Hybrid Energy Storage : State of the Art, Design and Development Potential

The Research Center for Electromobility, Power Electronics, and Decentralized Energy Supply (EMLE) develops hybrid storage solutions and, for this purpose, has several battery storage systems with different cell chemistries and capacities, as well as two hydrogen systems with electrolysers, fuel cells, and compressed gas storage tanks. Although batteries have become increasingly powerful in recent years and, in particular, more affordable as second-life solutions, they scale only linearly and are therefore not suitable for long-term storage. Hydrogen-based storage systems, on the other hand, require the electrolyzer and the fuel cell as expensive components; however, both depend not on the desired capacity but on the power that can be generated from wind and solar energy and stored. Capacity, on the other hand, depends on the size of the storage system, which, particularly for liquid derivatives, consists of inexpensive tanks. Here, however, efficiency is reduced by additional conversion steps. This article aims to provide an overview of the various hydrogen storage solutions in terms of technical maturity, efficiency, costs, and manageability.