Emission reduction of energy-intensive islanded microgrids: a high-fidelity thermo-economic optimization framework for a retrofitted GT-SOFC-PV hybrid hub

Despite extensive research on hybrid energy systems, three critical gaps persist for deep decarbonisation of islanded industrial microgrids in arid, resource-constrained economies: scarcity of triple hybridization combining closed-cycle gas turbines, high-temperature solid oxide fuel cells (SOFC), and large-scale PV (Photovoltaic) within a fully islanded context; absence of high-fidelity thermodynamic models integrated with detailed 4E (energy-exergy-economic-environmental) analysis and DC-subgrid optimisation; and lack of realistic economic assessments accounting for actual component costs and dynamic fuel pricing. This study explicitly bridges these gaps by developing and rigorously validating a novel GT (Gas Turbine(−SOFC-PV hybrid hub retrofitted to an existing large-scale industrial closed-cycle gas turbine fleet. The proposed architecture introduces two key innovations: a water-independent anode-recirculation SOFC topology and a dedicated DC-subgrid that minimises AC/DC conversion losses. The renewable integration is analyzed via a multi-site geospatial simulation in PVsyst, utilizing five distinct operational zones with a total capacity of 13.465 MWp. System-wide techno-economic optimization using HOMER Pro reveals that the hybrid configuration achieves a Total Net Present Cost (NPC) of −$3.57 billion and a Levelized Cost of Energy (LCOE) of −0.0582$/kWh, driven by substantial grid sales and high-efficiency self-consumption. The system demonstrates a renewable penetration of 4.73 % and a total annual renewable production of approximately 24.3 GWh. Environmentally, the retrofit acts as a massive carbon sink, with a net CO 2 emission reduction of over 1.15 million tons per year compared to the base scenario, primarily due to the displacement of grid electricity and efficient CHP operation. These outcomes deliver a replicable, high-fidelity blueprint for progressive, bankable decarbonisation of energy-intensive industries globally, particularly in regions facing similar climatic and economic constraints.