The transition to low-carbon power systems requires increasing integration of renewable energy, which introduces significant variability and uncertainty into power systems. Grid-scale energy storage is widely recognised as a key technology to enhance system flexibility, support renewable integration, and improve system resilience. However, the system-wide impacts of storage remain uncertain, and the roles of storage under dynamic transition and climate conditions across temporal and spatial scales are poorly understood.

This thesis investigates the role of grid-scale energy storage in low-carbon power systems from system impacts, transition dynamics, and climate resilience perspectives through optimisation-based power system models. The results show that storage deployment can not only decrease emissions of the electricity sector but also reduce economy-wide emissions from the supply chain, indicating that strategic storage deployment acts as a foundational pillar for multi-sectoral carbon budget compliance. In the early stage of the net-zero transition, short-duration storage plays a dominant role, while at the end of the net-zero transition, medium- and long-duration storage becomes increasingly important to address intra-day fluctuations and longer periods of variability as renewable penetration increases. Future climate variability results in a £39 billion difference in the cost of the 2050 GB power system across 50 climate years. The climate-induced spatiotemporal imbalance requires coordinated deployment of transmission expansion and multi-timescale storage. A climate-resilient 2050 GB power system should therefore combine high-density offshore renewables, strategic nuclear baseload, widespread battery, targeted long-duration hydrogen infrastructure, and heavily reinforced transmission corridors into a portfolio that stays close to the low-cost frontier in normal climate years while reducing exposure to extreme climate events.

These findings provide a comprehensive understanding of grid-scale storage roles from system impacts to transition dynamics and climate resilience, offering insights for power system planning and energy policy in the net-zero transition.