Techno-economic analysis of zero/negative carbon electricity-hydrogen-water hybrid system with renewable energy in remote island

Sourcing electricity and freshwater from renewable energy has emerged as crucial development pathway for remote islands. In this paper, a hybrid self-sustaining system combining solid oxide fuel cell, hydrogen production unit, direct air carbon capture unit and desalination module is proposed, which could convert wind and solar energy into electricity, hydrogen and freshwater with zero/negative carbon emissions. The electricity‑hydrogen-water production, carbon absorption and economic analysis under different hydrogen production modes and operation strategies were investigated by a self-developed energy and economic model. The results indicate that, in addition to meeting electricity demand, the system produces 14.42–17.67 tons hydrogen or 43.49 t syngas and 5.64–13.11 k tons freshwater per year without carbon emissions. Under the export strategy, annual net hydrogen or syngas production increases to 359.1–387.2 t and 2958.8 t. Furthermore, in solid oxide electrolysis cells mode, the system transforms into a carbon-negative system with an annual CO2 absorption capacity of 54.73 t and 3636.76 t under demand and export strategies, respectively. The hydrogen energy storage under reversible solid oxide cells mode is the most economical, with a levelized cost of energy of 0.732 ¥/kWh. Additionally, selling excessive syngas under the export strategy reduces the system's levelized cost of energy by up to 34.7 %. This work provides a promising solution to the energy and freshwater demands of remote islands.