Multi-objective sustainability optimization of a solar-based integrated energy system

Integrated energy systems combine multiple energy sources to improve efficiency and reduce pollutant emissions. However, the diversity of energy types within integrated energy systems results in a more complex structure. Analyzing economic, environmental, and energy performance alone does not accurately reflect the comprehensive performance of the system. Describing the various types of resources input to the system uniformly and thus comprehensively assessing the structure and processes of the system pose significant challenges. Therefore, based on conventional emergy analysis methodology, the materials consumption and costs of pollutant emissions over the whole life cycle of the system are considered, and a multi-objective sustainability optimization model is proposed to search for the optimal configuration of the solar-based integrated energy system. Optimization results show that the sustainability optimization model proposed in this study achieves better emergy performance compared to the conventional sustainability optimization model, the emergy yield, emergy investment ratio, environmental loading ratio, emergy yield ratio, and emergy sustainability index of the integrated energy system for the proposed model are 1.54 × 1017 seJ/y, 0.011, 20.08, 90.31, and 4.50, respectively. Sensitivity analysis indicates that the emergy yield is significantly affected by capacity, whereas the emergy investment ratio and emergy sustainability index are more sensitive to costs. The multi-objective sustainability optimization model proposed in this study provides a new perspective for addressing the relationship between different resources within integrated energy system, and is expected to guide the design of energy supply systems.