Multi-objective planning and sustainability assessment for integrated energy systems combining ORC and multi-energy storage: 4E (economic, environmental, exergy and emergy) analysis
Juntao Han, Kai Han, Yongzhen Wang, Yibo Han, Zhaonian Ye, Jiayu Lin
Abstract
Sustainability assessment and flexibility enhancement are the key to achieve efficient and economic, supply-demand matching and comprehensive evaluation of integrated energy systems (IES). Therefore, a joint optimization model of economic, environmental and exergy for IES combining waste heat driven organic Rankine cycle (ORC) power generation and multi-energy storage is developed, and the emergy theory is introduced for system sustainability assessment. Firstly, the mixed-integer nonlinear optimization models for three scenarios of gas turbine (GT) without ORC, GT with ORC (GT-ORC) and solid oxide fuel cell (SOFC) with ORC (SOFC-ORC) are established, and the Pareto curve is obtained by using the augmented ε constraint. Secondly, the economic, environmental and exergy efficiency of the optimal decision-making scheme are analyzed, and the system sustainability is evaluated by solar emergy. The results reveal that in the optimal scenario, the SOFC-ORC scenario reduces CO 2 emission by 33.2 %, but the annual cost is increased by 45.7 %, and exergy efficiency is lowered by 8.1 % compared to that of the GT-ORC scenario. Then, the emergy sustainability index of the optimal solution for SOFC-ORC scenario is 0.031, which is significantly lower than that in GT-ORC scenario, which is 0.152. The proposed emergy analysis method covers energy, economy, society and environment, and elucidate the developmental sustainability of the system.