July-August 2021

COMPRESSED AIR 52 HYDRAULICS & PNEUMATICS July/August 2021 www.hpmag.co.uk Why aren’t more small and medium-sized manufacturing operations recovering the heat from their compressed air systems? Why has the usual ‘trickle-down’ effect from larger operations taken so long? The potential in energy savings is obvious. The emission reduction benefits are clear and the return on investment (ROI) is high in a short span of time. All the talk is of energy efficiency and waste reduction or elimination – and for a good reason too! It is estimated that the industrial sector in the European Union is responsible for 20 to 25% of the total energy consumption. If the EU wants to achieve carbon neutrality by 2050, a huge and largely untapped opportunity lies in industrial energy efficiency and waste elimination. Regardless of the continued ‘Force Majeure’ clause, eliminating waste energy is not only the right thing to do but makes good business sense too – no matter the size of your operations. The writing is proverbially on the factory wall. In this article, I will attempt to illustrate the significant advantages of Heat Recovery Systems (HRS) for small and medium-sized manufacturing operations. How much heat are we talking about? In a typical oil-injected compressed air system, the theoretical recoverable heat is 96% of the overall electrical energy consumption. It consists of heat dissipated in the oil cooler (78%), the aftercooler (13%), and the heat radiated from the drive motor (5%). The heat dissipated by the oil cooler can be used for heating water and heat dissipated by the aftercooler and drive motor can be used for supplemental space heating. The remaining 4% of heat cannot be recovered since 2% radiates through the canopy and the other 2% vents inside the canopy. There is no one-size-fits-all approach for heat recovery. Factors such as the placement of the air compressor to the process heat, hot water, or air system plays a significant role, but so does the type of compressor running. Oil- lubricated compressors are by far the most commonly used compressors in industrial applications, due to the technology acceptance and reliability. It is estimated that 90+% of all screw air compressor installations in Europe are oil lubricated. They provide a variety of industries, such as automotive, general manufacturing, and packaging, with reliable compressed air. To help the majority of industries, the heat recovery system works well together with all oil- lubricated air compressors. From the beginning Using waste energy is of course not a new concept. For decades, energy savings were recognised by various industries where the immediate payback from a small initial investment was clear. The most expensive component in the total cost of compressed air is energy. In fact, over the lifespan of a typical compressor, energy typically costs several times more than the purchase price of the compressor. The bottom line, maximising energy efficiency saves you money. Large operations in the industrial sector were some of the first movers – with operations involving large capacity compressed air systems, running 24/7, and requiring process heat in their operations. Such industries included food and beverage, pharmaceutical, and textiles sectors. Simply put, the larger the scale of operations, the higher the energy savings. At the same time, small engineering firms were transforming or creating spin-off companies which are also known as Energy Services Companies (ESCOs). Their bread and butter is a broad range of energy solutions including designs and implementation of energy savings projects, retrofitting, energy conservation, energy infrastructure outsourcing, power generation and energy supply, and risk management. However, the adoption of HRS among small and medium-sized operations has been quite low. The European Commission, in its report on ‘Waste Heat Valorisation: improving energy efficiency in process industries’ noted: “Industrial waste heat recovery potential is still untapped due to several technical and non-technical barriers. Among them, the need for efficient and cost-effective technologies to recover heat losses and to re-use, upgrade or transform this heat for its valorisation.” Heat recovery uses As mentioned earlier, those operations that gain the most from heat recovery are typically those that also require process heat and have 24/7 operations. Typically, we see that for these types of operations, they will witness a significant return on investment from heat recovery – often in under a year and rarely in more than two years. While not all recovered heat use is Untapping the potential of industrial waste heat energy By David De Pril, head of product management and marketing, ELGi Europe. David De Pril: “While there are benefits regardless of the size or the industry and operational aspects of the processes, significant benefits are to be had in recovering and repurposing heat from your compressed air system.”