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COMPRESSED AIR
ENERGY EFFICIENCY IS AT THE CORE In this article, David De Pril, Director, Product Management, ELGi Compressors Europe, examines ways to use less energy, produce more, and achieve lasting sustainability and profitability in your compressed air applications
t is not a revelation to anyone in the industry that energy is the largest operating expense, accounting for the majority of utility costs. With increased energy prices, it’s important that we look at energy efficiency improvements in more detail. Especially as investing in energy efficiency can provide real savings, ensure superior process performance, and real financial outcomes. In manufacturing processes using compressed air, air compressors consume approximately 12% of the total electrical energy, and over the lifespan of an air compressor, 80% of the cost is energy use, and 20% is the cost of the unit including maintenance. The revised EU Energy Efficiency Directive (EU) 2023/1791, published in September 2023, will accelerate energy efficiency across the European Union, requiring EU countries to collectively reduce their energy consumption by 11.7% by 2030, relative to the 2020 reference scenario.
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Embracing energy efficiency practices is much more than compliance, it is also the right thing to do. Decarbonisation of heavy industrial processes is central to reaching targets combatting climate change. With the industry being the third-largest carbon contributor, energy efficiency measures in industrial processes have enormous decarbonisation potential.
Whether you’re considering a new air compressor or planning to upgrade the existing system, working closely with a subject matter expert capable of designing or redesigning your compressed air systems, and one that could then remain as your service provider, is critical. This will ensure you get the true picture of all areas that need to be addressed when aiming to improve the energy efficiency of your operations. Your expert partner would conduct a compressed air system energy audit, or Air Audit to identify areas of loss or inefficiencies within a compressed air system. Moreover, skilled energy audit engineers can then identify and modify faults and disorders. A complete analysis looks at everything from the compressor to the environment in which it operates, as well as operational demands such as peaks and troughs in air demand and operational expansion planning. A finite analysis of the bigger picture allows understanding of how even the most minor system elements impact the energy
16 FEBRUARY 2024 | PROCESS & CONTROL
consumption associated with the compressor. The aim is to strike the right balance in technical and economic choices - in compressor units, capacities, operational parameters, energy efficiency, planning for future air demand changes, and considering all energy costs.
A proper Audit Report details
recommendations on short-, medium-, and long-term measures for energy conservation, along with financial estimates and analysis for their implementation. These
recommendations come with databases and fact sheets generated by measurements and tests conducted in your plant and the field. Manufacturers can then make educated decisions about their assets, upgrade investments, and ultimately achieve a reduced compressed air energy consumption.
A complete analysis looks at everything from the compressor to the operating environment
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With so many air compressor technologies in the market today, the right selection for your production can be overwhelming. When choosing an air compressor, assessing the load type is critical. For example, a screw air compressor doesn't shut down immediately and goes into unload state to limit too many motor starts and stops. This unloading process consumes up to 30% of energy, increasing the company's operating costs. When selecting the unit for your facility, duty cycle, operating pressure, and airflow demand should be some of the key considerations.
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Different industries like pharmaceuticals, automotive, food and beverage, etc. are powered by various pneumatic applications that demand a specific airflow (m3
/min).
Selecting a suitable compressed air system is crucial to ensure that the air compressor meets the airflow and pressure demands of the pneumatic applications while ensuring optimal performance and energy consumption.
The duty cycle, referring to the operation cycle or the time the compressor runs to provide compressed air at a consistent pressure and specific flow rate, is one of the
critical parameters that help decide if a fixed speed drive or a variable frequency drive (VFD) is required. In the case of a fixed-speed air compressor, the compressor runs at the same rate, consuming the fixed power for the air demand. The electrical motor runs at the maximum constant speed irrespective of the compressed air requirement. On the other hand, the air compressor with variable frequency drive can automatically adjust the speed between its minimum and maximum range, ensuring that the compressed air generation matches demand, consuming less energy at low demand. The VFD air compressor benefits industries and applications with largely varying airflow demands. However, it’s not a given that a VFD compressor is the better technology in all cases. It’s important to look at the size of the air receiver that provides a certain buffer capacity. This air receiver will ultimately handle smaller flow fluctuations and therefore will be very beneficial to avoid too frequent starts of the compressors, and even help VFD compressors as too fast of air demands will lead to quick pressure drops which the VFD cannot cope with.
Looking at the quality of air requirements, the capacity of the compressor, duty cycle, and utilisation together with your compressed air partner will also help you choose the right solution. Whether it’s reciprocating and screw compressors, VFD, or Fixed Speed technology, one of the other factors to look at is the overall design of the system and reduction of pressure drops – the reduction in air pressure from the compressor discharge point to the application point of usage.
High-pressure drop in the distribution system and the hoses, pipes, and joints results in lower operating pressure to the user and means additional pressure generation and a significant increase in energy consumption. The most typical areas where “Pressure drop” occurs include the pressure vessel, aftercooler, air treatment equipment like dryers, filters, check valves, and the piping
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