Abstract
<jats:p>Remote and isolated island power systems face persistent barriers to deep decarbonization due to heavy fossil-fuel dependency, renewable energy intermittency, and limited operational flexibility. This study develops an integrated system modelling and assessment framework to evaluate the long-term feasibility of nuclear–renewable hybrid energy systems for isolated islands, using Sumba Island, Indonesia, as a representative case study. Two development pathways are comparatively assessed over a planning horizon extending to 2060: a Renewable–Fossil Transition Scenario based on solar photovoltaic (PV), battery energy storage systems (BESS), and gas-engine generation, and a Nuclear–Renewable Hybrid Scenario integrating floating small modular reactor (SMR) technology alongside renewable energy and storage. The framework couples hourly operational dispatch, generation expansion planning, techno-economic analysis, reserve margin evaluation, and sustainability assessment. The renewable-transition pathway remains structurally dependent on gas-engine generation, with the renewable share declining to 15.61% by 2060. Integrating floating SMR technology from around 2043 raises the renewable share close to 100% in several years, reduces fossil-based generation by approximately 87.9%, and lowers long-term electricity cost from 21.9 to 16.3 US cents/kWh. The findings indicate that combining floating SMRs with renewable energy and storage offers a reliable, competitive, and sustainable decarbonization pathway for isolated island systems.</jats:p>