Energy Savings at Municipal and Industrial Pumping Facilities
Energy costs for electric motors that drive large pumps account for much of the annual cost of operation of municipal
and industrial pumping facilities. For example, a 250 hp pump and motor has an initial cost of around $30,000, but the cost
to power that pump the first year will exceed $80,000 (at 6 cents/kwhr). The cost of electricity to power a large motor that
operates more than 6000 hours per year can account for over 80% of the life cycle costs.
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Most large pumps at municipal and industrial facilities are centrifugal designs, which should operate at an optimal flow rate
and head condition, referred to as the Best Efficiency Point (BEP) on the pump curve. Many facilities have undergone
changes in function from what they were originally designed to do. An assessment of the current system requirements will insure existing
equipment is suitable for the task and in good repair.
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Potential savings are identified using the software program "Pumping System Assessment Tool" (PSAT). This program requires data
obtained from motor and pump nameplates,
flow rates,
suction and discharge pressures,
power data obtained from electrical switchgear,
and energy costs. Click for example screen from PSAT . Potential energy savings are calculated by
comparing energy costs using existing equipment to costs for operating properly sized pumps and motors.
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Significant savings can be found in pumping systems that:
- are throttled to control flow
- have bypass (recirculation) lines normally open
- operate multiple pumps in parallel with the same number running
- have cavitation noise anywhere in the system
- have high maintenance
- have undergone system changes
Contingency planning is another benefit of any energy assessment. In addition to saving money by reducing energy consumption, alternatives to the existing pump and motor are identified that can be implemented upon failure. The alternative pump or motor may be less costly than to simply repair or replace the existing component.
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