April 2021

These ten best practice tips will help to reduce running costs by making a compressor installation more energy efficient now and for the years to come: 1: Reduce unloaded running hours Air demand in an industrial compressed air system typically fluctuates. Using these patterns to reduce unloaded running hours is a first step to optimising energy efficiency. Compressor controllers offer user-friendly ways to reduce unloaded running hours. If there are multiple compressors, then they should have been set up to do this automatically. But if there is no central controller, then the compressor pressure bands should have been set up in a cascade method, and the on-board controllers will stop the machines if they are not needed when the compressed air target pressure is achieved. Most on-board machine controllers have the function of programmable start/stop timers. If compressors are left running unloaded after working hours, they still use as much as 25% of the energy consumed at full load. What’s more, if there are leaks in the system, the compressors may switch to loaded running occasionally, consuming even more energy. The shorter the production time, the more that can be saved by switching off compressors instead of letting them run unloaded. If production is reduced but not stopped, a possibility would be to isolate areas of the factory that are not currently being used. 2: Eliminate air leaks Leakages are the most significant source of energy waste in older compressed air systems, with a leakage point as small as 3mm costing an estimated £980/week in wasted energy. It is estimated that up to 20% of total compressed air consumption may be lost through leaks. If there are people still working on-site that have some spare time, we recommend they take the opportunity to detect the leaks in the system. For example, they could run the air compressor with no production to check for leaks. Fixing air leaks will lead to money savings immediately. 3: Reduce the pressure band As a rule of thumb for most compressors, a reduction of 1 bar in pressure (14.5 psi) could lead to a 7% saving in electricity consumption. The pressure settings of the compressor should be adjusted until the lowest pressure can be reached, and the pressure band reduced without affecting the applications. For centralised systems using multiple compressors, by using a central controller, the network can be set to run within a narrow pressure band which ensures that the compressed air network matches the precise needs. The controller can also allow manufacturers to manually or automatically create two different pressure bands to optimise energy use within different periods, drastically reducing energy costs at low-use times. Also, lowering the system pressure reduces the impact of leaks. A 1 bar pressure reduction decreases the effect of air leaks by 13%. 4: Turn compression heat into useful energy with heat recovery One area that offers manufacturers a significant opportunity for savings is to recover the waste heat from air compressors. Without energy recovery, this heat is lost into the atmosphere via the cooling system and radiation. The amount of electrical energy that can be recovered depends on the size of the compressor and the running hours. Typical recoveries are between 70-94%. It is estimated that90% of all industrial air compressors used in the UK could be equipped with heat recovery systems. Recovering heat from compressed air reduces the need for purchasing energy, for example, to heat water or using exhausted cooling air for space heating. It is this reduction that results in lower operating costs and CO2 emissions, also reducing carbon footprint. To illustrate the vast untapped potential of compressed air heat recovery, it is calculated that compressor heat recovery technology could save 1.99% of the total industrial electricity consumption in the UK. If that statistic isn’t compelling enough, it is the equivalent of removing the emissions from 913,000 diesel/ petrol cars per year or recovering the energy required to power 1.544 million households’ electricity consumption per year. Calculations are based on total industrial electricity consumption in the UK and an average of 10% of industrial electricity consumption being used by compressors. Process, Controls & Plant Focus on: Compressed Air 20 | Plant & Works Engineering www.pwemag.co.uk April 2021 Ten ways to make a compressor installation energy efficient Compressed air accounts for a significant part of total energy costs for industrial manufacturers - typically about 12% and may be as high as 40% in some facilities. This means that any compressed air energy savings that are achieved will have a big impact on a factory’s total energy consumption and CO2 emissions. PWE reports. 1 Based upon 0.3kW/I 2 Based upon 7.3p/kWh Source: The Carbon Trust $ L99@)>$=3,.$3?$)6/$>+)<,$ 73>+$56)4+.+/$ [44\$ L6/$>+)<)*+$ L.$]A)/[*\$ $ !3:+/$.3$)6/$>+)<,$ ! $ [<"\$ 13,.$3?$>+)<$ " $ [V$;+)/\$ $ T6./+R,$ =?4$ $ EXD/,R:++<$ &BFD/,R:++<$ FGSF$ FGBF$ FGEB$ FGF^$ &F$ B^$ &GS$ &GX$ UGX$ FGSE$ WS$ BUE$ UGF$ ]G&$ &S$ BG&$ U^S$ WBF$ ^GF$ BX$ SW$ XGE$ &E^F$ U^SF$