AWWA IMTECH57863

This paper presents results obtained from the design and implementation of a sewage pumpingcontrol algorithm developed by E&C Engineering for a pumping station owned and operated bya California agency. The control strategy was optimized to minimize commercial power chargeswhile meeting pumping requirements. Pacific Gas and Electric (PG&E) provides commercialpower.To minimize electrical costs, pumping was maximized during low electric billing periods, andminimized during high billing rate periods. For large users, power companies billed forenergy (kWh) and maximum usage, or "demand" (peak kW). Summertime, mid-day energy(kWh) rates were considerably higher than night-time rates. Furthermore, a single, short-term highelectrical load condition will result in increased demand (peak kW) charges for the following 12months. Minimizing operations during peak rate periods can provide significant savings.The control algorithm uses onsite reservoir storage to defer pumping to lower rate period(s).Analog level measurement at the reservoirs and net system flow (flow in - flow out) informationis used to calculate the overall mass balance and the time required to fill or empty the reservoirs.This calculation is performed continuously, and it also depends on the pumping rate based on thenumber of pumps running. Transient conditions are "filtered" by the control system by requiringthat a change in pumping condition wait for a configurable interval prior to adding or subtractingpump(s).Based on the time of day and day of the week, the number of pumps running is optimized.During peak rate periods, the number of pumps running is minimized such that the time requiredto fill all reservoirs will be as close as possible to the time until the next partial-peak billingperiod.The algorithm was implemented with a pumping system consisting of 10 constant-speed verticalturbine pumps. The system storage capacity is provided by three reservoirs each with a volumebetween 8 and 11 million gallons, for a total storage of 29 million gallons. Includes figures.

Product Details

Edition:

Vol. - No.

Published:

04/27/2003

Number of Pages:

7

File Size:

1 file , 210 KB