In the context of increasing renewable energy integration and the push for decarbonization, this research addresses the need for long-duration electricity storage to ensure the reliability and adequacy of the future European power system. The variability of renewable energy sources such as wind and solar, coupled with the challenges posed by climate change, requires advanced storage solutions to balance periods of low energy generation and high demand.

This thesis explores how long-duration energy storage (LDES) and short-duration energy storage (SDES) can effectively contribute to resource adequacy by assessing various operational strategies, storage capacities, and system conditions. Using the Calliope energy system modeling framework, the research simulates a future interconnected European grid in 2050, considering different weather conditions and storage configurations to evaluate metrics such as Expected Energy Not Served and Loss of Load Expectation.

The results demonstrate that increasing the energy storage capacity and discharge duration of LDES significantly reduces LOLE, particularly during extended periods of low renewable output. However, SDES plays a complementary role, addressing short-term reliability challenges by reducing EENS during shorter disruption events. This combination highlights the need for a balanced deployment of both SDES and LDES to optimize grid performance and ensure resource adequacy. Through these findings, the thesis contributes valuable insights for energy planners and policymakers, aiming to foster a resilient, low-carbon electricity grid capable of meeting the demands of a renewable-dominated future.