Air compressed (pressurised) in a container can be used as a power source. Applications for compressed air include pneumatic tools such as jackhammers, drills, spray-painters, and processes like mineral sorting, automotive manufacturing and water treatment. Around 10% of all electricity generated in Australia is expended on the production of compressed air.

An advantage of pneumatic tools is that several can be run in a system without each needing its own internal motor. This means the tools can be more compact, lighter and easier to use in confined spaces.

The cost of compressed air is (or has been) many times that of other energy transfer methods. Although air itself is a clean resource in endless supply, it requires electrical energy to compress it for industrial use.  As much as 30% of a site’s electricity use can be consumed by this process. Also, up to 90% of the energy used to compress air can be wasted in the process.[i] On top of this, up to 50% of compressed air is lost in leakages, even in new equipment.

Positive displacement compressors

Positive displacement compressors operate by trapping a given quantity of air or gas in a compression chamber and mechanically reducing the volume which it occupies, causing a corresponding rise in pressure prior to discharge. At constant speed, the airflow remains essentially constant with variations in discharge pressure. Types of positive displacement compressors include reciprocating and rotary screw compressors.2
  • Reciprocating – Use a reciprocating piston to compress air into a storage tank through a valve. They can be a single or two stage system. ‘Reciprocating compressors are generally the most energy efficient compressors, both at full and part loads.’
  • Rotary screw – Consist of two meshing helical screws located within a casing which rotate in opposite directions to compress the air. They may be oil-injected or oil-free.

Dynamic compressors

Dynamic compressors impart velocity energy to continuously flowing air or gas by means of impellers rotating at very high speeds. The velocity energy is changed into pressure energy both by the impellers and the discharge volutes or diffusers. In the centrifugal-type dynamic compressors, the shape of the impeller blades determines the relationship between air flow and the pressure (or head) generated. Types of dynamic compressors include centrifugal air compressors.

  • Centrifugal – High-speed rotating impellers accelerate air and raise air pressure. Several impeller stages are required to reach the required operating pressures, and are oil-free. 3

For more information

The resources below provide more information on each of these types of compressors, including the advantages and disadvantages of different technologies and most suitable applications.

Footnotes ~ Show 3 footnotes

  1. Lawrence Berkeley National Laboratory (2003) Improving Compressed Air System Performance: A Sourcebook for Industry U.S. Department of Energy (Opens in a new window) 1 MB
  2. Energy Efficiency Equipment Committee (2010) Improving the Energy Efficiency of Industrial Equipment (Opens in a new window) 3.8 MB
  3. Energy Efficiency Equipment Committee (2010) Improving the Energy Efficiency of Industrial Equipment (Opens in a new window) 3.8 MB