To Lift or Boost? Modifying the Operation of an Existing Pump Station toMaximize Energy Efficiency

摘要

At the Greater Cincinnati Water Works (GCWW), energy management is an importantrncomponent of operating all pumping facilities. During a recent energy managementrnanalyses of a 35 mgd pump station, it was determined that significant energy savingsrncould be achieved if the pumping operation was radically changed. The normal operationrnof the facility was a “dump and pump” operation, where the water from the upstreamrndistribution system fills the reservoir, and then the water is pumped from the reservoir tornthe next pressure zone. Because the inlet pressures to the reservoir were significantlyrnhigher than anticipated (70 psi versus 20 psi), an innovative solution was developed tornconvert the pump station from a “dump and pump” operation to a booster pumprnoperation. Extensive hydraulic and economic analyses were performed to determine if thernexisting pumps could be modified to efficiently operate as booster pumps, therebyrnlowering the required horsepower usage and capturing significant energy savings.rnHowever, the pump’s ability to also operate as a lift pump had to be maintained torncontinue using part of the 2.5 MG storage reservoir for water quality purposes. Thernhydraulic analyses showed that by carefully trimming the pump impellers, the pumpsrncould be converted to pump efficiently in both the booster mode and the lift mode. Therneconomic analysis showed that the cost of modifying the existing pumps could bernrecovered with the projected energy savings in less than three years. The long-termrnelectrical savings were estimated at about 20 percent of the current electrical costs. Also,rnthe 70-psi inlet pressure had to be reduced to about 10 psi before entering the reservoir.rnThrottling the water into the reservoir was causing premature failure of a critical inletrnvalve and resulted in undesirable pressure fluctuations on the upstream distributionrnsystem. In conjunction with the pump modifications, the control valve to the reservoirrninlet was replaced with a unique valve called a sleeve valve.