A robust approach based on time variable trigger levels for pump control

An approach for the control of a pumping plant feeding a tank at the inlet of a water distribution system is presented. The approach is aimed at minimizing the energy costs by maximizing pumping during off-peak electricity tariff periods. It is based on trigger levels which are variable during the day according to a prefixed pattern in order to ensure that the water level in the elevated tank is at its minimum and maximum values at the end of the peak and off-peak tariff periods, respectively. The pattern of the trigger levels is defined by solving a multi-objective problem aimed at minimizing the energy costs and the number of pump switches. The approach was applied to a couple of real cases with a single tank. The approach was compared with other methodologies typically used for pump control, i.e. fixed trigger levels and pump scheduling. The results show for the two particular cases that the proposed approach achieves energy costs that are lower than those obtainable by using fixed trigger levels, and comparable with those obtainable by using pump scheduling. This is based on achieving a similar number of pump switches.