An airy issue: why you should audit your compressor system

Compressors generate only a portion of the air pollution coming out of Australian factories, however their high level of electricity consumption makes them the ideal place to start saving costs and the environment.

With climate change and energy costs at the forefront of the public and political agenda, the environmental impact of industrial facilities has become a pressing issue, particularly for manufacturers who are already facing the pressures of the strong Australian dollar.

Now is the time for manufacturers to look at saving energy in non-traditional areas, such as air compressors, which are often overlooked. 

National manager of CAPS Australia’s Energy Efficiency Services department, Quentin St. Baker, says while air compressor systems are found in almost all industrial plants – accounting for 10 to 15% of all electricity consumption – they are in fact an inefficient form of energy. 

“As an energy source, compressed air is about 10% efficient compared to using electricity directly, and the main reason for this is because when we compress air, about 90% of the electrical energy we put in ends up as waste heat,” said St. Baker.

Only 50% of compressed air is typically used for productive purposes. Often, compressed air is used for jobs that could be performed using an alternative energy source, St. Baker said.

Air audits

One way to measure the energy efficiency of an air compressor system is to carry out an air audit. These assessments vary depending on the manufacturer and the systems used, but they generally involve measuring the power, pressure and flow of the air compressors, as well as checking for leaks.

According to CompAir Australasia key account manager, Gilbert McLean, manufacturers should think carefully about the provider used to conduct the audit. He says air ‘audits’ conducted in Australia are more like ‘assessments’ because service providers are not required to comply with an energy auditing standard.

“There is currently no Australian standard for auditing the energy efficiency of compressed air systems. The only standard that is currently valid or recognised is the ASME (American Society of Mechanical Engineers) EA-4 – so when a company wishes to have an energy audit on their compressed air systems, they’ve got to be careful about who they are going to have the audit carried-out by and what methodology will be used,” he said.

McLean recommends choosing a service provider who is a qualified mechanical, electrical or associate engineer with a minimum of five years experience in compressed air systems. He also says they should have a professional indemnity insurance of a minimum limit of $10 million. 

According to McLean, the International Organisation for Standardisation is currently working on an energy auditing standard for compressed air systems. But, he says, it is unlikely the standard will be introduced before 2013. 

CAPS Australia’s St. Baker says the energy savings gained from carrying-out an air audit properly can be up to 50%.

“If you exchange a compressor with a variable speed drive compressor, which is essentially what air compressor companies aim to do, you might save 20% of energy. With a more holistic approach, you could save double that. Energy savings of up to 50% aren’t that uncommon,” he said.

Air audits should be conducted at least annually, according to St. Baker. 

“For more complex systems, you might want to do it more often than that. But an annual audit will at least allow you to make sure that the measures you’ve put in place are being maintained and to identify any new opportunities for improvement,” he said.

The carbon issue 

Under the Federal Government’s carbon price, which is set to commence on 1 July 2012, around 500 of the biggest polluters in Australia will be required to pay for their pollution. According to the government, the carbon price will kick-start Australia’s ‘clean energy future’. 

Though air compressor systems make up only a portion of all industrial air pollution, St. Baker says carrying out an air audit is a good starting point for companies trying to slash their energy use.

“When we think about general industrial companies, they’ve got a whole range of things that will affect their energy bill. Compressed air is a utility, which is only one of many areas a company could investigate in order to save on energy,” he said. 

“Generally, air compressed projects have fast paybacks, so conducting air audits might get companies to start looking at other areas in the business [where they can reduce their energy use].”

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