From Standalone to Interconnected: Sector-Coupled Optimization of La Gomera’s Renewable Energy Portfolio for Integrated Energy Planning

Small island systems are exemplary candidates for testing energy system decarbonization strategies. The planning of energy sectors within these systems should be approached in an integrated and flexible manner to facilitate the transition to 100% renewable energy penetration. Due to their isolated nature, energy systems in remote islands offer a controlled environment for studying the complexities of renewable energy integration, sector coupling, and grid flexibility. La Gomera, part of the Canary Islands, stands out as a particularly strategic case study due to its ongoing transition away from fossil fuels and the planned interconnection with the Tenerife grid. In contrast to mainland Spain’s diversified energy mix, the Canary Islands remain heavily reliant on imported fossil fuels, highlighting the necessity of local, system-integrated energy planning. This study provides a replicable pathway for energy system planning in small island contexts, highlighting the importance of integrated approaches in local decarbonization strategies. Using EnergyPLAN in combination with a MATLAB-based optimisation tool, a stepwise modelling approach was used to progressively increase the complexity of the system. The analysis starts with La Gomera as an stand-alone energy system, optimizing the installed capacities of photovoltaic (PV) and wind power. The subsequent phases introduced some further key components: - the interconnection via a submarine cable to Tenerife, - the integration of a Waste-to-Energy (WtE) plant, - the optimised sizing of an energy storage system, - the electrification of transport sector at three different penetration levels. Each phase involved a re-optimization analysis to account for updated features of the system. A simplified model of Tenerife’s electricity demand was also incorporated, facilitating a revised assessment of the submarine cable’s planned interconnection capacity and supporting simula- tions that included offshore floating wind generation. In the final stage, four representative scenarios were selected for detailed economic evaluation. The findings of this study indicate that, even under conservative assumptions, optimized renewable energy portfolios for La Gomera are economically competitive within the Canary Islands’ context. The analysis confirms the value of interconnecting energy systems and coordinating multi-sectoral planning, particularly in remote and resource-limited territories. This approach highlights the potential of Smart Energy Systems in enabling sector coupling and maximizing synergies between renewable energy sources. While the scenarios analyzed do not represent a global optimum due to spatial and regulatory constraints, they offer a robust foundation for energy system planning. The methodology presented here is transferable to other island contexts, promoting resilient, regionally integrated, and decarbonized energy systems.