On the expansion of renewable energies in Germany and the problems related to fluctuation in the German electricity grid

The expansion of renewable energy in Germany—particularly in the solar and wind sectors—is a key factor in the transition to net-zero carbon emissions. Both sources experience significant seasonal fluctuations in production. Even though the technologies complement each other—with solar contributing more in the summer and wind in the winter—these contributions are not guaranteed; there may be a shortage of supply or even a so-called “Dunkelflaute,” a period of very low wind and solar energy production. However, it is precisely these periods of low wind and solar output that prevent conventional power plants from being shut down, as they must fill the gap. To raise awareness of these issues, a further expansion of wind and solar power plants is simulated based on 2023 data, and the need for storage technologies is calculated to address imbalances. The calculations are not intended to accurately reflect the energy supply in future years. Instead, the aim is to illustrate the fundamental relationships between the production and consumption of carbon-neutral/green energy. Therefore, an energy system model for Germany is developed as an energy flow model using MATLAB. For cross-validation, the Python-based PyPSA model is employed. An integrated energy transition scenario—assuming full energy self-sufficiency (no energy trade across German borders) and the exclusion of conventional power plants—is built around the energy flow model. The calculations show that the expansion of wind and solar power plants alone will not lead to a stable electricity supply and that storage technologies will play an important role in the future. In the summer, there is energy that must frequently be stored and retrieved within short cycles (24 hours). However, there is also a substantial energy surplus during the summer months that needs to be shifted to periods of low production in the fall and winter, requiring storage over timescales ranging from weeks to several months. Therefore, this paper analyzes scenarios involving both battery and hydrogen storage. The required storage capacities are calculated at 0.6 TWh for battery storage and 24.12 TWh for hydrogen storage for the year 2023. It becomes evident that both technologies contribute in distinct and complementary ways: batteries are well suited for high-frequency, short-term storage with limited capacity requirements, while hydrogen plays a crucial role in storing large amounts of energy over extended periods. Future work will include a more detailed analysis of regional differences and financial aspects, with the aim of refining and optimizing the proposed storage scenarios.