Compressed Air

Compressed Air for your business

Generating compressed air consumes a lot of energy and is expensive. Around 75% of compressed air costs are related to energy and over 90% of the energy used by a compressor is turned into waste heat. The first question to ask is whether compressed air is needed – is there another way?

How you can save

Compressed air needs are defined by the air quality, quantity, and level of pressure required by the end uses to which it is applied. Analysing needs will ensure that the compressed air system is configured correctly. Savings come from selecting the right compressor to match your business needs, controlling the quality of the air, minimising air leaks in the distribution system, and regular maintenance.
The following are some no cost, low cost and investment opportunities for reducing air compressor energy costs:

No and low cost

• Make sure that compressed air is not being used inappropriately – are there alternative methods of achieving the desired service or output?
• A quick inspection of a compressed air system is a simple way to identify potential efficiency improvements and savings. A more detailed audit will determine compressed air usage and annual running costs in order to establish a baseline against which improvements can be measured
• Inspect and maintain the air treatment system on a regular basis.
• Initiate an effective programme for managing leaks.  Carry out an “out of hours” survey, to listen for leaks, locate and tag them and ask staff to participate also. Check all piping/hoses, joints, drains, valves, fittings, filters and lubricators etc.
• Shut off compressors when they are not required, e.g. during down time or lunch breaks.
• Generate compressed air at the lowest possible pressure for each task.
• Ensure that air filters are regularly cleaned or replaced when necessary.
• Check the pressure drop across pre-filters and after-filters. If this is above 0.4 bar the filter may need replacing.
• Aim for the minimum acceptable level of air quality and ensure that the treatment plant is not over-treating the air.
• Ensure that air inlet temperatures are as cool as possible. If possible, the air inlet to the compressor should be on a north-facing wall, or at least in a shaded area.
• Permanently isolate or remove redundant pipework.
• For areas that use compressed air at different times, zone valves may be beneficial to control the distribution routes for the air. Similarly, for parts of the system that serve plant with lower pressure requirements, install pressure-reducing valves.

Investment projects

• Match the supply from the compressor with the air demand so that it operates at full load. This can be achieved by controlling or sequencing compressors to operate on a “demand-controlled” basis. Investing in intelligent controls can sequence compressors to work efficiently in isolation or in parallel.
• Consider installing a stand-alone compressor for equipment that operates under significantly different parameters, e.g. different pressure or those that operate for longer periods than the rest of the system.
• Pressure fluctuations in older compressor equipment can be addressed by using pressure storage tanks.
• Compressors offer opportunities for heat recovery due to the high proportion of energy used by a compressor that is turned into heat. The heat recovered can be used elsewhere in your buildings.
• Ensure that energy efficiency is a key selection criterion for new compressors, ancillary equipment and controls.

For more information

GIL150: How to find and repair compressed air leaks. Carbon Trust UK. http://www.carbontrust.co.uk/Publications/publicationdetail.htm?productid=GIL150&metaNoCache=1 

GPG385: Energy efficient compressed air systems. Carbon Trust UK. http://www.carbontrust.co.uk/Publications/publicationdetail.htm?productid=GPG385&metaNoCache=1

Compressed air: savings of 30% are quite normal. IEA Caddet. http://www.caddet.org/newsletter/display.php?id=1162