Compressed air systems are large consumers of energy consuming around 10% of all industrial electrical consumption.
The efficiency of compressed air systems is often poor. Typical causes include:
- Ad hoc system expansion
- Air leaks
- Poor control
- Over pressurisation
- Inappropriate use
- Inefficient ancillary equipment (e.g. dryers)
In the majority of compressed air systems efficiency improvements can be made by installing improved controls, such as master controllers. Further energy savings can be achieved by replacing low efficiency dryers with more efficient dryers (refrigerated and desiccant types) which incorporate energy saving controls.
Compressed air equipment listed on the ETL
The following sections describe the compressed air equipment covered by the ETL. The diagram below identifies those components that are eligible and their relation to each other. Air compressors themselves and air receivers are not listed on the ETL, but master controllers and dryers are.
Controlling multiple compressors around a single set pressure prevents pressure fluctuation common in simple cascade or sequence controls
Optimising which compressors are selected ensures that utilisation is maximised while closely matching demand
Example: for a compressor with a 90kW capacity, delivering 14.25m3/min for a total of 8,000 hours per year at full load, the potential annual savings of installing an ETL listed master controller are:
- 108 MWh
- 38 tonnes CO2
Refrigerated air dryers
Refrigerated dryers are used to remove the moisture present in compressed air before it is used. Drying the compressed air prevents liquid water forming downstream where it can contaminate or damage the system causing operating problems, costly maintenance, and repairs.
Drying is achieved by cooling the air so forcing any moisture present to condense. The moisture is then collected and drained from the system.
A refrigerated air dryer typically increases the energy used in the compressed air system by between 2% and 5% depending on product type and how it is controlled.
Refrigerated air dryers with energy saving controls can moderate their energy use in line with compressed air demand. As the compressed air demand falls so does the demand on the dryer. Dryers with such controls typically use 30% less energy than non-modulating products.
Example: for a compressor with a 90kW capacity, delivering 14.25m3/min for a total of 8,000 hours per year at full load, the potential annual savings of installing a new ETL listed refrigerated air dryer over a non-ETL listed unit are:
- 8.8 MWh
- 3.1 tonnes CO2
Desiccant air dryers
Desiccant air dryers are products that are specifically designed to extract water vapour from industrial compressed air systems by absorbing moisture using a desiccant material which is then, for example, regenerated by blowing air through the dryer.
Desiccant air dryers are commonly fitted to compressed air systems to prevent moisture from condensing within pipe work and equipment. They are typically utilised where compressed air is needed at higher quality or with a lower dew point than can be achieved by a refrigerated air dryer.
Desiccant air dryers available through the ETL must incorporate a dew point sensing control and must either use a regeneration method which is heatless or electrically heated (either internally or externally).
Example: For a compressor with a 90kW capacity, delivering 14.25m3/min for a total of 8,000 hours per year at full load, the potential annual savings of replacing an existing desiccant air dryer with a new ETL listed one are:
- 21.1 MWh
- 7.4 tonnes CO2