Flexible and optimized operation of integrated energy systems based on exergy analysis and pipeline dynamic characteristics

Abstract

Given the energy crisis and severe environmental pollution, it is crucial to improve the energy utilization efficiency of integrated energy systems (IESs). Most existing studies on the optimal operation of IESs are based on the first law of thermodynamics without considering energy quality and direction attributes. The obtained strategies generally fail to accurately reflect the difference in energy quality. Based on the second law of thermodynamics, we first analyzed the energy quality coefficients of energy in different forms and expressed the exergy flow as the product of energy quality coefficients and energy flow. An exergy analysis model of the electric–gas–thermal integrated energy system was also established based on the energy network theory. Second, modeling and analyzing the dynamic characteristics of gas–thermal networks and the corresponding energy storage capacities were explored. Considering the dynamic characteristics of the gas–thermal pipeline network, the useful energy stored in the pipelines was analyzed based on the energy quality coefficients of natural gas and the thermal energy system, and the flexibility capacity of each subsystem was also analyzed in combination with the operation of units. A simulation analysis was then conducted on the electric–gas–thermal IES 39-20-6 system. The results demonstrated that from an energy perspective, the loss in the coupling equipment only accounts for 29.05% of the total energy losses, while from an exergy perspective, its proportion is as high as 46.47%. Besides, under the exergy analysis, when the dynamic characteristics of the gas–thermal pipeline network are taken into account, the wind curtailment rates of the system decrease from 11.22% to 8.27%.