How to cut energy costs using compressed air

THE most costly part of running a compressed air system is energy and with the cost of energy rising steadily, Australian manufactures are now more than ever looking at more concrete measures to cut their electricity, water and gas bills.

In Australia, compressed air systems reportedly consume up to 10% of all industrial electricity and can consume up to four times their energy budget compared to their initial purchase price. But depending on the application, this ratio can reportedly be even higher.

According to Michael Knowles, national marketing manager for Sullair Australia, a leading manufacturer of rotary screw air compressors, the biggest contributor to energy waste in compressor systems is poor design. 

"Choice of air compressor design determines energy efficiency," Knowles told Manufacturers’ Monthly.

"The wrong compressor for the job often results in energy inefficiencies. A compressor that is too small for the task will run at a higher level than it is designed making it energy inefficient, while a compressor that is running below its recommended parameters is not being used to its full potential will also be inefficient," he says.

In terms of design, Knowles says there are four key areas that constitute any compressor: the drive and motor, the method of compression, the method of heat removal and the air-end intake point. The other is the removal of heat. 

"By its very nature, compressing air generates heat. Any compressor therefore requires the input of cooling air or liquid and the output of heat energy," said Knowles.

"The efficiency of both of these processes combined with the design elements previously noted determines the overall energy efficiency of the system. 

"All these components are designed to achieve two things: reduce the amount of energy required to drive the compressor, and minimise the energy wasted through heat generation, pressure losses and poor compression techniques."

Kaeser national sales manager, Mark Dudman, says that the best approach for manufacturers looking to cut their energy costs is to undertake an assessment of their production processes and requirements.

"Choosing the wrong compressor for the application may result in poor energy usage, higher energy costs and potentially higher maintenance costs," Dudman said.

Assessments, such as air-audits, can help firms analyse their current compressed air usage as well as helping to determine load variations and potential weak points in the system.

While the audit process can take up to two weeks, including observations, site visits, evaluations and recommendations, Dudman says the benefits of getting a proper assessment can reap significant savings on energy bills as well as overall cost of production by enabling the right system is chosen.

The findings from the analysis will not only determine the correct sizing, but the system configuration in terms of utilising either one or more compressors which is often referred to as base load splitting, he says.

The control of a compressor system is also a major consideration and can again result in significant energy savings, with many options available on the market enabling multiple unit stations to be set up where compressors are load matched to meet the demand.

Poorly positioned compressors can also result in higher maintenance cost due to such issues as bad ventilation, resulting in higher running temperatures, clogging of filters and reduced life expectancy of parts.

The key thing to remember, Dudman says, is not to be misguided by the conception that the bigger the compressor, the more powerful and efficient it is for the task, but to fully assess the plant air usage in order to determine the correct solution.

According to Sullair’s Knowles, there are a number of steps for manufacturers can take to help to reduce the amount energy consumed of running compressors. These include: providing a clean and appropriate environment for the compressor; choosing the right compressor for the application; maximising efficiency improvements on existing equipments; signing-up for regular servicing; and continually looking for heat recovery savings where these can be applied.

"It is essential that manufacturers and people in the industry understand the importance of choosing the right compressor for the task," says Knowles.

Image courtesy of Kaeser.com.au

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