Plant & Works Engineering
Improving energy efficiency
Published:  07 May, 2014

For manufacturers concerned about energy costs and carbon emissions, examining their compressed air system is a good place to start. Andy Jones, general manager at Mattei, discusses a range of solutions available for increasing energy efficiency, and highlights some new innovations that are on the way.

A recent joint survey by the manufacturers’ organisation EEF and energy supplier npower has highlighted that British manufacturers are increasing their investment in strategic energy management and efficiency to reduce energy bills and their carbon footprint.

It’s not surprising that energy costs and carbon reduction are on manufacturers’ minds. The survey from EEF and npower demonstrated that since 2002 the industrial price of gas has increased by 122 per cent, and electricity prices have increased by 94 per cent. Meanwhile, recent reports from the Intergovernmental Panel on Climate Change suggest that scientists are 95% certain that humans have been the dominant cause of global warming since the 1950s, and that climate change poses a threat to global food stocks and to human security, as well as already being responsible for melting sea ice and thawing permafrost in the Arctic, killing off coral reefs in the oceans and leading to heat waves, heavy rains and mega-disasters.

And, with compressed air often considered to be the industrial sector’s fourth utility, a manufacturer’s compressed air system can be a good place to start in terms of making savings. However, unfortunately, not all manufacturers realise that compressors can have a big impact on utility bills and carbon emissions.

A seven-day data logging exercise, or preferably a more detailed energy audit in accordance with the international standard ISO 11011:2013, Compressed air – Energy efficiency – Assessment, has to be the first step. This will help manufacturers to understand how much compressed air they use, how much it costs them and if their compressors are actually suitably sized and appropriate for their production processes.

This knowledge is essential if any improvements are going to be made. Through carrying out data logging and an energy audit, Mattei found that one company running a 75kW compressor could actually fulfil its compressed air requirements with a 45kW machine, with estimated savings being in the region of £10,000 a year.

This process will also reveal whether changes to the system can increase efficiency; even altering the location of a compressor or changing the layout of the pipework to reduce bends can have a significant impact.

The system must also be checked for leaks, and if any are found they will need to be immediately repaired. This is a simple and cost-effective exercise (the average cost of a Mattei leak detection survey is less than 10 per cent of the overall leakage costs). In many companies in excess of 30 per cent of air generated is wasted through leaks. We often see compressed air systems with around 150 to 300 leaks, and a company using 50m3 of compressed air per minute could potentially save around £63,000 by repairing them. Leak detection in itself could be enough to actually make an inefficient installation efficient, without replacing the compressor.

If investment in data logging, energy audits and leak detection reveals that a new compressor would improve efficiency, it’s important for a compressed air specialist to specify the new equipment.

When selecting a new compressor, it must be remembered that the main cost will always be the energy required to produce the compressed air, and that the initial purchase price actually makes up a very small part of the total lifetime costs. Some businesses have a misconception that compressed air is ‘free’ once they have invested in the equipment, but the electricity consumed during operation over a five-year period typically accounts for around 75% of the total cost of ownership, including the initial capital outlay for the compressor.

Therefore a slightly higher-priced compressor could pay for itself in just a matter of months by reducing energy consumption. As an example, a standard Mattei 30kW compressor will deliver 5.62m3/min (199cfm) and our highly efficient Maxima30 (also 30kW) will deliver 6.45m3/min (228cfm), while some other 30kW compressors only deliver values like 4.7m3/min (166cfm) or 3.9m3/min (138cfm).

Understanding that reducing energy bills and carbon emissions are important focuses for today’s businesses, over recent years compressor manufacturers have been investing in making their compressors more efficient.

Some companies have been approaching this task through the use of more efficient electric motors and drives. However, Mattei’s use of vane technology gives us an advantage, as we will actually be able to significantly improve the efficiency of the compression process too.

At the IMechE International Conference on Compressors and their Systems 2013, a paper given by Professor Roberto Cipollone highlighted the unique features of Sliding Vane Rotary Compressors (SVRC) and their potential to be the most energy efficient seven bar compressors available on the market. The paper stated that the use of SVRC provides the end user with the opportunity to achieve the highest possible energy savings. Professor Cipollone also noted that additional potential savings can be achieved using SVRC by reducing machine speeds and improving lubrication processes, which in turn produces a direct reduction in friction losses.

Energy efficiency and carbon reduction clearly remain key focuses for manufacturers, as confirmed by a recent survey. And, with compressed air being widely used throughout industry, making changes – whether repairing leaks, altering the system layout or investing in a new compressor – can have a big impact on energy costs and carbon emissions.

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