Optimal configuration of an off-grid hybrid wind-hydrogen energy system: Comparison of two systems

Abstract

Due to the uncertainty of renewable energy power generation and the non-linearity of load demand, it becomes complicated to determine the capacity of each device in hybrid renewable energy power generation systems. This work aims to optimize the capacity of two types of the off-grid hybrid wind-hydrogen energy system. We considered the maximum profit of the system and the minimum loss of power supply probability as optimization goals. Firstly, we established steady-state models of the wind turbine, alkaline electrolyzer, lead-acid battery, and proton exchange membrane fuel cell in matrix laboratory software to optimize the capacity. Secondly, we analyzed the operating mode of the system and determined two system structures (system contains batteries whether or not). Finally, according to the wind speed and load in the sample area, we compared the economics of the two systems and selected the optimal configuration for the area. In the same calculation example data, the non-dominated sorting genetic algorithm-II (NSGA-II) is used to optimize the capacity of each device in the two systems. The results showed that the profit of the without battery-equipped system is 32.38% higher than another system. But the power supply reliability is the opposite. To avoid the contingency of the calculation results, we used the traditional genetic algorithm (GA) and ant colony optimization (ACO) to calculate the same example. The results showed that NSGA-II is significantly better than GA and ACO in terms of iteration steps and calculation results. The required architecture for the System-I composes of 3 numbers of 10 kW wind turbines, 61 sets of 12 V·240 Ah lead-acid batteries, 8 kW electrolytic cell, and 6 kW PEMFC. The net profit and LPSP are ¥44,315 and 0.01254 respectively. The required architecture for the System-II composes of 2 numbers of 10 kW wind turbines, 24 kW electrolytic cells, and 18 kW PEMFC. Net profit and LPSP are ¥58,663 and 0.03244, respectively. This paper provided two schemes for the optimal configuration of the hybrid wind-hydrogen energy system in islanding mode, which provided a theoretical basis for practical engineering applications.