31/05/2008
Download8 Way to Save. Maximising energy savings in compressed air systems
Author : John Forman
8 Ways to Save
Maximising energy savings in compressed air systems
By far the largest proportion of the total lifecycle costs (at least 79% on average) of a standard compressor is taken up by energy consumption, and of the total electricity consumed in the UK for generating compressed air, 30% is thought to be wasted. Here, John Forman of Atlas Copco Compressors, identifies eight ways for compressor users to maximise energy efficiency and avoid energy penalties:
1) Ensure the compressor is the correct size
One of the key ways of preventing energy wastage is to ensure that the practical demands of the compressed air application are met by the most appropriate compressed air system. This starts with compressor sizing. The nominal compressed air requirement of a system is determined by all of the consumers – tools, machines and processes. Therefore, the size of a compressor should be based, not on the total air using equipment, but on the usage factor at any given time.
2) Use air audits to provide a true picture
To be certain that the right choice has been made, it is advisable to carry out a compressed air audit. This will give a highly accurate, independent survey report and provide a true picture of how much compressed air is being used on site, as well as showing how much energy is being wasted in producing it.
3) Match air supply to air demand
The installation of Variable Speed Drive (VSD) compressors may well be one of the recommendations for improvement that is highlighted by the air audit. In 80% of all installations, air demand shows important fluctuations. In 70% of installations, load cycle lies between 40% and 80% meaning that there is big potential for energy savings if VSD compressors are used instead. This is because VSD compressors use an integrated frequency inverter that varies the speed of the compressor motor to match its output to the air demand – providing energy savings averaging 35%.
When implementing a VSD compressor installation, not only do the energy costs shrink by 35% on average, but up to 22% can also be saved on the total lifecycle cost of the compressor. There are other convincing user benefits too: Pressure flexibility, pressure stability, no starting current peaks, high power factor, and EMC-compliance.
4) Detect and control leaks
Leaks in a compressed air net can account for a substantial waste of electrical power. Around 20% of compressed air is wasted in this way - that’s £4.00 per hour based on a typical 250kW compressor at £0.08p/kWH. By repairing the leaks, energy consumption will be reduced and bring about immediate financial savings.
The most frequent sources of leakage problems are poorly serviced condensate drains, leaking pipes and joints, leaking hoses and couplings, air cooling lines left permanently open and inefficient pneumatic cylinders.
5) Remote control and monitor compressors around the clock
In applications where the system comprises a multiple compressor installation, intelligent remote control and monitoring of the units can also help to reduce power costs and optimise the total system for minimal pressure band and maximum energy savings.
For example, Atlas Copco’s AIRConnectTM is an aftermarket service that links compressed air installations to a sophisticated and highly automated 24/7 Internet-based monitoring system. It provides increased availability and reliability of operators’ compressed air systems and allows service optimisation to ensure the right service is given at the right interval.
6) Keep compressors in top condition at all times
Regular compressor maintenance not only keeps the production facility operating at top efficiency, it is also an opportunity to reduce running costs. A major portion (80%) of the lifecycle cost of a compressor is electricity, whereas servicing is around 10%. Regular servicing will reduce the energy running costs of a compressor significantly, so the potential gains are enormous.
7) Use compressor generated heat to save energy costs elsewhere
Most of the electrical power used by a screw compressor is transformed into heat, but up to 94% of compressor generated heat can be recovered rather than wasted. A well-planned investment in energy recovery can provide a payback on the original capital outlay within a 1-3 year period. The available heat from a water-cooled, oil-injected compressor, preferably with a motor power above 30 kilowatts, can be recovered as hot water that can be used on site to reduce energy costs.
8) Use an energy efficient air treatment dryer
Air in the atmosphere always contains water vapour but this can be separated by using accessories such as after-coolers, refrigerant dryers and adsorption dryers. The quantity of water that is released during compression is considerable. For example, a 100-kilowatt compressor that draws in air at 20ºC, and with 60% relative humidity, will decant approximately 85 litres of water during an 8-hour shift.
Whilst some of the tips above may sound obvious, it’s amazing how many operators don’t follow these basic steps towards saving energy costs. Any one of these suggestions will of course make a difference, but combine all eight and your energy savings will be more than impressive.
The author can be contacted at: +44 (0)1442 222235 john.forman@uk.atlascopco.com
| 
http://www.atlascopco.com
http://www.atlascopco.com