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Secure compressed air energy savings

21 October 2014

Keith Findlay, AIRScan manager, Atlas Copco Compressors looks at how expanding on ESOS regulations can help secure compressed air energy savings

The clock has begun ticking towards December 2015. That is the date by which all UK companies with 250 or more employees, or annual turnover in excess of £42m, must have completed a comprehensive audit of their energy use. The countdown has already been heeded by some firms but others remain unaware of the requirement, which has been introduced by the government under the Energy Savings Opportunities Scheme (ESOS) in response to the EU’s efficiency directive.

Every four years after the first audit, all aspects of energy use must be assessed and reported, including compressed air, which accounts for 12% of industrial electricity use, on average, across Europe, and up to 40% in some cases. However, while the ESOS initiative is a welcome step towards greater understanding of energy usage, it does not oblige participants to carry out any improvements, which could see firms diligently completing the administrative exercise without experiencing the real-life benefits of acting upon recommendations to reduce energy consumption.

It begs the question, why would firms invest in meeting the requirements of ESOS without taking the next logical step and implementing changes that result in genuine day-to-day efficiency – and financial - savings over the long term?

One strategy to both comply with the regulations and reap the benefits is to work proactively towards a more comprehensive and results-orientated voluntary framework for energy saving, such as the worldwide energy standard ISO 50001, which not only encourages practical improvement by requiring that an audit is carried out and recommendations are acted upon, but would automatically incorporate compliance with ESOS regulations.

Covering the full extent of energy consumption across a business, ISO 50001 comprises specific guidelines for different areas of energy, including lighting, boilers and compressed air. It is within these areas that specialist advice and coordinated activity can produce demonstrable savings. Under ISO 50001, for example, is ISO 11011, a worldwide standard introduced in 2013 for compressed air, a large consumer of electricity that is often overlooked as a target for efficiency measures but offers scope for significant savings.

A compressed air audit carried out under the conventions of ISO 11011 would assess the entire compressed air system, from the supply that emanates from the compressor room, to the way air is distributed via pipework, and finally the handling of demand from end users.

Under ISO 11011, this data must be analysed, reported and documented along with an estimate of energy savings. The standard specifies that "the overall goal of the assessment shall include identification of performance improvement opportunities in the compressed air system being assessed using a systems approach”. In doing so, it is possible to eliminate wasteful practices, leaks, artificial demand and inappropriate use. Instead, the standard aims to create and maintain an energy balance between supply and demand, as well as optimising storage and control.

This proactive approach can be summed up by the "six steps of optimisation” that Atlas Copco recommends for compressed air users. The process begins with a site visit to estimate  the potential energy savings at stake, based on an overview of the size and complexity of the plant. Next comes AIRScan, a highly detailed and objective compressed air audit carried out by a specialist team focused on specifying and calculating the potential savings, based on an accurate measurement of current status using an array of tools that quantify flow, pressure, electrical current input, ambient conditions, air quality, dew points and leakages.

The latter is a particularly damaging culprit in terms of compressor energy waste. Leakages are the biggest source of energy waste in compressed air systems, with a leakage point as small as 5mm costing an estimated £3,800 in wasted energy over the course of a year.

Once potential energy savings in the compressed air system have been estimated and identified as part of a comprehensive audit, the third step towards optimisation is to deliver a detailed report recommending system improvements, which are then carried out under step four of the process.

The priority is that the potential savings detailed in the audit are delivered as projected, a commitment that Atlas Copco is unique in offering.

Costly leakages, for example, can be repaired. In one recent project undertaken by Atlas Copco, a leakage detection programme instigated across a UK vehicle manufacturing plant identified leaks costing £102,000 a year in lost energy. A similar programme conducted by Atlas Copco’s AIRScan team at a confectionery manufacturer, over the course of three days, pinpointed £31,000 worth of leaks that are now being repaired.

Process leaks are another reason for overspending on energy and these can be corrected by replacing production line equipment, for example, establishing greater control of pressure or shutting down systems when they are not in use.

Another energy-saving measure that can go under-exploited among compressed air users is the concept of energy recovery. After compression, air is often at a high temperature and before it can be distributed into the piping system and delivered to the end process, the heat has to be extracted. As much as 94% of the electrical energy used by an industrial air compressor is converted into heat, which can be redirected into process applications or for general heating purposes within the building, which can reduce reliance on external electricity and gas supplies.

However, a properly coordinated process of optimisation should not end there. Step five seeks to maintain optimised performance over the long term. With the introduction of a monitoring system such as Atlas Copco’s SMARTlink, energy performance can be continuously measured and assessed.

The sixth stage of the optimisation cycle involves repeating the original audit at regular intervals to ensure that new saving opportunities can be identified and acted upon, rather than being overlooked.

By following these six steps in a coordinated manner, compressed air users can not only begin to fulfil the requirements of ISO 50001, as well as meet the ESOS obligations, but also implement a pattern of good practice that can deliver calculable financial and sustainability benefits year on year.