Jaguar pounces on energy savings
November 1st 2009

Colin Mander,MD of CompAir UK, outlines how an energy audit of Jaguar's compressed air network has helped the company reduce power consumption at its West Midlandbased plants by 26% per year

Compressed air is an essential utility in many processes and manufacturing operations. However, generating the volume of air required can be a costly exercise if the network is not configured to optimise energy use. Furthermore, industry averages suggest that energy consumption accounts for more than 80% of the total cost of ownership of a compressor over its lifetime – so operators are keen to ensure that the installation produces precisely the right volume of air required by the process and does not consume power unnecessarily.

Data logging service With every 0.5 bar of air pressure generated equating to about 5% of energy costs, it is important to ensure that the compressor network is sized correctly for the application and is producing the right volume of air to meet plant demand.Many compressed air manufacturers and OEMs will provide a data logging service that can provide a very accurate overview of air use, without disrupting the production process or the smooth running of the facility.

CompAir, for example, offers this service free-of-charge where a small logging device is fitted to each compressor in the network.

Every few seconds during a one- to two-week period, readings are taken of parameters such as pressures, flow rates and dewpoints.

These can then be analysed to build an accurate overview of compressed air requirements.

At Jaguar, this process was first implemented at its design, research and development centre in Whitley. Here, the audit showed the peaks and troughs in compressor use for a given period, which when analysed against the corresponding production run could give an accurate overview of typical compressed air demands.

Other reports helped Jaguar to highlight the inefficiencies in the network, such as the compressor's idling in off load mode or redundancy within the system.

Because air is non-hazardous, leaks in the pipework are unlikely to affect process safety and can either go undetected or are considered too expensive or time consuming to rectify. However, any leak in the network means that energy is being wasted, sometimes by as much as 20% – put simply, the compressor is having to work harder to produce the required air pressure at the point of use.

Leak detection In conjunction with the air audit, the compressor manufacturer or service agent can conduct a simple leak detection survey to help identify the leakage rate and associated energy costs, with remedial action undertaken at little cost. Based on the findings from the air audit, Jaguar chose to upgrade the Whitley network to two fixedspeed and one variable-speed rotary screw compressors. The system is configured so that one fixed speed unit and the variable speed machine run constantly, with the remaining fixed speed compressor coming online to cope with increased demand.

After one year of operating the new compressor system, Jaguar reported that the energy savings has exceeded the original calculations, resulting in a faster payback period than anticipated – less than two years.

The second stage of the programme saw the upgrade of the compressor system at the Browns Lane veneer-manufacturing centre.

Production at this site had been reduced by around 80% and moved to the Castle Bromwich plant, leaving the existing compressed air network oversized for the application. In addition, the compressor house needed to be moved to a new area of the site where manufacturing would take place.

Higher plant efficiencies This gave Jaguar the opportunity to resize and modernise the compressed air network in order to maximise energy efficiency.

CompAir engineers recommended a threecompressor network incorporating two fixed and one variable speed 75kW compressor, with the necessary filters and dryers to provide high quality air for the manufacturing process.

The final site to benefit from CompAir's energy audit programme is the Castle Bromwich assembly plant. Here, there are four compressor houses; three serving the main ring network and one for the paint shop. Jaguar is continuing to log the air usage of each system and to date has replaced one machine with an L132SR variable-speed compressor, to help meet demands from the network more efficiently.

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