Gelpack cuts compressed air energy bill by 45%

Hereford, UK - A compressed air audit at Hereford-based packaging company Gelpack Industrial Ltd has revealed that 40% of the input energy used to power the compressors was not productive, and that the system pressure was kept above what was required. This was due to the inefficient operation of two fixed speed, 75kW, Worthington Rollair compressors, which were used on a rotating system to provide compressed air to the factory.

The audit, which was caried out by EnergAir, highlighted the potential savings that could be made by retro-fitting a variable speed drive (VSD) package to reduce offload running and match air generation more closely to system demand. The project lasted a total of 187.9 continuous hours, during which data was logged every five seconds.

Gelpack's site consists of two 75kW compressors, both of which were fixed speed compressors. However, EnergAir's study revealed that 40.18% of the energy used to run the compressed air system was non-productive. The pressure in the system also fluctuated between 7.64 bar and 8.63 bar – the optimal system pressure for the site is 6.97.

Demand for compressed air fluctuates on most sites and fixed speed compressors produce the same amount of compressed air regardless and regulate between a loaded (low pressure set point) and unloaded (high pressure set point) state. By contrast, a VSD connected to a control pressure feedback loop is able to measure the demand precisely, regulate compressed air generation and replace low and high pressure set points with a single ‘target pressure’ set point, thereby keeping the system at optimal pressure without generating excess air.

“We were aware that compressed air systems often run inefficiently so decided to examine the possible savings that could be made," said Paul Burns at Gelpack. "EnergAir was able to show how a variable speed drive, sensor feedback and a basic communication box could almost halve the cost of running the system. Recommending a retro-fit VSD package rather than a whole new compressor also made the costs far more manageable.”

Gelpack retro-fitted a VSD to one of the existing compressors, opting to install an EnergAir Solutions retrofit VSD & control package to ensure that the system synchronised well between the two compressors. Installing the VSD resulted in a substantially lower peak current draw and less non-productive energy usage.

Using the VSD to generate compressed air that matches demand has meant that Gelpack has seen massive savings since installation. The system now runs with over 92% efficiency, at all times keeping within 0.21 bar of the optimal system pressure. This increased efficiency has reduced annual energy costs by over 45%, saving over £15,000 a year.

With the savings that the new system has generated the equipment had paid for itself within a matter of months, meaning that real saving were seen in the first year. The installation was so successful that the group company Gelpack Excelsior Ltd has also now completed a similar upgrade to its compressed air system.

“With the new EnergAir system it is extremely simple to manage the entire compressed air system," concluded Burns. "The energy savings that it produces has made the entire site far more economical. As well as the savings we make on energy we are also eligible for a government grant that meant a substantial discount on the equipment purchase."