Integrated optimization of multi-carrier energy systems: Water-energy nexus case

This paper focuses on the optimal operation of integrated electrical and water energy networks at the distribution level considering the demand response program. In this manner, the water network with various components including reservoirs, tanks, fixed and variable speed pumps, and control valves is modeled. Newton-Raphson method is adopted to solve the water flow problem. This technique, unlike existing methods, can be applied to any network with any type of topology, whether radial, circular or hybrid. The electrical network is also modeled with the relevant constraints and coupled with the water network to supply the required electrical power. The optimization problem in a practical energy system, including a standard IEEE 33-bus electrical network, and the North Marin water network has been solved by a teaching learning-based optimization algorithm as a parameter-free method. The objective is to minimize the total operation cost. With the participation of the water network in a demand response program, the optimal charging and discharging of tanks, and pumps scheduling has been carried out, which consequently has led to operation cost reduction. In addition, numerical results have proved that the utilization of variable speed pumps can reduce about 7% of the total costs. (C) 2022 Elsevier Ltd. All rights reserved.