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Gelpack Industrial has made an annual saving of more than 45 per cent on energy used to generate compressed air using a retro-fit variable speed drive package from Energair.

A compressed air audit conducted at Gelpack Industrial revealed that 40.189 per cent 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 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.

One area that can use a lot of non-productive energy is compressed air generation.

Many companies are still unwittingly operating systems inefficiently through excessive compressors idling and unnecessarily over-pressurising systems.

Careful management of a compressed air system can therefore lead to large savings on energy as well as reducing a company’s overall carbon footprint.

Suspecting that this was the case with its own system, Gelpack Industrial commissioned an audit to test its compressed air system’s efficiency.

The audit lasted a total of 187.9 continuous hours, during which data was logged every five seconds.

The site consists of two 75kW compressors, both of which were fixed-speed compressors.

The audit revealed that 40.18 per cent 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 bar.

Demand for compressed air on most sites will fluctuate.

Fixed-speed compressors will produce the same amount of compressed air regardless and regulate between a loaded (low-pressure set point) and unloaded (high-pressure set point) state, consequently a large amount of energy is wasted on unloaded running.

A variable speed drive 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, speaking for Gelpack Industrial.

‘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,’ he added.

In order to improve the sites efficiency it was recommended that Gelpack retro fit a VSD to one of the existing compressors.

Gelpack opted to install an Energair Solutions retro-fit variable speed drive and control package that ensured the system synchronised perfectly between the two compressors.

Energair’s drives and controls package is able to maintain the mechanical integrity of the compressor and enhance electrical protection, thereby ensuring the upgrade would not adversely affect the compressor.

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 significant savings since installation.

The system now runs with more than 92 per cent efficiency, at all times keeping within 0.21 bar of the optimal system pressure.

This increased efficiency has reduced annual energy costs by more than 45 per cent.

With the savings that the Energair system has generated the equipment had paid for itself within a matter of months, meaning that savings were seen in the first year.

The group company, Gelpack Excelsior, has also now completed a similar upgrade to its compressed air system.

Energair has produced a free, online Compressed Air Energy Savings Estimator, which can be found on its website.

This provides users with an estimate of potential savings, both in cost and kW.

Energair Solutions

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