چكيده به لاتين
Natural gas is a major component of the energy resilience system due to its inherent resilience and support for massive productions and renewable energy in the first half of the present century. Due to the complex and extensive structure of natural gas transmission network and uncertainty in costs and demand, Design of natural gas transmission network is a suitable tool to improve this industry. On the other hand, the complication and vastness of natural gas transmission networks lead to increase vulnerability to disruption. So, it is necessary to pay attention the resilience concept while designing natural gas transmission network that enables it to have proper performance in the face of disruption.
Review of previous researches shows that mathematical modelling of natural gas transmission network design problem that considers resilience in various sectors such as refinery, gas storage, transmission and consumption simultaneously is under investigation as a research gap. To achieve this purpose, two models are proposed for the optimal design and planning of resilient natural gas transmission network under business-as-usual and disruption risks in this research.
In the first model, a two-stage approach based on risk evaluation of each pipeline route and a two-stage stochastic-possibilistic optimization model is developed in order to design resilient natural gas transmission network according to the pipeline and consumption challenges. Also, the proposed model is designed under a dynamic condition such that enables to determine network decisions in different periods. On the other hand, the vulnerability of Natural gas transmission network through minimizing the maximum ratio of the Natural gas shortage to the total demand in each scenario and total risk due to pipeline installation in each period is defined as the second goal beside minimizing network costs. In the second model, a two-objective model with two strategic and short-term time horizons was developed such that the challenges in the natural gas supply sector, i.e., refineries and storage tanks are considered in addition to pipelines and consumption sectors challenges. In order to reduce the effects of the challenges that occurred in this network, mitigation and reactive strategies were utilized at different levels of the network. Also, the aims of the problem include minimizing total costs and maximizing network resilience by minimizing the maximum cumulative fraction of unsupplied demand (relative to the met demand before the disruption). Finally, the performance of both proposed models has been evaluated using the data of a real case study in which important results have been obtained based on executing different sensivity analyses.
The results showed, the rate of network resilience reduction due to the challenges of cutting production of Hashemi Nejad refinery is 40%, failure of the third pipeline before Rasht compressor station is 64% and increase of 8% in NG demand is 96%. On the other hand, employing the resilience strategies such as underground gas storages, expansion of production capacity in refineries, backup pipelines and fortification of pipelines have the numerous impacts on the network resistance respectively. At a certain cost, they will approximately increase network resilience by 54%, 49%, 41% and 34%. Furthermore, the result indicated that the satellite facilities has also affected the resilience of the network, but the extent of their impact depends on the number of unites used in different regions of a province.
