Variable Speed Drives for Pump Systems

Adjustment of the pump speed an efficient way of responding to fluctuations in flow and pressure demand in the system, particularly if the system in question is dominated by friction head. Variable speed drives enable a higher degree of control on the pump speed – adjusting the speed of a single-speed motor to precise levels over a wide range by electrical and mechanica methods. VSDs are practical for situations where the demand changes continuously and with varying increments. In high- static-head systems, reducing the pump speed can cause a pump to operate close to shut-off head conditions, generally leading to poor performance or, in severe cases, damage. In such situations, use of VSDs may not be appropriate (US DOE, 2006. p.17).

Development Status Products

Variable Speed Drives for Pump SystemsCosts & Benefits

Parent Process: Pump Systems
Energy Savings Potential

This measure is estimated to offer following improvement potentials (UNIDO, 2010):
• 25% for low efficiency base cases;
•15% for medium efficiency base cases;
• 10% for high efficiency base cases;/p>

Electrical and primary energy savings potential of this technology for different countries is estimated as following (UNIDO, 2010): 

  Final* (GWh/y) Primary* (TJ/y)
US 12706 139919
Canada 3791 47229
EU 9119 85688
Thailand 724 7289
Vietnam 407 5820
brazil 1078 12036
CO2 Emission Reduction Potential

Total emission reduction potential of adopting VSDs in pumping systems, as kt CO2/y for different countries are estimated as (UNIDO, 2010): 

US 7658
Canada 1885
EU 3977
Thailand 376
Vietnam 200
brazil 157


Estimated typical capital costs of this measure for different system sizes (S) are:
• US $4000  for S < 37 kW;
• US $9000 for 37 kW < S < 75 kW;
• US $18000 for 75 kW < S < 150 kW;
• US $30000 for 150 kW < S < 375 kW;
• US $65000 for 375 kW < S < 745 kW; (UNIDO, 2010)

Cost of conserved energy, expressed as US $/MWh-saved, in different countries are estimated as following (UNIDO, 2010):

US 44.5
Canada 44.2
EU 43.7
Thailand 24.9
Vietnam 17.7
brazil 27.8

Variable Speed Drives for Pump Systems Publications

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17, 51-55

Variable Speed Drives for Pump Systems Case Studies

Variable Speed Drives for Pump Systems Tools