A wind-solar-hydrogen production complementary system is an important technical method to promote the local renewable energy utilization and reduce wind and solar power curtailment. However， the fluctuation of wind and solar outputs and the variety of system equipment challenge the capacity allocation optimization of wind‒solar‒hydrogen production complementary systems. A life cycle assessment（LCA）method was used to address this problem. Taking the levelized cost of hydrogen（LCOH），carbon emission intensity per unit of hydrogen， and energy loss rate as optimization objectives， an off-grid wind‒solar‒hydrogen production system with an annual production capacity of 20 000 t of hydrogen was constructed based on the improved NSGA-Ⅲ multi-objective optimization algorithm. The carbon emissions and economic benefits of the system were further analyzed. The results showed that after the optimization based on the wind and solar resource characteristics in Inner Mongolia， the LCOH of the system was 25.88 yuan/kg， with a carbon emission intensity of 0.59 kg/kg. The annual renewable energy utilization rate increased to 91.09%， demonstrating efficient resource utilization. The LCA showed that the system's total carbon emissions amounted to 250 300 t， and the carbon emission per unit of hydrogen was reduced by 97.05% compared to that of a typical coal-based hydrogen production system. The research results provide a reasonable reference for the utilization of wind-solar-hydrogen production complementary systems.
