OPTIMIZATION OF LOOPED WATER SUPPLY NETWORKS

Abstract

The paper approaches the optimization of looped networks supplied by direct pumping from one or more node sources, according to demand variation. Traditionally, in pipe optimization, the objective function is always focused on the cost criteria of network components. In this study an improved nonlinear model is developed, which has the advantage of using not only cost criteria, but also energy consumption, consumption of scarce resources, operating expenses etc. Discharge continuity at nodes, energy conservation in loops and energy conservation along some paths between the pump stations and the adequate `critical nodes´ are considered as constraints. This problem of nonlinear programming with equality constraints finally turns into a system of nonlinear equations to be solved by the `gradient method´. The nonlinear optimization model considers head losses or discharges through pipes as variables to be optimized in order to establish the optimal diameters of pipes and is coupled with a hydraulic analysis. The paper compares a nonlinear optimization model to some others, such as the classic model of average economical velocities and Moshnin optimization model. This shows the good performance of the new model. For different analyzed networks, the saving of electrical energy, due to diminishing pressure losses and operation costs when applying the new model, represents about 10...30\%.