Hydrogen is becoming an increasingly important energy carrier in sector integration for fuel cell transportation, heat and electricity. Underground salt caverns are one of the most promising ways to store the hydrogen obtained from water electrolysis using power generation from renewable energy sources (RES). At the same time, the production of hydrogen can be used to avoid energy curtailments during times of low electricity demand or low prices. The stored hydrogen can also be used during times of high energy demand for power generation, e.g., with fuel cells, to cover the fluctuations and shortages caused by low RES generation. This article presents an overview of the techniques that were used and proposed for using excess energy from RES for hydrogen production from water and its storage techniques, especially in underground salt caverns, for the aforementioned purpose, and its feasibility. This paper compares and summarizes the competing technologies based on the current state-of-the-art, identifies some of the difficulties in hydrogen production and storage, and discusses which technology is the most promising. The related analysis compares cost and techno-economic feasibility with regard to hydrogen production and storage systems. The paper also identifies the potential, technical challenges and the limitations associated with hydrogen integration into the power grid.

Large shares of renewable energy production in the electricity grid make grid expansion and new technologies necessary. The unavailability of grid models to address upcoming research questions led to the development of open source grid models. Our work contributes to establish the open_eGo model for grid simulations by validating its assumptions and results for a rural region with high share of wind energy. In particular, assumptions on electrical parameters and the graph structure of the model are compared to the grid owner's model along with a validation of AC load flow results at the model boundaries. It was found that the graph structure deviates in the degree of nodes and connection characteristic. These deviations are less exterior nodes and a lower maximum degree of nodes as well as a higher number of parallel lines in the open_eGo model. The AC load flow results differ slightly in active power and significantly in reactive power, but are more reliable than an aggregation of loads and generation to the extra high voltage (EHV) nodes. Concluding, the open_eGo model has a limited usability for simulating, understanding and optimising DSO grid operation but can enhance EHV‐only analysis in large area contexts.

This article provides an overview of the requirements for a grid-oriented integration of hydrogen energy storage (HES) and components into the power grid. Considering the general definition of HES and the possible components, this paper presents future hydrogen demand, electrolysis performance, and storage capacity. These parameters were determined through various overall system studies aiming for climate neutrality by the year 2045. In Germany, the targeted expansion of renewable energy generation capacity necessitates grid expansion to transport electricity from north to south and due to existing grid congestions. Therefore, electrolysis systems could be used to improve the integration of renewable energy systems, by reducing energy curtailment and providing grid services when needed. Currently, however, there are hardly any incentives for a grid-friendly allocation and operation of electrolysis or power-to-gas plants. Two possible locations for hydrogen plants from two current research projects HyCavMobil (Hydrogen Cavern for Mobility) and H₂-ReNoWe (Hydrogen Region of north-western Lower Saxony) are presented as practical examples. Using power grid models, the integration of electrolysis systems at these locations in the current high and extra-high voltage grid is examined. The presented results of load flow calculations assess power line utilization and sensitivity for different case scenarios. Firstly, the results show that power lines in these locations will not be overloaded, which would mean an uncritical operation of the power grid. While the overall grid stability remains unaffected in this case, selecting suitable locations is vital to prevent negative effects on the local grid.