Optimal pump operations considering pump switches

A methodology for determining optimal pump operation schedules for water-distribution systems is presented. In addition to minimizing the energy-consumption cost, the model includes a constraint to limit the number of pumps that are switched on during the planning period. A two-level approach is adopted whereby the system hydraulics are analyzed in an off-line mode to generate simplified hydraulic and cost functions for an on-line model. These functions developed for each pump combination allow for rapid evaluation within a dynamic programming optimization algorithm. Constraints can also be included for tank levels, rate of change of tank level, pump switches during each period, and maximum energy consumption. Solution times for small to medium-sized systems show that the model can be used in an on-line mode to determine pump operation schedules; however, the applicability of the model is limited by the number of pumps in the system. An extensive sensitivity that highlights operational problems and the utillity of the approach is presented.