Stationary energy storage systems such as sodium-nickel chloride batteries are essential for the future energy supply with high proportions of renewable energies. Based on intelligent operation, design, and testing concepts as well as specially developed battery cells, Fraunhofer ZESS implements battery modules and systems for various applications, including hybrid systems for combination with other energy systems. The work also focuses on the design – and, if necessary, certification – of test benches and production facilities.