Instrumental in cutting costs
14 July 2014
The costs of generating compressed air can be reduced in many companies by as much as 20 to 50%, according to VPInstruments, a Dutch producer of ‘state-of-the-art’ measurement and analysis equipment. It believes companies can easily save tens of thousands of Euros a year and, in many cases, much more
Not only is it financially interesting to take a critical look at the compressed air system, but this fits well with the European obligation to make structural savings on energy use in the coming years. The European Energy Efficiency Directive came into force on 5th June 2014, which means that large energy customers are obliged to cut their energy use by 1.5% annually. This measure is supposed to ensure that in Europe the ambitious energy-saving plans for 2020 will actually be realised.
Compressed air is used in a wide range of companies to drive production machinery, to move product, to clean off packaging material, etc. This is generated in compressors, which take in outdoor air via filters and compress this air to such an extent that it can be conducted under high pressure (usually 6 to 8 bar) through a pipe system to machinery (or to your car tyres). This compression is an expensive affair. For even if much has been improved in the areas of compressors over recent decades, nevertheless, 75% of the (electrical) energy consumed is still lost to heat, making compressed air is one of the most expensive energy carriers. It is precisely this which makes compressed air a tremendous contender for successful energy savings. This is particularly so in the case of large factories, where there are often five or more compressors. But even if there are only two compressors (see the arithmetical example), the costs are appreciable and often much higher than many chief financial officers suspect!
Of the total lifecycle cost of a compressed air system, the energy costs account for as much as 75%.
The other 25% are the costs of acquisition and maintenance. Worldwide, about 5% of all electrical energy is converted into compressed air. Within industry, this amounts to 10%. But that can be severely reduced, sometimes by as much as 50%. In order to achieve this, a systematic approach is required. In this process, we distinguish three phases with compressed air systems, namely: permanent monitoring, leakage management, and system optimisation.
Monitoring and analysis
In order to save, first the savings potential must be known. With a modern energy management system, focused on compressed air systems, the system is mapped out and automatic reports can be generated. In the report, the efficiency, the total costs and the consumption per department are displayed. Subsequently one can go to work purposively, in order of savings potential, in which process the result is directly visible in the follow-up reporting.
Awareness on the part of the staff plays an important role too. By presenting results to the staff, their awareness grows and wastage will decrease. Specially for the monitoring and analysis of compressed air systems, VPInstruments offers VPVision. Via a web browser, VPVision maps out the complete compressed air system, from compressor system to end-users. Permanent monitoring and analysis is the first step in identifying savings and in maintaining them, so that savings are realised year after year.
Leakage management goes further than tracing leaks and fixing them. It involves a systematic approach, with a permanent monitoring system as the starting point. By tracing and repairing leaks, energy savings in terms of dozens of percentage points are often realised. It is very simple and almost incomprehensible that in many companies, nothing is done about this. It is the ‘most normal thing in the world’ that when all machinery is switched off, the compressor simply carries on running, in order to keep the leaks alive. Many compressed air leaks can simply be heard (hissing sound), but there are others which are more difficult to detect. For them, there is special detection equipment, and there are specialised companies which can trace these compressed air leaks.
Over the course of time, there can and will be important changes in compressed air usage. Leakage has decreased, production may fluctuate or the composition of the machinery inventory has been altered through expansion/modification. Thanks to permanent monitoring, changes are indicated in a timely manner. Subsequently, optimisations can be carried out. In this context, think in terms of changes in the number of compressors or the type of compressor. Or think reduction in the working pressure, because high-pressure machinery has been replaced, which likewise means a further energy saving. One can also think in terms of heat recovery through the exploitation of compression heat for the central heating system. In collaboration with specialists, supplementary improvements can be carried out, resulting in an optimally cost-effective compressed air system.
There are few situations in which investments in energy-saving measures are so quickly recouped as with the optimisation of compressed air systems.
As a case study, we discuss a modestly-sized compressed air system with two compressors: one compressor of 125kW which runs for 7000 hours per year and one compressor of 75kW which runs for 5000h/year. At 10%kWh in electrical power costs (in many cases this is higher), the energy costs of this compressor station amount to €125,000 per year. Using the VPVision monitoring system, a large number of leaks became visible, and the maintenance schedule was adjusted. The savings were: 15%, or, €18,750.00 per year. Investment was a few new hose fittings and two hours repair time. Subsequently, it was observed that a number of production lines continuously used air during standstill periods. By turning off the machines during change of product, another 5% was additionally saved, or, €6250. The total savings in this case study are thus €25,000 per year, which means that the investment in the measuring and analysis system (about €12,500 in this example) had been recouped within roughly half a year, and there remained more than sufficient budget to invest in repair materials. In view of the fact that many compressed air systems are larger (3 to 5 compressors), the savings in these situations are also appreciably higher, and investment is recouped in two to three months.