(200a) Incorporation of Network Topology for Resilient Design and Optimal Operation in the Framework of Water-Energy Nexus
It is crucial to design resilient regional water-energy networks, which can withstand disruptions in their connectivity or in their facilitiesâ capacities and still manage to satisfy the end-use power and water demands. Plenty of works have discussed the effect of network topology in the performance of ideal or real networks under disruptive cascading failures [3,4]. However, accounting for network resilience in the design phase is still an unresolved question in the literature. To this end, we utilize our proposed WEN superstructure to represent a regional water-energy system . The superstructure is comprised of energy and water resources, energy and water consumers, and intermediate potential energy and water sources to be allocated. The intermediate sources are characterized by a conversion factor (eg. power per fuel, water output to water input), an intensity factor (water needed for power, power required for water treatment), a capacity factor and a generating design capacity. The objective of the MINLP formulation is to minimize the total network cost (resource supply, generation, transportation), satisfy consumer demands, and obtain optimal selection of generating technologies, capacities and connectivity.
To account for the resulting nexusâ resilience, we incorporate network topology-imposing constraints in the design phase. Specifically, we utilize the binary variables of selection of facilities and connecting streams, to dictate, (i) node centrality, (ii) the degree of how much centralized/distributed is the nexus (network density), and (iii) the number of alternate paths for a product to reach from a resource to consumer (equivalent to the betweenness centrality). In the expense of network cost, the resulting network becomes more resilient by imposing larger node degrees, more distributed generation, and more alternative paths for power and water to reach the consumers. Resilience is then quantified by testing the resulting nexus for feasibility (satisfaction of demands) after removing connections and restricting the capacity or shutting down sources. Then, the optimal pareto curves are obtained for network cost versus resilience. Finally, the combined effect of nexus design attributes, such as minimum allowed flow and capacity factor, and network properties, such as average degree and network density, is investigated and a framework to obtain resilient networks for grass-root designs and retrofitting existing infrastructures is developed.
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 Tsolas, S. D., Karim, M. N., & Hasan, M. F. (2018). Systematic Design, Analysis and Optimization of Water-Energy Nexus. Foundations of Computer-Aided Process Design 2019, Paper ID 101