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Energy efficiency in the baked goods sector

15 November 2021

As pressure mounts on bakeries and their suppliers to cut energy consumption, their compressed-air systems should be at the forefront of their minds. BOGE Compressors’ Mark Whitmore, explains why. 



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The production of bread and morning goods is a £3.8-billion industry in the UK,?with nearly 12 million loaves sold in the nation each day, but, despite these impressive figures, the industry is under significant pressure. In the UK, wheat prices are at their highest levels since 2012 and are not expected to fall any time soon, which is having a predictable impact on the profits of those operating in the sector. At the same time, like manufacturers operating in wide variety of sectors across the nation, the impact that bakeries have on the environment is coming under increasing public and legislative scrutiny. Fortunately, bakeries can ease both of these pressures by conserving the amounts of energy they consume—boosting both their sustainability and their bottom line.  

Vital resource
As these companies look to slash their energy consumption, their compressed-air systems should be at the forefront of their minds. Compressed air is a vital resource for major bakeries and suppliers to the baked goods industry, which use it to convey flour from silos to other locations within their facilities, among other applications. 

Compressed air is, however, energy-intensive to produce. Each year in the UK, over 10 TWh of electricity – equivalent to the output of almost one-and-a-half power stations – is used to generate compressed air, resulting in over five million tonnes of carbon dioxide (CO2) being emitted into the earth’s atmosphere. Looking at the lifetime costs of owning and operating an air compressor, only around 15% of the total is represented by the initial investment, and 10% by servicing and maintenance. The balance, around 75% of the total cost of ownership, is taken up by the energy needed to run the system.   

Heat recovery
Fortunately, there are a number of steps that a company can take to reduce this figure. A 20% energy saving can be achieved through the recovery of waste heat. A large amount of the energy taken in by a compressor is converted to heat and diverted away via a cooling medium. Using a recovery system, this heat is not lost and can be put to use in another way, such as for heating domestic or process water. Indeed, a heat recovery system can pay for itself in as little as seven months (see boxout).  

Intelligent systems
A further 9% reduction in energy consumption can be achieved through the use of multi pressure systems. Booster compressors can be employed where a limited flow of higher pressure is needed—every 1 bar saved on pressure can save businesses 7% on electrical running costs.

The use of intelligent control systems, meanwhile, can reduce energy consumption by up to 12%. Electronic sequential controllers control multiple compressors around a single set pressure, and make them available as needed. So, for instance, instead of using a 100kW compressor at 60% of its output, the system will select two 30kW compressors at 100% of their output. These systems can operate numerous separate air compressors and can be set to vary pressure according to the requirements of production (for example, providing lower pressure at weekends). 

The BOGE S-4, is fitted with a focus 2.0 control system that is designed to optimise how the compressor operates, and can be set to adjust the running of the compressor to the customers’ requirements. Further, the system enables the operating parameters and running conditions of up to four compressors to be controlled simultaneously. As such, S-4 screw compressors are suitable, for example, for three-shift and 24/7 operation.

Further, by upgrading a compressor motor to a variable speed drive option, a reduction in energy consumption of 15% can be achieved. While fixed-speed compressors are generally cheaper than equivalent variable speed drive compressors, they can consume between 20–70% of their full load power when idling, also called off-loaded running. The additional capital investment in variable speed drive compressors can therefore be recouped rapidly through energy savings.

Regular maintenance
Energy savings can also be achieved without making significant capital investments, simply by ensuring the compressed air system is properly maintained.  All compressed-air systems – even new ones – have leaks, and this wasted air is wasted money. The leak rate on an unmanaged compressed air system can be as high as 40–50% of the generated output, and in certain applications even higher figures have been measured. Indeed, one 3-mm hole in a compressed air system could cost a business over £1,000 a year in wasted energy. 

To rectify this, businesses should ask their equipment providers to include leak detection and/or an annual energy audit as part of their service. A well-maintained system should only lose around 5-10% of the compressed air it generates to leakage, and operating at these levels could reduce energy consumption by as much as 20%. 

Excessive energy consumption can have a significant impact on both the profits and sustainability efforts of a bakery, and compressors are power-hungry systems. Fortunately, cost-effective solutions to this problem exist, helping bakeries to become both leaner and greener. 

((Duotherm boxout))
BOGE’s Duotherm external heat-recovery can be fitted easily to both new and older machines, significantly improving their energy-efficiency. It is available in five different models and can be purchased for oil-injected compressors requiring between 7.5 and 110 kW of electrical power. It can also be fitted (or retrofitted) to compressors from other manufacturers.

Duotherm does not require an additional supply of energy and can easily be connected to the oil circuit of the compressors. Its compact design means that external heat recovery can be carried out in a minimal amount of space.

Further to optimising energy efficiency, an external heat recovery system can also cut expenditure; savings of up to €10,000 can be achieved annually. For many customers, the investment in an external heat recovery system pays for itself within 6 to 9 months. 

Sign up to BOGE’s latest webinar on air purity today at: https://oil-free.co.uk/air-purity-webinar-series/ or get more insight on heat recovery at https://uk.boge.com/en


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