Techno-Economic Analysis of Renewable-Powered Communities with Seawater Reverse Osmosis for Remote Islands Using HOMER Pro

Remote islands face interconnected challenges of high dependence on diesel, expensive electricity, and limited freshwater availability. This study develops an integrated renewable energy–seawater reverse osmosis (SWRO) system for the Cocos (Keeling) Islands, Australia, and evaluates its technical, economic, and carbon performance using HOMER Pro. The proposed system simultaneously supplies community electricity demand and a 240 m3/day SWRO plant with a specific energy consumption of 3.5 kWh/m3. The optimal configuration consists of 2656 kW Flat-plate PV, three 100 kW wind turbines, 6640 Li-ion battery units, an 870 kW converter, and diesel backup, achieving a renewable fraction of 98.3%. Compared with the diesel-based system, the proposed configuration reduces the net present cost from A$51.7 million to A$7.55 million and the levelized cost of electricity from A$1.30/kWh to A$0.189/kWh. Annual diesel consumption decreases from 1,107,017 to 13,579 L, while CO2 emissions decline from 2,923,510 to 35,860 kg/year, corresponding to approximately 98.8% reductions in both indicators. The system provides a 1.12-year payback period, a 92.1% return on investment, an 89.9% internal rate of return, a A$46.8 million net present value, and A$2.44 million in annualized savings. Sensitivity analysis across diesel prices of A$2–4/L and discount rates of 4–12% confirms high renewable penetration (93.5–98.8%) across the investigated conditions. The novelty of this work is an integrated, renewable-dominated electricity and desalination pathway for a remote Australian island community that addresses energy security, freshwater security, lifecycle cost, and operational carbon emissions.