Energy Saving for Pump

Pump speed control instead of recirculation

Centrifugal pumps can be controlled by methods similar to those for controlling fans.

In practice, the most common method is throttling by means of a control valve. Recirculation is also used, but it is most inefficient from an energy point of view. Fitting a frequency converter to the system with a 30 kW motor running 5,000 hours/years saves:

  • Total energy saving: 100,500 kWh/year
  • Reduction in CO2 emissions: 50,250 kg/year
  • Other benefits: Soft starting, less maintenance, short payback period, better flow control, less noise

Pump speed control instead of recirculation

Throttling causes losses both in the pump and in the valve itself. Regulating flow with a frequency converter (inverter), in the case of a 30 kW motor running 5,000 hours/years saves:

  • Total energy saving: 58,500 kWh/year
  • Reduction in CO2 emissions: 29,250 kg/year
  • Other benefits: Soft starting, less maintenance, short payback period, better flow control, less noise

Pump flow control – PFC instead of fixed speed

When a European water utility compared the energy consumption of a fresh water pump with an existing on-off control against proposed variable speed AC drive with PFC (one 55 kW pump with variable and three 55 kW pumps with fixed speed), the results, based on 7,000 hours/year, were:

  • Total energy saving: 195,000 kWh/year
  • Reduction in CO2 emissions: 97,500 kg/year
  • Other benefits: Payback period only 3 months, better water pressure control, less reactive power

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