The role of energy storage towards net-zero emissions in the European electricity system

• Definition of archetypical countries for optimal energy storage mix in Europe. • Evaluation of impact of spatial resolution on optimal energy storage mix. • Assessment of trade-offs between short- and long-term energy storage. • Impact of fossil fuels phase-out and European development scenarios. • Results are relatively robust to sensitivity analysis. This study investigates the role of different energy storage technologies in a European electricity sector that complies with the target of net-zero carbon emissions in 2050. We consider three energy storage technologies, namely battery, pumped hydro, and hydrogen storage. We find that the cost-minimal energy storage mix in a country depends on the generation mix, and we identify three country archetypes in Europe based on the prevailing energy storage technology. When available, pumped hydro dominates the storage mix, reducing the need for new battery and hydrogen storage installations. Overall, short-term battery storage best captures solar fluctuations and is optimally combined with solar generation, while long-term hydrogen storage compensates for both solar and wind peak generation. Moreover, we quantify the impact of modeling the European system with different spatial resolutions and net self-sufficiency scales, from regional to continental, on the optimal energy storage mix. The comparative assessment of different spatial resolutions shows that the amount of energy storage installed, and especially the amount of hydrogen storage, increases significantly for higher spatial resolutions.