Optimised by Frequency Converter (Inverter)

Pump or fan efficiency is usually at its highest arround the rated flow and head (+/-78%). In case the flow rate is reduced by speed controlo, the efficiency stays close to the maximum (+/-77%). In case the flow is reduced by throttling, the efficiency is much lower (+/-60%). If we look at 100kW pump motor at 5,000 h/year, we get:

  • Energy saving about 85,000 kWh/year
  • Reduction in CO2 emissions: 42,500 kg/year
  • General rule: Install a frequency converter instead of throttling if significant flow variations occur

Fan speed control instead of dampers

In the past, control of air flow in ventilation systems was mainly a way to alter performance, not to save energy. Although there is a number of methods, not all are energy efficient. The most basic and inefficient way of controlling the flow rate is adjustment of a damper in the ventilation duct. Using a freq. converter with a 30kW motor running 5,000 hours/year gives the following savings:

  • Total energy saving: 76,500 kWh/year
  • Reduction in CO2 emissions: 38,250 kg/year
  • Other benefits: Soft starting, less maintenance, short payback period, better flow control

Fan speed control instead of on-off

In the past, control of air flow in ventilation systems was mainly way to alter performance, not to save energy. Although there are a number of methods, not all are energy efficient. A very basic way of controlling the flow rate is to modulate the fans on or off. Fitting a frequency converter to a 30kW motor running 5,000 hours/year gives the following savings:

  • Total energy saving: 51,000 kWh/year
  • Reduction in CO2 emissions: 25,500 kg/year
  • Other benefits: soft starting, less maintenance, much better flow control, a more comfortable indoor climate

Fan speed control instead of two-speed motor

A quite simple way of controlling the flow rate is use a two-speed motor, but it has two flow rates only. Using a frequency converter gives the following savings for 30kW motor running 5,000 hours/year:

  • Total energy saving: 52,500 kWh/year
  • Reduction in CO2 emissions: 26,250 kg/year
  • Other benefits: soft starting, less maintenance, much better flow control

Fan speed control instead of inlet vanes

Inlet guide vanes is more sophisticated method for flow control, but using a frequency converter instead gives the following savings for a 30 kW motor running 5,000 h/year:

  • Total energy saving: 37,500 kWh/year
  • Reduction in CO2 emissions: 18,750 kg/year
  • Other benefits: soft starting, less maintenance, much better flow control

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