An air compressor’s biggest output is not what you think

Sept. 29, 2020
The biggest and most overlooked step in greatly improving the efficiency of a compressed air system is to capture the heat and send it to where it can be used.

Many people think that compressed air power is the biggest output of an air compressor, and if you do you are missing something big.

Analysis of the output of a typical air compressor shows that only about 12 percent of the energy consumed by an air compressor is transferred to any compressed air driven tool or machine down the line. Where does the rest of the energy go? Mostly to the heat of compression, which is typically wasted by expelling it outdoors.

The biggest and most overlooked step in greatly improving the efficiency of a compressed air system is to capture the heat and send it to where it can be used. Air compressors come in air or liquid cooled variants, and lubricated or non-lubricated types. Regardless of the type, each offers the opportunity to use the heat they create in the compressor process to displace fuel driven or electrical heated processes.

For example, every 1 hp of fully loaded compressor power produces about 2,545 btu per hour of heat. If you remember your conversions from high school physics, you will realize this heat output is equivalent to about 746 W, or one horsepower of heat.

How can an air compressor produce one horsepower of heat and still output 12 percent in compressed air power? Simple: air compressors usually consume about 12 percent or more power than their nameplate rating due to motor losses and auxiliary equipment (like fans) which are not counted in the nameplate rating.

Some common uses for heat of compression include the following:

  • Space heating of buildings
  • Hot water for process heat
  • Boiler make up
  • Hot air drying of painted items
  • Heat of compression air dryers (non-lubricated only)
  • Input to adsorption chillers

Next time you are looking for a cheap heat source, consider your air compressor and save some cost.

Reference link: https://www.compressedairchallenge.org/data/sites/1/media/library/factsheets/factsheet10.pdf

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