A wastewater lift station uses a centrifugal pump on a VFD. At 60 Hz, the pump operates where the pump curve intersects the system curve in the table provided. A portable power meter shows the motor is drawing 22.0 kW at that operating point.
During low-flow hours, the operator plans to reduce speed from 60 Hz to 48 Hz (a 20% reduction). Assume pump and motor efficiency stay the same and use the affinity law for power: P2/P1 = (N2/N1)^3.
The pump runs an average of 1,200 min/day and the electric rate is $0.11 per kWh.
Motor nameplate (extraneous): 40 hp, 460 V, 3-phase, 52 A, 92% efficiency, SF 1.15.
Based on the affinity law, what is the approximate DAILY dollar savings from reducing speed to 48 Hz during the entire run time?