NERGY is the most costly part of running a com pressed air system, accounting for 75% of the lifecy cle costs of the system. However, compressed air is one technology where most businesses can improve efficiency and in doing so reduce their associated energy costs.
Compressed air demand fluctu ates depending on shift and pro duction patterns. For some users these fluctuations may be greater in the current economic climate. Producing more air than is required creates unnecessary cost.
Where appropriate, investing in a frequency controlled com pressor can exactly adapt to demand fluctuations producing the required volume at a con stant pressure, thus reducing energy costs.
Controlling frequency minimis es idling time and evens out air demand fluctuations by working strictly in accordance with the compressed air demand, there fore producing the exact volume of compressed air at the pressure required.
A correctly-sized frequency compressor will virtually elimi nate off-load running costs and stop starting current peaks. As a result, energy savings can be made. It is worth consulting with a compressed air energy expert.
Choosing to upgrade to a fre quency controlled screw com pressor will not be the right option in every application.
Introducing a control system that monitors and optimises the compressed air system can also assist in reducing energy costs.
It has been estimated that the leak rate on an unmanaged com pressed air distribution system can be as much as 40% of the output. And, just one 3mm leak ing hole can cost roughly 3kW which equates to some $3,400 per annum (depending on your local kW power cost). Additionally, unmanaged air leaks heighten the maintenance required on the associated equipment as unnecessary com pressed air is produced.
Significant low cost savings can be made by simply identify ing and repairing leaks. It is even possible to identify air leaks while also assessing the efficiency of your compressed air system yourself. At the end of a working day record the pressure on the air receiver before you turn the compressor off, then start your stop watch. By timing how quickly the pressure drops in the receiver, you can deter mine the rate of air leakage in your compressed air system.
If your system is efficient, the pressure will remain the same once the compressor has been switched off and, in an ideal world, it should still be the same when you come to switch on the compressor the next day. However, if the pressure has dropped it is a sure sign that the system is inefficient and that you have air leaks.
Of course, the most compre hensive method is leak detec tion. By using an ultrasonic leak detector, a compressed air pro fessional can detect and locate the air leaks precisely. Leak detection will often form part of a wider compressed air audit.
You may also want to assess the airline distribution system. Traditional screwed steel pipe can develop an average leakage rate of 10 to 15% in old com pressed air systems. Opting for modern aluminium piping can improve flow rates reduce pipe diameter and eliminate leakage.
Almost the entire energy con sumption from the supply net of a standard compressor is con verted into heat. Taking the example of an oil lubricated screw compressor, up to 94% of the input electrical energy is available for heat recovery.
Heat recovery provides anoth er energy saving opportunity for many compressed air users. The waste heat generated by the compressor can be re-directed into heating spaces, such as workshops, or for pre-heating domestic water. The associated energy costs can therefore be reduced.
Invest to save
Although a number of efficiency remedies can be made at no or low cost (such as repairing air leaks) most of the opportunities will require investment. The good news — most will be self financing in terms of the energy savings they will create!
Where investment into low car bon technologies is recommend ed a compressed air expert will be able to identify the likely pay back period.