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The right choice of compressor type must be based on energy efficiency

In a factory, a responsible for compressed Air is assigned. This can be the owner, the technical director or service technician.

5 min.
The right choice of compressor type must be based on energy efficiency

When designing a compressor room, the responsible will select the capacity for its peak consumption and will add a safety margin (or redundancy), to be sure that the factory never gets short on Compressed Air. The avg consumption is much lower than the peak consumption.  Depending of the type of manufacturing process, factory design, the avg consumption can easily be "30-50% of its peak consumption.   The result is that an installation has a lot of sur-capacity and  the avg consumption of the total installation  is most likely to be below 30-50% of the installed capacity. A knowledgeable responsible will of course select multiple compressors, in order not to be depending on a single air-compressor.  By installing multiple compressors, the regulation or partial load is more efficient while the redundancy is better. Still, one or two compressors will run in partial load all the time.   From experience, most installations are NOT well designed, due to lack of knowledge or due to changed demand in the factory.   Lack of knowledge on compressed air systems is very common.  Unfortunately, often the sales rep is not knowlegeable either and is eager to sell a machine rather than to advice on  the best solution for his installation. Changed demand is happening continuously, a production line is stopped, a new investment is done for which the air consumption changed,.... When selecting a new compressor, often the performances are compared only at full load.  The performances of full load machines, supplied by the different compressor manufacturers, is often confusing due to incomplete information. Data on partial load, is for sure in-complete. Most common pitfalls :
  • Electrical power of the electrical motor is the frame size and not the real power (to be multiplied by the Servic Factor SF)
  • The flow is specified at which ambient temperature ?  At 0 deg C the compressor will provide more flow than at 20 deg C
  • The specific energy consumption at reduced flow will increase substantially (worst case is a centrifugal)
  • Oil-separation reduces at reduced flow
  • You will save energy when installing a Variable speed drive ? The power consumption of frequency converters is left out, overall power consumption of a frequency converter can vary between 3-10% of the total installed power
  • pressure drops over filters, especially in Oil-injected compressor systems