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CASE STUDY

Turbine Well Pump Efficiency Improvement

Situation

Lance Owen Farms asked SSVEC’s Advanced Pump Efficiency Program (APEP) to review one of its turbine well pumps for its operating efficiency and the possibility of using a variable frequency drive flow control system rather than a standard throttling valve. After evaluating this 125 hp turbine well pump, hours of operation, and higher than expected energy consumption, the APEP Program qualified the pump for free testing. This well pump was operating under constant speed to meet system demands. Flow control was being accomplished using throttling and turning the pumps on and off based on demand. This type of on-off throttling control is typically not an efficient method for flow control. First, APEP arranged for the qualified pump tester to evaluate the existing operating characteristics of the pump and found it was producing 1,065 gpm with a total head of 307 ft. from the pumping water level of 238 ft. With the proposed improvements, Lance Owens’ water production cost per acre foot was reduced by $5.71. Overall pump test results indicated the following:

Based on APEP’s experience with thousands of pumps across the western states, the majority of energy and cost savings for pump system are made through bowl and motor improvements.

Solution

APEP evaluated the existing pump for reasons of inefficiency and options for upgrades so that it would operate at its recommended design condition and proposed two solutions:

Turbine Well Pump Efficiency Improvement:

This recommendation was based on energy efficiency improvement from 60.6% to 69%, saving the customer 42,434 kWh or $3,819 per year (equivalent to a 12.2% energy cost reduction in the utility’s rate for the customer).

VFD Installation and Pumping System Optimization:

There are many hours during the seasonal crop irrigation when well pumps may not be able to operate at full load or may be over-designed for one type of irrigation, while exact-designed for others. Rather than modulating the flow with a throttling valve, a VFD can make adjustments for the required pressure and flow rate so that the pump will be used for only what is needed. In many cases, the pump is already over-designed by as much as 25%, and VFD is currently the economical way to reduce this over-capacity while requiring significantly lower power to deliver the flow rate and the pressure needed for day-to-day operations. In this case, a 125hp VFD applied to this turbine well pump is expected to save as much as 60,000 kWh or $5,400 per year with a simple payback of 3.4 years.

If you operate well or booster pumps sized at 50hp and greater that run at least 1500 hours per year (or more than four hours per day) that have not been tested in the past 24 months, please contact your Utility’s Program Manager to schedule your free pump test at: 1-877-333-1070 or apepssvec@lincus.com. Please note that this Program has a limited budget and free pump tests are available on a first come, first served basis.

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