Realizing Energy Savings Through Variable-Speed Pumping--A Primer

摘要

In certain circumstances, upgrading a pump station to provide variable-speed pumping can significantly reduce energy consumption and operating costs. But before a utility refits all its pumps with variable-speed drives, a thorough analysis of pumping requirements is necessary. In retrofit applications, this process is aided by having a SCADA system that permits retrieval of historical trend data. When the trend data are available electronically, they can easily be sorted to develop frequency distributions for each billing classification. Without a few years of trend data, utilities must estimate the demand distribution using monthly production records and common sense. Careful examination of the system curve provides a quick evaluation of the potential for energy savings that may be realized from variable-speed pumping. Generally, systems with flat curves benefit less than systems with steep curves. Using this step-by-step procedure, operators and utility owners can avoid projects that don't make sense economically and develop realistic predictions of energy savings that may be realized from variable-speed pumping. Many times, variable-speed pumping makes sense from a process control standpoint, rather than for energy savings alone. For example, some wastewater processes, such as filtration, work better when throughput is variable and continuous, rather than intermittent, as might be necessary with constant speed pumps.