Optimization and comparative analysis of operating modes in a multi-energy complementary system using NSGA-III algorithm

The increasing demand for building heating and cooling under dynamic load conditions poses significant challenges to the efficient operation of multi-energy complementary systems. This study proposes an operation-mode-oriented multi-energy complementary system integrating photovoltaic, wind, natural gas, and geothermal energy, with a focus on the operation modes of cooling and heating source dispatch. A TRNSYS-based dynamic simulation model is developed for a hotel building in Xi'an, China. Four distinct operating modes, characterized by different start-up priority sequences and dispatch strategies of cooling and heating sources, are evaluated as independent candidate operating modes. A simulation–optimization framework for each operating mode is established by coupling parametric analysis with multi-objective optimization using the NSGA-III algorithm, considering energy, exergy, economic, and environmental indicators. The entropy-weighted TOPSIS method is employed to identify the optimal compromise solution among Pareto-optimal candidates. The results reveal that different operating modes lead to distinct trade-offs among energy efficiency, economic performance, and environmental impact. Under the optimal operating mode (Mode 4), the system achieves an energy utilization efficiency of 74.28%, an annual energy saving ratio of 72.69%, and an exergy efficiency of 78.03%. Meanwhile, the levelized multi-energy cost decreases to 0.033 $/kWh, with a net present value of 1.98 × 106 $ and a dynamic payback period of 9.79 years, while the annual pollutant emission reduction rate reaches 34.46%. The results demonstrate that operational mode design plays a critical role in balancing energy efficiency, economic performance, and environmental benefits in multi-energy complementary systems.