-intensive plants during a transition period.