Multi-nodal optimisation of energy storage requirements for 100% renewable energy grid: A South Australian case study

The transition to 100% renewable energy systems presents significant challenges in maintaining grid reliability, particularly in systems with large amounts of variable renewable energy sources. This study develops a comprehensive multi-nodal optimisation framework to assess the long term storage requirements of 100% renewable energy grids under conservative operating assumptions. Using South Australia as a gigawatt-scale case study, the developed mixed-integer linear program is used to assess the storage requirement across seven regions incorporating transmission constraints, DC power flow with linearised losses, multiple storage technologies with temporal classifications, and correlated renewable generation profiles. Under conservative operating conditions, the results indicate a maximum storage requirement of 7.28 GW and 644 GWh across the investigation period (2045–2051). Winter emerges as the most critical season for storage sizing, with widespread renewable energy droughts occurring across geographically correlated regions, limiting the availability of interstate support. Sensitivity analyses demonstrate that modelling more realistic operating scenarios, such as including modest amounts of dispatchable generation (1%–3% of total annual demand), can reduce storage requirements by up to 78%. In contrast, the importance of considering multi-year climate data is demonstrated with storage sizing varying by more than 500 GWh between weather years. Across all analyses, the median requirement of South Australia is 4.27 GW and 162 GWh. The modelling framework and subsequent findings provide valuable insights for policymakers and grid planners working towards the goal of a 100% renewable energy grid.