Topic editor:
Marion Beaver
LeekSeek Ltd
- Saving 1 unit of compressed air saves 10 units of electricity
- People think it’s free, or very cheap so it is wasted and misused (download BCAS fact sheet on costs).
- High leakage rate inherent in most compressed air systems
- Compressed air systems and work practices evolve in an ad-hoc manner over years, rarely in an energy efficient manner
No energy saving measures should compromise either the reliability or the safety of the compressed air system.
The largest single saving which can be made in a typical system, is implementing a leak management programme. Many carry out leak detection but never reap the potential savings by then repairing the leaks on an ongoing basis. You can instigate your own leak programme in-house or employ a specialist contractor (download BCAS fact sheet on leakage).
Another major influence on air consumption is the users. People often use compressed air just because it’s there, not because it is the most appropriate or best solution. Cleaning down workbenches and overalls with compressed air blow guns is both extremely wasteful and an unsafe practice.
Comments
Nick Osmaston, an independent energy management consultant (nick.osmaston@btinternet.com) sent us this comment on the above:The author mentions both leakage and unnecessary use as opportunities for saving energy. In principle this is of course correct, but in many cases the output of air from the compressors is not proportional to the electricity input. In other words, the generation efficiency is both low and variable. If the effect of reducing leakage or consumption is to lower generation efficiency, then the potential savings will not be realised. To give an example, I recently surveyed an industrial site with a number of compressors each rated at about 75-kW. I determined by inspection that one was running unnecessarily, and by energy analyser that it was drawing 73-kW. When the compressor was pneumatically isolated the load dropped.....by just 5-kW! This is not an isolated incident - on virtually every multiple compressor installation I look at there are control deficiencies that mean that simple leakage reduction measures will not produce pro-rata, or indeed any savings in energy consumption. Even quite fancy centralised control systems do not always produce a perfect result - I have also seen variable speed compressors running as the "lead" machine (at full output) with a fixed speed unit on and off-loading to top up the system. Compressors' off-load mechansms are ofen defective, and compressors run off load for long periods of time unnecessarily. The quickest and easiest way of saving money on your compressors may be to improve the control, and the best way to find out is to monitor their individual electricity demand for at least a week using energy analysers. This may sound demanding, but the potential rewards are huge, and at the end of the day you pay for what goes into a compressor, not what comes out of it.
Links
For an introduction to the technology see Alliant Energy's compressed air systems overview
BCAS is the trade association representing manufacturers,
distributors and users of compressed air
and vacuum equipment and services. It acts as a one-stop shop for all compressed air related
matters such as technical, legislation, health and safety and energy efficiency. Follow these links for:
compressed air training courses ;
energy saving information;
energy saving publications;
walk-round survey checklist to get started