Optimization of Long-Term Power System Planning Toward Net-Zero Emissions: A Case Study of Sumbawa Island

Achieving deep decarbonization in power systems requires a strategic shift from fossil-based generation to new and renewable energy. On Sumbawa Island, continued coal reliance, evident in the operation of the 2×7 MW CFPP in West Sumbawa and the planned 2×10 MW CFPP Bima FTP-1 by 2029 under the national electricity planning document (2021–2030), challenges decarbonization efforts. However, Sumbawa and its neighboring island Sumba offer considerable solar potential, making them key regions for renewable deployment. This paper develops a Generation Expansion Planning model using OSeMOSYS and the GLPK solver to assess electricity transition scenarios from 2025 to 2050. Four configurations (BAU and NZE under isolated and interconnected systems) are evaluated based on investment, operating cost, and emissions. Results show that the NZE interconnected scenario achieves full decarbonization by 2033 while improving reliability. In both BAU and NZE interconnected scenarios, Sumba supplies up to 372.44 GWh annually to Sumbawa by 2050, aligning with the national directive to maximize solar energy use in Nusa Tenggara. Although NZE pathways require higher capital investment, they reduce long-term fuel costs and enhance sustainability. The findings highlight the value of inter-island synergy in meeting Indonesia’s NZE targets.