Optimal operation of off-grid integrated hydrogen energy utilization systems: Life-cycle cost reduction considering waste heat recovery

The integrated hydrogen energy utilization system (IHEUS) exhibits great potential for microgrid applications. However, its practical deployment faces significant challenges, primarily due to the low energy conversion efficiency and rapid aging of electrolyzers and fuel cells, especially when handling highly fluctuating power flows. To address these issues, this study proposes a multi-objective optimal dispatch scheme for off-grid IHEUS operations, incorporating waste heat recovery and life cycle cost considerations. First, a mechanistic model is established to characterize the electric-hydrogen-heat output characteristics of the system, with a specific focus on waste heat recovery and utilization subsystems. By correlating the aging behavior and lifetime degradation to voltage decay, a life-cycle operational cost function is formulated for the multi-objective optimization (MOO) model. Within this framework, comprehensive energy efficiency and energy supply loss probability are adopted as performance metrics to enhance energy utilization and stability. The resulting MOO problem is solved and prioritized using a proposed NSGA-III combined entropy-weighted TOPSIS strategy. Comparative studies demonstrate that this strategy effectively identifies the optimal dispatch scheme, achieving operational cost reductions of at least 17.53%, comprehensive energy efficiency improvements ranging from a 0.13% decrease to a 0.61% increase, and a limited increase in energy supply loss probability (4.14%).