With innovation it is possible to save energy and further exploit the advantages of proven technology.
Compressed air technology provides indispensable services – in the modern day, people no longer think of industry and technology without it. It is compressed air technology which enables the filling of widespread PET bottles with compressed air, and compressed air helps in the purification of water in sewage treatment facilities. However, the economic and energy efficiency factors of compressed air as a working fluid are common topics of criticism. Compressed air technology expert Prof. Dr.-Ing. A. P. Weiß, of the Amberg Weiden university of applied sciences, has conceded. “In the past, it was the efficacy which most came to the fore not the expenditure / benefit ratio”. Climate protection and energy conversion have called for people to revise their thinking. “The focus is now on efficiency.” As it is, economic and scientific fields have for a long time pursued new examples whereby proven technology goes hand in hand with innovation. The common aims are clearly outlined: continuous improvement of the energy efficiency of compressed air, and to make compressed air technology sustainable. Prof. Dr.-Ing. Weiß is convinced of it: “When one makes use of the full potential, compressed air as used in operations is indeed a form of rational energy usage of the future; when it is used correctly there is no need for anyone to shy away from making comparisons!
A study conducted by the European Union shows that 18% of electrical energy in industry is consumed in the generation of air pressure as a service fluid. According to this study, a third of this electricity can be saved with the application of appropriate technology and more efficient systems. Competent skilled workers (technicians) are necessary for this. Compressed air technology was included in the teaching curriculum and scope of research at the HAW Amberg-Weiden institute as early as 2000, together with the establishment of a test stand for air pressure technology and pneumatic motors. The university has worked in close collaboration with the industrial sector since this time. To the mechanical engineering body on these premises – DEPRAG – became the congenial partner in the development of innovative compressed air machines / tools. For example, the development of fast-running turbines for compressed air, CO2, natural gas, steam and other vapours, and the conception of generators necessary for the same would lead to DEPRAG’s GREEN ENERGY turbine system – a technology with which small residual quantities of process gases can be profitably converted to electricity.
Compared to electrical motors, compressed air motors and compressed air-operated tools distinguish themselves for their high output in terms of short-term-sudden release of power (impact tools), speed (cylinders), overload and usability under duress, high duty cycles, robustness and relative immunity to humidity and dirt. In addition there is the “EX” protection of the compressed air motors. In an explosion risk environment, where a single spark can pose a significant threat, electronic tools can be used only under specific circumstances, but there are no such pre-requisites with compressed air equipment. The design of a compressed air motor and its normal operation involve no risk of overheating, and there are no electrical connections.
However, critics fault the economic factor of compressed air technology. They claim that, depending on the type, a compressed air motor does not optimize the expansion process of compressed air; and that as a result, more compressed air is consumed than that which is absolutely necessary. They argue that this means that the consumption of energy for electrical compressors is higher than when the same amount of power is used directly for an electrical tool. The DEPRAG compressed air motors project manager counters thus: “Compressed air motors and electrical motors cannot be compared one-on-one. The application is determined by the drive solution.” the following example highlights the point: “In a packing machine, a motor should produce 450 revolutions per minute with no load. In application a load torque value of 25 Nm is induced at a reduced speed for an extended period of time at the end of the packaging line,. Electrical motors cannot be overloaded over extended periods. This would lead to overheating of the motor. Thus, an electric motor for said packaging machine is planned for the load torque, and would require an output of 1170 W (25 mm x 450 revs/minute divided by 9550).”
The calculation realized with a compressed air motor is completely different. Dagmar Dübbelde: “Both demands of the packaging machine can be accomplished with the favourable torque of compressed air motors, using a smaller motor. For this application we would select a compressed air motor with a nominal torque of 15 nm and a nominal speed of 275 revs/minute. Given that the working torque is less than the nominal torque, the motor runs at close to the no load torque, with 450 revs / minute, under low demand. Based upon this, the required output of the compressed air motor is only 430 W.” Dagmar Dübbelde adds: “When applying a compressed air motor,only one third of the output of an electrical motor needs to be considered for this packaging machine, the energy balance of the compressed air motor appears in a completely different light.”
Compressed air motors are at their most effective when they operate close to their nominal revolution speed. With this, Dagmar Dübbelde advises all users: “The pneumatic motors must be carefully designed for their use in such a way that it saves energy and running costs.” Here, simple conventional measures alone are enough to increase economic viability. Dagmar Dübbelde: “The internal pipe diameters recommended by the manufacturer must absolutely be observed at all times. Every bottleneck works as a throttle and reduces the output of the pneumatic motor.”
The manufacturers of the compressors required for the compressed air installations, also make their contribution to reduce the energy consumption of compressed air generation comprehensively (by 30%). Market leader KAESER KOMPRESSOREN AG (“KAESER COMPRESSORS INC.”) offers users a PC-supported compressed air audit which determines accurately the actual air requirement for new systems and also for existing installations. Dipl.-Ing.(FH) Erwin Ruppelt: “The more transparency a compressed air system offers over costs saving potential, the closer all those involved come to the aim of throttling the energy consumption related to the generation of compressed air by a potential one third – an advantage in terms of company results and the environment.” through the audit, all savings potential is exposed and the compressed air installation can be configured for maximum reliability, energy efficiency, and also optimised for future requirements. Modern compressor controls which communicate with industry PCs, allow for precise data collection and evaluation, and form the basis of a complex system management which can reduce energy consumption significantly, including existing installations.
Yet compressed air technology is capable of even more. Dipl.-Ing. (FH) Erwin Ruppelt shows his enthusiasm: “In the domain of heat recovery, more valuable heat energy can be saved. 100% of the drive energy supplied to a compressor is converted into heat. Up to 96% of this energy can be used a “second time” – either for heat purposes or as process heat!” He says that, specific use of compressor waste heat allows not only for a reduction in consumed electrical energy but also of the heat energy requirements of a company. Read More