Capacity Configuration Optimization of Off-grid Wind-Solar-Hydrogen-Electrolyte Ammonia Coupled Energy Supply System

At present, electrolyzers in off-grid wind-solar-hydrogen multi-energy complementary systems predominantly utilize water electrolysis for hydrogen production, which is only suitable for above-zero temperature environments. Liquid ammonia is not easily condensed at low temperatures, hence this paper replaces the electrolyzer with an electrolytic liquid ammonia hydrogen production device. To ensure stable operation of the off-grid microgrid and maximize the utilization of renewable energy, a wind-solar-hydrogen power generation model considering hydrogen storage capacity and equipped with batteries is established. The multi-objective function aims to minimize the load power deficiency rate, maximize the renewable energy penetration rate, and minimize system costs. When wind and solar power generation are abundant, the power allocation ratio is used to improve energy utilization and promote multi-energy complementarity. With the capacity of each operating device as a constraint, the genetic algorithm is employed to solve for the optimal capacity configuration, and the entropy weight method is used to determine the weight of each indicator. To verify the practicality of the system, the optimal configuration is solved based on actual weather and load data from a northern region, and the operation duration with 50 L of liquid ammonia raw material is analyzed. The results indicate that the optimal system configuration consists of a 42.7W electrolyzer, a 7.3W fuel cell, a 1L hydrogen storage tank, and a 33.3W battery, corresponding to a minimum system cost of 3343.6 yuan (weight coefficient 0.673), a load power deficiency rate of 0 (weight coefficient 0), a renewable energy penetration rate of 51.2% (weight coefficient 0.327), and a maximum operation time of 2060.6 days.